1975 350 small block issue

[Ross F.]

hello!
I just picked up my rebuilt 1975 small block 350 from Victor at Knights auto in Union Lake.
it looks great. I had some improvements made during the rebuild. 383 rotating assembly, roller cam, roller rockers, etc.
I thought these changes would be unnoticeable on the outside. But, I was wrong.
The 383 upgrade necessitated a new harmonic balancer, not too big an issue. The problem is the valve covers. Victor, being a friend, put on a new set, explaining that mine looked crappy. Well, I wanted the originals. So I cleaned the old ones up. But when I went to put them on, the anti splash fixture will not fit between the roller rockers.
Has anyone run into this problem?
Can I cut down the Splash fixtures without issues?

[Michael W.]

Re: 1975 350 small block issue

Has anyone run into this problem?

Many have when they start adding zoomy race stuff. Ditch the roller rockers.

[Joe L.]

Re: 1975 350 small block issue

hello!
I just picked up my rebuilt 1975 small block 350 from Victor at Knights auto in Union Lake.
it looks great. I had some improvements made during the rebuild. 383 rotating assembly, roller cam, roller rockers, etc.
I thought these changes would be unnoticeable on the outside. But, I was wrong.
The 383 upgrade necessitated a new harmonic balancer, not too big an issue. The problem is the valve covers. Victor, being a friend, put on a new set, explaining that mine looked crappy. Well, I wanted the originals. So I cleaned the old ones up. But when I went to put them on, the anti splash fixture will not fit between the roller rockers.
Has anyone run into this problem?
Can I cut down the Splash fixtures without issues?

Ross------

I don't know what you're referring to by "anti splash fixture". If you're referring to the cast-in drippers found on original C3 aluminum valve covers, they can be removed with no significant detriment.

However, if you are talking about the OIL BAFFLE (i.e. the rectangular box-like assembly under the PCV orifice), that cannot be removed without seriously affecting oil consumption control.

[Jeff P.]

Re: 1975 350 small block issue

Ross sounds like the baffle is to wide. Or is it just sitting to tall in the valve cover? Sometimes you can add 2 gaskets to clear the height problem. you can alter the thickness of this baffle and should be fine.

hello!
I just picked up my rebuilt 1975 small block 350 from Victor at Knights auto in Union Lake.
it looks great. I had some improvements made during the rebuild. 383 rotating assembly, roller cam, roller rockers, etc.
I thought these changes would be unnoticeable on the outside. But, I was wrong.
The 383 upgrade necessitated a new harmonic balancer, not too big an issue. The problem is the valve covers. Victor, being a friend, put on a new set, explaining that mine looked crappy. Well, I wanted the originals. So I cleaned the old ones up. But when I went to put them on, the anti splash fixture will not fit between the roller rockers.
Has anyone run into this problem?
Can I cut down the Splash fixtures without issues?

[Ross F.]

Re: 1975 350 small block issue

Thanks for the feedback. I need to so what is actually causing the interference, height or width.
I will return with photos

[Duke W.]

Re: 1975 350 small block issue

"Roller rockers" - the kind with a roller tip are nothing but a scam. Modern small blocks have roller trunnion rockers with a conventional tip. On either vintage or modern Chevy engines the tip is curved so it "rolls" across the valve stem tip. There is no sliding motion, so a "roller" does nothing but add mass and a potential failure mode when the roller shaft breaks, and this does happen.

The best solution to your problem is to install your original rockers if you still have them, or just buy a new Sealed Power set.

Duke

[William B.]

Re: 1975 350 small block issue

Ross....Interesting post as I have just purchased a '75 L48 with beautiful paint and was thinking about a engine upgrade. Is there more then changing the camshaft to make it a L82? Are the heads different? Maybe a crate engine? I'm sure you weighed all the options as I'm doing now.Thanks, Bill

[Joe L.]

