Rebuild Advice 8BA

5

52flthed

Senior Member
Hi,

This truck is new to me. It's a 1952 F1 in great shape. I've only driven it a few months. Now at the mechanics finishing up a carb rebuilt as the accelerator fuel pump was bad. I felt there was a lack of horsepower especially when going up hill. Theres no smoke and it runs great otherwise. I asked him to do a compression test and the #6 cylinder came back 85 lbs while the rest were between 100-115. He put oil in the cylinder and it came back a bit better but then warmed up the engine tested it again, but even lower, 80lbs.

There is a popping noise heard through the carb when revved up really high. He thinks it's a bad intake valve. We are in Central NJ in Monmouth County.

So my questions are; What would be your general advice to me? Where to get this done? Any competent shop close to me, or a real Flathead specialist? What should I have them do, What to include or specify.. just fix the bad intake valve or rebuild the whole engine? I want it to be completely and authentically stock but also to do anything that would be well advised. I know a lot of people go off the deep end in terms of period hop ups and all the goodies. I don't think Im in that camp just yet. But would like to have it done really well and wouldn't complain about more horsepower, but aluminum heads are probably not my thing although I admire them. Im really out of my element here as Ive never had anything done like this and Im not as knowledgeable about mechanics as I would like to be. My mechanic can take it apart and put it back together, he's very good he just has to send it to a good shop. I wanted to get the whole truck rewired this Winter so I'm also wondering if I can afford all of this and the logistics of doing all new harnesses while the engine is out of the truck. What costs should I roughly expect to have an engine removed rebuilt and put back in the truck?

I appreciate any and all info.

John
 
The firdt thing to do is decide what the application of the engine will be. A bne stock flathead can be improved with EAB heads a better carb and ignition system at any time.
Most machine shops will do rge machine worl, >040/.050" Over bore and fit pistons, valvw job. Thus all you have to do is put it together. If the application includs open road driving an OD trans might be considered. But this will still be expensive, however, it might last until Gas is no longer sold..
 
It sounds like it may be a stuck valve. Had the truck been sitting for a while? I wouldn't be looking at a complete rebuild on an engine with 7 cylinders between 100-115. I think the "Marvel Mystery Oil" treatment may be in order to try to free it up. If that doesn't work, pulling the intake and checking for a weak or broken valve spring may be in order.

The engine sounds to be in good shape otherwise, so I'd pursue other avenues before a complete rebuild. Back in the day, it was not a rare occasion to replace lap a problem valve or replace the rings in one cylinder to solve problems like this.

One last question; does it have good oil pressure?
 
Hi Ron. Thanks for your response. I wouldn't want to change the heads. If anything, its supposed to have 8RT but that's debatable as a lot of these came with 8BA heads. I just want to bring it back to original condition. Stock. I would consider any internal improvements if there were any to consider? It has a 6v set up. I put black wall bias ply tires on it. Its a completely stock truck other than a few period correct deviations in the interior. I drive it on weekends on back roads 45-50 mph and Im happy with that.
 
tubman said:
It sounds like it may be a stuck valve. Had the truck been sitting for a while? I wouldn't be looking at a complete rebuild on an engine with 7 cylinders between 100-115. I think the "Marvel Mystery Oil" treatment may be in order to try to free it up. If that doesn't work, pulling the intake and checking for a weak or broken valve spring may be in order.

The engine sounds to be in good shape otherwise, so I'd pursue other avenues before a complete rebuild. Back in the day, it was not a rare occasion to replace lap a problem valve or replace the rings in one cylinder to solve problems like this.

One last question; does it have good oil pressure?
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Wow Thats encouraging!! MMO huh? LOL. How does that work? I just had an oil change and added Zinc additive. The engine is in great shape especially now withe the rebuilt carb and the timing corrected! It revs up really nice whereas before it just sort of flattened at a high rev. Oil pressure is low at idle then increases upon acceleration. It has its original gauges on it. The truck was sitting in the body shop since this February moved around some, mostly sitting though. I just got it back from body shop in late September, drove it on a weekend or two then it went to mechanics shop to get the carb rebuilt and other stuff done. So you have a point...
 
