My friend is looking for some cheap horsepower additions on his 1989 TA with 350 roller motor. We have a set of heads from a 1986 L69 305. Will these heads work well on the roller motor? I think we will have to use the pushrods from the roller motor, are there any clearance problems with the guideplates on the 305 heads? It will give us a higher compression ratio with the 58cc chambers, but I'm not sure about the valve train geometry with the roller cam & lifters being used with the early style heads & intake.
Dave

 

Just swapping the 305 heads in place of the 350 heads on a L-69 will not increase power. The compression ratio will be slightly higher only if you use the same thickness head gasket. Most replacements are thicker.
305 heads use smaller 1.84" intake valves. (1.94" stock 350)

You're not going to gain anything here. Why not just mill the 350 heads you have now for exta compression ratio?

What you're looking for is increaed airflow in and out of the engine.
"Home port" the L-69 heads. They respond very well to this.

 

My friend has an article in Hot Rod about using the 305 heads on the 350, he is going to port the heads by blending the edge of the combustion chamber to match the 350 gasket, eliminating the sharp edge that matches the 305 gasket. He is also doing some smoothing on the intake ports and around the valve guides.The reason that he's looking to change to the earlier heads (instead of milling the 350 heads) is to use the early bolt pattern Edelbrock intake and a Holly carb. He already pulled off the TBI system that was on the original car.
Does anyone know if we should use stock roller pushrods, or will something different need to be done when running these heads?
Dave

 

Do not try to match the 305 heads chambers to a 350 gasket.
You will remove way too much material and weaken the head. it will crack. You've totally missed the point of deshrouding chamber edge around larger 350 sized valves for extra flow. Only a small amount of material needs to be removed. Some people should just stay away from cars.
If you grind out the chamber walls to match the gasket they will be bigger than the cylinder bore. You've just make matters worse and gained nothing.

 

use 350 gaskets anyways

 

Pushrods and lifter type go together, not pushrods and head type.

Rocker arms and head type, however, go together. '88-later heads used self-aligning rockers, the pushrod holes are round, while the '86 heads would have non-self-aligning rockers with pushrod holes that are narrower and slot-like. You either need to use '86-like rocker arms, or drill out the push-rod holes round and use self-aligning rockers.

What the magazine article was saying with regard to the combustion chambers and head gasket was to use the head gasket as a guide to keep from over-grinding. It's a much better idea to scribe the cylinder wall to the head (which requires the pistons to be out of the block, of course), but if you just listen to what F-BIRD'88 is saying it really isn't an issue.

FWIW, '86 L69 heads would be very rare, as only a few went in f-bodies. Montes got them, I believe, but that probably doesn't matter a whole lot, since L69 and LG4 heads were identical in f-bodies. Casting #'s would tell the whole story - I'd certainly want to know what they were before assuming what they are and spending a bunch of time and money on them, only to find out they are something else.

 

Thanks Five7kid. That's the kind of useful information that I was looking for, we can run the 1986 heads with the rockers and springs that are on them as well. The heads we have are off of a 1986 Monte Carlo SS. So we can use the '86 heads with guide plates (not self aligning rockers) with the roller lifters & push rods? That's what my main question was.
Obviously anyone who is asking the question knows better than to port the head larger than the cylinder. Try not to take things too literally and stating that some people should stay away from cars. We do not need rude wise a-- remarks like this when I'm just looking for some technical information that is not common knowledge. alsoof course with a 350 block we are using 350 gaskets.
Thanks,
Dave

 

remember that the intake holes angles changed in 87

so you will have to do some modifications to the FI intake to bolt it unless you are converting to carb

or youre only gonna have 8 bolts holding your intake down

 

We are using an early intake and Holley carb.
Dave

 

a roller motor used different length pushrods then what you need for a flat tappet cam. Just thought i'd throw that in, in case you didn't know that.

Otherwise, good luck! I highly recommend lightly bolting a head onto the motor, scribe the bore onto the head, then mark that head as being passenger or drivers side. And grind away. I think sanding wheels were all that I used on my heads combustion chamber, you don't need to remove gobs of material.

 

You shouldn't use guide plates on heads that have the narrow, slot-like pushrod holes. The point being that only one constraint method should be used - slotted holes, guide plates, or self-aligning rockers - no two should exist together on the same engine.

 

Thanks a lot. This info is what I need, we are going to run the roller cam, lifters and pushrods with the 1986 heads slightly ported and smoothed out. We are also using the early style Edelbrock intake and Holley carb.
Dave