Flat Head Valve Clearances

[Dick Kemper]

I recently had my Rockne model 75 6 cyl engine re-built with new rings and bearings. Also new exhaust seats and valve re-grind. The engine runs great but there is a lot of valve clatter.

The manuals state that you should not lower the valve clearances to quiet the lifters but I have to say the motor was a lot quieter (although there wer other problems including low oil pressure and smoking) before the re-build.

My re-builder stated that the valves were adjusted much closer than the spec requirements when he opened it up. He insists that the specifications should be adheered to and that the settings should not be altered to quiet the clatter.

Since the engine was quieter before the re-build and ran well, would I be in trouble if I tightened up om the cold .007 Exh and .004 Int settings.

If any of the readers of this post have experience with valve clatter and spacings I would be grateful for yopur thoughts,

Thanks, Dick

[hwellens]

The specs for a 1932 Model 65 (Don't have the 75 specs and may be a different engine) are for engine cold - Inlet .004 and Exhaust .007

[Ivan Saxton]

My National Service Manual says Hot settings are 4 thou inlet and 6 thou exhaust.

It also indicates an initial setting cold of 10 thou for inlets, no figure for exhausts.

Four and six thou are about the minimum for anything. If the end of the stems and the tappets are not worn, you might be able to do the adjustment hot at slow idle.

[Rusty_OToole]

Did you check the camshaft? You may need a new cam and lifters to complete the rebuild.

If new parts are not available the old ones can be reground.

[Guest Backyardmechanic]

Hello,

Sound like the valves were set on the exhaust stroke.WE always set the valves when the cam lobs are in nuture(Other words when both lobs are half way thu the travel.Then we go thu the the fireing order we check these 2-3 times to ensure that every thing is right.On a rebuilt we will set them a few thousands more until the engine is started and warm up then we set them to the hot setting.

Vern.

[Guest DeSoto Frank]

DO NOT set the valves closer than factory recommendation.

Just because your engine "ran quieter" before it was torn-down, doesn't mean the valves had sufficient tappet clearance.

Better to err on the side of some valve " clatter" than to burn valves... a valve-job on a L-head engine these days is a pain, as most shops no longer have the tools to grind the valves with the engine installed in the vehicle.

Studebaker was one of the few companies that spec'd their tappet clearances on a cold engine; tappet clearance usually decreases slightly as the engine warms-up and the tappet plungers & valve stems expand along their long axis.

On a freshly re-built engine, tappet clearances will tend to decrease during break-in as the parts "wear-in".

Most old-time mechanics set the tappets "loose" on a fresh engine, and re-adjust after 500 - 1000 miles.

For the last 40-50 years, hydraulic lifters have been pretty-much standard on the majority of consumer vehicles; therefore we are no longer accustomed to valve-train noises...

Let your Rockne "rattle" for a little while rather than burn-up a fresh valve grind.

Studebaker had an excellent engineering division by the 1920's & '30s; follow their guidlines.

[Rusty_OToole]

I bet it was silent when new and would be silent now if the cam and lifters were in good shape.

Those old flatheads were very quiet and the valve action practically noisless. If you could hear the valves, no one would have bought the car.

[DavidAU]

I agree with Rusty

David

[Guest DeSoto Frank]

Gentlemen,

I will concede that L-head enginges usually have very quiet valves, but to revisit the OP's original question, it is never acceptable to reduce tappet clearance in an effort to reduce valve noise.

Doing so is just asking for burned valves.

OP mentioned the engine was "re-built with new rings and bearings. Also new exhaust seats and valve re-grind. The engine runs great but there is a lot of valve clatter.

The manuals state that you should not lower the valve clearances to quiet the lifters but I have to say the motor was a lot quieter (although there wer other problems including low oil pressure and smoking) before the re-build.

My re-builder stated that the valves were adjusted much closer than the spec requirements when he opened it up. He insists that the specifications should be adheered to and that the settings should not be altered to quiet the clatter. "

Nothing is mentioned about having the cam re-ground, or tappets re-faced; we don't know if this was an "overhaul", ie: "re-ring & valve grind" ( common Depression-era repair), or a full-blown rebuild / re-bore, etc.

When future Chrysler engineers Carl Breer and Fred Zeder went to work for Studebaker in the mid-Teens, their first task was working a bunch of kinks out of the Studebaker "Big Six" . Among the issues were valve-train noise - this was reduced by changing the cam profile so that the valves did not "slam" against their seats.

Also OP's term "clatter" is not highly specific... does he mean it sounds like a Slant-Six with 200,000 miles on it? Or just that the valves are noticeably audible now ?

Edited November 26, 2009 by DeSoto Frank (see edit history)

[Rusty_OToole]

He does tell us what was done. Rings, valves, and bearings. Cylinders were not trued, no new pistons, and no cam or lifters.

In other words a standard depression era overhaul, a little more than a ring and valve job but not a rebuild.

Your slant six comparison was very apt. I have owned many slant six cars and trucks. One was a real eye opener. It was a farmer's pickup truck with 160,000 miles on it and the engine was as quiet as a new car with hydraulic lifters.

The truck had led a hard life but was always maintained by the book including regular valve adjustments. The lifters and rocker arms never got pounded and they were as quiet as new after 160,000 miles.

I had others with much less miles that always had a little valve noise no matter how carefully I adjusted them. I assumed it naturally came with miles and wear. Not true. If valves are kept adjusted they don't get pounded. But once the rocker arms cam and lifters get worn and pounded they will never be completely quiet again.

Unless you have the cam and lifters reground. This costs around $200 for a flathead 6. In the case of the Rockne I doubt anyone has the original cam profile but they have profiles for other flathead engines that will work.

You may even be able to find NOS cam and lifters. You never know your luck.

Edited November 26, 2009 by Rusty_OToole (see edit history)

[Rusty_OToole]

You mention redesigning the cam profile to reduce valve noise. This is called clearance ramps. A solid lifter cam must be designed to take up the clearance slowly before opening the valve.

Some old time flathead racing cams dispensed with this nicety. They made more power but they made more noise too.

Hydraulic lifter cams don't have clearance ramps either, they don't need them with no valve clearance.

[Dick Kemper]

Thanks for all of the comments, I have learned a lot.

Think I'll live with the noise for now and be on the lookout for a cam and lifters.

Dick

[Seldenguy]

Dick--- I don't think you will need a replacment, as the one you find will no doubt be in the same condition as your's. Check with your engine man he probably will recomend sending it to a cam grinder to resurface the lobes to factory specifications and reface the lifters. The few thousands of an inch that are removed can be compensated for in the tappet adjustment. ---Bob