Silber, I am not a professional engine builder by any means.. but to build a performance engine that will last a long time, I would suggest sending the parts that you want to measure to a professional engine builder (or a specialized engine machine shop) that use precision measuring tools that will give you 100% accurate readings, I strongly believe that the cost would be cheap compared with a no so good build due to questionable measurements.

Please don't take me wrong I have used plastigauge in the past on a few engine builds (air cooled VW's, Alfas, Chevys, etc.,) and I feel that got lucky perhaps because the tolerances on those applications were not as critical) but after attending the Flat6innovations M96/97 engine building class, IMHO would not do it on a Porsche engine with very tight tolerances..
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You bring up some good points. Thanks for taking the time to reply. Probably my best plan is to measure both ways, Plastigage and traditional measuring tools. I will have to buy a bore gauge and Mics, but those can be had somewhat reasonably nowadays. Always better to check and doublecheck, I don't want any surprises when I turn the key.

I am taking my crank to a specialist to get Magnafluxed, found a great shop about an hour out of the city. I will have them measure as well as do so myself. If I have any doubts about my measurements of the bearing carrier, I'll find someone to double check my work. There are a couple Porsche shops in town that might be willing to do that if I asked nice and paid for the service.

Silber

Dude, you are going through crazy lengths (and expenses) here.

I don't think it's a good idea to put 3.2 heads on a 3.8 case. The vales are going to be way undersized, even with a high lift cam. When Porsche redid the 3.4 for the x51 package one of the things they did was increase valve size significantly (I wanna say over to% but that's off the top of my head).

I'm not an engine builder, but it is important to make sure these types of things all match up in design or else a single aspect (like undersized valves) will choke the entire system down. It would be one thing if you can bench dyno the motor out of the car with different setups, but not many of us have that type of setup available and I would loathe the idea of building and installing the engine, only to have to pull it to redo the setup after a disappointing dyno. Speaking of, don't forget about tuning here. I don't care what people say about off the shelf tunes from fvd and related companies.... Unless you have a tuner who truly knows me 7.2 and the tools to do it right (which if you do please share because I'm not sure there is anyone in the US that really does) then the setup will never be optimal.

Just my 2c.

If it were me and I were going through this trouble, id do the least I had to in order to get that engine running properly, then sell it and buy an Audi abz or a 2.7T and do a swap that will put out 400hp. Please rember that in any configuration other than stock, even if it is all genuine Porsche products, you're extremely unlikely to ever see your money back from modifications like this when you go to sell it.

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First off I read that the 3.2 and 3.4 5 chain heads have the same valve size. Difference between the two is the 3.2 has a smaller combustion chamber. So, I’ll be using valves sized for 3.4 with 3.8. A stretch, but not ludicrous. Engine design is trade offs, like you say. Bigger valves give higher ultimate horsepower but you sacrifice low end torque. Smaller valves enhance low end, but sacrifice high end horsepower. I want my engine to pull more low and middle, and if I lose some bragging rights on the high rpm end I’m ok with that. I decided the cams were too much craziness, stock 3.4/3.2 cams will do fine.

I contacted a bunch of tuners, and explained what I was doing and most of them said they had no idea.Softronic, however, said they could tune for it no problem. Not sure if they are making claims they can’t back up? Anyone that has any input there I would appreciate it.

This gets into more of a philosophical question. Would you take the vintage jaguar with the V 12 and all its problems, or with the LS swap? See, I would take the V 12. Other people would take the LS. Neither way of doing it is better, they’re just sort of different philosophies. When I’m sitting at the starting line at autocross and I’m about to put my foot in it, do I want to hear the roar of a V-8 or the scream of the flat six. I want the flat six. Other people rightfully so would say that the expense of getting an M96 engine which is not too arguably a piece of junk to do this reliably is not worth it. I like building engines, I’ve done several and had a lot of fun doing it. There’s something about putting your foot into it with an engine you built that is very satisfying.

