Replace additional engine parts?

[Larry M.]

My '72 LT-1 has an L-82 cam installed. If I switch back to the original cam and solid lifters, should I replace the pushrods, as they may have formed a fit with the top surface of the hydraulic lifter, and therefore not be compatible with the new lifters, and cause premature wear?

And carrying that thought forward. would new pushrods require new rocker arms for fit compatibility at the top end; and would new rockers require new valves for fit issues there.

The engine parts were new GM when installed, and have 17,000 miles on them.

It seems to me as if changing the rockers and valves would probably be excessive, but that the pushrods might be a different story, so I wanted to gather some opinions more educated than mine.

Thanks in advance!

Larry

[Timothy B.]

Re: Replace additional engine parts?

Larry,

I don't think you will have any problem reusing the pushrods and new lifters.

Unless the pushrods are bent from over rev or the pushrod length is not correct because of having the block deck and heads excessively milled causing bad rocker arm geometry you will be fine using stock parts.

[Duke W.]

Re: Replace additional engine parts?

Generally there is no need to replace anything else on a cam and lifter change, but give the pushrods and rockers a close inspection with a magnifying glass and look for any ridges or erosion on the wear surfaces, and make sure everthing goes back in the same postion and orientation. Good wear surfaces with have a burnished (polished) surface appearance with no ridges.

There is little relative movement between the pushrods and lifters, but wear can occur at the pushrod/rocker interface and the rocker tip that contacts the valve. Those are the areas that need closest inspection.

Mark the lifter location front to back on each bank, so they can be installed on the same lobe. Given the low mileage on the cam/lifters I doubt if there is any wear, and you can probably sell the setup to someone who needs a L-46/82 cam.

Duke

[Joe L.]

Re: Replace additional engine parts?

Generally there is no need to replace anything else on a cam and lifter change, but give the pushrods and rockers a close inspection with a magnifying glass and look for any ridges or erosion on the wear surfaces, and make sure everthing goes back in the same postion and orientation. Good wear surfaces with have a burnished (polished) surface appearance with no ridges.

There is little relative movement between the pushrods and lifters, but wear can occur at the pushrod/rocker interface and the rocker tip that contacts the valve. Those are the areas that need closest inspection.

Mark the lifter location front to back on each bank, so they can be installed on the same lobe. Given the low mileage on the cam/lifters I doubt if there is any wear, and you can probably sell the setup to someone who needs a L-46/82 cam.

Duke

Duke------



There will be no need for matching the lifters to the original lobes as he will be replacing both cam and lifters going from the L-82 hydraulic cam to the LT-1 mechanical lifter cam.

I think that with only 17,000 miles on the other related parts, there should be no problem re-using the pushrods and rocker arms. However, I agree that close inspection of the pushrod ends and, especially, the rocker arm contact surfaces is important. Any "grooving" requires replacement of the part.

[Larry M.]

Re: Replace additional engine parts?

Tim/Duke/Joe,

Thanks for your replies.

Joe - I believe Duke was referring to a possible sale of the used cam/lifters when he mentioned keeping the lifters matched to their original lobes.

Larry

[Joe L.]

Re: Replace additional engine parts?

Tim/Duke/Joe,

Thanks for your replies.

Joe - I believe Duke was referring to a possible sale of the used cam/lifters when he mentioned keeping the lifters matched to their original lobes.

Larry

Larry-------


I think you are correct.

[Duke W.]

Re: Replace additional engine parts?

Yes. Given the low mileage of this cam/lifter combination, I think it's worth about half the price of new parts, if:

1. The heel-to-toe dimension of all lobes as measured with a precision caliper is in the range of OE tolerance, and

2. The lifters were marked so that they can be installed on the same lobe in another engine.

This is a very good cam. I recommend it for all L-46/82 restorations and also for the L-79 installed four degrees advanced from the OE indexing.

Its torque/power curve characteristics are very similar to the LT-1 cam, all other things equal. It's biggest downside is that on a 327 with pocket ported head, it will reach valve lifter limiting speed - about 6500 - before the heads run out of flow. The LT-1 cam with the same valve springs will produce a useable power bandwidth to about 7200, which is where false valve motion shuts down the party.

The 20 gross HP difference between the '69 L-46 and '70 LT-1 was primarily the LT-1 inlet manifold, which was more biased toward top end power. The L-46 manifold was basically the same as the base 300 HP manifold and the Q-jet and Holley had about the same flow ratings, so either would produce about the same top end power with the same inlet manifold.

Duke