RB Rebuild

[cheftrd]

It's fine, and even good, to hit the whole port with paper and completely clean it up. I just don't bother to do it at this level because it's a lot more work for not much gain. For your own engine where you're not paying the labor, I think it's a good step to take. But on someone else's engine, I have a hard time charging them for the time vs. return.

 

This is what I would call the "stage one" port. Stage 3, which is the end-game, is expensive with big mods that will kill low and mid power.

 

The only reason for that stupid hump in the exhaust port is the hump in the stock exhaust manifold to clear where the stud goes.

[Makenski]

Going to be hitting the squish pads any?

[cheftrd]

Going to be hitting the squish pads any?

 

Not on this head. The other head, which came off of this motor and is going on another motor has the pads removed and I'll get int that shortly.

[S15 200sx owner]

It's great to have you back posting here Matt. Thanks very much for sharing this with us. Looking forward to future installments.

 

Much appreciated.

 

 

.

[cheftrd]

It's been a while, and the engine is now almost complete. I'll finish up the head in this post.

While most of this stuff (steps) is available in the FSM, it's good to see the stuff in action with real photos and video. Please keep in mind that I skip lots of steps in this thread. To list and show every little thing would consume huge amounts of time to write up. I'll try to get the important stuff in.

Not going to show the valve clean up. It's really messy. I've found that the best way to clean the valves if you don't have access to specialized cleaning detergents, etc., is with a drill press, some 240+ grit cloth, and WD40. Chucking the valves up in the press won't hurt them at all, just do it lightly. Be careful to keep the paper off of the seat contact area, and don't go any higher on the stem than the carbon. The valves are very hard, and you won't be removing material with simple sandpaper any time soon. Hard carbon is almost impossible to remove from the valves by any other process than mechanically, like this.

Once the valves are clean and all the carbon is removed, the first thing to do is to check the guide play. The FSM gives the distance for the valves to be off the seat. The back and forth movement is checked with a dial gauge. Bucket-type lifted valves fare much better than rocker-type lifted valves. Rockers put a side load on the valve as it sweeps across the tip, opening and closing. Buckets take up the lateral load from the cam sweep.

Checking the valve guide clearance.





Here I'm lapping the valves. This involves a special grinding compound that essentially mates the valve to the seat. There are different grits, but 99% of the time, only the finest grit will be needed. Over time small pits develop in the seat and valve contact area, which can cause valve leakage. Most of the time lapping will remove the pits and restore a perfect seal. I set a stopwatch and do each valve for 1' 30", taking the next 30" to change to the next valve. Total time for each valve is 2 minutes. This ensures I lap each valve the same amount of time. After 12 valves straight (just for the intake), your arms and wrists have had it. If the first round doesn't remove all the pits, I do it one more time. If this still doesn't work, I cut the seats and valves. Too much grinding can cup the contact area. The other thing lapping does is allow you to see if the valve and seat are contacting 360*. If the valve was a little bent, or the seat was damaged and sunk in one place, there would be no contact mark. You can also see the size of the contact ring, but that's for another day.





Here you can see the gray ring on the intake and exhaust seat where the valve was making contact during grinding.





I did another short video to show you a couple of the lapping techniques.

http://http://www.youtube.com/watch?v=fhXsH12Rg6s



Next the valve spring seats go in. Don't forget them. Valve springs will grind into aluminum. Once all the seats are in, you can install the seals. A six-point, 10mm socket for the intake, and 11mm socket for the exhaust work well to install the seals. The size is just perfect for holding the seal without damaging the rubber, but small enough to push down on the steel collar. Dip them in oil, and push them onto the guide. You'll feel them pop into place. This shouldn't need to be said, but clean the sockets before you use them for this. For that matter, clean any tool you use for assembling an engine. It's not a good practice to install head bolts with the same socket you just used to change the brakes without cleaning it first.





Here's the spring seats and guide seals installed.





Next you can slide all the valves in. Use a drop or two of oil and spin them in to lube the guide. The seals will now hold them in place so they won't slide out.





Next I put all the springs and retainers in. Many valve springs have a top and bottom. Look at the coils. If it has tighter coils towards one end, that's the bottom that goes towards the spring seat. I have a spring tool that allows me to install all the gear at once. Most will have to do one at a time.





I took the next two shots to show you the normal way of compressing the spring, and then installing the locks. The other tool I have lets me place all the locks on top of the retainer and just collapse it. The locks install automatically.





