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I am waiting for a custom piston quote from race tec. I will sell the TM pistons. I am sure there is someone using iron heads that will want them??
here is my compression calcs. I may up the piston volume to 15 cc. I am at 2200 elevation so it is like taking another .5 off the compression.
That DCR of 8.93 looks like a pinging bomb, even at 2,200ft.
Using 20cc's instead of 13cc's doesn't do much better.
Have a look at the Edelbrock 2172 cam specs, as an example.
It has the same 204/214 @ 0.05'' lift as the cam you used, but the longer duration provides a milder ramp rate.
The 68* IVC would give a DCR of 7.9, which would definitely avoid pinging.
If you look close at the second picture, the area on the intake side near the valave relief is ~.080 higher than the rest of the piston. That high/taller section is what TM considers to be at zero deck. It is exactly that, my shop took .015 off my block and the piston is out ~.016.
The rest of the piston is ~.065 in the hole. My piston does not look like this one from 77 Hos
Mine look like yours with the step on intake side if look close st the picture their there. Heres a before install pic in my hand. The ones on website look same too its a bad pic on tmeyer site I didnt expect that when showed up in mail
Hois77
race tec is going to get back to me next week, If they can make a piston of they have something close from a previous customer and it is a few weeks i will wait. If they are 10 weeks out, and then back to my shop to check, balance, ring gap etc. it will be fall by the time i get it all back. I will probably run what i have.
The website says they are dished pistons. Step dish to be exact. I'm not an engine builder by any means, but that sure looks like a "step" to me compared to the "bathtub" style dish that most people are probably familiar with.
These are the dished pistons for my 521 build and they are a lot more obvious on the dish since the raised portion goes all the way around the piston rather than just that one edge like your 400 pistons have.
Couldnt find anyting doing a search online. What about a head gasket shim? I did come across that but .020 was thinnest I could find with the .038 gasket would still be .008 too tall for ya. Maybe they can make them .010 and use the .041 gasket.
Did you check your clearance after the piston install? is your piston above the block? Did you machine the block deck? I need a thicker gasket because the "zero deck" area of the TM piston is out .019 max when rocking. My block deck height is 10.282 now. stock was ~10.297
What i dislike the most about these pistons is my quench is still ~.100" (no better than stock) on the plug side of the chamber.
That DCR of 8.93 looks like a pinging bomb, even at 2,200ft.
Using 20cc's instead of 13cc's doesn't do much better.
Have a look at the Edelbrock 2172 cam specs, as an example.
It has the same 204/214 @ 0.05'' lift as the cam you used, but the longer duration provides a milder ramp rate.
The 68* IVC would give a DCR of 7.9, which would definitely avoid pinging.
I only went with the 13CC because that is what was available. So many parts are back ordered and pushed out to late summer at best. I am considering the comp 280 also, The springs are set to work with either cam. I agree with you, 8.9 is pushing the limits and when i went back and reran numbers with a .050 gasket and different deck heights I am unsure. EX; if i use +.016 for the deck height and then subtract 13ccs i get different numbers. I am trying to figure out the correct values to input.
If racetec or Gleggs can make me a set, I am going to sell these. If anyone is build an Iron head 400,, PM me.
the secret to no detonation is in the details. That is why i am considering waiting for a custom set of pistons. I will confess that i did not look close enough to the TM pistons. In the pics, along with hos77's pics, It looks like the lower area of the piston, near the plug, is also raised. It is the reflection making it look so. If I run it the way it is now I feel any detonation will occur in the .110" space between the piston and the head.
Hois77
race tec is going to get back to me next week, If they can make a piston of they have something close from a previous customer and it is a few weeks i will wait. If they are 10 weeks out, and then back to my shop to check, balance, ring gap etc. it will be fall by the time i get it all back. I will probably run what i have.
Did you CC the pistons? are they really 13cc??
I did not cc them. When installed it was questionable when feeling by hand if they were taller than the deck. Stuck a .005 feeler guage next to a few of them and was less that .005 out of the hole below the feeler guage thickness and thats all I did.
My machine shop was instructed to square, deck heads only min as needed. He told me barely anything came off maybe .005 at most
I told them as little as possible to try and keep compression as low as possible to try and avoid detonation. Mines a tow rig so I'm a little worried about it.
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