Re: 1975 350 small block issue

Ross....Interesting post as I have just purchased a '75 L48 with beautiful paint and was thinking about a engine upgrade. Is there more then changing the camshaft to make it a L82? Are the heads different? Maybe a crate engine? I'm sure you weighed all the options as I'm doing now.Thanks, Bill

Bill------


There are many differences between L-48 and L-82. Among them are:

pistons

cylinder heads

connecting rods

crankshaft (forged versus cast)

harmonic balancer

block (4 bolt mains versus 2 bolt)

[Joe C.]

Re: 1975 350 small block issue

hello!
I just picked up my rebuilt 1975 small block 350 from Victor at Knights auto in Union Lake.
it looks great. I had some improvements made during the rebuild. 383 rotating assembly, roller cam, roller rockers, etc.
I thought these changes would be unnoticeable on the outside. But, I was wrong.
The 383 upgrade necessitated a new harmonic balancer, not too big an issue. The problem is the valve covers. Victor, being a friend, put on a new set, explaining that mine looked crappy. Well, I wanted the originals. So I cleaned the old ones up. But when I went to put them on, the anti splash fixture will not fit between the roller rockers.
Has anyone run into this problem?
Can I cut down the Splash fixtures without issues?

What kind of roller cam did you install, and what valve springs did you use?
You should have roller trunnion rockers with that setup. If you do, then you should use a double gasket under the covers. If that isn't enough, then you can install a 1/2" spacer under the covers, which is very well disguised.
Removing the baffle under the PCV valve is not an option. You might be able to modify it, depending on how much interference there is.

[Robert R.]

Re: 1975 350 small block issue

Oh Joe,
that sounds like too much work.
just put on a set of finned aluminum valve covers and call it a day.

[Joe L.]

Re: 1975 350 small block issue

"Roller rockers" - the kind with a roller tip are nothing but a scam. Modern small blocks have roller trunnion rockers with a conventional tip. On either vintage or modern Chevy engines the tip is curved so it "rolls" across the valve stem tip. There is no sliding motion, so a "roller" does nothing but add mass and a potential failure mode when the roller shaft breaks, and this does happen.

The best solution to your problem is to install your original rockers if you still have them, or just buy a new Sealed Power set.

Duke

Duke------


As far as Gen I and II small blocks go, I do not know of a rocker arm with roller trunnions which does not also have roller tips. Even the roller rockers which GM used in PRODUCTION on Gen II LT4 engines had roller tips. So, if one wants the benefit of roller trunnions, one has to abide by the roller tips.

[Duke W.]

Re: 1975 350 small block issue

Those earlier generation small blocks that had roller tip rocker arms used aftermarket parts because they were low volume, and as I recall the LT4s were recalled due to failure of the Crane-supplied roller tip rockers.

All of the LS engines have roller trunnion rocker arms, but none that I am aware of by reading PowerPoint presentations on the Web by GM Powertrain have roller tips, including the current LT1.

All roller tips do is add mass and another moving part that represents another potential failure point. They do absolutely nothing to reduce internal engine friction or improve valve train durability. They have absolutely no positive benefits, which is why OEM designs don't have roller tips.

They are purely an aftermarket gambit to get more of your money. From and engine system engineering standpoint they are abolutely, totally worthless!

OE rocker arm tips, both vintage socket and ball, and current roller trunion type have rounded tips with a radius the same as the distance from the rocker fulcrum to the tip. If rocker geometry is in the correct range, i.e. the head and block have not been excessively machined with a thin gasket, then the when the valve is about half open the contact point should be at the center of the valve stem, and this contact point effectively "rolls" back and forth centered on the tip, so there is no sliding motion.

This geometry should always be checked on a racing engine that has a very high lift cam and lots of head and block machining if it has to last, such as a road or circle track racing engine. Longer pushrods are available, and custom length pushrods can be ordered to get the rocker geometry back into the correct range if it is off.

On road engines with OE cams that haven't had a lot of machining in the field, it's rare that the rocker geometry is off enough to cause any problems.