This shot shows the locks on. Dip them in oil so they'll stick better. The frustration you'll have here will help you understand why I have the other $350 compressor that installs the keepers automatically.





Here's the finished product.





Here's where the shims go. Make sure the side that was against the valve is still against the valve. Sometimes it'll be slightly dented (only by micrometer), and will change the gap. It's just good practice to place things the way they were, even if they don't need to be.





However, the first thing you're going to do is measure all the shims. Even with pon cams, chances are you'll be changing a few, and it's better to know what the beginning thickness is. Some cams you'll be changing all 24. This shim is 2.99mm





Here's the new Tomei 260 compared to a stock cam. Big difference.





Place the cam in a neutral position where it's close to where it would be at #1 TDC. Neutral means not just lifting one set of valves to max lift, but putting even pressure on at least two sets of valves. Then tighten the caps evenly, and DO NOT BEND THE CAM. It needs to drop into the front thrust area evenly and straight down.





Once all the caps are down, torque them appropriately.





I lay all the thickness gauges I'm going to use out, so I'm not constantly looking for the one I need in the pack.





Checking the clearance. It's tricky with the RB26. Too much clearance, add shim in the amount it's out. Not enough, take shim away in the amount it's tight. Simple. Bad thing is you need to take the cams back out to change them. Before checking anything, turn the cam at least twice to make sure everything is seated. The head needs to be propped up front and rear because the valves will protrude past the deck.





On the final cap installation, you need to add some sealant to the front of this cap. Very sparingly. There is a small passage in there from the rear of the seal to the inside of the head. If you block it, oil pushing out of the front journal to behind the seal won't have anywhere to go and will blow out the seal. Not fun to take it all back apart and clean it up. Wipe off the excess or it will cause the cover gasket to leak.





All done.






Like I said, I skipped some steps. Installing the lifters, make sure they spin freely once installed. They turn while in action, and if they're tight, it'll burn up a lifter and cam lobe. The baffle plates only go on one way. Installed any other way, the covers won't go on. They're on in the pics, but need to be off for timing the cams, which I'll cover later.

Dirt is the enemy. Compressed air is your ally. Be as clean as you can and try to use lint-free rags for touching the motor. Cheap paper towels work well. Shop rags do not. I know my blue bench top looks dirty in these pictures, but I assure you it's sterile (literally) before I start. All the discoloration is from years of burn marks from welding. At over US$40,000 for 500 square feet (just for the property, not the structure) I don't have a clean room yet.

On valve lapping: Someone asked me, why not just cut the valves and seats? The main answer is because there's nothing wrong with the valves and seats that are in this motor. If it requires more than about 2 minutes of lapping with a fine compound, I'll usually cut them. Cutting is not so simple in a high performance application. You also need to cut the other two angles in the seat to adjust the placement and contact size on the valve. Then you need to completely reshim everything. The above "pon" cam installation required changing three shims vs. 24.

Edited February 8, 2015 by cheftrd

[RB26powered74zcar]

Thanks for that Matt!! I can't wait to see Your write up on timing the cams. This is one area I know nothing about, and I'm sure I can gain something on my motor by properly getting that correct.

 

I just set my HKS wheels to zero, and went with that. I don't have any info on my cams other than being told the lift and duration (and that may not even be correct...). I know I had to clearnce the head for the lob wipe, so they are not stock spec.

 

BTW, great pic showing what needs to be milled for a high lift cam lob to clear the bucket area!

[wax]

Excellent thread

good pics and info

In my experience with jetski porting and other two stroke engine porting i have found that running in the carbide in a buffing stick stops the alloy sticking to the teeth

[cheftrd]

Just a note... I haven't forgoten this thread. My computer crashed and I lost a lot of pictures...

 

In the coming weeks, I'll do the build up on the new race motor going in a long-time friends R34 GT-R. It'll have the full port and chamber mods. I won't really go too much into the bottom end, because it's about the same, but the head is substantially different.

[TurboSouthAfrican]

Great post and thank you sir for sharing your knowledge with others, I have found that most people with the know how, never want to share, which I guess is some what justified but thanks again.

[Careless]

Great post and thank you sir for sharing your knowledge with others, I have found that most people with the know how, never want to share, which I guess is some what justified but thanks again.

 

I agree. sometimes it's not what you learned or experienced, but it's what you had to do to get to the point to where you had the opportunity to do so.

 

the people with good beating hearts, and heads on their shoulders know the difference between the two, and when helping goes a long way.

 

I think that's why I like this thread.

