Head Swap, Change Timing?

[67Satty]

Hi All,

I recently switched from stock, unported iron 452 heads to aluminum Edelbrock 84cc E Streets with mild cleanup porting. Compression went from 9.5:1 to 10.2:1 or so. From iron open chamber to aluminum close chamber. From no quench to quench. 91 octane pump gas in California.

Right now the timing is still set to what I used before, 17 initial and 34 total.

My question is, do you think the new heads will want more or less timing? Right now is starts right up without seeming to work against the starter at all.

I plan on setting it up the timing with a vacuum gauge to see what it seems to like but was curious. Thanks!

 

[Jerry Hall]

More compression usually likes more timing, but with 91 octane fuel your going to end up with a trade off. You don't want detonation.

 

[Burns69RT]

On B/RB motors I tend to run them on 12 mechanical, and 26 on the crank. Total of 38 degrees of total timing. But that’s with a good cam, heads, intake. But it’s always worked for my motors and motors I build for customers.

 

[bigbluedodge]

17 initial and 34 total

Sounds about right, depending on how much cam you have. 30 years ago, a 440 I built with stock heads but "hemi grind" cam wanted 18 degrees initial and 34-36 degrees total. That gave it bottom end pull and it never pinged.

 

[LemonWedge]

There’s only going to be one way to find out what it likes best: Make full pass as it sits; adjust timing, make another pass. Look at MPH.
My guess would be that it will make more power at upper RPM’s at 36.... but that’s just a guess. You should be just fine at 10.2:1; I’m at 10.6:1, all in at 1800 RPM IIRC on non-ethanol pump swill. No issues.