Will Dome Toped Pistons Create Detonation Even With Large Combustion Chambers?

fiveohlover · Oct 18, 2013

I bought a car with afr 185 heads and i took them off and they have the part #1387. I looked it up and those heads have big 72cc combustion chambers. I am in the process of rebuilding a 347 and the car is N/A and i want to have 10:1 compression.I could get them milled down, or should i get domed pistons? I have heard from some tech guys that domed piston will increase detonation and not allow me to run pump gas. Any body have any experience with domed pistons and pump gas?

A5literMan · Oct 19, 2013

fiveohlover said:
I bought a car with afr 185 heads and i took them off and they have the part #1387. I looked it up and those heads have big 72cc combustion chambers. I am in the process of rebuilding a 347 and the car is N/A and i want to have 10:1 compression.I could get them milled down, or should i get domed pistons? I have heard from some tech guys that domed piston will increase detonation and not allow me to run pump gas. Any body have any experience with domed pistons and pump gas?

I'd mill the heads down and put the correct pistons in it. I believe most 347 flattops with around 60-64 cc heads give you around 10.1-10.5:1cr. Keep it under 11:1 and you're good to go on 91-93 oct

fiveohlover · Oct 19, 2013

But do domed piston make you have to run race gas even if your compression is below 10.5:1

Noobz347 · Oct 19, 2013

jrichker · Oct 19, 2013

fiveohlover said:
But do domed piston make you have to run race gas even if your compression is below 10.5:1

Want the real answer to your question and are willing to spend 5-10 minutes thinking about it?
See http://en.wikipedia.org/wiki/Engine_knocking

clement · Oct 19, 2013

a 5cc dome will put you at 10.3:1 with a 72cc chamber and .041 HG thickness at 0 deck. if domes caused detonation they woundnt be used in every big bore 14:1 engine that runs a 400 shot of nitrous, regardless of octane used. itll be fine. a smaller chamber and flat top would theoretically be more ideal, but by the time you angle mill those heads to get the chamber down the deck will be so thin HG retention might be an issue. not to mention that every piston for an old 426 hemi is basically a huge dome (like 88cc for a 10:1 comp stock hemi head) and they still do fine at that compression with pump gas and a big bore.

fiveohlover · Oct 19, 2013

clement said:
a 5cc dome will put you at 10.3:1 with a 72cc chamber and .041 HG thickness at 0 deck. if domes caused detonation they woundnt be used in every big bore 14:1 engine that runs a 400 shot of nitrous, regardless of octane used. itll be fine. a smaller chamber and flat top would theoretically be more ideal, but by the time you angle mill those heads to get the chamber down the deck will be so thin HG retention might be an issue. not to mention that every piston for an old 426 hemi is basically a huge dome (like 88cc for a 10:1 comp stock hemi head) and they still do fine at that compression with pump gas and a big bore.

so you are saying i should get domed pistons and not mill the heads?

clement · Oct 20, 2013

given the two options that is what I would do if it were mine.

Will Dome Toped Pistons Create Detonation Even With Large Combustion Chambers?

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