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#21
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I had these trw domes in a 71 Ho with ra4 cam. Car went low to mid 12,s on Polyglas tires
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WWW.GLASGOPERFORMANCE.COM. Updated... Sort of! |
#22
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The cam they had used in my 72 was just wrong. The cylinder pressures were crazy high when I did a pre-teardown compression check: https://forums.maxperformanceinc.com...te=1&p=6105727
Cyl 1: 230 psi Cyl 2: 220 psi Cyl 3: 225 psi Cyl 4: 230 psi Cyl 5: 227 psi Cyl 6: 230 psi Cyl 7: 220 psi Cyl 8: 235 psi |
#23
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Doug, the stock design seemed to work good as far as I could tell.
The trough (no eyebrows) made a little more CR. The engine with a higher lift roller cam made good power. With the addition of the domed pistons really woke the engine up. (compression to 10.4 to 1) If it had 12 to one it would have been a beast. But the chambers were too big probably to get that CR. Unless the head was milled of course. (would have made a killer turbo engine back then )
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
#24
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I have a set of those domed TRW pistons in the box if anyone is interested. These are new and need to be machined to desired dome height. Standard bore. Got them for my HO build but came across of heads that were milled thus wont be using them.
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1972 HO Trans Am auto White/white 1974 SD Trans Am 4 spd, no a/c dk blue/ white & blue 1978 Trans am gold/ black ,T56, t tops, EFI 474, Build: http://www.pro-touring.com/showthrea...1978+g+machine 1999 30th Trans Am 6 spd, T top |
#25
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Quote:
Even at zero deck (actually we had the pistons .007" out of the hole) and the HO heads were milled down to 107cc or somewhere in that area (again paperwork not in front of me) I had to use a .045" gasket to keep quench comfortable, and even with that dome on the piston that I pictured above the compression was still only 9.98:1. Take that dome away and you'd have to mill the crap out of the heads to get it back, so far to the point you'll be cutting intakes to fit, valve clearance and geometry becomes an issue etc...Not to mention a set of expensive factory heads that have now been chopped so far they sort of become married to that combo and not much good for anything else. There is nothing wrong with using a domed piston in a Pontiac as I and many have shown, it works if done properly. Chevy used them all the time. There is something to be said about flat tops and flame travel for sure, but a dome isn't going to hurt anything if the rest of the combo is chosen well. Here's a shot of the narly dome used in my DZ engine. These are NHRA legal reproduction from JE to produce the factory 11:1 compression this engine originally came with, compared next to the original OEM TRW piston that came out of it. I run an LS7 dome piston in my 454, which is quite common in the BBC world because cylinder head chambers are also quite large for these engines. |
#26
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SD 455 valve relief design
Someone who sold me one of those pistons told me that the SD 455's single trough was for higher compression.
But Pontiac was adjusting the compression ratio (except for the 428s) by changing the size of the combustion chamber. So a few ccs via the trough design would have been minor. What I am thinking is that the single trough was for higher compression, as in higher anti knock resistance with such, and hence was developed initially with a smaller chamber head, as part of the high performance Pontiac V-8 engine development during the Ram Air IV/LS-1, and hypothetically, a higher compression version of the SD 455. Imagine such an engine, with the smaller chambers and the single trough. What other engines ever used such a design. Quote:
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1970 Lucerne Blue Firebird Trans Am, deluxe blue interior. Original Ram Air III, M-21, 3.73. Being built as a 4" stroke "434" with SR 614 Ram Air IV heads 1972+ Lucerne Blue 4-door hardtop "what if" T-41 Le Mans Sport GT/Grand Am concepts. Equipped with future 3" journal "455 HO"/"what if" prototype "SD 455". What if GM had continued production of the 1970-72 GM A body somewhere in the southern hemisphere? |
#27
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SD 455 single trough valve relief design
I myself am intrigued by the idea of using the higher compression round-port heads, either the 1968 "96" Ram Air II or the 1969 "722" or 1970 "614" Ram Air IV heads on a 4" stroke.
Quote:
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1970 Lucerne Blue Firebird Trans Am, deluxe blue interior. Original Ram Air III, M-21, 3.73. Being built as a 4" stroke "434" with SR 614 Ram Air IV heads 1972+ Lucerne Blue 4-door hardtop "what if" T-41 Le Mans Sport GT/Grand Am concepts. Equipped with future 3" journal "455 HO"/"what if" prototype "SD 455". What if GM had continued production of the 1970-72 GM A body somewhere in the southern hemisphere? |
#28
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Problem is they aren't falling off trees, and I can't see spending $2000 plus for a set of heads that I have to sink another $1000 plus in rebuilding. There has been talk by a couple different people of making an aluminum version to look the part, maybe with modern chambers that I'd love to jump on board with, but that never seems to go anywhere. |
#29
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My engine build thread:
http://psp.aquacomp.net/topic.asp?TOPIC_ID=13682 Quote:
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1970 Lucerne Blue Firebird Trans Am, deluxe blue interior. Original Ram Air III, M-21, 3.73. Being built as a 4" stroke "434" with SR 614 Ram Air IV heads 1972+ Lucerne Blue 4-door hardtop "what if" T-41 Le Mans Sport GT/Grand Am concepts. Equipped with future 3" journal "455 HO"/"what if" prototype "SD 455". What if GM had continued production of the 1970-72 GM A body somewhere in the southern hemisphere? |
#30
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I have a 70 RAIII Formula that I'd like to make a RAIV clone from just for giggles, but I want to do that with a smallish stroker engine, probably end up with 470-480 cubes but dress it to look stock and have some fun with it. I quit actively looking for 614's though as the prices rose, and I'm not going to wait another 10 years for someone to make them. I will likely end up heavily modifying current aluminum round port offerings to look the part. |
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