Re: [Amc-list] Rebel Station Wagon upgrades- Brakes, 4.0, Auto O/D

[Frank Swygert <farna@xxxxxxx>]

Yeah, they made pistons mainly for Jeep racers, as that's where they most likely figured the sales to be. For a street engine I wouldn't deck the block, which might keep compression closer to 9.0:1. 

Quench isn't that much of an issue with these engines, though some want to believe it is. The factory piston is 0.080" down in the hole and there are no issues with it, but when running high compression (much higher than 9:1) a tighter quench area might be beneficial. I don't know -- I ran 9.7:1 for a while, just had to use at least mid grade to keep pinging down by driving a bit careful. Would still ping under a heavy load on premium, but only when I should have down shifted anyway. I was, however, running a Renix system, so it was keeping the timing down to the max retard level (I think it was 6° retard or advance -- 12° total range). An HO system would have pinged on all but premium, and then you'd have to drive carefully. I eventually dished the stock 4.0L replacement pistons and it ran MUCH better, doesn't ping even on regular except under severe conditions, and has at least as much power as it did before. I went down a whole point in compression, back to the stock 8.7:1. 

If I had to pay near custom piston prices for a compromise piston, I'd pay the extra too. I think they would have been better off to make a hypereutectic cast stroker piston that would deliver stock compression in an unmodified block, doesn't matter which rods they were made for. Then if someone wnated higher compression they could deck the block and/or shave the head. 

------------
Date: Fri, 12 Dec 2008 03:36:16 +0000
From: Wrambler242@xxxxxxxxxxx
	
Last I looked at Jeepstrokers forum the forged pistons were still a bit of a mistery as to exactly what they do spec at!

IIRC, they are not quite as "ready to run" as we had hoped.
Still require decking and leave the compression slightly higher than we wanted.

I have not read over there recently, so I may be wrong.
KBB's website had some "fuzzy numbers" too.

Last, they were priced a little on the high side, almost placing them in the custom piston range.
Depending on the build many guys were saying they would spend the extra $$$ to do the piston exactly how they wanted.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
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