Technical Update on the 241 from hell

Had two leaking freeze plugs. Ordered the expansion type from Hot Hemi Heads. Were a challenge but successfully installed. Filled up coolant system and ran it for about 5 minutes. Then tap tap tap. Stuck #8 exhaust valve. Has anyone else had these issues? I had stuck the #7 exhaust valve some months ago. Getting pretty tired of the setbacks

 

I’m sorry you’re having these problems,,,,but it’s not the engine .
Hemi’s are an excellent engine,,,,,,very well designed .
It usually goes back to the machinist,,,,,,not all of them are very well designed,,,,,LoL .
Some are determined to make things with Zero tolerance,,,,,and in the real world,,,,,engines just won’t run that way .

Tommy

 

Tommy. You are so right. When my builder did my 241 he accepted the finished heads from someone else. Went through them and bolted them on. He takes full responsibility for the entire build and will redo this one as the last, for free. Just sucks I gotta keep yarding the parts off! It’ll get there. Just another set back. Just time I keep telling myself. But good lord cut me some slack. Ha ha

 

Is the gas old?
That will stick valves in a hurry.

 

As this the second stuck exhaust valve, I’m inclined to thinking varnish from old fuel wheather from the tank or lines/ carb

 

I would drain the tank and have it steamed, dry and re- filled with premium, any varnish in the lines or carb should work its way thru with little effect ,if that’s the problem, if not at least you know that’s not the problem

 

Maybe ... just maybe . . .

When the heads were rebuilt, new valve guides were installed. Maybe they weren't reamed for the proper clearance. Or maybe the intake and exhaust guides were both reamed to the same size. I could see the exhaust valves calling for just a bit more clearance.

 

Badshifter no the gas is fresh. It’s been running just fine

 

I'm with @ClayMart on this one. I've seen the mess tight valve stem guides cause. I know some machinists want to keep them on the tight side, to give a bit more room to 'wear in' but depending the guide type, they seize the valve when the engine warms up. Each guide material has its suggested clearances... You would think that after the second time it came back, they check each and every valve stem clearance and ream as necessary.

 

Fauj. I agree. My gut kept telling me to take both heads off but the builder said the unaffected one should be ok. Well now I get to tear it apart again

 

I had a Buick nailhead redone for me, by a machine shop with a pretty good reputation. Ran it less than 40 miles and a valve stuck. They wanted the engine back but I convinced them I should just send them the heads. When I took the heads off I took them apart to see for myself what was wrong. Aside from the valve guides being contaminated with grindings from the machine work, the valve guides were all too tight. It's really tough getting quality machine work in these parts, and I suppose it's like that all over in small town America.

 

...labour issues seem to be all too common these days...

 

I've dealt with stuck valves in engines due to rancid, varnishy fuel in several engines. Every time it's been only the intake valves that stick.

 

Did they put seals on the ex valves?

 

They certainly are. I just had a formerly reputable crankshaft shop over-cut the rod journals on a Hemi crank. They tried to blame it on me, as if I would chose a cut for which there is no bearing shell.

I am now down to only one single machine shop that I can trust. I guess everyone feels the same way, as he is now backlogged for months.

I have two engine builds that he has not even been able to take in yet.

 

George. I’m not familiar with the exhaust valve seals. Help me out brother

 

Center of the Galaxie. I’m thinking my guides are too tight. On the first head there were actually 2 exhaust valves that were gauled from the guides. Hoping for the same this time

 

Hemis don't use ex seals, reportedly can cause them to sieze from lack of lube. Oil tends not to flow up hill.

 

Look inside the valve spring. You should see the top of the valve guide.

Chrysler parts shown. Others similar.

 

Typically machined guides for PC like seals are on the intakes only. Anytime seals are used you should be able to see them by looking thru the spring slots. White, red and blue are colors I’ve seen and used.

 

sloppy valve work, seats not concentric with valve face because the guide bores are off can cause sticking valves.

 

Could there be an oiling problem resulting in insufficient oil delivered to the top of the heads?
Are the little oil holes in the rocker arm tips, that indirectly oil the valve stems, clear?

 

I would run some Marvel Mystery Oil in the gas for the first couple of tankfuls.It is good to lubricate that kind of stuff,it helps with old gas too,it seems like snake oil but it really works,i run it in everything i have that has carburator,lawn mowers,chainsaws,etc.I swear by the stuff. Harvey

 

Beanscoot. It oils like a dream. I’ve pressurized the oil system several times and first ran it with valve covers off. Oil flows!

 

37 caddy. You sound like my dad. Ha! That’s all he ever used in everything. When he died I found half a dozen unopened cans of it!! I’ll start using it as well

 

Good stuff - Honestly So.

 

If it is flowing oil well to the heads, I doubt that this is an oiling issue.

If there are no valve seals on the exhaust valves, I suspect that the guides were replaced, and not reamed to size, or not to the proper size.

If the valve seats were cut out of concentricity by with the guide, it should have been evident during valve lapping.

 

I don't want to 2nd guess what was or wasn't done. I spend a lot of time in a machine shop that has good equipment. If you go into a shop and all they have is a stone seat grinder, you will be limited of how good the work can be. I'm around Serdi's and Newans and the Epoch which was the latest and greatest. Their accuracy and speed are second to none. If your machinest deals with ten thousandths, he is doing the best he can do. If he talks thousandths, that's the old way of doing things. In regard to the OP's engine, if the machine shop has little exp. with a hemi and is unaware how exhaust flow affects guide clearance, you can be the victim of good intentions and poor results. I think few machine shops attempt to do poor work. They have mass engine rebuilders' to set a standard to live above. If for some reason, there was no lube put on the valve stems, it would lead to this problem as most know. Unless you have equipment to measure everything that gets done to your engine, you will have to find a way to double check as best as you can. The fact that the builder has you bring it back is a positive note to me. The parts available now are not as good as many we used to use. However, that's all there is. Best wishes with your engine. I had one of those in a 27 T roadster. It was an original engine with few miles. I was surprised to see that it had a dual point distributor from the factory.

 

A precise valve job should include first reaming and then honing to size with a Sunnen hone or equivalent.

 

Look for holes in the exhaust guides top side at the bottom of the guide. This allows oil to the guide. When the head is on the engine oil would have to run uphill because the retainer end of the valve is lower than the head end. No valve seals. Have the guides been replaced if so do the exaust guides have the oil holes and located right.