[cheftrd]

We're in the home stretch now. I'm going to skip over the stuff like measuring the rod bearing and piston pin clearances because it's the same as we did back with the main bearings. Same goes for the piston clearance. Measure the bore, measure the piston or pin, the difference is the clearance.

With the new rings from Arias in hand, we can set the end gaps. Generally accepted ROT (rule of thumb) is .004 (.1mm) per inch of bore is the minimum gap. This bore is 3.464" (yea, that's 88mm), so the minimum gap would be .014" or .35mm. It's not always good to use the minimum gap. Engines that have high thermal loading like forced induction, nitrous oxide, etc., should use more gap. If you were running a fuel like alcohol, you could close up the gap a little. Don't worry if you accidentally grind a little too much and make the gap too big. You could effectively double the gap and not see a decrease in performance. It'll affect a leak down test, etc., but won't really hurt performance, especially in the rpm range where you're making power. I've seen engines with broken rings that you couldn't even tell something was wrong until they were torn apart. Basically, don't get too hung up on ring gap. Too much=OK. Too little=Very Bad.

On ring expander tools: I hate them.
First, if you have a deft hand, it stretches/tweaks the ring a lot less when it's twisted on by hand. A ring expander that stretches the ring out enough to completely clear the piston is scary business. I used one once and threw it away. If the ring binds up, just stop and back up. People break rings when installing them in a hurry and using the armstrong method. In 25 years of assembling engines I've broken exactly one ring, and that was about 25 years ago.
Second, every pro engine builder I know, including the heavy-hitter mainstream guys, installs the rings by hand.

Checking the gap .016".





Soldiers, ready for battle. Once again, don't bust my chops about the "dirty" bench. It ain't dirty!





An army of one. Arias pistons and Carrillo rods.





The Carrillo SPS bolt. The best and strongest rod bolts money can buy.





These rod bolts torque to 65 lbs. Normally I use a stretch gauge, but it’s impossible to get in there, so for the RB it gets torqued.





All masked up and ready for paint.





Here's the almost complete short block. Pistons in, studs in, gasket on. Check that shiny new paint job.





A few words on studs. Studs are not necessarily stronger than bolts (ARP are). The main advantage to a stud is that they use a fine thread at the nut end vs. the course thread in the block. This makes for smoother torquing, and allows you to take the fastener closer to the yield point safely. For instance, say a fastener has a yield strength of 200,000 psi. With a course thread, tightening can be erratic from one fastener to the next, so the manufacturer may set the tightening torque to achieve 60% of the fasteners yield to ensure it never goes over. A fine thread like those from ARP is set at 75% of the fasteners yield. That's 120,000 psi vs. 150,000 psi of clamp force.

You never tighten a stud in the block more than hand-tight, or just barely snug. There should be zero upward pulling or pushing of the block threads before the top nut is tightened. If a stud like those from Tomei, with an extension to bottom in the bolt bore, is tightened into the block, it pushes up on the area of the block around the stud, creating a high spot. These high spots guarantee that the seal around the cylinder is a weak one. There's nothing wrong with the fastener, per say, but in the wrong hands... The ARP studs have a shoulder machined above the threads as a positive stop. If you were to tighten it, it would only clamp the threads together, but would still pre-stress the block in the area around the fastener. Don't do it.

It's much easier to lube the threads before the head is on. Lube 100% of the threads. Do not lube the threads in the block. You don't want those turning. If you use a threadlocker or sealer with studs (only in the block), it needs to be tightened within an hour, or so, before the locker sets up.

SR20 studs can not be pre-installed like this. The head can't slip down on the studs and clear the chain guide.





Where the power is made. This is a touge engine. The quench (squish) pads stay in place. Much better mid-range power with the pads. This head is pristine. Perfectly flat, with no imperfections, so it's not getting cut. It's a waste to machine things that don't need it. My thought is that you're taking away rebuild-ability.





The head installed.





Another shot.




Here's where people are going to bust my chops...

It's info I've been sitting on for about a decade and a half. Well, the cat's out of the bag. I know I've said I never did an extra "oil return" on an RB26, and that's true. But I never said (I don't think) I never added anything for crankcase ventilation to aid oil return through the stock pasages. Semantics...

Why do I discourage people from doing this mod? BECAUSE YOU DON'T NEED IT! And, if it's done wrong, you'll end up with more problems than you've solved. Originally, this engine turned around 11,000 rpm, boosted way over 30 pounds, and made hp north of the millennium mark. The new configuration doesn't need it, but because the mod is already done to the pan, the parts are there, etc, it's going on this engine.

