[A390GT]

I picked up a set of refreshed 6x-8 heads for the ye block I’m building
The engine was from a 68 bonneville 4bbl car
I want to get the compression down so the engine won’t ping like the yc engine that’s currently in my Catalina. it’s an auto and has a 068 cam and 215 heads and a q-jet l.
it a rattler with a heavy load of kids and stuff

What do you think the compression would be with the 6x-8 heads on the stock block and what would be a good cam if the comp. Is more in the high 8’s then mid 10

Also how hard is it to swap out the heater hose nipple on the back of the pass side head?

[Sirrotica]

Instead of trying to retrieve an old rusty one, you can purchase new ones at Summit:

https://www.summitracing.com/parts/o...YaAnbtEALw_wcB

The heads you have will make the possibility of spark knock pretty much non existent. You'd probably be able to run regular in the car with them.

I'd guess low 8 to 1. They're advertised at 7.8 on a late model with the bevel edged piston. You don't have the bevel edged piston, so bump it up a couple tenths.

[A390GT]

So I can run a 2820 camshaft or is there something else I should run?

[Sirrotica]

Some good discussion on this thread:

https://www.speed-talk.com/forum/viewtopic.php?t=27723

The 068 cam would work, but with highway gears in a big car you might want to drop back a notch to the 067, which was just a 4bbl cam for about any Pontiac with stock gears and convertor. Putting too much cam in a daily driver kills the mileage, plus if you never get into the RPM range that gives the cam an advantage over stock, your wasting money for something that will be disappointing at low RPM where you spend most of your time while driving.

[A390GT]

The Catalina has an 068 cam in it now so swapping the heads on to that yc engine isn’t a good option.. I’ll stick with putting the ye engine together with a 067 cam.
Is there a part number?
I see 2800-2802 at summit
Can’t seem to find the comp cam 268
They were talking about

[Sirrotica]

Originally Posted by A390GT

The Catalina has an 068 cam in it now so swapping the heads on to that yc engine isn’t a good option.. I’ll stick with putting the ye engine together with a 067 cam.
Is there a part number?
I see 2800-2802 at summit
Can’t seem to find the comp cam 268
They were talking about

9779067 is the GM part number, you can cross reference it to an aftermarket copy. It's the Pontiac 4 bbl cam used for many years in stock 4 bbl engines.

The comp cams number is HE268. HE is high energy, 268 denotes the the advertised duration. I've used it in quite a few performance street builds with lower compression heads. It has about .045 thousandths lift more than the factory cams, but still works with stock style valve springs.

It was conceived in the late 70s to be compatible with low compression V8s. It does run out of breath at like 5200 RPM, which only you know if your build will get beyond that. It also has some cam advance ground into the cam to pickup low RPM torque.

I know quite a few members here have used the Summit series of cams, I can't comment because I've never used any of their cams. Someone else will probably chime in with their results.