TR2/3/3A Rebuilding a cylinder head

[sp53]

Rebuilding a cylinder head. I am working on a head that I bought off Craigslist many years ago and have had it under my work bench since. The guy was cool, and said he had the head checked for cracks at a shop and I think he said new valve guides. He only charged me 50.00 bucks.

I took some pictures to see if people thought the valve guides look new. Can I get some opinions of the conditions of the guides by these pictures or would a different angle of picture be better? I have never rebuilt a head before so any ideas are very welcome

Thanks steve

 

[TFB]

I would clean the guide bore , visually inspect and then check fit with a new or good valve.

tom

 

[CJD]

+1...you can't tell anything by just looking at the guides. Place a new valve in a clean guide and check for rock in the same plane as the rocker arm. Iron guides can be as little as .0025 rock...bronze guides (which yours are not), have to be closer to .005" rock. Of course, repeat with every guide to be sure. Also, I would emphasize "clean" guide, as it looks like the head was sand blasted, and every last spec of sand must be removed from the guides!

 

[bobhustead]

When I have a head to put together, it always goes to a machine shop for crack check, flatness check, guide assessment and valve grind.
Bob

 

[mctriumph]

My favorite trick is to install new guides then have them knurled to make up for stem wear.
It acts like an oil seal and greatly reduces oil consumption .Assuming the old valves are
in good kit of course.
Mad dog

 

[sp53]

I tried a couple of my old valves from different heads. The valves are a looser than .0025 which is 1/400 of an inch. My measuring skills stop at about 1/64 because I am old carpenter. I could probably deal with .025 which is a 1/40 of an inch. I wanted to do this work at home and thought perhaps if I get some new intake valves and guides I can feel the amount of play and then get a feel for it.

Looking at prices I should get some new 5/16 intake valves and see how the fit in the head. The exhaust valve guides in the head are the larger 3/8 and more money.

The last time I had a head rebuilt it was $$$$. The shop used 5/16 guides and valves for intake and exhaust. They also did away with the 3rd spring on the exhaust-- plus-- put in some seats which I still cannot still wrap my mind around. How can you put a new steal ring into cast iron?

Anyways, whoever cleaned the head from carbon did a poor job there are little piles of carbon everywhere. Can I take a ½ drill and wirer wheel and clean the area in the combustion chamber where the valves sit down in that bevel seat? I do not want to damage anything and do not know how aggressive I can be cleaning. Any ideas welcome and thanks guys.

Steve

 

[CJD]

.0025 is about enough that you can feel there is looseness, but you cannot hear any clicking as you wiggle. At .005" you start to hear the valve click as you wiggle it back and forth...not a scientific check, but a quick one to use at a swap meet for head condition. Installing seats amazes me too. In cast iron it is an easy machine shop job that rarely goes wrong. Because aluminum expands more than steel, installing steel seats in an aluminum head can cause serious trouble if the machine shop screws it up!

 

[mctriumph]

I know it is that knurling the new guides to account for the .0025 is not completely
Kosher , but when the engine burns less than a Qt every 1500miles because of this
acting as a seal, I am all in. Try it!
Seats only on the exhausts, as the run hotter. intakes dont need it.
Mad dog

 

[sp53]

It seems to me the difficult part with rebuilding a head is getting the valve guides in place. How would a DYI person do something like that? The rest of the rebuilding looks like work with grit gridding compounds on the edge of the seat and valve. I do not how long something like that should take, but the area looks small. They used to charge 35.00 bucks when I was a kid and it did not look like rocket science at least now it does not.

I do not know anything about valve knurling MD. I always like to hear about a plan MD. I can always pay to have it done by an expert, well if I have resources and can find an expert. Anyways I enjoy leaning about different ways to do stuff.

Steve

 

[CJD]

Knurling was a way to displace the metal inside the guide to extend the life of a worn valve guide. You insert a tool that rolls around the inside of the guide, making metal burr edges that stick up. Then, you come back with a hone and bring the edges back down to the desired clearance. Since there is less material actually touching the valve stem, a knurled guide will wear faster than a new guide.

The guides are actually pretty easy to change. I made a tool from an old valve stem, and welded a steel sleeve to it. I then knock out the old guides using a BFH. I then use the same sleeve to drive in the new guides. The valve seats take more expensive tooling. They place a mandrel in the new guide and either cut or grind the new 3 angle seat, so it is perfectly concentric with the guide centerline.

Lapping with compound is used after a new valve job to ensure the valve makes an air-tight seal when closed. It should not take much on a new valve job. Lapping can also be used on a valve that has some miles on it, but is a little rough at the seat...a "poor man's" valve job.

 

[mctriumph]

Think of knurling like rifling the barrel of a gun. Tiny ridges of metal in a spiral , tighten the clearances
and capture oil in the guide instead of letting it slip past to be burned. Motors I have built this way burn a lot
less oil than new valves & guides.The plus is saving slightly worn valves that have lots of life left in them.
New guides are dirt cheap.
Mad dog