Are the 305tpi heads that come off the 85/86 tpi motors the same as the 87 and on tpi motors? if not would 86 305tpi heads still be a good upgrade on a L03 motor?

 

yesh, 85 and 86 TPI had the 416 heads, same as the L69. They are a great head with lots of pontial when ported.

I myself am rather fond of them.

 

There are slight differences between the pre 87 and post 87 heads. Performance wise they are the same. The post 87 heads had center bolt valve covers along with self alligning valve rockers. The intake bolt patter also changed. The post 87 heads are more of a true bolt on on your TBI car but the 416's (that Dewey mentioned) will work just as well with the right prep work.

 

You'll have to enlingate (make oval) the bolt holes on a 87-92 intake manifold to fit the pre-87 heads (416 casting). Other than that, the 416's are a exact fit. The 87-92 intake manifold with not need this if you use 87-92 tpi heads (081 casting).

 

those heads are a good upgrade, but only under certain conditions.

first, the intake valves are 1.84. to see any real performance from them, you'll need to upgrade to 1.94 intake valves.

second, if you're not experienced at it, head porting can be a real bitch of a job, and you can easily screw up the heads. if you have someone else do it, you're looking at at least 500 bucks.

finally, before you do ANYTHING to those heads, spend 50 bucks and have them hot tanked and magnafluxed. If they're cracked, you'll be out the cost of the heads and the cost of the magnafluxing, but better that than spending all that time porting them only to find out they're no good later (let's just say i learned that lesson the hard way once and leave it at that, ok? ha ha ha).

IF you can do your own porting and think you would enjoy the process of doing it, have access to inexpensive machine shop services and already have the intake you plan to run, this makes sense (although i think you would be better off spending a few hundred more bucks for 58cc aluminum zz4 heads ... then port them).

if you don't have all of the above, i think vortecs are the way to go, especially the pro-topline vortecs. you can find them on ebay regularly for under 600 bucks, figure another hundred to have a machine shop dissassemble them and mill .036 off to bring the combustion chambers down to the correct size, and you can get the gmpp vortec tbi egr intake (pn 12496821) at gmpartsdirect.com for 288.00. that's 60 bucks cheaper than from sdpc2000.com.

by the time you get done with those tpi heads, you'll have close to that in them (if you have to buy an intake, too), and you can port on them all day and still not get them to flow anywhere near as well as the vortecs.