Tony D

Those are some very dangerous assumptions to be making for such a critical component. If the head of the bolts only had an '8' on the head, then by the industry standard, it would be a manufacturer's identification and nothing more! When they say it should say '8.9' that is what it will say. The markings for bolts are very specific! Lacking of a specific rating marking denotes the minimum quality standard for the class of fastener. For the costs involved, I would not be 'cheaping out' on head bolts, studs, connecting rod bolts, main cap hardware, etc... Japanese manufactured automobiles, just in the way they interacted within the supplier network and the integrated governmental oversight they had usually had supplier relationships that allowed them to have much higher standards for hardware in many applications than would normally be supplied to general industry. Head bolts/studs would be a prime location for this kind of 'cooperative relationship' where the supplier gave them a beyond industry standard bolt or stud, thereby cementing a supplier relationship longterm, and insuring there would only be ONE source for the bolts. Everyone made the maximum profit. American engines at the same time were really a 'low bidder' application, where each engineering decision was MBA'd and Accounting Department/Purchasing Department lowballed. Consequently they engineered to industry standard fasteners to keep construction costs as low as possible. There's advantages in each way to engineer the package, but on German and Japanese vehicles, I would be VERY wary of exchanging ANY engine hardware in critical locations for run-of-the-mill industry standard hardware. On a SBC...sure, I can see lots of stuff that has Gr5 in it and a possible cheap upgrade to a Gr8 fastener would work fine. But on the 'ungraded' application specific hardware like a Nissan Head Bolt... Not for me! Stick with OEM or BETTER quality.

SU's are another bag of tricks altogether. I have heard of British Applications where they were used blow-through, but have never seen one firsthand. All my experience with SU's has been drawthrough application on the Corvair. I would just run them N/A and save your money. I wouldn't want to tackle SU Blowthrough, at least on early carbs (pre 73) because I really don't know what the limits of the fuel feed tube are, and how the jet sealing area works under the various pressures. It is all 'sealable' through the use of clean air piping and drilling holes, etc...but that's a lot of work to go through when other alternatives are far more practical. And the boost threshold point has nothing to do with tip-in pops, it's the combination of plenum sizing, engine draw, and compressor flow that causes the transitional popping issues. If you lag the compressor so much that the carburettors are on the 'main' circuit when boost comes on, then it won't be an issue. Though you limit your useable rpm range. The solexes run on the idle jets till almost 3000rpms, that is how they get such great fuel economy. On an SU, the fuel metering is totally different and much more complex in regards to spring weight versus vacuum exposed to suction piston weight compared to needle station height when coming on boost. Egads, my head is starting to hurt to see how that interaction would be attacked! The 'problems' are not related to turbocharging, it's related to 'blow through turbocharging of solex style carburettors', it's not an issue with an EFI turbocharged application. Which was a point made early on in this discussion. If you suck through a carb on a supercharger, you will have the same success as if you suck through a turbo. And the reason I say 'early' SU's as an issue is they don't have an integral float bowl like the later carbs do. So that fuel transfer line just looks like a problem area, one crack or break when you are under boost and you are gushing fuel directly onto the exhausts. Not something I would look forward to during 'testing to failure' in the real world. Of course, dealing with a power valve under boost on the later carbs would present it's own issues, but it would seem like they are much easier to attack in a blowthrough application.

