Rebuilding heads and adding a cam on older engine
 

So I want to pull the motor and trans in my 67 Bonneville and do some work. This is the kit I’m looking at.

COMP Cams K51-232-3 High Energy Hydraulic Camshaft Kit, Pontiac V8
Pontiac V8, Hydraulic Flat Tappet Camshaft Type, 268 Intake Duration, 268 Exhaust Duration

I’m going to bring the heads to a local shop. Should I be looking at different heads to put in? My motor is a 4bbl 400. Am wasting my time building an older motor? It runs well now but I want a bit more power. I’m changing gears to 3.73

I mainly drive around 40 miles round trip to the next town over for lunch or ice cream. Occasionally I’ll do a 120 mile trip to pick someone up at the airport.

https://content.speedwaymotors.com/P...e2ac1c94e.webp

The hardest part may be finding a set of 3.73 gears for a full size Pontiac - that was an uncommon ratio when they were new, and i don't know if any companies are selling them now.

The first thing to do with any motor of over 20k miles before installing a new Cam is to confirm that the Cam bearings are still usable, as many times they have some good size pot holes in the Bearing surface.

Your heads will be fine and your compression will after the valve job that the shop does be a little under the 9.5 or so that the motor was born with.
Just be sure to change out the valve springs to better handle the lift of the new Cam and have the shop cut all 16 guide tops for Viton type valve seals.

While you have the Cam and Distributor out get and re- assembly the motor with a HD oil pump driveshaft.

I used to get tired of people recommending factory cams all the time but this is a case where the ole 068 is probably a better choice. Similar size/power but more exhaust and wider LSA is a better match for a largely stock engine in a big car. Still has enough character to sound like a Pontiac especially with a little better muffler.

^ I disagree. The cam he picked only has 4 more degres at .050" lift and the cam lift on that little 268 (advertised duration) is only .454". Sure it will require matching springs but he's buying the complete kit (cam, lifters, springs, reatiners, locks) which is good as his car's engine is 54 years old so new springs would be needed for the 068 too. Yeah more exhaust would be good but at low revs won't make a noticeable difference. IMHO

(My brother has used cams like this in big '60's Impalas with 283's, 327's and 3.08's and he was real happy with the power. Our op has a 400, think he'll be fine.)

Yep, and anything lower than 3.42's are a pain out on the highway. Going from a higher ratio rear to those or lower will feel like you're going down the highway in 2nd gear. With the money you'd spend on gears, pick out a new converter with a slightly higher stall.

Since you are replacing the complete valve train I would suggest picking out a cam with more lift, a wider lobe separation, and a split duration profile. If you are sticking with a hydraulic flat tappet I'd be inclined to go with something like a Crower 60242 or equivalent along with their cam saver flat tappet lifters. Your machinist can pick out the associated parts. I'd also replace the valves since the original 2-piece valves have been known to come apart when subjected to higher spring pressures.

Thanks for the reply’s. I’m starting to rethink my gear selection. I have a set of 3.08 I bought a while back. I live in Montana. We can pay speeding tickets with cash and I have a lot of open road around.

Sounds like new valves, oil pump, radiator should be purchased as well as my kit.

I’ll be getting my trans rebuilt too. Any recommendations on stall speed?

A couple pics for fun. I just did the intake manifold gaskets and painted her up.

That's a pretty mild cam, you don't need much converter, and you won't want a lot of converter if you stick with taller gears. I'd think something like a Hughes GM25 would be just the ticket for this.

IMO you should put a RAIII auto cam in it. Maybe a RAIII stick cam in if you want more lump. I consider the 268 a POS. never have been happy with them. With the intended purpose of this engine I do not see the need for a adjustable valve train either.
Might want to see about hardened ex seats if you are bringing the heads a a machine shop.
Keep it simple and have fun with it.