I have a 91 firebird that I just got and it has TBI. I also have a set of 305 heads which I have been porting, i believe the casting is 416 ( i need to go look). Are thes TBI heads much, or any better than these others that I have. Also what would be the best 305 heads? I have 1 other on in the shed and dont know what it is. maybee I need 1 more to match it if it is any better than these others.

 

it's not really clear what you're asking here... did you port the TBI heads? or something else... what are you trying to do?

Also... given that you are on an F-body site "DAN94GT" is a great way to make sure you are ridiculed. Try picking "DAN91TBI" and you will likely get more help... advertising that you own a Mustang is a good way to get laughed at around here.

Back to the heads... GM changed the bolt pattern in 87... your TBI intake will not fit on heads built before 87. The best heads are of the aluminum variety.

 

Well, the best factory 305 heads are usually thought to be L69 heads. I only say this because SCCA American Sedan racers use them for racing. Maybe their rules require an iron head but I ported my L69 heads and they seem to do well, it pulls beyond 6000 rpms with the cam i have.

 

Ultimatley both castings have about the same potential.
Not worth the bother to switch to the old style "416's".
The "081" castings look not to bad and have the centrebolt covers and angled intake bolts. If that's your TBI heads I'd use those to port up on a budget. I would avoid the swirl port heads.

 

which ones are the swirl ports?

I was asking which heads are better to start with so that once I spend all my spare time porting them I have the best head for the money and time spent.

And thank you for your opinion on my name. ill stick with it. The mustang is my car. The firebird is my girlfriends. Plus I never forget my name and passwords if I use the sam ones for everything.

From what I can see around here most people are pretty cool and sometimes someone who knows more about "the enemy" can be very usefull. Im not here to brag that I have a mustang and that chevys suck. That is not what I am about, or why would I have bought a chevy, and have all these chevy parts laying around.

 

L69 cars use the same heads as the LG4s and the early TPI cars. These are usually "416" casting and have good potential. They are perimeter bolt with the 86'-earlier intake bolt angles. TBI cars use the swirl heads and these are the absolute worst heads to use for any kind of performance, there a huge cast-in ridge in the intake port that restricts flow. My 91' RS will be getting a set of ported 416s to replace the awful swirl heads, since I'm also going to run a ported Crossfire Injection setup ( run by my TBI computer ), this swap keeps the intake bolt angles right.

 

The one TBI motor I messed with had the "high swirl" heads on it. If you looked behind the head of the intake valve it looked like almost 1/2 of the intake port was blocked off to induce swirl in the chamber. Of course, it choked the snot out of the motor. I swapped on a set of 87 305 TPI motor heads that did not have this "feature" and it helped considerably.

HOWEVER.................

I have had as many people tell me that their TBI motors did NOT come with high swirl heads- that they were the same heads as a TPI motor (down to the casting number) so you better check for yourself.

Something was out of whack with my TBI motor becuase it also came with a flat-tappet cam even though it was a late-style one piece rear main block. I have heard from a FEW people that their TBIs also came with a flat tappet cam, not a roller like it was supposed to have.

It is my opinion that GM might have slipped a few TRUCK 305 TBI motors in the F-Body over the years. They use the high-swirl heads and a flat tappet cam.