[techsol]

How far can you go with compression to stay with pump gas?

It seems that 9.5 or 10 will cut it but what's real world on todays gas with a mark IV 454 in a 70's muscle car?

 

[fabio]

it depends on the chamber design along as squish clearance as well as cam specs. You can also throw in timing and jetting in as well. They all play a roll in deciding if your motor detonates. Hot weather doesn't help either. Also aluminum heads run cooler so you can add more compression when compared to iron.

 

[ironhead]

How far can you go with compression to stay with pump gas?

It seems that 9.5 or 10 will cut it but what's real world on todays gas with a mark IV 454 in a 70's muscle car?

I have 11.26/1 in the ironhead 427 BBC on 93 pump gas.With 38* total all in at 3k..no detonation.Seems like no one took the time to tell the 427 that it is actually coupled up.lol.

3250 lbs
3.73/1 12 bolt
700r4

 

[norvalwilhelm]

I too ran 11.4 compression with a 454 but the cam drained off alot of compression so I never had a problem with 93 octane.
The cam was 256/264 @ .050

 

[keith66]

I wouldn't go more than 11:1. Just my opionion.

 

[ddeennis]

11.8 to 1 in my 454 .060 over running on 89 octane so far. solid roller, timing locked out at 38 starts super easy. i'll have to keep an eye on the plugs.

 

[mkube396]

How dus squish clearances affect it?

 

[461RAT]

11.6 to 1 on my 461 RAT with 93 octane,iron heads

 

[fabio]

How dus squish clearances affect it?

more power, cooler combustion temps. A good number to shoot for is 180 cranking pressure. Google pat kelley site as he goes talks about compression.

 

[Aaron]

I'm surprised you guys are getting away with 11 to 1 pluse compression. Must have a AWSOME tune and big cam.

 

[mkube396]

what about the hemi it has no quench?

 

[ironhead]

I'm surprised you guys are getting away with 11 to 1 pluse compression. Must have a AWSOME tune and big cam.

Correct Aaron.:hurray: :hurray: :hurray: The total combo and the tune up dictates.Every package is unique to its own..thats why some work well and others..ummm,get by.

 

[ironhead]

what about the hemi it has no quench?

It does have a centrally located spark plug that wards off secondary flame fronts.A wedge engine uses quench pads to squish the mixture into the combustion chamber..so no far off flame front can occur and collide with the intended burn.