Rebuilt a 396 with a new camshaft and lifters. Had a noise, could not identify it, drove about 2,000 miles and I imagined it was getting louder. Multiple people diagnosed it as a lifter. I replaced the lifters, the noise persisted. I drove it about 200 miles on the new lifters. Then tore engine down, found a wrist pin was the culprit. The local NAPA machine shop recommended a .030 overbore and new pistons.

I know swapping lifters is not acceptable. I identified the lifters when I removed them. Did I do damage to the camshaft in the two hundred miles with the new lifters?

Thank you for your opinion or voicing your experience.

 

You didn't say however based upon your question I assume you have a flat tappet camshaft. One camshaft that saw two different sets of lifters is not something I would try again after the engine is built again. My advice go hyd. roller and forget ever having cam break in issues and the ability to choose from a multitude of cam profiles. Also they are not zinc oil particular like flat tappet cams are.

A few on here are cheap and can't see the forest through the trees on this and still go down the flat tappet cam route. For how much money we spend on these cars another 600 dollars is not a big deal. In all the engines I have built I have only used 1 flat tappet cam in 20 years.

As you can see as you are spending money an overbore and new pistons, balancing. I take it the wrist pin scared the engine bore as they say an overbore is required.

 

Hydraulic lifters. There was no damage to the bore, it was stock bore and about 118,000 miles. The side clearance of new rings in the used original pistons was out of specs. Is machine work required to convert to hydraulic roller cam? I suppose there are kits available for the conversion.

 

If you are running a stock cam with stock valve springs the standard flat tappet hydraulic lifters have worked for years.
If running a high lift than stock or a performance cam the switch to a roller is almost mandatory.
Even with a stock profile roller cam, smooth idle engine, a roller set up is proven to give more power and torque than a similar flat tappet cam, other than the initial cost the rollers are a great upgrade for these engines, no argument there.

Any time you switch flat tappet lifters they must be broken in to the camshaft. On Start up this means a 20 minute run in at 1,500-2,500 RPM, immediately on start up this must be done. This encourages the lifters to spin and mate to the camshaft. After this break in they are good for life of the engine. If your lifters were broken in already and you mark them and put them in the exact location they came out of using the exact camshaft that came out they don't need another break in but it is always a good idea. After sitting for a rebuild it may take encouragement on start up to get the lifters spinning again.
If they don't spin the cam will go flat and the lifter foot will cup out. All that metal will now be in your newly rebuilt engine where it can cause more damage.
With all this said I have had to replace cams on Roller Engines also, factory GM roller lifters where the factory roller wheel failed (at 100K miles). I also saw a big block Chevy where the aftermarket tie bar lifter type roller set up failed and allowed the lifter to turn destroying the camshaft. Much less common than flat tappet failure for sure but it happens.

 

It is a stock 10.5 CR, 396, 360 HP. Powerglide transmission with 3.31 rear end gears.

 

its possible if over tightened adjustment on old lifters or did not pre pump up new lifters in can of oil before installing. Then adjusted rockers by book. General motors published 1.5 turns from no slack. Thats way to much. Once lifters begin to hydralic they would hold valves open an possibly hit piston causing damage to lifters pushrods rocker studs valves wrist pins rod bearings. Adjust them to no slack turning engine over by hand multiple times. With valve covers off start engine an loosen each one at a time. till just barely pings then tighten very slowly till no ping. Then slowly tighten another 1/2 to 3/4 turn. Engine may lope a bit if lope lasts more then 30 seconds loosen back up an 1/8 turn to 1/4 turn. Simple common since old school mechanics chevy guys been doin in back yard an race track for 60 plus years.

 

To answer the basic question...no...you didn't hurt anything with the new lifters. Just look at the cam and lifters closely just as you would with any rebuild.

To the hyd roller idea....it's always a good idea. Good for power and reliability. Just dpends on what your plans for the car are.


JIM

 

If this assembly has 118,000 miles on it, I'd do a complete rebuild/replace before is went back in the car.

No sense messing with a camshaft that has that many miles on it either.

 

If the new lifters you installed were going to cause a problem it would have shown up in 200 miles. You should be good to go. Hydraulic rollers fail as well. If you don't have an Everwear gear installed for the distributor drive the you run into incompatibility of your distributor gear and the cam. You can have issues with the fuel pump push rod also.

 

I don't understand why the shop wants to overbore your engine, unless they have some extra pistons they need to sell??

 

I agree with pop23235, I would stick in a new set of rings and be done with it.

 

I would say that a 10 thousands over set of rings and a hone of block would suffice...but if the machine shop wants to feel happy about thier work they will want to bore to 30 over and use new pistons and rings. No body here can see what edge has formed at the top of the cylinder...and they may very well have worn oval...the machine shop just has to take a few measurements inside the walls to see what needs to be done.

 

Cam and lifters are relatively cheap...if you are going to tear it down, I'd replace them too.

 

The only way to find out if your cylinders need boring is to know what the taper and out of round is in each cylinder.

If the cylinders are within spec just replace the rings with a set of 10-ups and file them to proper clearance, that is if all the pistons are OK.

Bill

 

I think the idea was if the engine lost oil pressure on any of the hydraulic lifters, they would callapse, valves would not open, and cause less damage....but i agree, and seen it myself in the manuals, 1 and a half turns??? That seems excessive...yes the valve spring is suppose to overcome hydraulic pressure, but ive always done them by ear as well....never had a problem...i was told by an old engine builder that the hydraulic part of lifter is suppose to settle into the 1.5 turns of pressure applied...seems kind of like over tightening lug nuts to me...and ive ran motors with that i adjusted that way....seemed to run like it was missing while putting them to the 1.5 mark,but they did settle into it and smoothed out after a second or two.

Could be worste....could be running rockers like a ford had....no adjustments at all!!! When they tick...time for an oil change...

 

You have to remember the lifter 1.5 turns adjustment simply sets the pushrod into the lifter a bit more so the hydraulic lifter compensates for lobe wear and will take up any clearance without any additional maintenance. The 1/2 turn adjustment eliminates that and will prevent the lifter from pumping up at very high rpm if the valve action allows. It's something most of us will never experience and I would always use the GM spec. The engine stumble while adjusting is simply the valve held off it's seat until the oil inside the lifter allows the pushrod to seat.