Jim bailey - 928 International

OK so "A stroker is not 7500 in parts. The crank is under 3k, and the rods can be about 1k to 1500 if you find the right situation. Then the pistons are easy, and under 1300 a set of 8 from JE. " then add the $1500 for the block Nikasil ....so add the numbers and what do you get ? 7,300 Or you use real Mahle pistons at $250 a hole 2,000 per set and get the block honed for $500 spend some money on heavy metal.... like I said $7,500 just for the basics.

GaryJ

Thanks Jim:

10K is probably a low number to add to the build to get the stroker to work making the additional 50HP and 100 ft lbs even more expensive. I don’t expect Chevy numbers for the extra power but I definitely need to way the benefit for the money spent.

Gary

bcdavis

I'd supercharge it with Carl's kit.

Why?

Because if you blow the motor someday, you can slap that supercharger back onto a stock engine, or a used engine, with no problem. You can re-use the parts.

If you blow up a stroker one day, you will most likely have damaged the engine internals, making them useless. So you'd be back at ground zero, starting from scratch.

Once you buy a supercharger kit, with the prices of used 928 engines being so low, you can just keep blowing engines, and slapping the supercharger back on another used engine... The same comment applies to your CIS mods. If you have the parts to mod your CIS system, you can transfer them over to your next engine. It's all external stuff, not internal mods. And both the supercharger and fuel mods can be added to a stock engine.

I would not consider either strokers or supercharging to be totally perfected. People still run into problems. They are still custom-built, custom-tuned, and people do have problems with them from time to time. Sure, most well-built strokers are trouble-free. But so are most of the supercharger kits. None of them are totally failsafe. But the big advantage of the supercharger, is that you can use the kit again, or sell the kit, if you ever blow your motor. It's going to be a lot cheaper to build a motor for boost, than it will to build a stroker. There is a lot more to figure out with a stroker. Most supercharger kits will bolt up to a stock motor. Building it for boost is just a way to make it more reliable, and make it easier to run higher boost levels. But if you run it with low boost levels, it should be pretty reliable. Plus you can add more power as you go. If you have an engine built for high boost, you can start with just 5psi. If you need more power, slap on a new pulley and go for 10psi. If you want even more power, go to 15psi. If your motor was built to take it, you can make it as mild or as wild as you feel comfortable with...

GaryJ

Thanks BC:

You offer some really good points.

Gary

hacker-pschorr

When he built the motor, he measured the CR to be about 10.4 if my memory serves. This is in a race car, two weekends on the supercharged motor before the season ended. He completed 5 track days (4 sessons per day per driver)with this car at Road America - with two drivers. That is 40 20-30 minutes sessions at WOT at Road America. More abuse than any street car would see. Ran like a champ.

GaryJ

Thanks Hacker,

That is very interesting, very attractive numbers and stamina.

Gary

John Veninger

Cool!
Gary, you have your answer and the HP you want.

hacker-pschorr

Anyone who knows JL will tell you this is not a babied 928. Yes he takes very good care of his vehicles, but on the track, the gas pedal is an on & off switch. If he's not WOT - someone must be in his way

GaryJ

Thanks John and Hacker:

It looks like I am going to have to learn about supercharging since there does seem to be a path to where I am trying to go, and the good part is that it has been done before. A little more research to get comfortable with the concept and I could just have myself a plan.

Thanks,

Gary

bcdavis

Every stroker has been built differently. With different pistons, different coatings, sleeves, no-sleeves, etc... People have had problems with honing, clearance issues, etc. There is no set stroker kit that works perfectly. Even the Devek kits have had problems where people did not get what they expected in terms of the parts.

But the superchargers are actual kits, that are exactly the same, unless you choose to modify them. And many people have installed them. So you have the kit dealer, and the owners, who are all very willing to offer help and guidance.

I'd simply drill the stock crank for the oiling issues, get forged rods and pistons in the stock size, or perhaps slightly lower compression ratio, and just install those in the stock bore. Carl just build a new engine for his car, so he can tell you exactly what pistons and rods he used.

hacker-pschorr

FYI - Carl plated his block. For a bigger bore using the stock block material there are known issues finding pistons. The only off the shelf, OEM pistons are from the 968 / 944S2 - not easy to find either.

For the money, I would look into simply dishing the pistons for lower compression. If that is not an option, different 928 or 944 pistons. This route should be cheaper than custom rods. Switching to a 4.7 or 5.0 block will offer one more advantage - cheaper rings. Rings for the 4.5 are around $80 per hole. 4.7 & 5.0 closer to $20. At least they were the last time I checked. This is why I plan on pushing the stock motor in my 81 pretty far. If it blows, I'm not going to rebuild it. I already have a 4.7 & 5.0 short block on stand by.

GaryJ

Thanks guys:

Definitley good and promising information. I think I may well have a new direction for my build.

Thanks again.

Gary

SwayBar

This is both right and wrong.

There is NO doubt a 4-valve head flows better than a 'comparable' 2-valve one, such as when Porsche moved from the 2v to the 4v. Whenever one has a better flowing head, less camshaft is needed to produce power, and is one reason why the Porsche 4v camshafts have such relatively conservative timing and lift compared to the 2v Euro cams. With less camshaft comes better low and mid-range power, as well as being more emission-friendly as N has stated.

A great example for us 928-ers is the 85-86 (..S3) heads/camshaft combo versus the S4 heads/camshaft combo. The S4 has less camshaft than the S3, but despite that, has greater output at the crank. When Porsche reengineered the 4v heads with bigger valves, ports, etc, they discovered they needed less camshaft for their target-output because the new heads flowed so well compared to the S3's.

Even though Porsche put tamer cams into the S4 versus the S3 for whatever reasons, due to the S4 head out-flowing it's predecessor, will put out more horsepower yet with beefier cams such as the S3 or GT cams.

The punch-line: 4v heads make it easier to produce greater output levels with less camshaft, whose benefit is better driveability due to greater low and mid-range power production, and with less emissions, versus their 2v counterparts.

hacker-pschorr

Oh c'mon - nothing beats a lumpy idle coming out of a set of headers

No - it's not a stuck injector either!!!

John Veninger

What SwayBar said!