new heads, compression loss?

[Charger1970]

Will there be compression loss switching from stock 76cc heads to Edelbrock 84 cc heads? If so how much? This is a stock 440 Magnum. Thanks in advance.

[Ghoste]

Effectively, yes, there will be a drop with all other factors being equal.  Myself, I can't tell you how much.  There will also be a loss in thermodynamic efficiency by going from the cast iron to aluminum and this reduction in cylinder heat will lower cylinder pressure which is also going to feel to your engine like a compression loss.

[firefighter3931]

   Ideally, you want 10.5:1 static compression with a tight quench build to maximize power and efficiency. 


Ron

[bee_fishy_6869]

Will there be compression loss switching from stock 76cc heads to Edelbrock 84 cc heads? If so how much? This is a stock 440 Magnum. Thanks in advance.

Plug your #s in to get some figures

V1 + V2 + V3 + V4  / V2 + V3 + V4    = compression ratio

V1=cyl swept volume
V2=deck clearence
V3=head gasket thickness
V4=Comb Chamber Volume (minus dome vol OR plus dish vol)

increasing CC volume will drop you comp ratio as you can see when you plug in the numbers

[jg68]

Will there be compression loss switching from stock 76cc heads to Edelbrock 84 cc heads? If so how much? This is a stock 440 Magnum. Thanks in advance.

You say its a stock 440 magnum, if its a 68-70, it should have the 906 heads, there around 90cc open chambers, so with the 84cc eddys, your comp. will go up.

[Chryco Psycho]

even with the 906 heads your real compression will strill drop , the 906 could be giving you 9.4 now so with the eddys you will have you compression will rise to 10.0 but with the heat loss to alum you need 10.4 to equal the 9.4 you had with the iron heads
if you have 76 cc chambers now you lose .8 in compression ratio + 1 more full point of compression to the alum so if you have 9.8 compression now your effective compression with the eddy heads will be approx 8:1