Replacing a loose valve seat

[alexiskai]

Some of you may recall I started a number of threads about troubleshooting a valve problem I had. Here's a summary from the most recent one:

A vacuum test indicated "worn/loose valve guides." A compression test showed 60-65 psi on all cylinders except for cylinder 2, which showed 40 psi on a dry test and 45 on a wet test. A leak-down test on cylinder 2 showed hissing in the exhaust.

I pulled the head and valves and discovered the culprit: the valve seat on cylinder 2's exhaust was loose. Just sitting in the block, not particularly attached to anything.

So... how do I fix this? I have pretty limited tools and the engine is in the car. I can't deck the block or machine a new seat to 45°. How do I get a new seat that will work out of the box?

Edit: I did check the block for cracks that would have caused the seat to loosen – didn't find anything.

 

[Jim Brierley]

It should be done by an automotive machinist, some will make house-calls.

 

[Kurt in NJ]

If the recess in the block is round and square, not beat up from the failure careful measurement and choosing a proper sized one is possible out of catalog one can be installed, or if odd size one can be made to size
If the recess is damaged then you need to either find someone with portable machine or strip the block to fit on shops machine

 

[jetmek]

Oversizes
Are available. 1625-1 +005 and 010

 

[johnneilson]

If the recess is not too badly beat up, measure and contact;
https://tuckervalveseat.wordpress.com/

Custom sizes without the custom price/minimum order issues

John

 

[alexiskai]

OK, I just cleaned up the recess and measured with digital calipers. Came out to 1.629. I measured the loose seat and it came out to 1.579, about a full millimeter smaller.

I've been calling around and there are no machinists within 100 miles of me who could work on the engine in the car, let alone at my house. So it seems like my best option is to buy a seat off the shelf, have a regular machinist cut the seat into it while it's off the car, and then use the old dry ice trick to try to get the new seat into the block with a dead-blow hammer. I saw a reference on another forum to Seal-Lock Fluid Weld as a product that I should apply to the recess before fitting the seat.

Someone also suggested just applying Fluid Weld and then slapping the old seat back in there, but I'm gonna save that for plan B (or C or D).

 

[Big hammer]

.05 loose thats a gaping hole, where the parts the same temperature?
When I was working in an aircraft engine repair shop doing valves and seats our technique for installing seats they would drop in to easy. We would heat the head and cooled the seat and ended with a cocked fit. We came up just heating the head and installing the seats at room temperature, no more bad fitting seats...... a lot less grinding!

 

[alexiskai]

This is the only bad seat of the 8, I dunno why it was off. Installation error of some kind, perhaps. This engine was overhauled in '84 by the original guy, that must have been when they put in the new seats and adjustable tappets.

 

[Mark in MT]

If you can find someone with an old hand powered seat install kit, they can do that in the car.( Mine is a K O Lee from the 1940's). I have used seats that are about .032 oversized from stock.

 

[alexiskai]

I called more places and still cannot find anyone who would do this job or has the right tools. One guy said his dad would have done it 30 years ago, but he sold all those tools on eBay.

There is a vendor based in India that will sell hand-powered carbide valve cutting sets with any combination of cutters you want. I know I need a 1-5/8" 45° cutter. I should probably also get 30° and 60° cutters so that I can reduce the width of the seat if I cut too much. I'm using modern valve guides, so I assume I should measure the OD of the guide bore and request a pilot with that diameter? Do I need anything else?

 

[jetmek]

Heres an option. Photo from aroundtheblockengines

 

[BRENT in 10-uh-C]

I called more places and still cannot find anyone who would do this job or has the right tools. One guy said his dad would have done it 30 years ago, but he sold all those tools on eBay.

There is a vendor based in India that will sell hand-powered carbide valve cutting sets with any combination of cutters you want. I know I need a 1-5/8" 45° cutter. I should probably also get 30° and 60° cutters so that I can reduce the width of the seat if I cut too much. I'm using modern valve guides, so I assume I should measure the OD of the guide bore and request a pilot with that diameter? Do I need anything else?