The difference is most guys with 4bbls that are blowing through them is that they make a 'pressure box' that equally pressurizes both the venturis and the float bowls. Many times it encloses the entire carburettor! The design of the Mikuini (and the other horizontal carbs like Weber, dellorto, etc) is such that the float bowl can easily be pressurized separately. Some use a divided plenum, or like SHO showed, you can put a separate line, plug the normal breather port for the float bowl, and pressurize it from something added under the jet cover, or direct tapping to the float chamber. (Some Weber Guys will make a round 'standoff' for the jet cover, and put the boost in there, instead of through the front opening...that opening on the front is covered by their plenum, which only has the throttle bore openings in it.) Most of the 4BBLs have simple tubes and they usually are right in the center of the throats, making it difficult to segregate. Sure, you can tap and plug them and then drill the bodies, but most guys just 'buy the big box' and go from there. This is the same approach Cartech took when they designed their plenum---it pressurizes both chambers equally, so as a result you need MUCH larger jets in the main side than you would running any of the Japanese Boxes. We had a clubmember at GroupZ who had the full Cartech Setup and his jet sizes were MUCH larger than mine were. He also got fuel mileage that was in the very low teens. Granted he had a 3.0 and mine was only a 2.8, but the performance was equivalent when dynoed. Somewhere I have a video of him saying his jetting setup... I could find that, and then compare what was in my Solexes, as we both had 44's. One of the things that impressed him about driving my car was the lack of the transitional popping. Same for another clubmember that had a 2X4 plenum, and was making somewhere north of 300HP on his 3.0 as well. No matter how they jetted it, they could not get rid of some transitional popping. I didn't know what they were talking about until I changed to the smaller 2X4 plenum without segregated float bowl pressurization. Really, it's a twofold issue. Transitional drivability problems---which I link to the generic 'plenum style' not enriching the main circuit enough on-boost for transitional stability, and the Instant Boosting you get on the smaller plenum. What I found myself doing was driving with a much heavier foot simply to get the car from vacuum to +3psi boost so I didn't get t he popping. It was the worst from 0 to 1psi. My fuel mileage dropped (even with carbs) roughly 2mpg with the smaller plenum due to this driving technique. What I'm getting at is it doesn't have to be that way, it can be a nice smooth drive where you aren't going to 25 and 30% throttle just to pass someone on the highway under normal speed conditions. And that kind of drivability really rewards you with fuel savings in a daily driver. Regardless, the 17mpg I was getting was 'acceptable' but when that dropped to 15 or lower on the same jetting it's when I started considering EFI. I can live with an occasional pop or sniffle from the carbs, such is the beast. But I had a 'driving circuit' south of my place in Corona that had a slight grade on it, and if I took it at highway speeds it would sneeze and cough the whole way. A larger jet would have solved it, but I didn't need them with the segregated plenums I had run, and that is what got me looking at 'why' instead of just throwing more fuel at it and saying 'it works good enough'... 4BBLs in a plenum (the big box that surrounds the whole carb, not just a 'top hat' style pressure apparatus) will be a PITA to get at anyway, just because you have to disassemble the box to get to the jets! And if it's not a mechanical secondary, then tuning the diaphragm and spring combination to open those secondaries would be something I would not choose to tackle. I don't even know if running non-mechanicals in a blowthrough ap would work. Most of my time with 4BBLs was in draw-through where they seemed as easy to tune as anything else running a 4BBL. All that being said, there is another way to do it, and that is called "Modulator Rings"---basically you make a plate to fit over the main throttle bore that has a hole roughly the size of your main choke (say you are running 44PHH Mikuinis with a 32mm Choke--you make an 'orifice plate' of 32mm). This does the same thing, and could be done on a Cartech or other 'box style' plenum. Under normal aspiration, the orifice doesn't come into play, but during boost when air is being pushed through at a higher velocity the modulator ring (orifice plate) will act as a pre-venturi and make the main circuit tip-in much earlier through the same effect as the segregated plenum. This is how you did VW's. And with their pressure boxes it was easy enough to pop em off, and make the hole slightly larger to trim/tune the on-boost enrichment characteristics. The general rule of thumb is to start at main choke size and work up from there until you get the enrichment characteristics you want. I won't say it's an easy task... it's kind of a PITA if you ask me, but if you are running blowthrough carbs it will work to enrich you under boost without having to change to humongo jets that just make the car sloppy above 3000rpms without being under boost. I hope this is making sense? There are a couple of ways to do it, IMO the easiest way is to either externally vent the float bowls like SHO diagrammed, or use one of the pre-designed boxes. Screwing with Modulator Rings was just something I wasn't willing to do on another vehicle at that point in time. Even with an external vent, you may well end up orificing the entrance of the plenum for more pressure differential. Sure...it's a restriction, but making ONE orifice is a heck of a lot easier than precisely trimming six modulator ring orifices to put back in between the plenum and the carbs!