The following three pictures are of the additional crankcase vent. I first started doing this mod on the 26 in the mid 90's. It's a common mod for high rpm engines, so it was a no-brainer for the RB26. Soon thereafter, the Internet got a hold of it and speculation as to its function ran rampant. "Additional oil drain-back" became the consensus, and consensus became fact. Now it's well known as the additional oil drain back mod. Then it became a fact that all the oil in the engine will pool in the head and the engine will blow if you don't have it done.

Really? Let's examine some facts. The RB26 has been lapping the Nurburgring starting years before the R32 came out in 1989. Lap after lap at full-boogie. Since then, the R33 and R34 have been lapping the same track. The N1 GT-R that races in the N1 class doesn't have this mod done. Super Taikyu RB26's don't have this mod done. I can assure you that the RB26 does not have an oil drain back problem that warrants modification to implement an additional one.

On Youtube you can find some videos of the Porsche Turbo engines in a cradle that simulate a run of the Nurburgring to test the oil system. Nissan has the same thing.

http://http://www.youtube.com/watch?v=fv53RbvgfGc

So what's the deal??

Windage and blow-bye in ultra-performance engines. You get an RB26 up in the 10,000rpm neighborhood and lean on it with 2+ kg of boost and you have a nightmare.

See, all but one of the oil drains back into the sump on the RB26 are on the left side of the block. When we examine crank windage, that's the side of the engine where the crank counterweights, rods, etc., are moving in a downward direction, essentially "pulling" oil back down out of the head. In the right-rear of the engine, there's another port. This port is on the "pressure" side of the motor, and windage blows up this passage, creating an actual suction on the drain-side of the motor.

At high-rpm, high-boost, windage and blow-bye gasses can be so severe, that the single port on the right side isn't adequate. Gasses are moving up all the ports, sometimes at high velocity. This effectively keeps oil from returning to the sump. What the large hose from the sump to the back of the head does is give the blow-bye gasses another path to the head, and allow the oil to return down the normal returns along the left side of the motor. It needs to be above the oil level in the sump, but below the baffle.

In a drag motor, if we accelerate forward at 1g, the oil in the sump will stand up at 45 degrees. It'd be neat to hear an explanation of how the oil in the head overcomes the laws of physics and somehow runs forward to the front of the engine. In a circuit/touge motor like this one, oil will indeed return down the hose to the sump because not all of the acceleration is forward. This is the reason it needs to be lower than the baffles in the pan; on that side of the engine, any oil returning will simply be picked up by the crank and added to the hurricane in the crankcase.

What we found was that under these extreme conditions, we were pumping a quart of oil out of the breathers and into the overflow in a 400m pass. Not only was it not returning, but the blow-bye gasses were pushing it out of the engine. Additional vent was added, and the problem disappeared. It needs to be said that in engines turning 9,000 rpm and boosting 1.7 bar, engines making north of 750hp, this "problem" has never presented itself. That, and the problems you can create if it's not done properly are the reason I've been so against it in more reasonable engines. An example is if you put the tube below the oil level in the pan, not only are you choking any venting action, you're giving the oil another place to go during acceleration. Like I said above, oil will leave the sump through the hose.


Hate away.


On 88mm. There's talk on the Internet that it weakens the cylinders too much... I don't know what others have experienced, but I've never had a problem. This engine made BIG power for a long time and had two failures. Dropped a valve both times. I don't recommend going all the way out the first time. I leave the bore stock with a new hone, if I can. Then it's up to 86.5mm, and so on. "Rebuildability" (is that a word?).


Next I'll write up the race head and put that on an engine like this one, but with Pauter rods, a new N1 block, and 280* high-lift cams.

Edited February 8, 2015 by cheftrd

[TurboSouthAfrican]

Very interesting Matt and thanks for letting the "cat out of the bag" so to speak. I was wondering why I had not seen this return oil mod on all high hp RB's.

 

Another point, is that I have heard everyone and their brother talk about, if you punch out the block to 87mm, the walls will "flex" because of material thickness of the cylinder walls. Good to know that once I rebuild after 86.5mm, I can reliably run 87mm and not have worry to much.

 

I was wondering what you thought about Wiseco pistons?

[cheftrd]

Very interesting Matt and thanks for letting the "cat out of the bag" so to speak. I was wondering why I had not seen this return oil mod on all high hp RB's.

