Gave in and pulled the pan to properly fix the oil leak around the studs/castle nuts with Permatex Ultra Black. While I was in there I checked on the bearings and made sure everything was still torqued. The bearings showed some signs of wear but nothing alarming. Thoughts? Everything is back together. I’ll fill er up tomorrow and see if there’s any leaks fingers crossed.
Could you feel the wear marks in the bearings, did your fingernail catch in them? It's hard to tell just by looking at a picture but it is probably just normal run in between the bearing and crank.
No wear marks that I could feel which was a big relief considering the headache with installing the bearings during the build.
Of all days for it to be 97° in the garage. Got a surprise in the mail. Once it cools off this evening, the work starts!
Exhaust valves were hitting the radius in the aluminum head’s combustion chamber. On first start up, I couldn’t hear it, the engine was running smooth as can be. Let the engine warm up and cool. Re torqued the head nuts to 55 lb*ft after it cooled and took her out. Wow she ran great with tons of power for about 20 minutes until she didn’t. Limped around the corner and started diagnosing. Cyl 1 was producing much less compression than the rest so I pulled the head. That’s when I discovered the exhaust valve snapped below the taper! Not only did it snap but it beat the crap out of the valve seat as well. Turns out the 1,2 and 4 exhaust valves were making contact with the head. I’m now trying to figure out what the next steps are. I really don’t want to pull the motor but I may just have to. Looking at Neway seat cutters to possibly try to salvage the seat but would like to hear some opinions. There’s about a 1/32” gap from the seat to a new valve that needs to be cleaned up. Really disappointed that a “bolt on” head created this much trouble.
That valve circled in yellow is bent I believe. Take it out and spin it in a drill press or sumthin to check it. All that touched the head should be checked, then have a machine shop do a tiny fly cut for clearance
The valve circled is a new valve. The light you see under it shows the beating the seat took. I'm curious if one of those Neway manual valve seat cutters could provide a new seat surface. Seen that they work wonders but not sure how it would work without a perfectly concentric surface to cut. The fear is that it would make an oblong cut. The two other cylinders that had contact witness marks both showed 128 psi of compression and the valves show no sign of wear. Not too worried about those. Although the intake valve next to the broken valve doesn't look harmed, it's getting replaced for good measure. Not quite sure what you mean by fly cut for clearance…where? The plan is to take a die grinder to the places on the head that need clearance, pretty much the radius in the chambers. After, I’ll smooth it all out and maybe polish if I’m feeling motivated.
I thought maybe that was the new valve, after I posted my comment. Fly cut the head where the valve touched the combustion chamber. Next time, the 20/20 vision of hindsight, a guy could place the head on with no gasket and turn the motor to see that there is clearance. I think to fix that seat, you will get too deep and not have the valve above deck where it should be. And, it will be messy. Not what you want to hear, but, there is a lot of money in that motor, perhaps its best to tear it down so a machine shop can put in a new seat on the mill and have everything back to perfect. Hope to hear more from some pro motor builders here, best wishes
New way style cutters work well... should correct this valve seat as long as you get the correct fitting pilot. The problem is you wont know how deep you will have to go until you try and its hard to tell from picture how deep the damage is. If its too deep it will have to come out and have a seat put in.
Agree ^^^^, and, that seat is a a removable insert. weld a short 1/4' bead on it, let it cool, and it shrinks and pops right out. hammer in a new one and fit your valve with the new way cutter.
It might be the camera angle, but the head of that exhaust valve looks pretty thick to me. I would track down some dimensions and verify before going farther. Find a (scrap) shorter valve and lap it in a bit to actually see what shape the seat is in. When reassembling, put a glob of modelling clay on every valve head, install the cylinder head, and hand crank it over. The deformed clay thickness will tell you the clearance. Good luck.
Not my car, not my money, not my time, but my two cents... Bearings look like they had dirt running through them. That would make me want to do a full cleanup, but would run it if that was the only issue. You also need to fix the main bolt leaks. That can be done in chassis, but the fixes are stacking up. Also, call Permatex tech line and see what they suggest for the studs. RTV has it's place, but it is not typically for oil drenched studs. This looks like a better selection, but I'd get suggestions directly from the guys that develop it. www.permatex.com/products/thread-compounds/thread-sealants/permatex-high-temperature-thread-sealant/ With the amount of gap on that exhaust valve and required machining on the top of the block (while minimizing the additional grit and dirt), you are getting into the point where I'd want everything out of the block, including the crank, which points to pulling the engine. 60 years ago, a basic shop would do an in-frame rebuild, but the engine also wouldn't last much more than 40-60K before needing a redo. I doubt many shops have the equipment used back then to machine in place. I also doubt many machine shops now have the space to have the whole car sitting there. With the effort and cost these days, pulling it and having the work done on the block, lapping in every valve and checking/fixing head clearance, then doing a full-on scrubbing and clean room assembly is more typical.
