240Z Turbo

I was told the ridge between the valves does, in fact, help performance. It is said to help direct charge and also hinder the ability to flow out the exhaust during valve overlap. The combustion chamber is critical to power for several reasons: 1) unshrouding of the valve to help increase flow 2) directing the charge towards the center of the bore 3) swirling of the charge to help promote a better burn these can all be very significant in making power. I don't claim to understand the dynamics of this event as it relates to reshaping of a chamber. However, the important thing to realize is this has a significant affect on power. BTW, someone posted a pic of the Maxima N47 combustion chambers. Very interesting...heart shaped chamber...small cc....looks promising....me likes!

I just want to spark some interest and in the process learn something. I checked out a book today from the library entitled, "The theory and practice of cylinder head modification" by David Vizard. This was recommended to me by the fellow who is an expert on cylinder heads. I would advise you read this if you can find it. However, I need to find if any differences in the designs of port and combustion chambers will be necessary when turbocharging is considered. This book details how to mod the combustion chamber, how to design a port for maximum flow. How increasing the valve size can decrease flow if there is increased valve shrouding. What is the optimal port size based on the valve Diameter. Anyway, this is very exciting stuff to me and the thought of making 250+cfm from these ports is worth the time/money. Now...can someone donate some money to me? Actually, this guy is willing to develop a port on this scrap head to test the possibilities. This includes the modifications to the combustion chamber. He said he would not rake me over the coals, but it will cost a few hundred bucks. WEll, I will keep you posted on the progress.

It is indeed a P90 head. All mods to the chamber will be done by welding material and then removing it to the new desired shape. I am going to do one cylinder on this junk head and have it flowed. I hope I can have it modded by the end of next week so I can slap it onto a flow bench. If 250cfm is realized below .600" lift then.... In the how to hotrod book they have flow #'s for an early 260Z head. It made 238cfm at .500" lift and 251cfm at .600" lift. I will probably run the Web .585" cam on this next head.

You were bound to get the answer right and you did. Better flow in/out. I have heard the combustion chamber can enhance flow by 20% or more. The port shape only gets it to the valve, the combustion chamber shape helps get it out of the intake port and helps to funnel it back into the exhaust valve. Look at the how to modify Datsun book, the one with the engine on the cover and there are a few pics of the modified combustion chamber. It all adds up in the end....50cfm for opening the port inlet....10cfm for blending the valve guide area....20cfm for modding the combustion chamber....etc. In the end you have realized 80cfm more of flow. Although my numbers are made up you get the idea.

OK, here is what I am proposing for the combustion chamber mods. I went out and purchased some sculpting clay to reshape the chamber. I think the work required on the P90 chamber will be more than on any other head, but I also feel the results will be better. Because the valve is sunk into the head .080" further you have a better short turn radius on the intake port. You have a bigger squish area and the funnelling effect of reshaping the chamber will aid in air passing the valve. Here are some pics of what I propose. I could be dead-nuts wrong about this, but it would seem to make sense. BTW, I probably will not be a clay sculpter any time soon!

I feel this is the problem. It would seem a standard port job yields in the 190-200cfm range on the intake. I am not sure at what lift, but???? In the case of the pics you have shown we still have the classic case of the port entrance being smaller than that of the valve seat. It would seem that removing the casting flash and smoothing around the valve guide is the norm. I measured the ID of the intake runner on a RB25 today and it was 2". Holy crap, that is quite a bit larger than the stock 1.25" of the stock intake manifold runner ID. Let us figure this out. Hell, this technology on these heads is 20 years old. That's right, 20 years ago they were making over 700hp on these motors. As it is now, my setup kicks serious street booty. Hell, I raced a nova at 18psi and no nitrous and whipped it in a street race this past saturday. Yesterday this nova ran 11.4@119. If we can get a solid port job to yield 250cfm on the intake ports we can expect to get 400RWHP on pump gas without breaking a sweat at boost levels in the 15psi range. Of course this is with the proper turbo. In recent times, TimZ had his head re-ported(not as drastic as I am proposing) and the results were in the 225cfm range. I have no doubt he will see 475RWHP on pump gas(smart bastard) . Anyway, I will post the proposed combustion chamber mods tomorrow.