Exasperation is more like it. I don't know how much clearer those statements can be! I'm not asking my words be taken as gospel, but I do ask that those who ask the questions give me the common courtesy to actually read the replies I have given to their previous questions. Your question about the MAP reading being inaccurate is so far afield, I don't know where it's coming from, I can not draw a logical link between the highlighted sections above---which are in direct response to 'why's that'---to me saying the MAP readings are innacurate. The reason the mileage goes to hell is precisely because the MAP is accurate. I thought that was clearly and adequately addressed in the above passages (the first two sentences of each paragraph specifically). I'm not getting defensive, I'm getting exaasperated as I am at a loss to figure out how to convey what I'm saying as from my point of view it looks fairly clear if it was read. What I was getting at as a side point was that if you have specific questions relating to MAP based plenums then I'd recommend addressing them in another thread and not muddying up the water in the Carburetted Thread. Pointing out the differences of what works why in the two different systems is one thing, but starting to explain why each operates the way they do in the same thread will invariably lead to someone confusing statements about MAP based EFI Setups and Carburetted Setups. Again, I don't know how much clearer I can be on the subject and why I said what I did. If you want clarifications on the statements (if required), I'd follow on in another thread, as I would hope this one could stay on the Carburetted setups, and not get muddied by talk on MAP.

He set up the CAS yesterday, and is bugging me about availibility to go to the dyno in the coming month... But my wife's car would work nice with his box as well... Oh, and on the 3" DP and Exhaust, regardless of what size the outlet of the turbine is stock, JeffP showed 20HP from the addition of the 3" exhaust and DP on his otherwise stock T3 (long ago, but documented on his webpage). I can't believe you are running 12.004 and don't already have a 3" system on there!

That really depends on what 'Stocker' you are using! JeffP about dumped in his drawers after measuring the I.D. of the Euro Turbo Manifold compared to his ported US Spec Stocker, and his SFP Tubular Header. The 1 5/8" I.D. of the SFP Tubular Unit is actually smaller than the Stock European Stock Unit! And given the photos above of what appear to be the 'modified' SFP unit with 'expansion joints' installed in almost the same places as the Euro Turbo Manifold has! Short of MONZTER's efforts which look a bit like Electramotive's efforts for all-out HP, a stocker will haul you a long way. And a Euro Stocker (if you can find one) will go even further. Getting 500HP on an internally-wastegated stock-looking turbo does have some advantages, depending on where you are living in the country...

Yeah, ITT-Canon Style Plugs... Of course that site is recomending Raychem wiring, though not specifying if it's Tefzel coated, or what... A/N is a standard, but there are other more secure tubing standards out there, depending on how severe the service. A/N is popular as they are light, easily available, and at one time were very cheap and available as surplus. That's how "Earls" got it's start!

3/4NPT is almost an INCH is diameter, nowhere near 9/16"! Tapping for 1/4NPT is about right at 7/16" +/- You can't find a pipe plug to screw in there and check? Home Depot sells them, and if you bring the fuel rail into the store (or any decent hardware store) you can try fittings until you find one that fits...

Forrest, I don't know if you are intending to be a smarta-- throwing in little comments like this or not, but I really have no idea what you are talking about! THE MAP SENSOR IS IN THE MANIFOLD BELOW THE THROTTLE PLATES AND WILL NOT BE AFFECTED BY PLENUM SIZE, incipient boost conditions below the throttle will be difficult to judge. If you have ITB's and are sensing MAP in the plenum above the throttles, I don't know how I can help you. Best I can say is that the comments in this thread are SUPPOSED to be directed towards CARBURETTED applications. You seem to have a real problem with my statements. I guess that will have to be your problem from this point. You're muddying the post asking about MAP in a Carburetted Thread. I've tried to expalin exactly what I've been referring to, and you seem to not be getting it---I don't know how to make it clearer. If you live at WOT, then so be it. You are picking flypoop out of pepper with boxing gloves and lumping the 2X4 plenum voulme problems with your personal choice of the Cartech plenum (in a NON-CARBURETTED APPLICATION). Though similar in the sense that it's terrible as a CARBURETTED PLENUM compared to the HKS or SK, it may well have suitable volume as an EFI plenum. You seemed to take offense that I said the Cartech Plenum was trash FOR A CARBURETTED SYSTEM, even though you are using it in an EFI setup and are having some sort of luck doing so. Frankly what you do with your Cartech Plenum is up to you. Keep it, but before you start making smarta-- commentary quoting me about 'chucking it in the bin' try it with carburettors and a turbo that will spool at 3400rpms and see if you like what it does... I don't really know what the problem here is, but partial throttle drivability and tractability while in transit at 60mph IS a concern. A 2X4 Plenum will not have sufficient volume to prevent any sort of...you know what? It's your problem, not mine. Figure it out. I don't know what more I can say other than what has already been said.