Ill add that before I bought it in August of 2019, it was sitting for about 20 years! It had some work done by the window that I bought it from in 2018 like gas tank, carb, fuel pump tune up work. But basically was an older restoration from 1989, used a few years, and then it probably sat in her garage from like 1995 lets say until 2018 had some work done on it, then I bought it in late 2019 drove it about 5 gas tank fulls then it went to body shop for 7 months and here we are late 2020 with a bad intake valve.
 
I hate to be a pest, but can you give us some actual numbers? "Oil pressure is low at idle" doesn't help much. What is it at 2000 RPM hot? You also might consider plumbing in a quality mechanical oil pressure gauge to make sure of the readings. These old "King-Seely" gauges can sometimes give false readings.

From what you are saying, I would consider a complete rebuild only as a last resort.

The "MMO treatment"? Add a half pint to the crankcase and then drizzle the rest down the carb until it's all gone and kill the motor. Let it sit a day or two and start it up. Do not be surprised with the copious amounts of smoke produced. If that doesn't work, try it again with "Seafoam"

Sorry guys, about the "Snake Oil" treatments, but it's better than an unneeded engine rebuild.
 
Thanks and sorry about the imprecise oil pressure readings as the stock gauges are general indices and a little interpretive to read them. I know that the readings were "normal" when I recounted them to a some old timers that own flatheads in my area in my local club. I will try the MMO thing why not? Thanks for the advice! I will also ask mechanic about the idea of broken spring? Anything else I should be looking at? Appreciate your help. -John
 
I would do a cylinder leak down test to determine the lower compression in that one cylinder . This is something you or your mechanic can do to find the problem before taking anything apart.
 
marko39 said:
I would do a cylinder leak down test to determine the lower compression in that one cylinder . This is something you or your mechanic can do to find the problem before taking anything apart.
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Hi Thanks for the response. What does a leak down test determine? It was also said to me that it could be a head gasket or a crack? -John
 
Not "stuck open"; just a little sticky. Could be stuck rings, too. It sounds like that engine has been sitting a long time.
 
52flthed said:
Hi Thanks for the response. What does a leak down test determine? It was also said to me that it could be a head gasket or a crack? -John
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You pressurize the combustion chamber and see if it will hold pressure. It will slowly leak down around the rings. If it is leaking down to quickly there is a leak somewhere.
 
Tubman has given you some excellent advice and the only thing I would add is drive it and see if the heating\ cooling cycles will free the rings or valve.
 
Thanks guys for all your advice I really appreciate it helps to put things into perspective I realize I’m probably over shooting assuming a rebuild. Speaking of oils I should also mention that since I’ve owned the truck in late 2019 I believe we have been mistakenly using a detergent straight 30 weight oil. NAPA labels there SAE 30 As simply 30 weight without dummy labeling identification as it being “a detergent” . While their non-detergent 30 they Clearly label it as “non-detergent“. Well I think we both got fooled by assuming a straight 30 was a non detergent oil. Yikes!

That would explain all of my recent oil changes as the oil being very black. Could this also cause this issue with this one cylinder being low compression?
 
Hold on a minute! You have been using non-detergent oil? If so, that is a serious mistake. It sounds like your engine has low miles on a rebuild and hopefully is not sludged up yet. Get that non-detergent oil out of there as quick as you can to prevent the engine from sludging up any further. Non-detergent oil was the main culprit that caused the sludging up in these old engines. Just about any oil available today with a valid API seal on it is vastly superior to anything available back in the day.

I don't know where this non-detergent fetish for older cars started, but it has to stop. Be glad the oil changes are coming out black; the detergents are doing their job.
 
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It all depends on what you want to do as far as doing the least to get the compression up on the bad cylinder (bare minimum), versus a rebuilt, some slight performance upgrades (to pull hills better), etc.. You can skin this cat a LOT of ways. Always keep in mind what do you want the end result to be - and if you're planning on keeping the truck, then do the job right . . . even if it takes longer to do.