 

Another point, is that I have heard everyone and their brother talk about, if you punch out the block to 87mm, the walls will "flex" because of material thickness of the cylinder walls. Good to know that once I rebuild after 86.5mm, I can reliably run 87mm and not have worry to much.

 

I was wondering what you thought about Wiseco pistons?

 

 

Wiseco's about all I use these days. Arias was having a hard time getting their act together where rings were concerned. A couple of years ago I bought around 10 sets of Arias pistons for the 26 and a bunch had the wrong rings... They were "kits" in Arias boxes and had the wrong rings. Some had four correct oil rings and two were the radial wall was too deep, some had ring sets that were for 86mm when the pistons were 87mm, and so on... The rings now come in boxes with sealed packages and high QC, but it's too late. You just can't beat the price of Wiseco kit pistons. They've been in the business for a loooong time. Years ago when import pistons were all custom, I was a Wiseco dealer. I stopped using them when they increased the minimum order for custom pistons to 50 from 24!!! I was like, when am I ever going to use 50 of the exact same piston?? Now that they've got their act back together, I'm back to using them but don't order direct. Race Engineering gives me a good discount on parts so I order through them.

[TurboSouthAfrican]

Interesting, I know they a good following amongst circle track guys here and alot of the domestic V8 guys running them around here, but had not heard a bunch of guys in the RB community running them, good to know, thanks.

 

I received mine last week and has a black coating on the skirt. Do you have any idea what company the skirt is done by? Do you ever have your crown ceramic coated, any negatives on this? I have heard people telling stories of how the ceramic coating came off the crown, got blown through into the compressor blades, found this hard to believe but what experience do you have with these coatings or just steer clear.

 

Thanks

[shockster0429]

One of the best descriptive/informative RB build I've read to date. Maybe because you didn't "hide" really anything. Awesome read I just spent the last 1.5 hrs reading through this 2 page thread and it was great!

 

What are you using the seal the rear vent you have on that 26 head? Is there a recess cut for an o-ring back there?

 

As for the quench pad removal. I'm currently starting a build up of an e85 67mm build. Looking to make mid 6's through it to the ground. Car will be mainly street driven/highway car, with the occasional journey to the drag strip.

 

My question (s) for you here is from your experience how much additional timing was a rb26 head able to take with the pads removed, keeping all other variables the same (boost, fuel)? What pistons did you have made, or did you use to bring the compression ratio up? Most say there will be a loss in mid range, and efficiency slightly but how much exactly?

 

What it comes down to is I'm questioning removing the pads or leaving them. I burnt up two rb25 cylinder heads really bad, and the quench area pretty much took all the heat, with no signs of pre-det showing on the plugs, when obviously inside it was blowing itself to bits. This issue was more caused by a ECU/CAS related problem in picking up the cas single properly. (timing was really low values like 15-16 from threshold on at 12-13 psi boost, engine was obviously seeing a lot higher timing that it was supposed to on 93 oct)

 

Any bit of information you can provide would be awesome, I really want a well running mid-higher HP RB to run correctly and for a while, its been a few year process of blowing cash, and engines, while finding the issue far too late..

 

-Cory

[stony]

I know cheftrd has talked about all your questions before but i cant remember where. I would suggest search for all the posts he has made in the rb forum and read through them. it may take some time but everyone of them are very informative.

[shockster0429]

I know cheftrd has talked about all your questions before but i cant remember where. I would suggest search for all the posts he has made in the rb forum and read through them. it may take some time but everyone of them are very informative.

 

Thanks for the tip Stony, Nice times in your sig too man. Very impressive Z.

[cheftrd]

Interesting, I know they a good following amongst circle track guys here and alot of the domestic V8 guys running them around here, but had not heard a bunch of guys in the RB community running them, good to know, thanks.

 

I received mine last week and has a black coating on the skirt. Do you have any idea what company the skirt is done by? Do you ever have your crown ceramic coated, any negatives on this? I have heard people telling stories of how the ceramic coating came off the crown, got blown through into the compressor blades, found this hard to believe but what experience do you have with these coatings or just steer clear.

 

Thanks

 

I've heard the same thing, but have no first-hand experience with the ceramic coatings on the crown. The way I look at it, I've never had a problem, so why should I introduce another potential problem into a critical area? No idea who does the coating for Wiseco, but they're a pretty big company, so they may do it in-house.

[cheftrd]

One of the best descriptive/informative RB build I've read to date. Maybe because you didn't "hide" really anything. Awesome read I just spent the last 1.5 hrs reading through this 2 page thread and it was great!

