1679 help
-
AirCooled71super
- Posts: 43
- Joined: Fri Nov 11, 2011 10:01 pm
1679 help
Well i decided to build a 1679 but i dont know what heads to use. One head on my 1600 says 043 133 , and the others says 043 158. I was wondering if that ment i had different heads on the same engine, or if its ok to port and polish them for my 1679.........and f not, what heads to buy. And just to make sure, all i have to do is machne my heads for the thick wall 88s not my case, right?
-
Marc
- Moderator
- Posts: 23741
- Joined: Thu May 23, 2002 12:01 am
Re: 1679 help
If you're talking about the new thickwall 88s from AA, they don't require any machining to the case. The heads will need to be opened up to the same size as for late 90.5s or classic 92s (98mm).
It's difficult to identify heads by casting number - a lot of machining is done after they leave the mold...the fact that yours both start with 043 implies that they're contemporary. Do they both use the same size exhaust valve stem (8mm or 9mm)? Does either have a "step" where the cylinder seats? If the chambers are of similar shape, CC them to determine if they have the same volume - if one head has larger chambers it can be flycut to match the other. Any differences in the intake ports will most likely be rectified during porting.
Go easy on "polishing".
It's difficult to identify heads by casting number - a lot of machining is done after they leave the mold...the fact that yours both start with 043 implies that they're contemporary. Do they both use the same size exhaust valve stem (8mm or 9mm)? Does either have a "step" where the cylinder seats? If the chambers are of similar shape, CC them to determine if they have the same volume - if one head has larger chambers it can be flycut to match the other. Any differences in the intake ports will most likely be rectified during porting.
Go easy on "polishing".