With all due respect, often we all speak about how the hobby is being hurt for the future because of hack repairs and cobbled messes. In my view, this potentially is just another one of those circumstances. There is a similar situation on one of the social media sites where a seat supposedly was broken because the main jet in the carburetor was sucked into the combustion chamber on a 1984 rebuild that has little drive time. Supposedly because the owner is 81 and does not want to remove the engine, they are going to try to pound a new seat in and retain it with either Loc-tite or Fluid-Weld.

To begin with in your scenario, I spoke in another recent post about how many Model-A engine rebuilders have/had worn equipment that won't/can't hold tight enough tolerances to do good work. While I have not inspected your engine block, but typically for a seat to come out of the block, the likely culprit is poor machining. So re-inserting another seat of the same size and expecting it to stay is likely a dream at best. So with a non-concentric counterbore that needs to be enlarged to do the job correctly, having some hand-held cutter to enlarge the counterbore and make it concentric again is going to be a struggle. Miss it again or make it worse and the 'aftermath' will likely slate the block for its final resting place in a junk yard. Just to illustrate the differences, my valve machine has a spindle shaft that is 2 inches in diameter and a column that is probably 4"-6" in diameter. The amount of extra rigidity that I have over a hand-held cutter is paramount, -and especially when you are trying to correct a mis-shaped counter bore. I would encourage you to think long & hard about how this repair should be made. There is a reason why no one has or uses the hand-held equipment any longer.

As far as the India-made cutter, there is a portable valve seat machine manufactured by Neway that will dress valve seats. The two or three issues I have personally seen with these is they are not really robust enough to cut the new angle on a new seat that is vertical in shape where the 45° angle usually is. The next issue is these hand-operated cutters are very easy to apply pressure on the pilot in a direction that pushes the cutter outside of perfect alignment with the guide bore. When this happens, the concentricity of the seat is not in alignment with valve face. The third thing is many times you will see start & stopping places from the carbide cutters when being twisted by hand that left tiny gouges in the seat. Generally speaking, compression pressure leaks across the seat and this can cause poor performance or even cause a burned valve.

Again, I realize this is a major inconvenience however you will likely never be happy with a hack-job repair.

 

[alexiskai]

often we all speak about how the hobby is being hurt for the future because of hack repairs and cobbled messes

I appreciate this perspective. Another perspective might be that the hobby is being hurt by the slowly increasing number of things that can't be repaired except at great expense. The DIY aesthetic, and the performance compromises it requires, have been part of the Model A hobby from day one. The fact that a motor repaired by hand won't go as fast, or as long between overhauls, as one repaired by a proficient rebuilder, doesn't mean that motor is "bad for the hobby."

If I know the risks associated with cutting by hand, I can pay particular attention to those risks. I can try to size the pilot more precisely. I can make a jig to hold the cutter steady. I can go slow and use cutting fluid. I can watch for little gouges and find a way to blend them out. I can check the valve with a borescope and leak-down test every few months to make sure it's not getting damaged.

Keep in mind, this motor was running and drivable with a valve seat that was sitting loose in the bore. A less-than-professional repair, done mindfully, will still be an improvement.

Edit: I guess a shorter way to say this would be that I genuinely appreciate the rundown of all the things that can go wrong doing it this way – but I'd rather take the approach of "so try to mitigate each of those risks" versus "so don't even try it."

 

[Russ/40]

I appreciate this perspective. Another perspective might be that the hobby is being hurt by the slowly increasing number of things that can't be repaired except at great expense. The DIY aesthetic, and the performance compromises it requires, have been part of the Model A hobby from day one. The fact that a motor repaired by hand won't go as fast, or as long between overhauls, as one repaired by a proficient rebuilder, doesn't mean that motor is "bad for the hobby."