So I guess what I’m saying is, I’m building the 3.2 to 3.8 because I want to not necessarily because I’m expecting it to have the most power per dollar. I’m pretty sure it won’t. To some degree I’m doing it because my car is worthless with a non-running motor. I tried to sell my transmission for the cost of machine work so basically you’re getting the transmission and the Quaife differential for free and no one was even remotely interested. I’m assuming any money I’ve put into the car so far is sunk, I’ll never get it back. I’m figuring, assuming my roller has minimal value, if I build a good engine and sort everything I can get the going rate for a decent S, not even a high value one, and break even. That’s good enough for me.

Off to LN tomorrow, I’ll take some pix if they’ll let me.

Regards,

Silber

Block is now at LN getting a 3.2 to 3.8 conversion.

https://adobe.ly/3o7iGRj

They said I should have it back in 6-8 weeks I was expecting longer.

Silber

OK, current status:

- Splitting of the cases went well, no FOD in oil pump, in fact internally it looked almost brand new. Crank and all rods move freely. I'm about 99% certain none of the carnage got sucked up into the oiling system. Hoping to break down the crank cradle this weekend and get the crank to the shop for Magnaflux next week. Brought both my original and the spare block to LN, they said build the spare for sure, my original block while technically still buildable, is best utilized as scrap metal.

- I thought long and hard about Gilles' suggestion to have a professional do my measuring. That makes the most sense. I'd have to spend ~$3-400 on the measuring tools, and even then I wouldn't know how to use them appropriately. I called a local High Performance Porsche engine builder, and they said if I bring Crank/Rods/Cradle in cleaned up and ready to assemble, they are willing to do all the measuring quite reasonably.

As an added bonus, they have their own dyno and an in-house expert Porsche DME tuner, so I can likely use them for my tuning once I'm up and running. They are doing a Cayman 3.4-3.8 right now, and were certain they can get me running right. That gives me more confidence than having Softronic do it remotely from a couple of dyno pull graphs. Never been to their shop, will check it out and make the final decision re tuning when I go in to have the measuring done.

regards,

Silber

Silber, I think there may be some misunderstanding here.

Oversquare engines (such as the m96), which typically have larger valves than undersquare engines because of space availability, historically make more horsepower because they typically can rev to higher limits (this was moreso true when materials were limiting factors in rpm capability, but that is a whole different discussion). They do not necessarily sacrifice low end power to achieve this. Look at nearly every american v8 put into a pickup truck during the 70s-90s. They are almost all oversquare designs and put out plenty of low end power. You can certainly take stock configurations and do cam swaps that will focus your power band at higher rpm, but again this is not a function strictly of valve size.

Undersized valves, on the other hand, can rob an engine of power. Especially on high revving oversquare builds. Again, the smaller valve isn't going to produce more low end power. Its just that your toque curve is going to look relattively flat becuase the output will peak sooner than it would with larger valves.

Again, look at the x51 modifications and the resulting power differences.

I am not trying to be a dick here, but the knowledge on which you are predicating your build is rudimentary at best. Your reaction to my comments clearly shows that you have made your mind up and that I am wasting my breath here, I'm just trying to share some knolwedge. I really do hope that your build ends well, I just want to see you get out of it what youre putting in.

I have dropped the engine off at LN last week, by now it has most likely been bored to 3.8 and sent to plating. I am building a 3.8, no decision left to make.

My understanding of engines may not be as deep as yours, but What knowledge I do have says I will be happy with the 3.8. I guess we will see what I get.

Regards,

Silber

I would ask LN what their advice on the valves would be. I would hope they've done dyno testing with different setups and will be able to guide you.

As an aside, I saw your posts about the accusump, deep sump, and x51 oil baffles. You should read up about the x51 engine, especially oiling modifications, and also look at Martin short's videos on the m96 build (specifically the discussion of oiling modifications). There's a lot of misconception about this issue, and the short version is the one modification that is truly the game changer for oiling troubles (additional oil scavenger pump on bank 1) isn't commercially available. Without it, none of the other stuff will save your engine when you throw on slicks and go balls out on a long right hand sweeper.

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Thanks for the great reply, Will read up more about the X-51 mods. The oiling issues on this engine are certainly not ideal by any stretch of the imagination

Planning only autocross, no track time. Autocross "sweepers" are pretty short, If I get a deep enough sump I should be able to ride out any that I run into. At least that is my thinking at this moment. The Accusump seems limited, it sounds like if you run it with the solenoid it is too slow, if you run it wide open you can overload the system with oil possibly.

