SBC parts in a Pontiac?

[Poison Heart]

When my motor guy first called me and told me it was ready he told me he had to use SBC roller rockers because the Pontiac rockers were "higher than he wanted." I mentioned this to a friend and he's worried about it. For whatever reason my builder wanted a certain height for the rockers and to get that height he had to use Chevy because the Pontiac ones he bought were too tall. It kind of worries me but I think he knows what he is doing and for whatever reason had to have that desired hieght. Anyone else share the same concerns? Keep in mind this is on a '59 389 and performance parts are not readily available.

[Mr. HARDCORE]

height for what? the valve covers?

[BigBadChris]

....

[65Catalina421]

Although I may be way off course here, it sounds to me here like you're dealing with a typical 'SBC' engine builder that thinks every engine should be built like a Chevy. I'm lucky that I have a couple of local guys that were line mechanics at the local Pontiac dealership back in the late 60's and 70's. They are very knowledgeable on the differences between Pontiac and other engines and what makes them run better.

That being said, he may very well have a valid reason for doing what he did, but I have just heard crap like that way to often.

[Poison Heart]

I don't know exactly why he wanted it a certain height. But he said the Pontiac ones were too high. If the Pontiac rockers worked then I don't see why he would try to make chevy ones work. I hope this thing runs as well as he says it will. It only took him 6 months when he said it would take him a month.

[The Chief]

It doesnt matter if its a 287,389,400 or 455 all the parts are the same. My 287 has 400/455 rockers so far the only thing i have found to be different is the oilpump and thats only on the fixing hole centres everything else was the same. My cam is a pontiac cam my roller rockers are comp and advertised to fit 55-63. The only thing i had to do to my heads was to remove the press studs for the rockers and have the holes machined for screw in studs. I have had to have a couple of custom pieces made but that was the pistons and pushrods.

[CoolBlueSS]

I do believe that SBC and Pontiac rockers are different. They may be the same ratio, but I believe the fulcrum point, or something is different. Doesn't make sense to me why he would do that.

[Mr. HARDCORE]

I think I'd be getting some detail as to why he's using Chevy rockers on a Pontiac engine. The only reason I can think of is the fact that Chevy rockers are cheaper, and he may have had some lying around the shop.

[Poison Heart]

You might be right Mike. This crap is the reason I want to learn how to do everything myself. When I get it running we'll see if I'm still complaining. You never know what you're gunna get.

Any guesses on how many horses this should be at the crank? ASSUMING his SBC parts work.

[sprint250]

"Too tall" for what?
What brand/type of roller rocker arms are we talking about here?
True roller or ball pivot with a roller tip?
You need to know " exactly what changed" in the build process to require the use of the Chevy rocker arms.
Did the rocker arm studs get changed to the fully adjustable non "bottle neck"type?
If you are converting to a fully adjustable valvetrain the stock Pontiac "bottle neck" rocker studs will not work correctly with the roller rockers.
The replacement studs for fully adjustable valve train will be the same diameter all the way up.
The reason for the stock bottle neck stud on the engines with hydraulic lifters is the way the stock Pontiac valve train adjusts.The pivot balls are machined to mate to the taper of the bottle neck stud.
On a stock engine with bottle neck rocker studs the rocker arm nut is merely tightened down until the ball mates with the taper on the stud? You tourqe the nut to the factory value and in a perfect world your'e done.Lash is set.

"Too Tall" could be the result of trying to fit a rocker arm intended for a true 3/8" stud diameter stud onto a bottle neck stud ?

Stock Pontiac engines with factory screw in studs are the same way.

If the valve covers were the only problem and taller covers would not pose any interference issues use the taller covers.
After you get your engine shop's/machinist/assembler's detailed explanation give Ken "Pontiac Dude" Keefer a call to verify if there is any good/ valid reasoning for doing this and if it in fact will work.May be Ken himself has encountered situations where this was the only way out to solve a problem.
He is very familiar with the differences between SBC and Pontiac valvetrain parts.



The part #'s from brand to brand even on stamped steel stuff are almost always always different.
If it was a common interchangeable part most manufacturer's would/should list it the same for Chev or BOP.

Get a second opinion for sure.

[Poison Heart]

I'll stop by his shop after school sometime next week.

Sprint, again, you know way more than I do. I cannot answer those questions. I do know tha he put in screw in studs. The roller rockers should be made by Crane.

So should I just tell him that some of my friends are worried about the chevy parts in a pontiac motor and ask exactly what he means when he says its "too tall?"

[sprint250]

Just have him explain it to your satisfaction.
If the part your machinist substituted has the same geometry as the Pontiac rocker arm nothing is wrong.Everything will work fine.
If he has converted to screw in studs it sounds like he knows what is going on.
You just want to fully understand the reason behind the substitution for the simple reason should you ever decide to change anything on the engine later on you will be getting the right things for it.

What year is the block and heads you are using? Just curious.

[Poison Heart]

The block is the original tri power motor from my '59 Star Chief. The heads are off of a '59 Catalina. I do believe this guy knows what he's doing but I also believe that it's possible that he made SBC rockers work. The good thing is that this guy works by himself. So if it doesn't work then there's no one to blame it on but himself. He said he also had to change the way the motor oils the heads. Correct me if I'm wrong but I have heard of this problem before with older blocks and newer heads.

[The Chief]

yeah the later motors oiled through the pushrods, i have done the same mod. I still dont see any reason to use cheby rockers though

[sprint250]

Exactamundo.

The older heads have an oil passage in them that feeds oil up through the rocker arm stud to the pivot ball.
Small passages in the studs were prone to clogging up with sludge on high mileage engines causing a lack of oil to the rocker arm pivots.When these old heads would get reconditioned very seldom if ever did the studs get pulled and the oil passages poroperly cleaned.
Converting to 100% pushrod fed oil supply to the rockers is the way to go.
If you convert to late model heads the conversion is mandatory.

[The Chief]

you need to check that the cam bearings were rotated to block the old oiling system ort thats what i was advised to do

[Poison Heart]

He did say he had to plug something in the block when he changed the oiling.