'91 Firebird 305

Well here we go, new toy in the garage. Well, almost. I pick it up in a week.

1991 Firebird, TBI 305 and autotragic. Car is pretty clean except for needing a hood and front bumper after getting intimate with a deer. A parts cars to supply a proper 5-speed and LSD is under negotiation.

The plan is to ditch the TBI and swap to a carb and better cam. The big question is the heads, are Vortec heads worth it in this case? The chambers are 64cc vs the stock 58cc resulting in a .8 comp ratio reduction if my math is right. Are 305 and 350 heads the same? I'm getting conflicting answers for that.

Tight budget and the use of a T5 trans means no 350 or LS1 swap. I don't need huge numbers, 225hp and 270lbs is the goal.

This should be fun when all is said and done. Lots of guys get caugtht up in massive power, and forget that they can't use it. Id rather have low power and be able to drive it flat out than high power that makes it a handful.

Wanna sell the 700r4?

Slow car fast... I do hope to have good suspension and brake upgrades as time goes on.

Sorry, the trans is already spoken for.

http://thirdgen.org is your friend when it comes to tips for the Firebird.

They have a forum there dedicated to the TBI engines. There is a lot of info there for upgrading the L03. If you are looking for cheap fixes at first, exhaust. Headers, y-pipe, etc. is very restrictive on the L03. It was the fuel economy V8 for the f-bodies.

Vortec heads are probably the best cheap head upgrade. But they will require a new intake. You can definitely get the heads milled down enough to keep the compression ratio up. The vortec heads do have enough material for this.

For some reason I don't think the valves in the Vortec heads will clear the cylinder walls. The 305 is a smaller bore than the 350.

Yes on third gen. I actually found the car there.

305 and 350 vortec are different casting / part numbers. Again its a different chamber size. Runners seem slightly different too. 350 heads are way easier to find.

What's low budget?

I swapped a 2.8 for a 400 with some goodies in a third gen Camaro for a grand total of maybe 2k well exceeding that HP goal with the stock 400 heads. Vortecs are great from what the mags say but I've never used them, and I've never heard of them going on a 305, so I am not sure if they fit. Likewise I have not used the 305 head on a 350 or visa versa. I don't think either of them are worth searching for.

A 350 short block should cost you like $200 - and honestly, that's what I would do, although you'll get really sick of hearing that.

Sorry, limited to 5.0 liters for future racing plans. Also don't have the coin for a trans that will hold up to that kind of power.

You could probably pick up a set of L69 305 heads for real cheap. They flow a little better than the TBI ones.

I've never hear of Vortec heads not clearing the bore on a 305.

L69 heads are my second choice. (unless I get some L98 aluminum heads at a give away price) We'll see what the pick'n'pull has to offer. Luckily I do have a fair amount time. Picking up the car Saturday, can't wait!

Vortec heads will work on a 305.

GM put 305 Vortecs in pickups from 96-98 and the 99 "Classic" prior to the next gen 99 and up LS1 engine family.

I always root for the underdog, interested to see what the 305 can do!

If you put 350 heads on a 305 it will have so little compression it won't pull itself.

305 heads on a 350 is an old cheap trick but they run out of wind on the top end.

I won't buy anything with a 305. They are junk. Unless I just love the car and I keep a spare 4bolt main to build at all times.

If you are limited in cubic inches... You want a 283. Or destroker 327.

Some 350 heads on a 305 will not work, some will. The yes and no's are in the details. The Vortec heads will work on a 305 successfully. I'll need to reference builds from "other magazine locations" for this one:

http://www.carcraft.com/techarticles/ccrp_9903_305_chevy_small_block_engine_build/viewall.html

http://www.fl-thirdgen.org/325-305sbcbuildup.html

http://www.popularhotrodding.com/enginemasters/articles/chevrolet/0667_phrs_305_chevy_engine_blocks/viewall.html

FranktheTank wrote: If you are limited in cubic inches... You want a 283. Or destroker 327.

This

Around 99-2000, I had a co-worker with a late 80's Camaro (87?). He wanted to be able to race without blowing out the T5 or the stock rear end. We swapped the Vortec heads onto his 305, Performer intake, used Holley 750, and a cam that would work with the stock Vortec heads without modifications. Cheap headers. Car ran high 13's with full power ops and a/c.

96-98 GM pickups may offer a used 350 Vortec cheap - since the LS1 swap has become big, used 350s are reasonable. But if you don't want the hassle of swapping out the 305, its obviously not a bad choice either - just a better choice for your circumstances or what you want to do.

Frank, I'm not looking for 300hp here.

Tig, looks like you've got the numbers I'm after. Do you recall what gear ratio was in that car?

tuna55 wrote:

FranktheTank wrote: If you are limited in cubic inches... You want a 283. Or destroker 327.

This

Or a 283 crank in a 327...

I recall he swapped in 3.73 gears. Stock rear. The 3.73's came out of another F Body.

There were a variety of stock gear ratios in those cars over the 3rd gen period. Auto cars most often had lower gear ratios:

http://www.camaro3rdgen.20m.com/Gear.html

The_Jed wrote:

tuna55 wrote:

FranktheTank wrote: If you are limited in cubic inches... You want a 283. Or destroker 327.

This

Or a 283 crank in a 327...

Sorry, I shouldn't post when tired. 283 crank in 327 = destroker 327.

Okey silly dokio, I'm an idiot!

Carry on.

I wasn't gonna say it ;)

lol

The 305 can still be fun with 3.73s. When I got my Monte I bet the thing to death and the motor never broke which is more than I can say for 2 trannys and many cheap rear tires

FranktheTank wrote: If you put 350 heads on a 305 it will have so little compression it won't pull itself. 305 heads on a 350 is an old cheap trick but they run out of wind on the top end. I won't buy anything with a 305. They are junk. Unless I just love the car and I keep a spare 4bolt main to build at all times. If you are limited in cubic inches... You want a 283. Or destroker 327.

I wouldn't mind a screaming 302, but don't have the cubic dollars for that. Even 283 an 327's are a bit rich for this project.

If you're not even after 300 HP, leave the stock heads on it. Mill them for compression, get a good intake and carb, get some decent headers, port match it, get a good HEI to recurve, a cam somewhere around 250 degrees and you should be pretty close.

I did a 400 like this, and you can expect something like 75 less HP than I had. That car ran 12.76 ET (also a third gen F body), so you'll be fine without adding cost. Figure a good used intake, distributor, carb, new headers and a cheaper cam, you'll probably only have $1500 in it if you spend a bit on overhaul and valvetrain parts to keep it alive.