Whenever an engine is rebuilt the valve stem tips and rocker arm tips should be carefully inspected for wear. If rocker geometry is in the proper range there is usually no evidence of wear, but if there is, it should be corrected with suitable length pushrods when the engine is reassembled.

Duke

[John H.]

Re: 1975 350 small block issue

All roller tips do is add mass and another moving part that represents another potential failure point. They do absolutely nothing to reduce internal engine friction or improve valve train durability. They have absolutely no positive benefits, which is why OEM designs don't have roller tips.

They are purely an aftermarket gambit to get more of your money. From and engine system engineering standpoint they are abolutely, totally worthless!

OE rocker arm tips, both vintage socket and ball, and current roller trunion type have rounded tips with a radius the same as the distance from the rocker fulcrum to the tip. If rocker geometry is in the correct range, i.e. the head and block have not been excessively machined with a thin gasket, then the when the valve is about half open the contact point should be at the center of the valve stem, and this contact point effectively "rolls" back and forth centered on the tip, so there is no sliding motion.

Duke -

We came to the same conclusion when we developed the second-generation Viper V-10 in 1995 - roller trunnions only, plain tips; between that and the Mahle-developed "beehive" single valve springs and Rhoads roller lifters to get us through the city portion of the emission test cycle, it became a bulletproof valvetrain, and continues today, 19 years later, with the addition of the "cam-in-cam" variable valve timing system.


ValveGear800.JPG

[Joe L.]

Re: 1975 350 small block issue

Those earlier generation small blocks that had roller tip rocker arms used aftermarket parts because they were low volume, and as I recall the LT4s were recalled due to failure of the Crane-supplied roller tip rockers.

All of the LS engines have roller trunnion rocker arms, but none that I am aware of by reading PowerPoint presentations on the Web by GM Powertrain have roller tips, including the current LT1.

All roller tips do is add mass and another moving part that represents another potential failure point. They do absolutely nothing to reduce internal engine friction or improve valve train durability. They have absolutely no positive benefits, which is why OEM designs don't have roller tips.

They are purely an aftermarket gambit to get more of your money. From and engine system engineering standpoint they are abolutely, totally worthless!

OE rocker arm tips, both vintage socket and ball, and current roller trunion type have rounded tips with a radius the same as the distance from the rocker fulcrum to the tip. If rocker geometry is in the correct range, i.e. the head and block have not been excessively machined with a thin gasket, then the when the valve is about half open the contact point should be at the center of the valve stem, and this contact point effectively "rolls" back and forth centered on the tip, so there is no sliding motion.

This geometry should always be checked on a racing engine that has a very high lift cam and lots of head and block machining if it has to last, such as a road or circle track racing engine. Longer pushrods are available, and custom length pushrods can be ordered to get the rocker geometry back into the correct range if it is off.

On road engines with OE cams that haven't had a lot of machining in the field, it's rare that the rocker geometry is off enough to cause any problems.

Whenever an engine is rebuilt the valve stem tips and rocker arm tips should be carefully inspected for wear. If rocker geometry is in the proper range there is usually no evidence of wear, but if there is, it should be corrected with suitable length pushrods when the engine is reassembled.

Duke

Duke-----


I'm not saying that roller tips are of any significant or, even, any value. However, what I'm saying is that if you want to use a set of rockers with roller trunnions on a Gen I or II small block (or, even, any Mark IV big block, for that matter), the only variety available from any manufacturer I know of are also equipped with roller tips.

Also, the failure and recall of LT4 rockers involved the roller trunnion, not the roller tips.

[Ross F.]

Re: 1975 350 small block issue

Wow,
Great responses. I know I have become a heretic. But i'm not throwing my new roller rockers away. I put in a roller cam. Very mild upgrade. The rockers are roller trunnion. It is the trunnions that are too wide causing interference with the valve cover.
Two gaskets won't give me enough clearance. See photos. Rockers, oem cover, tall cover.
Where do you find this 1/2" spacer?