Your donations help keep this valuable resource free and growing. Thank you.
|
TRW Pistons |
Post Reply | Page 12> |
Author | |
Nardo
AMC Apprentice Joined: Dec/21/2010 Location: United States Status: Offline Points: 174 |
Post Options
Thanks(0)
Posted: Oct/21/2021 at 5:15pm |
I'm finally getting around to a project I started over 30 years ago. I have a 390 I'm intending to build and install in a 69 AMX. 30 years ago I intended to bracket race the car. I might occasionally want to race it, but its really more of a street car.
I have a set of TRW racing pistons I acquired back in the day, Model No. 8-L2313F. I can't remember if they are 11:1 or 12:1. If they are 11:1 I think i can still use them but 12:1 is a bit much for a street car running pump gas. Anyone out there know what compression these pistons might be? Thanks
|
|
Mike
|
|
Ken_Parkman
AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1814 |
Post Options
Thanks(0)
|
L2313F is from the Competition section of the 1986 catalog, and the compression is dependant on the deck clearance. In a 69 engine with a .037" deck and the 51 cc head it is supposed to be 11.7 at .030" over. In a 70 engine with the .002" deck it is 13.3 compression. The 58 cc chamber head (71-73) with .037" gives 10.8, and the 60 cc head gives 10.5. Pretty much no way of getting the compression low with a .002" deck combo. Of course this is all theoretical, and you should measure the real specs. The high quench will make even the early engine a challenge on pump gas - I would not use those pistons in a pump gas engine that you want to tune for power.
Piston specs from the catalog are 1.560" CH, 596 grams, 4.5 cc valve reliefs.
|
|
Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6880 |
Post Options
Thanks(0)
|
Correct me if wrong in calculations please.
You could run those pistons with a Comp Thumper 279TH7 on pump gas, 58cc heads. Not very efficient at low RPM's, but could be tuned streetable. Definitely an automatic transmission with a factory stall would be fine. It would be a challenge for idle, but doable. Worth it, that's very questionable from a power/efficiency point of view, bleeding fuel/air at under 3200 RPM. Sure would attract attention at a cruise! Race it - certainly decent, but again, not the best power/efficiency. Looking at 430 to 450 HP @ 5400 RPM with assumed other performance parts.
|
|
PROSTOCKTOM
Supporter of TheAMCForum Joined: Jun/20/2010 Location: Indiana Status: Offline Points: 2450 |
Post Options
Thanks(0)
|
You would be far better off cutting the top of the piston of or at least milling a pocket in the piston than ever even considering a Thumper cam to bleed off compression. Any option would be a better choice than that.
Tom
|
|
Molnar Technologies Full Service Dealer - Crankshafts & Connecting Rods
1969 AMC Rambler Rouge Race Car 1974 AMC Hornet Hatchback, Wally Booth Outlaw Nostalgic Pro Stock Race Car Project |
|
amxron
AMC Nut Joined: Nov/18/2011 Status: Offline Points: 295 |
Post Options
Thanks(0)
|
That was the first piston approved by NHRA for stock class 390's.
I would think you could sell them to someone building a budget NHRA stocker. As mentioned you could cut the tops but, only if you cut a dish similar the stock piston as you want the edges to be .000 to .002 deck height and about .750" band around the top (like the stock piston). Goodluck, Ron. BTW; X-2 NO thumper cam!!
Edited by amxron - Oct/21/2021 at 10:48pm |
|
AMXron
Fleet/Jeep Mgr. Orbit AMC/Jeep 50-1787 |
|
Ken_Parkman
AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1814 |
Post Options
Thanks(0)
|
Pretty amazing someone got those approved as "stock replacement". 3 points increased compression is stock?????
BTW I do not believe (at all) the "dynamic compression" theory where you can crutch too much compression with a big cam. It might work in isolated cases with an incorrectly designed engine combo or where you design in an artificial restriction to kill power, but fundamentally it is a flawed concept. Measuring an intake closing point by itself has almost nothing to do with what really happens in a running engine. Design the engine combo to optimize it for the fuel you are using. A correctly tuned engine with matched components will always outperform a mismatched combo trying to crutch a too high compression ratio for the fuel.
|
|
Nardo
AMC Apprentice Joined: Dec/21/2010 Location: United States Status: Offline Points: 174 |
Post Options
Thanks(0)
|
You guys are awesome. Sounds like there are better choices out there for a pump gas vehicle.
I should have added that I plan to use Eldebrock heads which I think are 58cc, but 10.8:1 is probably still a little too high. I don't have a cam selected yet. I defiantly want to hear a lope, but not so radical it won't idle. The block is 30 over. I had the crank cross-drilled and the rod wrist pins free floated. I have a Mallory dual point distributor that was great back then but not so much now. Also have a Miloden oil pan, Lakewood scattershield, McCleod clutch, and a Torker and a R4B manifold. BW T10 4-speed & Hurst shifter from a Hurst American. Then I got married, had kids, and priorities changed. Sold everything except the engine & trans hoping one day... I'm not struck on using these pistons if they just aren't the right application. I'm thinking 10 or 10.5:1. Also thinking I want a RPM air gap manifold rather then either of the two I have. Recommendation on better pistons for this application? Or anything else?
|
|
Mike
|
|
Steve_P
AMC Addicted Charter Member Joined: Jun/28/2007 Status: Online Points: 3802 |
Post Options
Thanks(0)
|
I've said it here multiple times, and like Ken said, the dynamic compression theory of an 11:1 engine on pump gas with a big cam is BS. Actually do it if you think it works. The theory makes some sense. The reality doesn't. Which is why it doesn't really exist in reality.
OP, buy some lightweight custom pistons 9.5:1 and zero deck. Too high CR is just not worth it in a street car. |
|
Nardo
AMC Apprentice Joined: Dec/21/2010 Location: United States Status: Offline Points: 174 |
Post Options
Thanks(0)
|
My 69 290 AMX has stock 10:1 and it runs fine on midgrade. 9.5 seems kind of low. No?
|
|
Mike
|
|
purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16611 |
Post Options
Thanks(0)
|
I would not even think about a thumper cam. All its for is to sound radical and rough idle. Who needs that on the street? Believe me, that crap gets old when you cant drive it.
|
|
Post Reply | Page 12> |
Tweet
|
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |