I was wanting to know is there any power diff in domes. I have speed-pro 2256 (forged flatops) but was thinking of the direction of .1 or .125 domes, can I get away with a little more valve lift? Can someone school me on this? Thanx.

Just cause you switch pistons doesn't mean you'll have more power. You'll have more compression, but that also means you'll have to burn better gas, run the chance of pinging and having to turn your timing down in order to run the piston.
You need to give a little more info as to what you're going to bed putting this into.
Could just change to a smaller head gasket to bump your compression instead of changing the pistons.
Kind of asking a very open question there.

I should have posted specs and purpose. This will be very lil street, and 1/8 mile runs. I am going to try this in a s-10 truck, its light to 3010 with me in it. It has 4.10's th 350 wih 3500 stall, 355 with 291 camel humps ported/polished with race valves 1.94/1.5's I run a tunnel ram with 2 450's (still working on ign) the cam I run is solid with 300/310 256/270 @.050 and .500/.515 lift. I have these 2256 flat tops (4 reliefs -6.1cc) The comp is 9.7 with 64 head, mine been milled to 62. The .125 dome has 10.72 but will be close 11.1, myhead gasket is 4.100. 41 compressed. If I run these pistons I suppose I will have to flycut them maybe? But the intake set-up and camshaft will be respondive. The intake is the eddy version. Best so far is 7.70's with 1.86 60ft. footbraking at 3300. So would these pistons help me out more? Your reply seems yes. Gas octane not a prob nor street manners.

If the engine is assembled right now rather than replacing the pistons do a valve to piston check. If you have a bunch of clearance then have a machine shop angle mill the heads. Better compression, shortblock stays together, and no dome blocking the sparkplugs.

From recent readings, I believe flattops provide more effecient burn/better power than domed pistons.. Domes are only used to raise compression in a motor...
anyone else??
Hulk

Hey CWT

I think its time for better heads and bigger valves for your combo. Match the intake to the better heads. Then the next step would be more cam better valve train more carb. After that if the short block is still alive then it would be time for that. Maybe a trans brake is more important in the short term.

Keep after it sounds like your havin fun!!!

I agree with everyone but I switched from 2256F TRW to .100 KB and went from 12.53 @ 108 to 11.94 @ 111 no other changes so bang for the buck piston swap makes a big difference in seat of the pants and at the track.

Thanx, mwilson-thats what I wanted to hear, I've been kinda following you on your changes, the pistons I have now are the 2256's and was wondering to go to domes .1 or .125, just wanted to know really to see if the piston to valve clearence would be a issue, but I can always check. This set-up will se little street and plenty of 1/8 mile blasts.

Transbrake in near future, maybe some rhs heads or sportsman 2's.

The earlier 283's, 327's and 350's, (302's all had domed pistons), all used domed pistons when ordered as a hi-po engine back then and they were generally like 11 to 11.25 and 11.5 to 1 CR using the smaller chambered earlier than double-hump and double-hump heads so go from there!!

These old engine only used hi-po stock cams tho so higher lift cams need to be clayed to check piston/valve clearance like said.

And fwiw, these old stock engines ran like the wind back then when we could get leaded Ethyl Gas!!

pdq67

PS., there's two types of stock domed pistons too, the earlier 283, 327 and 302 that are the half round, 1/8" tall jobbers with distinct valve notches and then the later 302 and 350 that are more squared off and (I think??) a bit taller that have the valve trough if not mistaken..

Please check a Speed-pro or old TRW cat to see the difference in them back then.

Forged suckers are heavy, BUT STRONG!!!

[ the cam I run is solid with 300/310 256/270 @.050 and .500/.515 lift. I have these 2256 flat tops (4 reliefs -6.1cc) The comp is 9.7 with 64 head, mine been milled to 62. The .125 dome has 10.72 but will be close 11.1, myhead gasket is 4.100. 41 compressed.


yea whatever you do you definately need to get the comp. up with that much cam or its gonna be laaaazzzzzzy down low

With a Tunnel ram there is no down low, life starts at about 4200 rpm.

Imho, a 300 degree cam really need's at least 12 to 1 to run it's best!!

290 at 11 to 1 and I figure a good old Isky Z-30 solid lifter cam is a good old-school cam.... Sucker will really thump!!!

pdq67

MWilson, what were the dome volumes of your pistons that you swapped? 1/2 second is pretty unbelievable with nothing but a piston swap. From what I understand, 1 point of compression only picks up 3% - 5%.
Small chambers and flat tops are the most efficient way to make power.

From what I understand, 1 point of compression only picks up 3% - 5%.
Small chambers and flat tops are the most efficient way to make power.

I believe that also.However if you are running a big cam with a minimum amount of compression there is a greater chance of picking up not only the 3-5+ percent, but the torque down low and in the mid will be the big winner.

I think small pop ups aren't that bad.It gets bad when you install pop ups that net you 12:1+ with a 64cc head.That large of a dome will hurt flow and efficiency.Lot's of guys have shaved their huge piston domes and picked up.

I have read, not done, but that if using domes, to cut a path for the spark, so it doesnt have to jump over the pop top.

most of what i read, a dish is actually the best quench inducing piston. if you get your quench in the .035 with a dished piston, and your compression where you want it with right cc of head and gasket, all matching, it will make more power, burn more efficient, have less detonation, and take more timing than any other combination. IMHO. the physics of it makes sense, and i run dish, had a .036 quench with iron camels and had close to 11-1 with regular gas going through it.

that being said, i have a bunch of domes in the garage i will build something with...but it makes sense, the less the spark is interupted in the chamber, the greater the ignition, combustion, and force=power.

but like Paul and Cody said, that cam needs a lot more than the 9:4 area to be happy. I think i am pushing it on a cam swap and i have around 10-1 and in the 289 range duration.

I've posted this before..

250 = 8 to 1 CR.;

260 = 9 to 1 CR.;

270 = 10 to 1 CR.;

280 = 10.5 to 1 CR.;

290 = 11 to 1 CR.; and

300 = 12 to 1 CR....................

Check all this stuff out here by reading Pat K's GREAT DCR site at least three time's..

http://cochise.uia.net/pkelley2/DynamicCR.html

pdq67

Mine worked out to a +1.5 cc volume after I factored in the valve relief, 11.32:1 and as someone else stated my gain may have been due to a mismatched cam to start with? Mine have spark plug notches in them as well.

The ones i have i cut the spark plug path in them as well. i think the dish design cups the flame and mixture in an even "ball" to eliminate hot spots. thats the theory.

Paul-bucking the experts and going into the 278-282 range with a street centerline, could work nice, or piss me off. either way its something to try.

or i may just get a nitrous kit, try to blow mine, and put the 383 in.

with a 383 and 64 heads, would be around 11-1. with aluminum heads shouldnt be a problem, huh, with detonation?

then the cc4c solid would be great and a high 11 car maybe?

...that cc4c camshaft looks like a great cam for street/strip, with 11.1 c/r and low 3k lbs vehicle should get the job done. Anyone know the idle quality of this camshaft?