If i read somewhere they wont just bolt on, or will they, i want to know what the compreesion will drop down to and if they will just bolt on, i want to throw a LT1 cam in a 91 305 from a firebird for temporary with the vortec heads till my stroker is ready. Any clues fellas, the 305 has 110k on it and was driven pretty normal i think it will be fint if i dont have to modify to make the heads fit.

 

Ibelieve you have a speed density system so the ecu may need to be modified...that a side they will bolt to the block but the manifolds will need to be changed.. the intake only has 8 bolts(2 in each corner) and if the exhaust manifolds are stock they will have to be changed to headers... I think the stock c/r is 9.3:1 with 58cc the vortecs have 61cc (even though there said to be 64cc). From what Ive read the intake flow will compensate for the loss of c/r. Also the lift is maxed around .470 . Its probally the most sought after production chevy head.

 

Thanks man, so no interference with valves hitting? It is carburated, i have the matching carbed vortec intake and the car has headers already, i have a nasty motor on the way i just wanna driver my car till then, i think i might cut the heads down and put bigger springs to run my comp XE HR maybe, i just dont want any problems with bending valves.

 

It's not a very good idea to put Vortec heads on the smaller bore 305.

Even if they bolt to the block, the intake valve will be shrouded and the
lift will be limited.

There are countless articles about this combination and the problems
associated.

I'd advise against this even for a temp. situation.

 

the valves wont hit..shrouding will be more so than a 4" bore but nothing you can really do about that.. as far a lift goes the problem isnt the springs( even though they should be replaced with springs comp recommends) its the valve guide. You should have them machined down to take more lift when there being milled.. it should cost another $120 or so.

 

You will have less radial clearance, and max lift is limited because the of
the valve interference to the bore.

If I'm not mistaken, the valve angle is also different?

 

There is not a problem with bolting vortec 350 heads on a 305. I ran them on my 305 with a 1094 felpro steel shim head gasket to gain back some lost compression and they worked very well. I had my heads modified to accept .600 lift and ran a ZZ-4 cam with 1.6 rockers. With just bolt on's and those heads and cam the car ran mid 13's at 101 MPH.

 

We,, i have ported the hell out of the vortecs and ran them on a 383, the 305 will be using a stock LT1 cam from a vette. I just want to drive my car and refuse to use the TBI heads that are on it. If it made 250 HP at the flywheel id be happy till the real motor is ready.