dsolomon

I am going over a 1970 350 that I purchased. It was rebuilt years ago and never ran. Upon receipt I found it had excessive valve train noise. I went to check lifter pre-load and I have none. Its my understanding that you put the lobes down with the lifter on the base of the cam, loosen the rocker bolts then tighten finger tight until the push rod has resistance. When the lifter is down the pushrod is loose. I measured them with my calipers and get an overall length of 8.250"

I understand that a stock pushrod is 8.400" long. Could a pushrod that is .150" shorther than stock be correct for what appears to be a mild performance rebuild? How do I determine the correct length when they wont tighten up for me to measure at the base of the rocker? Do I need to consider that the lifters have leaked down?

Warhead

Stock pushrod is 8.234", not 8.400"

Lifters probably never got oil in them, if it was never started.
Don't pull the pushrods yet.

Pull the distributor.
Prime the oiling system for 10 minutes with a reversible drill. Not a cordless unit, either.
This should be done to any long term stored engine, to ensure initial lubrication when restarted.

Jim

dsolomon

Thanks Warhead...

Ran the drill and rotated the engine every couple minutes until I had oil coming out of the pushrods onto the rocker arms so i assume that they are now primed. It improved the loose rods but there still appears to be zero preload. If what I have are stock length, wouldn't a thinner gasket, possible decking and valve work require a longer pushrod. If lifters are now primed and I am actually a zero, then I am back buying pusrods. Looks like Summit has a set that are 8.275" long and Mondelo has some that are 8.300". Am I on the right track?

Rickman48

Zeroing the block, milling the heads, or thinner head gasket ALL move everything closer to the cam, making the pushrods shorter!!
You sure that isn't a solid cam?? Or the wrong lifters??
If it was me, I'd be pulling the intake anyway, to make sure those lifters have some moly cam lube on them! If it goes flat, you've got to rebuild it again!!
And make sure you use the diesel oil for break-in! No Fram filters, either!
[see the threads on todays oil!!]

ETA - maybe someone put a THICKER head gasket on it to 'reduce the compression'!!
All the cam manufacturers have a 'pushrod checker' - an adjustable pushrod, and directions on how to use it!
Guessing doesn't work very well -

Warhead

SOOOO, are ALL the valves tight now?

With all the valve gear bolted on, it will only fill the lifter to that point, no higher. I would not change pushrods, until you are out of the "travel" range of the lifter.

Rickman alludes to several things that can not be ignored.
Degree of rebuild, and what were the modifications that were done.
Any information you have is needed to make a fair diagnosis. Most people use composition (thicker) gaskets due to cost-steel shims are far too expensive for normal rebuilds, anymore. JMO

Even diesel oils have the zinc removed now, you need to have a zinc additive in the oil, also.
Jim

dsolomon

I already have the intake removed. The lifters are hydraulic if that was the question. I would have no way to know if they are the wrong lifters for the cam. It is my intention to pull the cam to see if it has any numbers stamped on it. If I can't ID it I will probably be replacing it.

The lifters are tight now but there is no load on the spring. If the lifters will only fill to the loaded point, how then do you perform the analysis of proper rod length.

Good on the oil, I have been using Comp Cam cam break-in additive in my Chevelle each time I make an oil change. I plan to do the same with this motor.

dsolomon

Think I may have found part of my problem. Laid a straight edge across the top of the valve stems and found up to a .040 variation in height. I am going to pull the cam and look into a shop that can level them for me.

What is the correct height and where is it measured from?

Rickman48

When a valve or valve seat are ground, along with 'cleaning up ' the tip of the valve stem, you can get quite a variation, hence your .040 difference.
Most of these procedures will in fact bring the valve 'deeper' in the pocket, raising the valve in the head, requiring spring spacers to obtain proper valve spring pressure.
Deeper in the pocket should give you more pressure on the lifter, which it can take, but all the proceedures previously mentioned, [except thicker head gasket and facing the stem] should do the same!
Instead of guessing, if I were confident the cam and lifters were fine, I think I'd go with an adjustabe setup - fixes all, if the pushrods make the rocker arm center on the valve tip!
Personally, I'd pull the intake and check the cam and lifters, and go from there!

dsolomon

Agreed. I will pull the cam and inspect. Hoping to determine its make and specs anyway. Seems like an adjustable setup is going to be the best bet. By the time I pay a shop to even the valves and possible pushrods... it seems like a no brainer. Thank you!

Fonz

also, if they put in a Higher LIFT cam, because of the higher lift, the base circle had to be made smaller to get the cam in the block on an oldsmobile. smaller lobe circle makes a need for longet pushrods. stock olds are 8.234, smaller base circle runs around a 8.3" (on mine it was. depends on what else they did to the engine