modern heads for a 307

[tom]

Are there contemporary heads that will work well with the small bore 307? Is the 80's 305 also a small bore?

Thanks,

Tom

[hotrod68]

Just curious....why are you messing with a 307?

[JohnZ]

The 307 bore is 3.875", and the 305 bore is 3.736".

[tom]

I'm messing with a 307 because it's the original motor. John, Thanks I think that means the 305 heads should work, and may even boost compression a bit.

Tom

[hotrod68]

Good reason...chuckle

[rich69rs]

Not everyone has or wants a ground pounder.  Wouldn't change the 327/210 hp out of my '69 RS either. 

[1968RSZ28]

I'm messing with a 307 because it's the original motor.

Not everyone has or wants a ground pounder.  Wouldn't change the 327/210 hp out of my '69 RS either. 

Tom & Rich -

You both have bigger engines than the one in my '68 Z/28!!     

Paul

[tom]

Wanna trade ?

Tom

[BILL69]

You can run the 305 heads without problems, I have run them on 350's iin stock car street stock classes many times.  The compression ratio will be raised but they will run out of power and quit pulling very early (4800-5000 rpm's) Just make sure you run the proper gaskets, as they vary in thickness.

[tom]

Bill,

Thanks! I just want to put a little more pep under the pedal. This is a budget toy, not a competition, or show car. Since the motor is smaller, the heads will probably rev a bit higher before they run out air anyway.  Which 305 heads would you recommend?

Tom

[hotrod68]

Rich...if my '68 had an original drivetrain it'd be like yours or Tom's! The original 327 and whatever manual transmission it had was long gone by the time it got to me...chuckle. When I got it in '83 it had a small-journal 327 with an ancient 4GC Rochester 4bbl and an M-21. The transmission tunnel had been butchered with a huge, gaping hole for a Mr. Gasket Vertical Gate shifter. On top of that, the cowl tag was gone, so I have no idea what factory stuff it had beyond a  327 with a manual transmission, console, vinyl top, and the Z21 trim package. So I just made a hotrod out of it. I actually envy you guys who have cars with pedigrees----be it a 327/210, a Z/28 or an L-78. They're worth a lot more than mine, and you know their history. Sorry if it sounded like I was knocking a 307 car--I was just curious because I've seen so few of them. 

[BILL69]

We ran them because they were cheap,  you would be better off with 350 heads but they are getting harder to find every day.  You want '80s 305 carburated heads, part # 14014416,  stay away from the TBI heads they are very restrictive.  Take a little time look around you may just want some new aluminum heads,  they are very cheap and with spray bomb will look "factory" but perform better than any older heads.

[tom]

Wouldnt I lose compression with the 350 heads?

[BILL69]

Using the 305 heads will raise your compression but it will be a very small amount.  These heads have 1.84/1.50 valves which are small with small ports also, this equals no flow, thus you run out of power about 4800 rpm.  Get a good valve job on your original heads, freshen up the valve train, add a cam that fits your needs.  You can only expect so much from the 307.  Or pull it, put it aside and drop in the 290hp 350 GM crate option.  I just don't think the 305 heads are worth it in my opinion.  The only reason we ran them in "street stock" were the availability, price, and the rule book.

[sdkar]

My first 69 Camaro had an original 307 with a powerglide.  It had a 2bbl carb when I got it.  I installed an Edlebrock Torker II intake (because it what I found at a swap meet) and a Holley 4bbl.  Other than that, the engine was completely stock.  I kept the original exhaust manifolds but I did get rid of the single exhaust and install a true dual exhaust system.  The car ran 15.1 second quarter mile with the powerglide.  When I swapped out to a TH350, I was running high 14's at the track.  This was with a 3:08 non posi rear.  To be honest, I didn't think the 307 was that bad of an engine.  It may not be the motor of choice for a high horsepower buildup...but it was no slouch.  My 69 with the 307 would beat my high school buddies late 70's Z/28's and Trans Ams with their 350 and 403 motors.