If I know the risks associated with cutting by hand, I can pay particular attention to those risks. I can try to size the pilot more precisely. I can make a jig to hold the cutter steady. I can go slow and use cutting fluid. I can watch for little gouges and find a way to blend them out. I can check the valve with a borescope and leak-down test every few months to make sure it's not getting damaged.

Keep in mind, this motor was running and drivable with a valve seat that was sitting loose in the bore. A less-than-professional repair, done mindfully, will still be an improvement.

Edit: I guess a shorter way to say this would be that I genuinely appreciate the rundown of all the things that can go wrong doing it this way – but I'd rather take the approach of "so try to mitigate each of those risks" versus "so don't even try it."

I love your perspective!

 

[Jack Shaft]

Fact is you can rationalize anything..hack work is just that,you never have enough money or time to do it once,but you always seem to have enough when you have to do it twice..

 

[alexiskai]

Fact is you can rationalize anything..hack work is just that,you never have enough money or time to do it once,but you always seem to have enough when you have to do it twice..

It was hack jobs by backyard mechanics that kept most of these cars on the road long enough for "hobbyists" with thousands of dollars to spend to come sneer at their work.

 

[Mister Moose]

alexiskai sounds to me like he possesses skills and tools far beyond the average hobbyist.

And if he does take a block out of circulation through Elmering it up, my impression is that there are blocks sitting around that can be rebuilt in numerous supply to the point where the value of a viable but needing overhaul block is extremely low. I am the owner of such an engine block.

On the other hand, if viable engine blocks are rare and valuable, someone please make me a large offer on mine.

 

[BRENT in 10-uh-C]

Edit: I guess a shorter way to say this would be that I genuinely appreciate the rundown of all the things that can go wrong doing it this way – but I'd rather take the approach of "so try to mitigate each of those risks" versus "so don't even try it."

It was hack jobs by backyard mechanics that kept most of these cars on the road long enough for "hobbyists" with thousands of dollars to spend to come sneer at their work.

But even your perspective on this is skewed IMO. Many hacks by backyard mechanics back in the day were done as a last-ditch effort as a way to get a little more service life out of necessity, -and not as preservation. Plus, those 'hackers' were doing the best they knew how to do. I would hope that we all know better now.

While your car is definitely yours to do as you wish, I would think most hobbyists today would rather look towards preservation of their vehicle, but maybe that mindset is changing also.

 

[BRENT in 10-uh-C]

alexiskai sounds to me like he possesses skills and tools far beyond the average hobbyist.

And if he does take a block out of circulation through Elmering it up, my impression is that there are blocks sitting around that can be rebuilt in numerous supply to the point where the value of a viable but needing overhaul block is extremely low. I am the owner of such an engine block.

On the other hand, if viable engine blocks are rare and valuable, someone please make me a large offer on mine.

Maybe you are correct on what skills the average Model-A hobbyist possesses. Based on some of the questions I read on social media sites, you are likely very correct.

In the case of "Elmering" up his current engine, it really does not need that much to do the repair job correctly and have a nice repair that he can be confident in when completed. For example, if the engine were in my shop, the repair costs to install a new seat and cut the seat to shape would likely be under $100 if his engine were all disassembled when it arrived. If the block gets damaged where a new replacement block is required, he is likely looking at over $3k to have a replacement engine rebuilt. Is that financial difference really worth the risk??

 

[alexiskai]

I have managed to locate a machinist who says he can do it. Thanks everyone for the advice.

Brent, I want to be clear that I think your perspective is really valuable and probably correct in the long run. I certainly see myself in part as a caretaker of this car.

But in practice there will often be times when, for budget reasons, a decision has to be made between doing a partial repair that kicks costs down the road or putting an engine, or an entire car, in mothballs for years. I'm not sure any of us are in a position to declare one approach categorically superior. And I hope we can all be sympathetic to folks who are facing that choice. The best thing we can do is try to make sure the decision is one that's informed by good information about risks, benefits, and costs. I certainly feel better informed, and I think the results of this repair will be better because of what I learned here.