4AG head on 4AC block?

[demby123]

Just a curious question, since I know it would probably cost more money than a complete 4age, but is this possible with a bigport head on a 3 rib block?

[McKenney]

4ac and 4ag 3 rib blocks are the same. So are the rods. The pistons and crank are different.

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[demby123]

Are there any examples of this combination running? Can't find much real sucess.

[McKenney]

Tedd did the opposite and ran a 4ag bottom end on a 4ac head. Numerous people have done it. It's honestly a waste because the 4ac crank is shite and it drops the compression really low where only a boosted setup would excel. I have a complete 4ag for sale, it's in pieces but all there...

[yotarolla]

so the stroke is different between cranks?

[Sam-Q]

same stroke of 77mm, compression is lowered because of a big combustion chamber. The short answer on this question is you need enough parts that it's easier to just use a complete 4age engine.

[McKenney]

exactly Sam. same stroke, bore, wristpin diameter(on 3 rib motors), same rod journal diameter(40mm 3 rib). Just go with a 4ag... a lot easier and the low compression NA will be a dog, faster than the 4ac but not near as much as a 4ag.

[86boy]

BOOOOOOOOOOOOOST!!!!!!!!!!!!!