If you have properly jetted the engine for N/A operation, with an HKS plenum up to around 5-10psi you will be amazed to find no (or very little) jetting is required to be changed. The temperature could come into play with higher boosts un-intercooled, but if you run a cooler, then it's not an issue. That is what I was getting at for the longest time: The pressuirzation of the float bowl, even by a fraction of an inch of water will allow MUCH more fuel in to the circuit under boost situations (same as if you changed the float bowl level the same ammount on an N/A) I'd say run it and go from there, there's no 'baseline' without knowing where the engine was as an N/A. I've pulled my plenum off, pulled the turbo and then reinstalled headers and run the car the next morning as an N/A vehicle! Did it at the last MSA I took my 73 to---Sammy trashed my turbo bearings and the next morning before the car show I pulled out the turbo and drove it into the show 80 miles R/T no problem.

Crank looks lightened slightly on the extreme counterwieght ends, but doesn't resemble any 'knife edged cranks' I have seen in the past. Does look like pistons/rods are aftermarket from the photos.

That's the mechanical end, here's the source for the electronics: http://www.lola332.com/camless.html

The MAP reading on an ITB setup is not from the plenum... Lag is a function of the turbo flow, changing the plenum does nothing to change the flow, so 'lag' may be a way to describe it, but 'drivability' is also a prime consideration. If you have 150HP at 3000 rpms, and 600 at 3400, driving that car may be slightly difficult in normal day-to-day situations. Similarly, if your MAP goes positive EVERY time your foot caresses the throttle pedal, your gas mileage goes to sh*t. In that case, a larger plenum will work as the appropriate accumulator allowing some 'lag' between partial throttle applications and manifold boosting. I hesitate STRONGLY to say it's 'lag' simply because of the negative connotations related to it, and because of generally the 'lag' everybody is talking about is from a WOT application, and NOT from a partial-throttle application. Generally lag is the time it takes to build FULL BOOST after WOT is initiated ABOVE 'boost threshold'----'lag' is not something associated to partial throttle applications. In partial throttle applications, you most definately DO NOT want boost happening instantaneously (which is an indication of improper plenum sizing in both ITB and single throttle body applications). There has to be some deadband in the throttle pedal application where boost does not occur, or you will have fuel economy that is terrible. The question you asked was two different things, and unrelated, so on the face of it, "NO and NO"----it's not an 'either or' situation. The key on carburetted applications is to have MORE deadband than you do with an EFI setup as the carburettor just doesn't function well at '0' manifold vacuum, while EFI can operate there easily. The problem with Carbs is transitional leans, and if you undersized the plenum, you hit those points all the time, and get lean pop on cruise. As a result a larger plenum gives you more useable throttle play without boosting. You could always go with a larger turbine and have the same effect...but at the expense of spooling at higher rpms, meaning your boost threshold is higher, and you have less of a useable rpm range. Which do you want more? Driveability and the ability to make 17 psi at 1700 rpms, and pull to 6000, or Drivability and the ability to make 17psi at 3400rpms, and pull to 6500? I know which setup I chose, and it was FAR better with a smaller turbo spooling at a lower rpm than a larger turbo spooling at a higher rpm. The discussions should really be separate: Carburettors and EFI. They are so totally different when tuning plenum sizing and other variables if you try to apply one to another you will end up seriously confused.

"Yes..believe it or not, I knew at some stage I was going to build a fire breathing L motor so started buying parts here and there over the years." I started that process in 1985....I'm almost complete with the bits. The 350HP blowthrough setup was just something 'to get me through till I get all the good parts', now 40K+ miles later I'm still not around to it, but then again, other things are getting in the way...like the 80 foot pine tree that blew over in my front yard last night...dammit!

