In the limited searching I've done the speed pro pistons are the most reasonable peiced ones I've found. My 402 has 3993820 casting heads (113 cc).

Are there any other reasonably priced ones that will yield a better compression ratio? Should I look for a set of closed chamber heads?

Using the open chamber heads, verify with the piston manufacturer that the piston has the correct dome shape. On a 402 motor it may not be that much of a problem. One thing you may want to consider is the 434 stroker that uses the Keith Black Hypereutectic +.030 pistons with a 454 crank. You can also look at the 396/375 pistons - again, check the chamber shape against the dome.

i responded to your other post.....113 cc heads are going to be tough to fill on a budget unless you find some used ones (pistons) the three pistons i like to use on the 396 motor is this........the stock style replacement pistons that are offered in cast.....these have a small dome around 10 cc and are cut for the intake valve on each side of the dome to be allowed to run in either bank these can be picked up for around 180 bucks or less. i used these in very mild motors with closed chambered heads becuase they allow for around a 9.0 to 1 compression and this enough to push a 3600 lbs car into the mid 13's using cheap used parts everywhere else.

the other pistons i like are the kb- 1600 series hypers these have around a 21 cc dome and give compression ratios in the 10 plus range with closed chambered heads at a $245 price it a deal.....with your heads they would give about a 9.2 to 1 compression with the piston .015 down the hole and a steel shim .020" gasket..

..shaving bbc heads could be an option for you ...every .006 taken of the head is approx. a 1.0 decrease on chamber volume....so shaving .030" off the head would reduce your chamber about 5cc's to a 108 volume which would raise the compression to about 9.7 to 1

and my favorite is the 396/375 horse replacement pistons these are big with about a 38 cc dome and these give you a great compression ratio about as high as you like depending on you head cc......these might be just what your looking for even thou the price is around 375 bucks.......playing with deck heights and gasket thickness you could achieve the 10.2 to 1 compression easy with these......

the cheap 180 dollar pistons give a very poor deck height all the 396 engines i have built with these have been down the hole anywhere from .050 to .060 on a undecked block.....so steel shim head gaskets have been used......

going closed chambered heads would help but getting the heads wouldnt off set the cost of the pistons of 375 bucks by the time you found the heads had them worked over and then maybe buy the cheaper 245 pistons then the difference would be more........either find a set of used ones(pistons) like off ebay or just buy the new ones for 375 bucks.......

Whats the bore on your block and what comp ratio are U looking for???? I have a set of the L78-375HP speed-pro forged with coated skirts new in the box. There 396 .060 over (4.155) which would be a .030 for a 402. They are advertised as a 10.6 with 109cc head, so with a 113cc head they should be right around 10.25 or so. If run with the popular #049 or #781 open chamber oval ports (119/120cc) there just under 10 to 1. I bought them a while back for a L78 block I had, but was offered a small fortune for the block. supersport6667@hotmail.com if they will work for U.

First and foremost thanks for all the input graemlins/beers.gif

Here's where I stand. Tonight I pulled the engine apart and got it off the trailer. That in itself could have got me on "America's funniest home videos graemlins/waving.gif ".

Everything I was told about the engine was confirmed. The engine was freshened up @ 60k ago when it was given a basic re-ring kit, heads re-worked inc cut for bigger valves, and a mild cam. At that point it there was a slight ridge in the bores which was removed and cyls honed.

Engine was in a chevelle, weekend driver/few 1/4 mile passes, twoard end said to smoke when you got on it hard.

Currently everything standard, very clean, guides although obviously replaces when the engine was gone thru, appear to be leaking (cause of smoke). Block currently has stock pistons, and absolutely no ridge, a bit of hone marks in the cyls.

I'm almost tempted to rework the heads and put it back together.

If I bore the block, could I get away with running pump gas using those L78 pistons? I would think not, but again I don't know how these engines respond.

Thanks again, Kevin

If the pistons are small dome (approx 3/16" high)which is typical, the motor has about 8.5/1 cr. You could run this with a small cam - advanced 4 deg. and get by. I have run into this same issue with the 402 motors. There are not a lot of options, you get stuck with 8.5/1 or jump to 10/1. If you intent is to run enough cam, 10/1 is no problem. I currently run 9.7/1 cr, have pushed the timing up and am down to running 92 octane. I could probably drop to 91 or maybe 90 octane when the temps drop.

Again, it all comes down to what do you want to do with the car? Maybe consider cutting the heads a little and run the .022 steel head gasket to get 9.0/1 and cam accordingly.

I am running the Speed Pro 396/375 .030 forged replacement piston w/109 cc heads. I can drive around on 92 all day giving ricers a bad time just with the sound. :D But if WOT is anticipated, I keep a barrel of 110 VP in the garage.
Just get in the car and DRIVE! :cool:

Have you tried looking over at Flatlander Racing's web site for needed pistons??

http://www.flatlanderracing.com/

And just maybe by chance Competition Products might have something??

pdq67

All of the 396/375 pistons I find say they cannot be used with open chamber heads? Is this correct?

I would be open to cutting the heads down, but how far is it safe to go before you start having to modify the intake?

Sorry I'm so lost graemlins/clonk.gif

Suggest you do 2 things. First have the heads CC'd. Published chanber volumes are often incorrect. Second. establish your intent on using the motor. You may wnat to look into Keith Black pistons. I thing they have some other variations in the Hyperuetectic pistons for the 402 motors.

I've done quite a bit of research and haven't come up with much.

Car will be a 71 conv with a M21 and a 12 bolt 3.73

The car is going to be a toy.........it has been sitting for well over 10 years, way too long graemlins/thumbsup.gif

I am finding few options in the piston department and they all (well most) claim to be for closed chamber heads.

I would guess if they were for closed chamber heads........a larger open chamber would have no chance of collision........but I don't know?

Wouldn't mind a nasty, rumbling beast with bad manners under the hood........but don't want to get to the point where I have to get way technical = $$

I sure hope I am making some sort of sense.

Thanks again, Kevin

The problem isn't pisotn dome volume, it is piston dome shape. Closed chamber pistons have a more oval shape dome and can interfere at the ends. You can make these work, but it will probably take some machine work.

I've gone back and checked and ALL the pistons I can find other than the stock small dome ones specify closed chamber.

Guess it will be easier to get a set of heads?

Kevin,
The Closed Chamber pistons will hit on the open chamber heads, but just slightly. All it takes is about a half hour with the die grinder on either the pistons or the heads to make them work. Its a very simple job.