Another note, if you look above the #6, #5, and #2 exhaust ports you will see a round spot on the head as shown below. Directly behind these areas is the water jacket. As the old IMSA cars did, just drill through and tap 3/8" NPT. We would need to determine the best way to do this, but I think this should help. The last area that we need to discuss is the combustion chamber modifications. This can add 20% flow if done properly. I will post some pics shortly and detail what I propose to do. I think the P90 chamber will require the most mods to be done right, but I think it will yield the best results over all other heads because the valves are recessed and additional .080". Stay tuned.

Metal will do for now. I can send it to you and you can have it analzyed! This "metal" insert wraps completely around the valve guide. I do not understand the thinking of spring pressure affecting the valve guide sticking out in the port. The spring works against the the valve seat, not the valve guide. There is more material than on the intake side even with the proposed porting. So you do a valve job every 3 years instead of 5 years. Most people break or upgrade in that amount of time. I don't see the issue with valve guides being affected in this case.

Although it is hard to tell from the pics of the exhaust side of things, there is a metal insert cast into the head around the exhaust valve guide. I have accented it in the pictures. This keeps the metal from expanding and loosening the guide which is your concern with having the knurl hold it. I do not think you will have a problem with as little material that needs to be removed and the ring that is cast into the head. I have drawn on the pic of the exhaust port to detail what I feel will free up exhaust flow. This does not address the floor of the port which needs to be modded right where it flows out of the valve, I just don't know what the best approach is at this time.

The valve guide on the exhaust side should be completely removed in my opinion. If you think there is a strength issue then compare it to the intake material holding the guide. There is roughly 1" of material holding the intake valve guide and 1.75" of material holding the exhaust valve guide. If we remove all the valve guide material from the natural path of the port it still leaves us with 1.375" of material which is .375" more than on the intake side. From all the info I have gathered thus far, the roof of the exhaust is key and the 1st part of the short turn radius. There is one advantage I see on the exhaust side. The piston will force all air out of the cylinder regardless, but that will take away from the power. On the intake side it is key to keep the sort side radius broad as you see stock has done. That does not mean you cannot remove material from it, just keep the flow path curve as broad as possible. This is a high flow area. You want the roof to flow just as well as the floor. I have sent the pics to someone who is a professional doing head work/design for Top Fuel and CART. He is going to send me back the pics with the areas shaded that he feels need to be addressed. In the mean time Hoover is going to punch out the port as I have specified and flow the results on a spare head he has.

Ok, I cut the head long ways down the port to get a better understanding of the angle of attack. The 1st pic shows the stock port configuration. Disregard the notch at the port inlet as this is the injector cutout. You can see the port inlet is roughly 1.350" and the valve seat ID is roughly 1.525". What I will do I run a 1.565"(1-9/16") end mill into the port and then smooth the transition. The necessary angle appears to be 17deg. At the port entrance I will make the inlet 1.625" by hand porting. This will allow for a good transition from 1.625" at the port inlet to 1.525" at the valve seat. Here is a pic of what I mean. Below is a pic of the exhaust side of things, looks can be deceiving, but it does need some work.

My buddy with the Turbo mustang(7.78@180) has the epoxy on his intake ports. The ports maxed the flow bench at 400cfm and he has had no problems with the epoxy leaking from the water jackets and massive boost. However, the Epoxy from Morosso is about $50. 290cfm would be an ultimate goal and I have no idea if that will be achieved from doing this, but it can only make it flow better in my opinioin.