You go onto boost mapping with the slightest touch of the pedal due to insufficient plenum volume. The Centrifugal compressor will overfeed the reciprocating compressor (engine) really quickly. It's why they put such large receivers on screw and centrifugal compressors (suction bottles is another name for them) when feeding a reciprocating booster compressor. As a result of the instant boosting in the manifold, you end up running in a 12:1 mapping, instead of something more conservative. Your mileage goes to hell... Now, if you put a much larger turbine section on, so it's slightly laggier you may restore the balance of NA cruising, but it kind of defeats the idea of having a turbine optimized for response. With a larger plenum, small throttle excursions will not result in the increased flow causing a bump to say 3psi instead of '0'.... In a megasquirt the difference in sized can be seen as a jump almost instantly from a 54kpa cruise to 108 or 110kpa instead of from 54 to 80kpa with the larger plenum. The only thing changed in the test was the plenum. I haven't had much time to play with the new setups and datalog everything to see what kind of numbers I get and relate them to what was seen on the same setups with carbs instead of ITBs. Also I note the BOV tuning has to be retweaked due to the plenum change. The blowoff action is much harsher on the smaller plenum from what I can hear.

The Coates spherical valve will require a new head for optimization, and JeffP called and they weren't interested in anything other than conversions of diesels in city busses, regardless of who paid development costs. Coates spherical valve conversions of Diesels to CNG in busses has been done for years. As I said then, working for the company that was supplying the CNG for the Busses and having an onsite Cat Rep fulltime in our corporate offices held no sway with the Coates People. The DEVAS system would use the stock head, remove the valve cover and all drive components (unless you wanted to drive the pump from the camshaft gear...but I would think retrofitting the Diesel front cover and driving the pump in the same way the diesel injection pump is driven would be an easy swap and use a lot of stock components.) bolt a plate on with your hydraulic actuators, and go from there. The DEVAS system could fit on just about any engine head, the actuators are not that big. But yeah, from a practical standpoint, a poppett valve is far more practical than the spherical valve. I would love to have the spherical valve...BUT the timing is not variable, and duration is not variable, etc etc etc... The spherical valve would be great for a FIXED camshaft profile. But the DEVAS allows infinitely adjustable cam profile and timing. Think VTEC with variable lift... It really ends up being far superior in regards to drivability and versatility when you think about the Coates design in that it's really nothing more than a fixed cam profile. It's just flowing so much more because of less restriction. But it's not adjustable, so for fuel economy AND power, it will suffer the same as a conventional camshaft. I had a rotary valve on my 360CC Suzuki Jeep from 1976............

One barrel maybe would use a linear response. If you have multiple barrels, then you want a dead tip-in for drivability. Why put anything at all in there or worry about designing the 'correct cam' for the application, and simply control the intake and exhaust valves via electrohydraulic actuators driven off an engine-based pump and accumulator setup? Variable valve lift, timing, and duration will give you EXACTLY the same response as a throttle valve without anything there to muck up the flow. And you can bet the advantages of variable valve events will make more power everywhere along the powerband as lift/duration/rpm is all optimized for each point on the curve, infinately recalculated realtime as the engine is being driven! Twin 140MHz ECU processors will do that easily on a 12Cylinder engine to 12K rpms I believe. "DEVAS" (Since we're throwing the stuff out there...)

Jeff, That is what many of the higher horsepower cars started doing with OER's since they have a separate vent for the float bowl. Like SHOZ's diagram, taking the pressure from say the Torus of the Turbo (or S/C) and ducting it directly to the float bowl is an option. You will then tune on-boost enrichment via the bleeder or fixed orifice size. What ended up happening was on twin turbo cars with really high HP, the two holes in the stock HKS plenum was over-richening the mix. Rather than enlarging the plenum holes and rebolting it, they took out the divider wall, or made the holes quite a bit bigger so it was not creating as much of a pressure differential, and then vented externally. The two holes in the plenum will be a flow restriction at higher HP levels, so they eliminated them as it was easier to change the venting externally. As I mention, though, neither the Cartech, nor many of the 4X4 boxes I see incorporate that enrichment feature. And on 2X4 box with the A.R I was running, I went immediately to boost on slight throttle application at highway cruise, and was at 0 manifold vacuum cruising. On the HKS plenum I was slightly negative, and slight throttle applications didn't make be go positive. On an EFI car, things would be different as tuning is usually MAP based. Then the only thing you notice is your fuel mileage goes to hell compared to a larger plenum....

