mustangboi

Just wondering if anyone knew... I have an Olds 403 motor im rebuilding, The heads are not the greatest but I have a set of 350 Olds heads. Would I be better off finding another set of 403 heads? Would the 350 heads ruin performance? What are my pros and cons about using the 350 heads?

BNaylor

Welcome to AF.

The forum you posted in is reserved for GM N body cars and your issue is generic in nature so it has been moved to Oldsmobile Non-Specific.

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'08 Pontiac Grand Prix GXP (Dark Slate Metallic) - LS4 5.3L V8
'08 Pontiac Grand Prix GXP (Liquid Silver Metallic) - LS4 5.3L V8
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xeroinfinity

What year is the 403 and whats the year on the heads, aproximatly.

IMO 403's are kinda dogy anyways .

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1999 Grand Am SS 3.4 OHV

mustangboi

The 403 is out of a 79 Olds, it has been gone through totally. I do have the original heads that have not been machined yet, but also have a set of heads from a 75 Cutlass 350 that are perfect. I was told at one time the 350 heads on a 403 is a better combination creating a bit more snap.

xeroinfinity

Sorry I didnt get back to ya sooner, I didnt get an email notification stating you posted again.

On with the heads, the 350 heads add better performance for sure. A friend of mine has a 79' TA w/403 which has 350 heads and he said its quicker and he gets a little better mpg, which we all love

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1999 Grand Am SS 3.4 OHV

mustangboi

Hey thanks dude, I will go with the 350 heads then. I can always go back to the stock heads if need be.

relic7680

you could keep the stock 4A heads and bump compression by swapping out the factory dished pistons....some mild porting would help flow. this is what i plan to do on mine.