Well, some know that I run the P90 on my turbo motor. I had a spare head and decided to chop it up to look at the port cross section. The inlet on the head is roughly 1.375" and the valve seat has an ID of roughly 1.525". This is not a good scenario when the port needs to taper from large to small, not small to large as the stock configuration. In looking at the cross section just before the valve guide the port is actually quite large. It is only the 1st 2" of the port that are really suffering from what I can tell. As far as the cross sectional wall thickness, it looks to be between 3/16" and 1/4" on average. I am sure most of you remember the pics of Franky's massively ported N42 head. This is what needs to be achieved to make the big power we all so desire. However, a custom intake will be a must to take advantage of this port configuration. If we take the inlet from 1.375" to 1.625" that is a 40% increase in cross-sectional area and according to Corky Bell, a 95% increase in flow potential. This is not to mention that we know have a scenario where the port tapers from large to small increasing port velocity. I am ordering a 1.625" 4-flute end mill and will practice on the other half of the head I did not slice up. What I hope to do is use the endmill to come into the head at an angle to punch it out and then smooth the rest of the transition by hand porting. I see alot of potential to get some drastic increases in flow #'s. I have heard 290cfm from the intake ports is possible. I will post some pics soon of the chopped up head.

TimZ runs a T64(o-trim .69) Joel S runs a T61(p-trim .58) I used to run the T64(p-trim .81) What is your specific question?

Do you remember what Option2 video it was from. My buddy is a distributer for the mag and videos.

Does anyone remember the discussion about the Option2 video of the L28 powered 240Z with 1300hp? I tried a search, but came up empty.

The C4 can be made to hold 900hp with no problems. However, the time between rebuilds is more frequent than a GM tranny. Another advantage is cost and the size of the tranny. It is cheap to build the c4 to hold for my application, especially when I don't make 900hp and my car weighs 2565lbs. Hell, I can get a Art Carr C4 race tranny for $1500. The tranny is also very small, much smaller than a GM tranny or the 200-4R. As far as OD, well....

Why, I have already worked out the shaft specs to use the VLSD into a 70-78Z. It uses CV axles and is a direct bolt in affair.

Well, my buddy supposedly trips the lights on his only pass so it did not record a time.

I am looking for an AWD oil pan to modify for AWD 240Z swap.

I will run at the track the next SEZS even, 17th September. I received the CAD files, thanks alot. Looking forward to the pan photos. I had borrowed an FJO unit from RickB while his car was down. I just drove around with it for several weeks tuning here and there. I am sad that I had to give it back. Perhaps I will buy one in the near future. I think slicks are more important at this point. My goal will be to get this motor into the 9's. I think all I need are some slicks, C4 tranny and a trailer for when I blow it up! BTW, the SR20DET'd RX7 is in Orlando tonight for a drag event. I will post the results later tonight.

I was running 100shot before, single wet fogger. Last track time was 11.15@127 with the nitrous running balls out rich on the FJO wideband(10.3:1 pegged). I rejetted it from a 100shot to 125hp shot and leaned out the fuel. On pump gas I am running 14psi and 125shot with 10.9:1 AFR, a bit FAT. On the race gas the jetting is 11.4:1. It hits like a SOB and spins the nitto drags(275/50-15) through the 1-2 shift and then hooks well. I will try to take a video of it. On a different note, my buddies SR20DET'd RX7 laid down 437hp@wheels @23psi NO NITROUS.

Sorry Rick, couldn't wait to post the pics. Please fill in the details regarding the testing before/after with stock intake.

You will need to call the FAST experts. However, Electromotive sells just the coil packs for 4, 6, 8 cylinder applications for running with units such as the Haltech and FAST. From what I remember the price is reasonable. I know with the Haltech the ignitor is not required to fire the MSD coils. I know the GN guys use the FAST to fire their stock coil packs so I guess it can be done. All I can say is call around to a FAST rep.

I have tuned the FAST system and it is very nice. The basic setup with wideband, non-fully sequential, is about $1700 and then you need to get some coil packs for the ignition. Supra ones will work well. Its fuel/timing map is 16x16 which is perfect. It has an awesome tuning layout that makes it very easy to tune. For the money it is a great unit.