That being said, I will almost surely be running A7's so I could conceivably pull enough G's to really have an issue. I don't want to find out a deep sump wasn't enough the expensive way.

regards,

Silber

[QUOTE=ike84;642380] also look at Martin short's videos on the m96 build (specifically the discussion of oiling modifications).
/QUOTE]

Ike, by any chance do you have the link for these videos? It sounds like it would be an interesting reading, thanks!
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Reading that reminded me of Dammit's 996 build on another forum. The whole thing is worth a look when you get time, but some modified scavenge pumps are about 1/2 way down this page: https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/porsche-9961-cab/122250/page10/

..and he refers to 'Martin's video': https://youtu.be/X7Lxrj6yYro

I havent seen that build thread before. Martin refers to building his own scavenge pump but never elaborated on how. I'll have to go through that thread to see if dammit explained the process.

The math here is pretty straightforward though, and plainly explains why that pump (or lack thereof) is the true Achilles heel of the oiling issue.

The main oil pump, which is driven from the crank, moves 20+L of oil per minute at high rpms (which is obviously where this car needs to live to compete in motorsports events). The problem is that the scavenger pumps are offset, with (on the 986) bank 1 being toward the front and bank 2 being toward the rear. On long sweepers at breakneck speeds, the oil will pool toward the rear of the engine. Do this around a left hand turn and the oil pools into the bank 2 scavenger pump. Do this around a right hand turn and the oil pools into a corner. Sustain the turn for 45-60 seconds and the main pump has moved the entire volume of oil through the system twice, with a huge amount of it being stuck in the rear corner of bank 1.

This is why acchsumps, deep pans, and improved baffles aren't the answer (although the last certainly does help keep the oil near the pickup tube without question). We're not talking about needing an extra quart or two to get through that turn, were talking the whole damn oil capacity. The real **************** of this that most aftermarket oil pumps, even the best like turbowerx, don't move over than a gallon per minute. You have to have crank driven pumps to move higher volumes (I don't know what the scavenger pump capacity is, I'd love it if someone could chime in on that). 1gpm may be enough to fix the problem though, but I've not ever seen anyone doument that approach.


Btw, Porsche knew this before they distributed the M96,. That's why the owners manual says to not use racing tires. They're not trying to cover their butts and stop people from racing, they knew the motor wasn't up to the task before it even left Stuttgart. How's that for a legacy of motorsports excellence?

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Sounds like I will be OK with added capacity, the entire autocross course is usually less than 60 seconds. No one turn will take more than 5 seconds or so. At least if I am doing the math right.

Silber

There was a book written about it. It's called Excellence Was Excepted.

No kidding? I'll have to check it out.

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I hate to open the valve discussion again, but found new information.

HP Calculator Using Intake Valve Size

This calculates maximum theoretical horsepower of a well optimized engine given valve size.

According to their calculator, two 37.1mm intake valves, which is what the m96.21 3.2 has, on a 6 cyl is capable of flowing up to 430hp. That is a ceiling I can happily live with, not really even sure what to expect peak HP wise, but we will find out when it hits the dyno eventually.

I think the MAF and Throttle body are the biggest bottlenecks on the intake side, so will address those. After that the Boxster intake is the next weak link, but the 996 intake has some compromises so I’ll build with the Boxster S part, and retune later with a 996 intake if I’m not happy with the results on the Boxster part. Exhaust I’m as optimized as I’m going to get with equal length headers, high flow cats, and a free flowing muffler.

Regards,

Silber

Silver, perhaps Len Hoffman can answer the questions you have regarding mixing and matching as his company has a very solid reputation building and repairing Porsche heads, Len is a gentleman and would be happy to explain the options you may have with your engine, he works closely with Charles at LN

This may be an interesting read for you, https://newsite.hamheads.com/porsche/
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Thing is I don’t have the budget for head work now so I’m building it with the heads I have. Head work isn’t cheap. If I’m not happy with the results I can always come back later and do something more extensive if I want. So I guess at this time I don’t really have any questions.

I have read that page a few times, it’s very good.

Regards,

Silber

Your heads will be fine like several others have already done. I plan on doing the same.