305 Heads???

[zman6988]

Hi guys new one here, I was just wondering based off the numbers of my block it is a 78-86 305. So I was wondering if 87-95 heads will bolt on my engine witout any problems. I guess I should state why I would like to know this huh... Ok my father in law bought a 25 cuddy regal with what he thought was a 350 but after I ran casting numbers turns out it's a 305, but it gets better the even side (2,4,6,8) has a 305 head but the odd side (1,3,5,7) has a 350 head, throwing the compression off with 56cc chambers on the even side and 76cc chambers on the odd side. Needless to say I need to know if the new heads will enterchange with the block. Any and all input will be greatly appreciated.

Thanks, Chas

 

[n2ostroker]

Re: 305 Heads???

The 87-95 heads will work. You'll need the valvecovers and an intake to fit them though.

 

[Bondo]

Re: 305 Heads???

Ayuh,...
Any SBC heads up to 1996 will bolt on,+ Run,....
The mid/ late-80s to 96 require intake bolt hole modifications,...
After 96, you need a Different intake....

But your Right,.. Another 305 head matching what's there would be Best...
Matching it's Casting # could do it..

 

[zman6988]

Re: 305 Heads???

So even if I buy new heads up to 96 model and new intake (8 bolt) I will still have to make bolt mods.??

 

[dr_bowtie]

Re: 305 Heads???

correct....

ALL 305 chevy engines have 5.0L cast into the bell housing surface rear of the head above the oil filter....right between the top and middle bell housing bolts....

350s after 78 have 5.7L cast into them....

I am sure the motor with mis-matched cylinder heads ran funny...

 

[jtybt]

Re: 305 Heads???

The heads will bolt up no problem. The bolt pattern for the intakes were changed...the two center holes had a different angle. For some reason I can't remember when that change was made.


Just match year/casting numbers.

 

[dr_bowtie]

Re: 305 Heads???

the change was made in 1986

 

[zman6988]

Re: 305 Heads???

I know it's a early 305 86 and earlier but I was wondering since it's much easier to find late model heads and intake will they bolt up to my 305 without any modifacation, or should I just keep looking for older heads and four barrel intake?

 

[lime4x4]

Re: 305 Heads???

What type of intake do u have on it now? Look at the 12 intake manifold bolts to cylinder heads? Do they all go into the head at an angle? Or is the 2 center bolts straight? You can also tell by the valve covers. Do the valve cover have 4 bolts down the center or are there 4 bolts on the outside of the valve cover? You can bolt any style of heads to that block just make sure u get a matching intake manifold. You could bolt a set of vortec heads just need a matching vortec intake manifold 8 bolts compared to 12 bolts.

 

[dr_bowtie]

Re: 305 Heads???

any head will work as long as you use the matching intake....

they started using the 58cc head on 305s in 1986 and only certain ones used that head not all of them...during those few years the center intake bolts went straight down like ford 302 while the rest were angled like normal...

this was for clearance more than anything...as the center bolts were a tight fit on some engines....

the only issue with running these 58cc heads on a 350 is that the ports are small....they make great torque down low but quickly run out of air around 3500rpm and actually make less power over that than the correct 350 head on a 350...

if your 305 had open chamber heads and you use the closed chamber 58cc heads make sure you back off the timing and use a higher octane fuel...

305s are prone to detonation and they will rattle them selves to death if you arent careful....

if you use the 58cc heads on a 350 its much more important to back the timing off and use higher octane fuel...