Hot Rods Identify 396 TRW pistons?

I am also shure it is the 12:5 to 1 piston but I have open chamber heads with 113cc, maybe that makes the difference? Or I may have typed the wrong numbers in the Summit Calculator.

 

However, it seems I got a solution to my question and I am very grateful. Thank You all for posting and helping. I will use the TRW pistons for my engine and I am shure I will have som other questions about in the future.

Thanks.

 

Hakno, by no means am I suggesting that the piston you pictured would be 12:5 1with your heads, that figure would have been with the 100 cc head of the time I believe the 113 head would be about the CR you figured on the Summit web site
I really never like running a large dome piston with a larger cc head I'd rather run a flat top with a really small chamber head with 0 deck height and a .040 compressed gasket,,,But you do have the pistons so go for it.
Make sure you have enough piston to wall with those old style pistons I would agree with .0055 or .006 that someone posted earlier.
This should be a cool motor to go beat on with all of your might.
Don't forget to resize the big end of the rods and add good rod bolts.
Have fun with it!

 

What he said and have them make sure the small end has a good fit.

 

^^less than .040, and after the chambers/domes were done, heads were angle milled down to 103cc's.

 

I might as well continue to ask questions in this thread, if that is ok?

The engine as I have it figured out now will have oval port open chamber heads (3999241) slightly ported (cleaned up) with 2.06/1.72 valves.
Roller top rockers, Comp Cams with Magnum pushrods.
Torker II intake.
Holley 750 DP.
Eagle SIR-I rods.
TRW 12:1 pistons.
A good guality counterweight.
ARP bolts.
Flowtech 1 3/4" full length headers.
2-bolt 402 block with cast iron crank.

Trying to build the engine to withstand high rpm and would like to have as much cam as possible without hitting the pistons.


I have the TRW piston in the engine and made a quick measure of the deck clearance and got 0.016in, do you think that is tolerable?

I have not looked at what cam I should buy yet. Have some measuring to do but I would like a Mechanical cam.

 

Forget high RPM with a cast crank. Even though it's a small BBC the rotating m*** is still considerable. Cast cranks break easily when RPM goes over 6000 with any regularity. I know some say, "...7000 RPM all day..." but I wouldn't do it. The top end isn't conducive to high RPM either. Small valves, small headers, etc, as RPM goes up in BBC heads the need for a bigger valve shows up fast. What you're building is a Sumo Wrestler. A lot of TQ from A Street to about 5500 and then it'll fall flat almost as fast as it builds up because the needed flow won't be there.

 

Now we're getting to the part where we have to ask what you plan to do with this engine. The more details you can provide, the better we can help you figure out what to do.

 

Absolutely, the car is a true SS/RS 396 Camaro 1970 with th400 and 12 bolt rear end. Just finished a nut n´ bolt resto. Next summer I hope it is finished as a Baldwin Motion Replica.

It has a Hurst street converter, with about 1000rpm over idle stall. It won´t be a strip car or a everyday driver. A saturday tire smoker maybe? I don´t mind rough idle.

 

to me, the 2.19s/1.88s and some pocket porting is just a no-brainer on oval port heads.

 

While the engine is something we like to talk about here on the HAMB, the car is not...so maybe you ought to just edit your listing to describe the specs of the car, and remove the pics, lest we get in trouble for talking about it

How much does race gas cost where you are? I'd be really tempted to put lower compression pistons in it...but if you are not planning to drive it much, and you can find and afford the really high octane fuel it will most likely want, then maybe you'll be ok. I've got a 396 to rattle pretty good on pump gas with the small dome pistons and those early oval heads.

I agree with the bigger valves, and especially with the pocket porting, suggestions.

There is probably about 2500 stall in that converter, so cam with around 230 degrees duration at .050" lift would be appropriate.

 

I removed the pictures, sorry about that.
I need to use the items I have to build this engine, I don´t have the budget to replace the pistons or the heads. The heads has been professionally restored with new valves and so on.
I noticed some wear on the crank so I may have to replace it to a forged type.

Today we will measure piston to valve clearance, so I will have a better idea how much lift I can allow for the cam.

 

I was just curious if you can afford the fuel to make it run, after you put it all together. Pay now, or pay later.

Choosing a cam, based on how big of one will fit the pistons you have, seems like a rather odd thing to do.

If the wear on the crank is less than 0.001" on the diameter, then it will probably be ok. If it's more, then you might want to get it ground, or get a forged crank. I still use original connecting rods in my big blocks, although I do put new bolts in them.

 

Thanks, we have 98 octane fuel in some of the gas stations so that´s what I will use. What I meant about the cam is I have to make shure it does not make the valves hit the piston.

 

Hakno, what Jim is saying is that regardless of piston to valve clearance the cam specs should be selected based on the intended power curve. I.E., a high RPM application will want high lift and duration specs in order to hold the valve open long enough to fill the cylinder at 'X' RPM range. Going off the reservation (just for purposes of the discussion) if nitrous or supercharging is used more exhaust duration is desired to get the spent g***es out as quickly as possible. High TQ at low RPM likes a bit more duration at conservative lift numbers to build cylinder pressure from idle to maybe about 5000. Still, with the small valves and header tube diameter mentioned above even a cam with a 7500 RPM power peak will never make it there due to the CFM limits in the cylinder head ***embly. Some oval port heads could actually be a good choice for a street application where a broad powerband is desirable, but bigger valve diameters and light weight operating components (rocker arms, push rods, valve retainers) are essential. Stock heads and valve gear are "all done" by 5000 RPM, and indeed will go into valve float at anything over that speed because the springs can't keep pace due to the weight of the stock components. While most any engine requires a well thought out cam/lifter/rocker arm combination, with the BBC it's nearly the whole world. There's way more to this that deserves serious attention but I don't want to get too far past the scope of the topic.