head help please!!!!
Thread Starter
|
Elder User
Joined: Sep 2004
Posts: 500
Likes: 0
From: midwest
head help please!!!!
does anyone know how much compression i will gain by bolting a set of E7s on my 78 302? it has stock 78 heads on it and its 8.5-1 now. i heard the chambers are 69cc on the 78s and 60cc on the E7, if thats true i will increase from 8.5 to 10-1 compression according to the rule of every 5.5cc drop is equal to 1 point of compression. im hoping for at least 9.5-1. if it does raise my compression to 9.5 or 10-1 why are the 302s those heads came off of only 8.9 or 9-1?
help with any info please, im itching to install these heads and i need to know what to expect cause ive spent alot of time porting them.......
help with any info please, im itching to install these heads and i need to know what to expect cause ive spent alot of time porting them.......
Elder User
Joined: Oct 2004
Posts: 541
Likes: 0
From: Fleming Ga
I think the e7 heads are more like 62-63 cc which should get you about 9.5:1 compression. The e7s are better heads than the 78 heads and you already ported them so why not install and see what happens.
Senior User
Joined: Nov 2004
Posts: 166
Likes: 0
From: Tucson, AZ
piston compression height and the volume of the piston dish and/or valve reliefs also have an effect on compression ratio. this could be one reasson for the difference in compression. i agree with ronclark, use the heads. i put a set on my 83 351W, replacing a set of late 70's castings and have had no problems.
if your burning regular, listen for detonation under load...you may need to burn higher octane gas. my 351W still runs with regular but my initial compression before the swap was probably lower than 8:1. cheers, garsten
if your burning regular, listen for detonation under load...you may need to burn higher octane gas. my 351W still runs with regular but my initial compression before the swap was probably lower than 8:1. cheers, garsten
