I am planning to bore out my b16a to 84mm. My question is do i need to bore out the head to match the block. I know when you bore out a bug motor you need to do the head. Is it the same for a Honda. Also, what is the highest CR you can run on 91 octane I live in S.F Cali.

 

i think so but im not sure

 

no you dont have to do anything to the head.
look at the B20/vtecs those are 84mm bore with regular GSR/b16a heads. not problems with clearance.

the only thing you have to consider is getting the proper head gasket to match. in this case, you can bore out the b16a head gasket to a 84mm.

We can provide that service as well.. contact is for any questions.

 

Are you a 100% sure. I will bore my block out then. If you are not sure tell me because I will not have enough money to do the head. So can make sure and let me know.

 

he's sure. The only time you'd need to modify the head is if the piston was domed and had clearance issues with the chamber on the head you're using, which shouldn't be the case unless you're getting some custom pistons or potentially a set from another engine with a different head.

 

Are you sleeving? If not, it is not recommended to bore engine to 84mm with stock sleeves.

 

Hang on just a second here... The stock bore is 81mm. If you bore out to 84, you're going to have a 1.5mm overhang at the head. That's going to create a hot-spot and possibly cause detonation.

You SHOULD deshroud the head and match the bore.

 

Not true. That overhang, when properly used by matching piston crown shape to combustion chamber shape, becomes quench area. Now whether or not it should have a sharp edge or a radiused one can be debated, but there's nothing wrong with additional quench (something 4 valve pentroof chambers are inherently weak in). The more quench area you create, the better the anti-knock properties of the chamber become.

 

Can you elaborate on this? The thought of such a sharp edge in the chamber just doesn't seem right to me. I'll buy the quench area idea, but radiused edges would seem better to me. What would be the arguement for sharp edges?

Also, is radiusing those edges something that HAS to be done by a shop, or could a careful person do it at home with a dremel and or hand tools?

Thanks,
G

 

Sharp edges out in the quench area are less significant compared to in the valve area. I had my head matched to 84mm, but it is NOT necessary. If you are going to have headwork done anyway though, might as well. Most places do it pretty cheap as it is a fairly simple procedure.