TRW domed pistons,compression loss vs. flame travel

I am getting ready to start putting together(again lol) my 466. I have a set of old, made in U.S.A. trw domed pistons. I have read that cutting the dome down flat which would drop my compression from around 13.75 to 13:1 but would help flame travel. Will the better flame travel off set the compression loss? Also the piston tops are "not finished" I know all sharp edges should be removed but should I polish the whole top of the piston? Thanks for all your help

Depends where your needs are.

If you are at 13.5:1 with the full dome in your combo and you mill the pistons down to a flat top, your compression ratio will become about 11.4:1.

If you mill the domes down to just 0.100" high, your compression ratio would be around 12.8-12.9:1. Whacking the peak of the dome down to a flat shape will significantly help flame-front travel and thereby reduce the amount of ignition advance required.

Detaing the piston tops can be helpful.

Paul

he domes are small enough on those they don't really affect anything, keep the compression.

Could a guy (or gal) use a "flame plow" and construct a path that the flame could navigate between the peaks without damaging compression very much?

Dave.

I'd just smooth over the sharp edges and run them. I would be more concerned about the weight if it is going to see any kind of RPM. Those old slugs are heavy. If you are going to turn it much more than 5,500 rpm I'd think about putting a better rod in it.

Steve

Ran those pistons to 7000 rpm for years..... with Truck / CJ rods, Key is keep it at or below 7000. But with the cost of Scat Hbeams, its probably better to get a decent set of rods now days.

dfree383 wrote:Ran those pistons to 7000 rpm for years..... with Truck / CJ rods, Key is keep it at or below 7000. But with the cost of Scat Hbeams, its probably better to get a decent set of rods now days.

Yes, understand. We did a lot of things years ago different. Properly prepped cj/truck rods can take a lot more than people think. My thinking these days is if giving advice to someone I don't know is best to be conservative and not have angry people when they throw a rod... LOL These days a good set of rods not much more than a properly prepped set of factory rods. Guys certainly have it easier these days.

Steve

dfree383 wrote:Ran those pistons to 7000 rpm for years..... with Truck / CJ rods, Key is keep it at or below 7000. But with the cost of Scat Hbeams, its probably better to get a decent set of rods now days.

So what would the uppeer rpm limit be with h-beam rods? By the way, thanks for the info!

IMO 7000..... they are heavy pistons. the reason for the up grade is reliability over the stock rods.

mudtrucker wrote:I am getting ready to start putting together(again lol) my 466. I have a set of old, made in U.S.A. trw domed pistons. I have read that cutting the dome down flat which would drop my compression from around 13.75 to 13:1 but would help flame travel. Will the better flame travel off set the compression loss? Also the piston tops are "not finished" I know all sharp edges should be removed but should I polish the whole top of the piston? Thanks for all your help

What size combustion chamber are you running to get the 13.75 :1? I have a set of domed TRWs( actually just seven, still looking for another), and would like to run them with some D3s. It was my understanding that this would give me about 11:1 compression.

Jess

Mustang-junky wrote:

mudtrucker wrote:I am getting ready to start putting together(again lol) my 466. I have a set of old, made in U.S.A. trw domed pistons. I have read that cutting the dome down flat which would drop my compression from around 13.75 to 13:1 but would help flame travel. Will the better flame travel off set the compression loss? Also the piston tops are "not finished" I know all sharp edges should be removed but should I polish the whole top of the piston? Thanks for all your help

What size combustion chamber are you running to get the 13.75 :1? I have a set of domed TRWs( actually just seven, still looking for another), and would like to run them with some D3s. It was my understanding that this would give me about 11:1 compression.

Jess

doves,74 maybe 70 ish depending on how much I have them cut.

so given the choice of pistons. would you opt for a super high compression say hypothetically,
edelbrock heads, 14:1 and use a super high octane race gas?
OR
lower compression 11.5 or so and make it up with cam and supporting parts?

D

danev2 wrote:so given the choice of pistons. would you opt for a super high compression say hypothetically,
edelbrock heads, 14:1 and use a super high octane race gas?
OR
lower compression 11.5 or so and make it up with cam and supporting parts?

D

If its a race only engine get the compression and do the proper parts to support it, your not going to "make up" power at the 11.5:1 over the 14:1.....

mudtrucker wrote:[quote= So what would the uppeer rpm limit be with h-beam rods? By the way, thanks for the info!

How heavy is the reciprocating weight ... ?