You mean on the Dyno Setting, right? That is a very good point. I was making mention since we ran the same settings when we dynoed our Bonneville Engine and with the same settings you could see more 'bumpieness' than with the Webers. But that is a very good point, many people don't ask about the smooting and interpolation settings of the dyno, and don't really see what their car is doing during tuning. Keep it fast-responding while tuning, and "Just up the smoothing for the final run you post on the internet" LOL:icon45:

With all the money you are putting into an engine, what is the realistic price differential between a set of NEW (not new-to-me) cast pistons, and a set of NEW Forged Slugs? At 89mm that sounds a lot like a Chevy Bore Size.... Keep an open mind on parts sourcing, and realize that Buick Pistons fit in a Chevy same as Chevy Pistons do... Parts is parts. In the 'old days' people were buying stock Chevy 2300 Vega Pistons because you got them for CHEAP, with rings, and they were forged (keeping with the aluminum block and special lining expansion rates). They were a popular 3L engine piston option, and anything for a Chevy is an order of magnitude cheaper than something with 'Datsun' tagged on it. In many cases you could buy a SET of TRW Aftermarket Forged Slugs cheaper than a set of new cast stock pistons! Other than some more noise (overblown IMO) and possibly some more oil consumption (again, not an issue for me) Forged Pistons will afford you a bottom end that doesn't need to be attended to if you suddenly realize that stopping the rush at 7000rpms is just a drag. For me, with the costs of parts, the differential in piston costs doesn't make much sense to not spend a couple of hundred more for forged and be done with it. It's not like they will last less long eh? That is what I was getting at. And I like the VH 45 Turbo Idea. Mmmmmmmmm Turbo.....LOL

Glad to do it. I'm always interested in finding out 'old school' forensics! Would make an interesting bit of facts to post as well.

You have to read my third paragraph closely, I thought I was specifying "Degrees F" in each of the temperatures, but apparently did only in paragraph three. It was a BIG 'off day' yesterday, sent e-mails out with references to attachments that I didn't attach, now this... Man, I'm slippin'...bad! >:^(

E F I Nice numbers, that is a strong car. I always liked the 'sharpie on the sheet' look to a Weber Dyno Curve. Not the jaggies found on some EFI systems. Then again, they don't vary with the season. Give sumpthin', get sumpthin'!

Curiously, the last drawing Braap put up looks a lot like the inside of the old HKS Type-1 Turbo Surge Tank. The smaller upper plenum was what was vented to the float bowl, and there were two metered orifices that bled pressure into the larger plenum between the ITB Pairs at 3&4, and 5&6. I haven't looked at the Type 2 Plenum closely, I got it and shelved it due to other jobs in progress (24 Hours of Lemons, anyone?) so I can check it in a couple of weeks to see how it compares. I know it has a similar plenum division, but is done differently than their Type 1 Plenums. Jeff, would you want to take a look at those old 80's Tech HKS Plenums in person? I could probably make my way your direction if you're interested in taking some dimensions. It would be interesting to see the CFD comparisons for 80's technology...

"I figured out that I can buy a GM-Performance crate motor for roughly the same amount it would cost to build a ~decent~ L-series. The GM engine comes with a warranty and ready-to-ship replacements. The bonus is that the GM motor will put out as much power as TWO L-series motors." Curiously that is exactly what many of the 'NASCAR EXPERIENCE' style driving schools use! The one where I was working used ZZ4 Crate Motors with a Big Block Oil Pump in a Winston West Chassis. If the motor blew, GM covered it under warranty (really!) SO as a result the engine costs through a season were virtually nil. It really is a smart move for people who will be racing. I didn't see the quote as out of line, but for KA24 pistons in the engine, you are overbuying the machine work AND the shop! If you are running cast pistons, go to a local machine shop that has a reputation as a competent general purpose machine shop and get your machine work done there, and as you said Assemble Yourself. Going back to my VW days, and my old standby Gene Berg, he would adamantly suggest you do all the engine assembly work yourself. He was the first to say there is nothing special about it, and if you do it you know what was done. If you really really really pushed, they would assemble the engine for you, but generally this was not the way they did business. The money for assembly is in the HEAD, not the block. Have the HEAD prepped/ported/assembled by a specialist shop, but the block can be done at home with a few specialized tools and care at home. Buy the "How to Modify" book, and have at it. The bottom end is fairly straightforward if you take your time, follow the recommendations, and have the tools to do it. Yes, TimZ, I noticed that as well! If it's not a serious build, then don't spend the serious money. It's a waste with cast pistons, no reason not to do it yourself with cast slugs and a 6500 rpms rev limit...