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Sounds like a plan ... i'll post some pics this week when i go in the garage.
It'll never meet the value $$$ of those friggin pistons but it will be a good side by side reference !!!
Keep in mind those pistons were a one off custom order for my application, not sure you can reproduce the same on a stock set of pistons ...
m42racer,
Let me know the name of your shop where you take your car so I can sneak in at night with my drill and grinding stones and go to work on your pistons. I would be honored to have your car as the first with the new flycut pistons. It would be an inspiration to us all. Your apology is accepted for criticizing my idea of flycutting pistons in the engine which turned out to be an old and commonplace procedure. You should have done your research first before you started whining. Looks like you learned something after all. I'm proud of you, son.
In the heavy duty truck industry, where engines are often more expensive than Porsche engines, sometimes grinding is done with pistons in place. When it is performed, grease is used to catch particles.
I know of one 944 builder that shaved his head so much the valve clearance wasn't enough & he resolved this by using a die grinder pad (aka "cookie" or disc). Seems pretty straight forward.
I think that pics of your pistons would add some value to this topic Phil.
Here you go Jay,
My JE pistons with the custom valve relief pockets measure .150 at the deepest part while a set of
OEM pistons measure .116 at the deepest part.
While not really visisble , i would imagine the extra .030 would make a big difference on a high revving race engine.
The major weak point i see are the valve springs, although i have brand new turbo springs that were measured
and dynoed on a spring dyno by the shop that put my head together , i understand there are better options which i will pursue over the Winter.
As you can see , the pistons have a 3cc dome as compared to an inverted dish on a set of stock pistons ...
This was all calculated with the help of Mike at Lindsey Racing and we sent the specs out to JE to have the pistons fabricated.
What C/R are you shooting for Phil? Curious how LR determined the dome volume unless he had all the data:
-Bore
-Stroke
-Effective dome volume (dome volume minus valve reliefs)
-Piston deck height (in your block and with your rods)
-Head gasket thickness (volume)
-Combustion chamber volume
Some of these are obvious, other vary with mods.
BTW, since there's .030 off your head, the valve reliefs are effectively only .020 deeper than stock, with deck height another consideration. Not saying this isn't ok, just a consideration. Also, Porsche turbo springs are the same as the NA springs, only set up differently due to boost and the smaller turbo exhaust lobe. I've found that unless you go to Porsche for them, they're likely inferior aftermarket springs.
Surely not trying to pee in your pool, only pointing out some things to consider. Hopefully there's some value here for you and perhaps others.
MM
Originally Posted by wildcat077
Here you go Jay,
My JE pistons with the custom valve relief pockets measure .150 at the deepest part while a set of
OEM pistons measure .116 at the deepest part.
While not really visisble , i would imagine the extra .030 would make a big difference on a high revving race engine.
The major weak point i see are the valve springs, although i have brand new turbo springs that were measured
and dynoed on a spring dyno by the shop that put my head together , i understand there are better options which i will pursue over the Winter.
As you can see , the pistons have a 3cc dome as compared to an inverted dish on a set of stock pistons ...
This was all calculated with the help of Mike at Lindsey Racing and we sent the specs out to JE to have the pistons fabricated.
I'm using .050 Cometic gaskets and the block was decked .004 from stock.
The head that is cut .030 was used in my first race engine with stock 10:6 pistons , it's now a boat anchor.I'm using a fresh head that was refaced less than .010 so i'm
all good compression wise with VP C10 unleaded fuel.As far as springs go , i'm aware that you have something better , perhaps i can procure a set from you after the season.
The new turbo springs all consistently tested 10 lbs stiffer than the ones that came with my head on a spring dyno, but like you say , they are the weak link.
I provided Mike with all the data and what i was after, everything was good until i had to scrap the last engine due to a screwup
from the shop that did the machine work... i won't publicly get into that part !
06-27-2021, 09:27 AM
