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

[Wrambler242@xxxxxxxxxxx]

I tend to not agree that quench does not matter on this engines.

It is bad from the factory and driving a stock one will show a tendency to be on the edge of ping all summer long.

Both of mine have been this way, 96 and 97.

I tend to think that while they are out of quench stock buidling a stroker that is out of quench results in near the same issues as stock, only with higher compression.  Lower the compression enough and it will stop pinging.
Even way down the hole as the budget strokers usually are. There are a few quench compliant strokers in the budget builds that do well, but there are so many variables it is near impossible to sort it all out!

I think KBB missed the boat on their pistons!
They aimed at a crowd that already has pistons available and limited their market by doing so!
They originally had mentioned doing these pistons as cast hypercan'tspelits. That would sit at the edge of quench to allow an .010" deck if needed, IIRC.  Anyway, This piston would have sold well as us peoples in the northern climes with drivers don't want forged pistons rattling.  I know people will now say, "the new forged pistons don't rattle" I have heard otherwise from people that had used forged pistons. They still rattle for a bit cold.

   Plain and simple, If i could buy cast pistons for what they are offering the forgings that ran 4.0L long rods and where quench close. I would buy them! Even cheap old RM me!

   Instead  I have gone for the set of new hypercan'tspelits in standard bore I found for $120 on evilbay.
My good standard bore 4.0L block will be getting these coated skirt pistons in the spring I hope. It will go in the American sametime as the new WC T5 trans, I hope.  

   As the last few years have gone a little rocky for me, I'm not betting it will happen though!

--
Mark Price
Morgantown, WV
1969 AMC Rambler, 4.0L, EFI, T-5
2004 Grand Cherokee Laredo, 4.7L, Quadratrac II
" I realize that death is inevitable.
I just don't want to be around when it happens! "

 -------------- Original message ----------------------
From: 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. 
> 
>

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