I agree with the idea of doing a leak-down test (I'd do all the cylinders). You need to figure out what you really are faced with - before making the big decisions. Also, a "leak down" test is not a simple compression check - it takes a specific tester and the knowledge how to use it (no big deal). Just "google it" and you'll see what I mean.

There are some performance updates that can be done with even a stock style rebuild that can give you another 10 - 20% horsepower - which does make the whole combination feel a lot better. It comes down to time and money (like always).

Once you decide to rebuild the whole engine (which seems to be where I always end up), then you will spend somewhere between probably $3000 - $6000 on it (stock style rebuild - without a lot of go-fast bling, bling performance goodies). Yes, you can surely spend MORE than this (big dollar high-end shops) - but you can also find competent builders that will be in this range on a quality rebuild with a few performance updates.

If you are going to have machine work done - then make sure the machine shop is very familiar with flatheads and have the correct tools and expertise to do the job. The area where many have issues is with the valvetrain (you can't just throw the block in your normal OHV head machine).
 
Okay guys again thank you, thank you for all of this great advice! A little update and more information to go on...This morning my mechanic called me on his day off! He was thinking about this and yesterday afternoon as he was putting everything back together, rebuilt carb, and adjustments, and here's the thing, he also advanced the timing and adjusted considerably. He said the timing was retarded. I will also tell you I was burning copious amounts of gasoline!! A Flathead friend from my local club said I was "running rich" when I brought the truck over his house last month. So my mechanic adjusted the timing and road tested the truck this morning and he couldn't believe how much better it ran and how much power it had! So he thinks that the timing caused a lot of carbon build up and he will do a decarbonization by dripping water down the throat of the carb to remove it. But I also want to try this Marvel Oil thing. What do you think of that? So luckily I might free whats a stuck valve or an improperly seating valve? He said there was no popping sound on the road with the truck at high revs this morning.
 
tubman said:
Hold on a minute! You have been using non-detergent oil? If so, that is a serious mistake. It sounds like your engine has low miles on a rebuild and hopefully is not sludged up yet. Get that non-detergent oil out of there as quick as you can to prevent the engine from sludging up any further. Non-detergent oil was the main culprit that caused the sludging up in these old engines. Just about any oil available today with a valid API seal on it is vastly superior to anything available back in the day.

I don't know where this non-detergent fetish for older cars started, but it has to stop. Be glad the oil changes are coming out black; the detergents are doing their job.
Click to expand...

No I haven't been using NON-Detergent Oil. I thought I was. But now there is NON-Detergent oil in the truck as of yesterday. I have no idea what the PO had in the truck. I bought it in 2019 from the widow. I also have no idea if the engine was ever rebuilt or not. I know a lot of work was done to it but maybe just top end engine work? I have pictures of the restoration from the late eighties and nineties and it shows the engine still mounted on the frame. So I assume not a complete rebuild. I tracked down the father and son that restored the truck but sadly the father died a few years ago and tragically the son just passed away last year.

My understanding is that you are supposed to use NON detergent oil in these engines if you don't know if the engine is rebuilt or not. Is that not correct? The detergent oil has lye in it that will clean sludge out and that will cause clearance problems allowing oil to be burnt and the engine to smoke is what Ive been told. At least there's a significant risk of that to be fair. Im the farthest thing from a engine or a flathead expert. But what I try to do is talk and listen to people with a lot more knowledge than me and form a consensus. Most people I've spoken with either by email, phone or online forums have told me something along these lines as well to add zinc or use a higher zinc oil. How can I tell if the engine has been rebuilt or not, by removing the intake manifold? Dropping the engine pan seeing if there is sludge in the pan? I just figure use a non detergent oil and do frequent oil changes?

John
 
Pulling the intake manifold (which involves also the fan, generator and some other bits) to determine the internal condition and at the same time check the valves, will be worth the effort in the long run. If it's sludgy inside, then I'd also drop the pan and clean it out. By all means run detergent oil after cleaning out those two areas.
 
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