Wow, thanks for all the awesome responses and suggestions. Now, to address some things… Dirt. The block was surgically cleaned before assembly. I’m fairly confident I got everything but being a brand new casting, it’s possible I could have missed some junk. The picture of the main bearing is after about 60 miles of driving so it feels like a full rebuild/clean isn’t warranted. Main studs leaking. Pulled the pan and properly sealed them with ultra black. I’ve had no leaking for about 30 miles of driving. Leaking in general. Still have a small leak from the flywheel housing. Dip stick shows oil right up to the full line. The leak has been slowing as I drive the car so it may just be overfilled. If that’s not the case, perhaps if the motor gets pulled, this should be addressed. Might just drop the oil level after everything is back together and see if it stops leaking. Other valves. All other valves look good. Cylinders 3&4 that had exhaust valve contact both measured 124 lbs of compression while cylinder 2 had 118. I’m pretty confident they’re ok. Snapped valve. The new replacement valve is a little taller so I lowered the lifters which reduced the valve gap significantly, duh! The new valve was lapped twice and revealed some interesting things. I won’t go into my detailed thoughts but I’ll let the pictures speak for themselves and see what you guys think. Below are pictures of the valve and seat after lapping twice, cleaning up and being rotated 360° in the seat with some blue sharpie. Clay. That’s an awesome idea and will be done after I work the head for clearance. New seats. If I have to, I will. I’d really love to know if precut seats are available and if they can be installed with the engine in the car.
It's hard to tell (camera angle maybe) but the first seat picture looks like the lapped area on top of the pic is kinda slim. Have you been able to verify the specified thickness of the valve heads? Those things sure look thick to me! It's been damned near 60 years since I rebuilt a Model A engine, but I don't remember any valves being that thick-headed! I would verify before I clearanced the head! YOMV
You’re spot on, there is a super thin strip on the seat after lapping. The other pictures are of all sides of the valve. I have not been able to verify the thickness of the valve heads from documentation which is damn near impossible to find for generic unmarked model A parts from the big suppliers. Measuring the vertical flat thickness (what I think you’re referencing) is 0.100”. Stock valves are muuuuch thinner.
That sucks' always use a little hy spot blue to check the valves to the head clearance. Easy way to spot any interference and adjust with a little hand grinder work.I have always run bigger valves so i know to check every time i change heads.
That's a real pain in the ass ya got goin' there. The valve seat definitely needs to be corrected and re-lapped. Better check the others, too. The valve head thickness (you interpreted my reference correctly) really bothers me. I'd be looking at machining them thinner, but don't know to what dimension. I wouldn't modify the head until I knew what valve dimensions should be. Correct the problem, don't accommodate it. Do some checking on the MAFCA (Model A Ford Club of America) or MARC (Model A Restorers Club) sites to see if you can find any info. Both of those clubs have guys that dug up some pretty obscure data over the years. Just be aware that some of them hate hotrodders more than they hate COVID masks!
Good info and pics! "I agree that the heads of those valves look very thick, but do not have 1st hand knowledge. 28 phonebooth offered good advise there. having a thick valve would be a way to increase compression, provide more mass for temp control and future machining. Heavy is bad for high RPM and works the valvetrain harder, but is that a big concern on this engine? You could go with a hand held grinder on the single seat, after fully protecting the rest of the parts from the junk flung off. Sounds like a typical fix back in the day. This is not a high compresion, high RPM, high CFM engine. Depending on how much the valve sinks into the block, the end of the valve may need facing to a shorter length? 289s have an installed height spec, do not know about bangers. As for head clearance, the suggestion of trying it with clay and/or assembling without head gasket should point to the areas of interference. Grind the head to provide clearance and smooth any casting chunks in the combustion chambers. It looks like there is a dam around the one valve area in the last head pic in post #220. Remember that any material removed lowers compression, so go easy.
One of the hardest things for me to get my head around when I first started doing this stuff was that when you change the specs of one part you change it's relationship to all it touches or operates. Thank God my dad was still around back then. When we gather pieces from different sources and assemble them the opportunity for error is multiplied. Back up as far as you have to to KNOW that all is right and proceed a piece at a time. At this point a tough way to go. What we think we know is worse than not knowing anything.
So after an extensive lapping session, this is where I am. The thin ridge on the seat created by the old valve hammering it has been smoothed out. The valve with blue is the valve used to lap the seat. The second valve was lapped on the seat after the ridge was knocked down. Would you call me crazy if I ran it?
Now it looks like you have too wide of a contact area on the valve. should be more like the thin blue line at the top, or about 1/16 to 3/32 wide. A cutter could take a light cut out of the 60 degree angle at the bottom of the seat to correct it. It would run like that, just a narrow seat is preferred to keep it cool and clean
rusty valley is right. I'd run it. You're not cranking 7500 rpm with it. It was designed and built as a slow speed engine, and as long as you don't trash on it you'll be fine. By the way, I was just on @trevorsworth's thread and he has a few pics posted on the last page or two that show his valve heads. Check it out and compare to yours. Good luck!
rusty, Wider seat = more contact area to transfer heat from valve to head. It does also mean less PSI to clean the mating surfaces, since more surface with the same pressure is going to decrease Pounds per Square Inch. Here is a Mopar flathead discussion about width. p15-d24.com/topic/44321-valve-valve-seat-contact-width-questions/ Provided OP has a good cooling system, not a bunch of old parts, I'd run it, after confirming those thick valve heads are reasonable. Trev's thread, page 42 https://www.jalopyjournal.com/forum/threads/jumping-in-the-deep-end.1201655/page-42
Here is a profile shot of one of my valves fully opened. Might be helpful, might not be. Yours look way thicker than mine. Let me know if another angle might be more useful. I wouldn't relieve the head to clear the valves. Either have material machined off the valve heads or just buy another set. They are pretty cheap compared to the head.
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