Low compression

[Malcolm Towrie]

Thanks, Michael. I found the "81" but only because you told me where to look. The cast number is almost illegible.
I didn't find a serial number of any kind. I did find a brass plate identifying a rebuild by RCEME in 1951.

I've got 9 valve/guide assemblies out and two pistons so far. Everything looks in good condition.

Malcolm

[Lynn Eades]

Thank you Michael R, for educating me on carrier engine numbers.
Malcolm, I am trying to get to the bottom of your low compressions (in the apparently good cylinders)

Ford did 3 different piston tops:
the flat top piston is for the early 21 stud engines.
There are two left:
The first is a sperical top. The profile when looked at from the side is a gentle curve going up one side over the center and back down.
The other is what Ford called a "Combination" When observed from the side it appears that the climb is a constant flat, coming to a point at the top and straight down the other side.
These pistons are not interchangeable.
The sperical one Part no 78C-6199-A
There are a couple of combination pistons.
If you look inside the piston skirt and you should find a number like 01T-6110-A

Cylinder heads. Some types fit both sides but mostly there is a left (6050) and a right (6049)
They may be hard to see, but as far as I know, they are all identified with part numbers
Those numbers above are the base number. All have prefixes and some have suffixes.
Your engine could/ should be wearing heads with:
81A-6049-A (or 6050)
81T-6049
C91A-60xx- B1

On compression ratios:
At sea level a comp. ratio of:
5.4:1 = 99psi
5.6:1 = 102psi
5.8:1 = 105psi
6.0:1 = 108psi
6.2:1 = 111psi
6.4:1 = 114psi
6.6:1 = 117psi

The above is all drawn from Ford service bulletins.
The whole point of my post is so that you can check that the combination of pistons and cylinder heads is a match.
In 42 the valve line changed. (design) Early heads could be relieved to fit the later blocks. If these heads were fitted to an early engine, they would have a lower than std. C.R.
Food for thought.

[Malcolm Towrie]

Thanks for the good info, Lynn. I'll check out what pistons and cylinder heads I have.

But I found something else interesting. I only managed to get one exhaust valve/guide assembly out. (The others are stuck in the block, apparently a common problem with flathead Fords.) Looking at the seats with the valves fully open, I flagged this exhaust valve as OK. (It's on one of the "good" cylinders.) But check out the photo taken after I cleaned it up. It's far from OK. It's blackened and pitted. Compare it to the photo of a good intake valve face. I'm beginning to think the whole low compression issue is down to bad exhaust valves.

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If penetrant doesnt loosen up the stuck valves, I'll have to make up the c-clamp tool to get them out.

Malcolm

[Malcolm Towrie]

Well, live and learn. I've only checked one rod bearing but I found it way too loose in the rod bores. (Two rods install on one bearing.)That's normally a recipe for disaster as if the bearing spins in the bore, it will damage the rod, bearing and crank. But turns out its normal for flathead Fords. They have "floater" rod bearings. Unlike typical rod bearings which are locked tightly in the rod bore. they ride on an oil film in the rod bore as well as on the crank journal. Trouble is the bearing I checked is 0.020" oval (2.030" at split line, and 2.010" 90 degrees around) so it's too snug in the 2.220" rod bore. The fix is to "massage" the bearing to make it round again. Sounds fiddly.

Also, anyone any idea what the recommended torque is on the rod nuts? The manual doesn't say. They're secured by cotter pins so on disassembly, I found the torques all over the map depending how much the previous rebuilder had to over-torque them to get the cotter pins in. I guess I'm looking for a minimum torque.
Malcolm

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[Malcolm Towrie]

I finally got the last 2 exhaust valves out of the block. What a pain they were. The problem is the early style V8's have mushroom-tip valves. You can see this in the photo below. The two parts below the valve are the split guide. So the guide halves are fitted on the valve stem with the larger end next to the valve head, the spring is installed on the narrow end of the guide, and the smaller horseshoe shaped retainer fits over the mushroom part of the stem to retain the compressed spring.
The lifter/tappet, just to the right of the valve, is fitted into its block bore just above the camshaft.
The whole valve assembly is then fitted into the block from the top side. The guide is a snug fit in a bore just below the valve seat. The guide is then pulled down into the lifter valley against spring pressure and the larger horseshoe shaped retainer is fitted into the narrow groove in the guide. When released, the spring pushes the guide and the retainer back up into its bore. The second photo shows the installed valve assembly, upside down.

The problem is that the guide can seize into its bore after many years of service, or after many years of non-service for that matter. And you have to get the guide out to get the valve out because of that mushroom tip. Damn you, Henry Ford. I couldn't free up two of the guides despite making a c-clamp tool to press them out. I ended up removing the smaller retainer, which releases the spring, pulling the valve head out as far above the block as it would go, cutting the valve head off, driving the now-accessible guide halves down into its bore with a brass punch, cleaning off the rust/varnish build-up at the top of the guide bore, slathering on WD40, and finally getting the guides out of their bores.

So the 8 intake valves came out easily. Of the remaining 8 exhaust valves, 2 came out with the c-clamp tool, 4 came out with the c-clamp and some serious prying., and the last 2 needed the drastic treatment.

If your planning on rebuilding a Carrier engine, put a few hours by for this job.

Malcolm

PS torque on connecting rods is 35-40 ft-lb.

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[Malcolm Towrie]

There are 4 really bad exhaust valve seats in the block, corroded and pitted. My local machine shop agreed they should be replaced, but he couldn't do it because modern seat removal/replacement tooling is designed to hold cylinder heads, not a whole block.
I decided to use the welding technique to remove the bad seats because i could do that at home, and buy replacement seats, figuring i could make up the simple tooling required to install them. I hit some snags.

The seats came out no problem by fitting a slightly loose 1/8" thick washer inside the seat bore and MIG welding it to the seat. This shrinks the seat and loosens it in the block so I was able to tap the seat out using a brass punch on the underside of the washer. One photo below shows the block with the seats removed, and the other shows the removed seat.

The first snag was the seat counterbores in the block were 0.005" out of round, varying from 1.625 to 1.630". This seemed a bit much considering the press fit of the seat in the block is 0.005" interference. The other snag was the new seats were 0.010" over nominal size on the outside diameter, which I found out is normal. The supplier assumes you will be cutting the counterbores 0.010" oversize to clean them up. Another minor problem was the new seats are 1/4" thick, when nominal size is 7/32".

So now I need to find a machine shop who can bore out the counterbores in the block to 1.635" ID so that I get the right press fit for the 1.640" OD seats. Parry Automotive in Orillia may be able to do this.

Malcolm

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[Frank v R]

which vehicle is this engine from?