Dished vs flat top

[biggels240z]

hey guys

 

just a quick question to see if anyone knows what sort of power difference there is between using dished pistons and flat tops .

I currently running L28 with stage 2 cam i think from memory its a 76 cam but it only has standard lift .496 from memory. It should be about 8:1 compression ration i was thinking i upgrading to flat top pistons but was wondering who else has done this and what sort of difference it makes, becuase i was thinking if is not a much i would get a small toyota blower and hook that up as a cheap alternative!!

 

cheers

Richard

[Zedman240®]

Depends what cylinder head you are running. With the P90 heads, they had a large chamber so with the flat top pistons, CR (comp ratio) is low. With the dished pistons and N42 head, chamber is closed a bit more but with the pistons dished, CR again is standard. So if you want to use flat top pistons and a N42 head, expect to hear a lot of anvils being hit under your bonnet! Try not to go too high in CR; with the crappy fuels here, unless you are planning on running methanol or C16 or similar, keep your CR at a realistic ratio.

[reverendzed]

Hey demitri, what do you mean when you say"  So if you want to use flat top pistons and a N42 head, expect to hear a lot of anvils being hit under your bonnet!  :-\

 

[pauly_adams]

I think he means that your compression will become high in high 9 or mid 10 and with bad fuels you will hear quite a lot of pinning.

 

Cheers pauly

[Zedman240®]

Yeah, sorry.. I should've just said pinging or pre-detonation to avoid any confusion. When I hear it to me, that's what it sounds like...Comp ratio might even climb close to 11:1.

[biggels240z]

yeah im running a N42 head with the larger valves and a quick port so maybe probably should look at a small blower and a holey !!!

[BenZed]

Depends what cylinder head you are running. With the P90 heads, they had a large chamber so with the flat top pistons, CR (comp ratio) is low. With the dished pistons and N42 head, chamber is closed a bit more but with the pistons dished, CR again is standard. So if you want to use flat top pistons and a N42 head, expect to hear a lot of anvils being hit under your bonnet! Try not to go too high in CR; with the crappy fuels here, unless you are planning on running methanol or C16 or similar, keep your CR at a realistic ratio.

 

 

I run 10.5:1 compression, no problem on 98-octane fuel if the car is tuned properly on a dyno.