Budget piston opinions- 351 (not the usual application though)

[barronj]

I'm building a '95 351 to replace the one in the boat ('93). The current one is a solid lift cam (I presume), the new one will be a roller motor. I just picked up a set of GT40 non-p heads off an Exploder (I did not expect them to already have 1/2" head bolts!?!), as the current motor has GT40 heads. I want a one day swap of long blocks, if I can.

The boat runs great cold, but at 850 hours, it smokes a bunch after it's warmed up, and always surges at idle (after warm). If I had to guess, I would say that at least two cylinders lose compression after the engine warms up, based on the loping. I really don't think it's the idle circuit, but I guess it could be. I've rebuilt the carb, and I've tuned it fairly well, but I'm no pro. I admit that i need to do leak down & compression tests.

The block I got had some damage done the pistons from a dropped valve, so I cannot reuse the original dish pistons, and I will have to order new.

I want to keep the compression low enough to run regular gas without detonation. My bronco has the dish pistoned 351 with small chamber aluminum heads on it & runs like crap without '93 (before I switched to higher octane fuel, it would always diesel when you turned it off). Hoping to avoid that.

What's the best low budget piston, for a motor that will never see more than 4500 rpm, usually no more than 2500 sustained?

Thanks in advance.

 

[TwoDalesDad]

ROSS makes a good piston...why do you want to go cheap on your boat pistons?..That engine gets quite a work out...

 

[barronj]

I'm looking for a stock replacement.

 

[70_Steve]

I built my 351 with a couple conditions in mind. High torque/low RPM performance and run on regular gas. I have huge (87CC) combustion chambers in the E6 heads I'm using. So I wound up going with Speed-Pro Hypereutectic Pistons ZH336CP40. They're the stock 8.5-1 pistons but the installed height was .028. So I had the block decked to reduce the installed height to .005. That raised the compression to around 9.0-1 and reduced quench height to .044.
http://www.summitracing.com/parts/slp-h336cp40/overview/make/ford

I don't know the combustion chamber volume of those GT40 heads, but the SpeedPro site had a very easy to use combustion ratio calculator.

 

[barronj]

Did you have to mill the intake to adjust to the decking?

 

[70_Steve]

Did you have to mill the intake to adjust to the decking?

I didn't. I asked the machine shop about it, and they felt that it was't enough to make a difference on the intake. I've had the intake off a couple times (don't ask...) and haven't noticed a mismatch in the ports. And, I don't have any leaks!

 

[bmc69]

I've had many blocks decked ..some as much as .050"..and still had no issues with the intake fitting OK. It's always a good idea to check via a dry fitup though..before you slap new gaskets on the intake and bolt it up. I've had several where the front and rear valley gaps had become so small that I couldn't use those gasket pieces because they would have prevented the intake from bolting down as it should. A bead of RTV instead.