 

What are you using the seal the rear vent you have on that 26 head? Is there a recess cut for an o-ring back there?

 

As for the quench pad removal. I'm currently starting a build up of an e85 67mm build. Looking to make mid 6's through it to the ground. Car will be mainly street driven/highway car, with the occasional journey to the drag strip.

 

My question (s) for you here is from your experience how much additional timing was a rb26 head able to take with the pads removed, keeping all other variables the same (boost, fuel)? What pistons did you have made, or did you use to bring the compression ratio up? Most say there will be a loss in mid range, and efficiency slightly but how much exactly?

 

What it comes down to is I'm questioning removing the pads or leaving them. I burnt up two rb25 cylinder heads really bad, and the quench area pretty much took all the heat, with no signs of pre-det showing on the plugs, when obviously inside it was blowing itself to bits. This issue was more caused by a ECU/CAS related problem in picking up the cas single properly. (timing was really low values like 15-16 from threshold on at 12-13 psi boost, engine was obviously seeing a lot higher timing that it was supposed to on 93 oct)

 

Any bit of information you can provide would be awesome, I really want a well running mid-higher HP RB to run correctly and for a while, its been a few year process of blowing cash, and engines, while finding the issue far too late..

 

-Cory

 

There's a 10mm deep pipe that goes into the head. It's a tight fit with the hole and uses regular silicone sealant.

 

I don't have any experience with E85, as we don't have it in Japan. However, with gasoline up to 600 I don't even mess with the quench pads. Over that and you may take just the intake side. Mid 6's with E85 and I seriously doubt you'd need to take anything out. Alcohol loves compression and boost.

 

As far as the exact amount of power and efficiency loss with removing the pads, I don't have an exact #, but let's say it's considerable. I tell people that removing both pads is a max power drag mod. The pads do more than increase compression and contribute to inert effects. They add to chamber turbulance and increase burn efficiency. It's a trade off. You give up efficiency and response to be able to make the big numbers. But if you don't really need to remove them for 600hp, you certainly wouldn't need to remove them with E85. The GT500 engiens I've seen have the intake side removed, but they're not running E85. That could also be done to unshroud the valves and has nothing to do with knock...

 

With Japanese Esso high-octane fuel and good fuel trimming, I can run 35 degrees of advance at WOT without pulling any timing until around 6-7psi. Without the pads I don't start pulling timing until around 10psi. Too-retarded timing makes for very high EGT's and will burn thins up, as well. I'm a big fan of efficiency in street motors, so as a rule, if I have to pull more than 15 degrees or drop below 11.5 AFR, I throw in the towel and look elsewhere like lowering compression or octane improvement.

[mattyice]

There's a 10mm deep pipe that goes into the head. It's a tight fit with the hole and uses regular silicone sealant.

 

I don't have any experience with E85, as we don't have it in Japan. However, with gasoline up to 600 I don't even mess with the quench pads. Over that and you may take just the intake side. Mid 6's with E85 and I seriously doubt you'd need to take anything out. Alcohol loves compression and boost.

 

As far as the exact amount of power and efficiency loss with removing the pads, I don't have an exact #, but let's say it's considerable. I tell people that removing both pads is a max power drag mod. The pads do more than increase compression and contribute to inert effects. They add to chamber turbulance and increase burn efficiency. It's a trade off. You give up efficiency and response to be able to make the big numbers. But if you don't really need to remove them for 600hp, you certainly wouldn't need to remove them with E85. The GT500 engiens I've seen have the intake side removed, but they're not running E85. That could also be done to unshroud the valves and has nothing to do with knock...

 

With Japanese Esso high-octane fuel and good fuel trimming, I can run 35 degrees of advance at WOT without pulling any timing until around 6-7psi. Without the pads I don't start pulling timing until around 10psi. Too-retarded timing makes for very high EGT's and will burn thins up, as well. I'm a big fan of efficiency in street motors, so as a rule, if I have to pull more than 15 degrees or drop below 11.5 AFR, I throw in the towel and look elsewhere like lowering compression or octane improvement.

 

i must say that you are doing an awesome thing by posting all of the info you have! im sure most of us cant say thanks enough for what you have took the time to post here!

 

so if im reading the above correct that once you would get above 600-650 HP only maybe the intake quench pad would need to be removed? what would be a power level to remove the quench pad/pads? and would it be beneficial to maybe leave them to slightly remove them/round off the edge or is it an all there or nothing situation with them at the powerlevels they should be removed?