I’m rebuilding my first Flathead and I have some questions

[50MercMetalHead]

Hello! (First off I wanna give a disclaimer: I’m 22 and while I’m not necessarily new to engines or even all that new to Flatheads, this is my first full rebuild of any engine and I still have a lot of learning to do.) So, I’m rebuilding the 8CM out of my 50 Merc, it’s bored .040 over from a previous rebuild, it has the mercury crank (unfortunately no matching numbers to my car though). It ran perfectly before I pulled it, except it was losing oil pressure, only making about 5psi at slow idle, but about 15-20 at fast idle, so I pulled it, and found a considerable amount of sand in the engine, I believe it’s casting sand but anybody’s guess is as good as mine. Bearings are all junk, but the cam, crank, valves, lifters, and cylinders all look really good, I assume the last rebuild didn’t have many miles, it was just done decades ago then sat for most of the time. So I’m basically going to reuse most of the internals.

I’ve managed to get down to just the block and I’m about ready to send it off to the machine shop to get acid dipped and to have new cam bearings installed, the only removable thing left is the crank breather/road draft tube that runs from the crankcase to the intake via the lifter valley. Im not really able to get the tube out without wrecking it, and it was already really misshapen from whoever rebuilt it last, so does anybody have a source for finding a replacement? I know it’s just a plain old 1-5/16” tube from other posts here, but I haven’t had much luck looking for a replacement.

Another thing that I’m wondering about is the cam/lifters in flatheads, I noticed before I tore down very far, when the valves were closed, the lifters and cam heel would lose contact with each other. To me it looked intentional, because they all did it, but my dad (who has no Flathead experience but plenty of OHV experience) said that seemed odd to him. So I figure I should make sure they’re supposed to be like that, but I didn’t see much information about it in my searches.

Also, I wonder about my oil pump. It spins nice, and looking at the rod and cam bearings I see they’re more than likely the cause of my low pressure, but I’m worried about putting this pump back in as is. I’m really stuck on the fence about whether I should reuse, rebuild, or replace. I’ve heard the issue with Melling pumps and I’m worried about going that route, has that issue gotten resolved at all? If this pump turns nice should I just clean and run it? Is there an easy way to bench test it that I may be overlooking?

I think that’s all that I was wondering for now, I’m sure I’ll think of more in the future though. Thanks in advance for any input or for simply just taking the time to read this.

[drolston]

With mechanical lifters (not hydraulic) there must be a specific gap between the lifter sitting on the heel of the cam and the bottom of the valve stem. That clearance is there when the engine is cold, so that when the valves get hot and grow a little longer, there is still enough gap that the valve will completely seat. Too little gap and the valves may not seal, and leak and/or burn. To much gap, and the valves will be quite noisy, and will not open as far as the should. The gap between lifter and valve stem end should be about .014 on intake valves and about .016 on exhaust valve.

Get a good flathead engine book before you go too much further. Folks on this site will recommend the good ones

[50MercMetalHead]

I meant there's a gap between the cam heel and the lifters, like the lifter and cam lost contact after the cam rotated from lobe to heel. Sorry for explaining it weird, I'm not great at using the right words sometimes. Hopefully that clears it up.

I should get a book, yes. I hadn't thought to do so.

[Brian]

I meant there's a gap between the cam heel and the lifters

Yes, but if you pushed the lifter down until it contacted the heel of the cam, the gap would then be between top of lifter and bottom of valve stem....don't worry

[Tim Ayers]

Welcome to the Barn and good luck with your rebuild.

First thing you need to do before getting the block acid dipped & cleaned is to get that casting sand and muck out of the water jackets. The more you can do at home, the cleaner the block will come back to you which is a good thing.

There are many threads on here as to how to do it. You can use the search function and I'll do the same and post the thread links as I find them.

[19Fordy]

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Congrats on your rebuild. Before you dip your engine block remove any of the parts that will be dissolved by the acid dip such as the rear main bearing seal seats, etc. Also, don't mix up the bearing caps.

[19Fordy]

Here's your oil fill tube.
https://www.ebay.com/sch/i.html?_fro...+tube&_sacat=0

[Ol' Ron]

Yes. welcome. One of the best books you can use is an old motors manual of the 50's. Hard to find these days, but the information in these is priceless.. You might consider having the block "Bake cleaned". Take the coveer off the oil pump, see if the casting and cover plat is scored. If smooth, put it back in the engine.
Gramps

[glennpm]

You've come to the correct site for getting help on your rebuild.



VanPelt's site has a wealth of info and parts.


https://www.google.com/imgres?imgurl...MygAegUIARC5AQ

[TomT/Williamsburg]

Welcome and good luck with your rebuild - as others have said, you have come to the right place for questions and answers!

[tubman]

Here's a link to a discussion that I started re : oil pumps. https://www.fordbarn.com/forum/showt...light=oil+pump.

It all started when I decided to install a new Speedway pump in a fresh engine I was building. You can read the whole thing or I can summarize it for you. Original Ford oil pumps are as good if not better than aftermarket pumps (and a lot better than some!). Since they run in oil, they rarely wear out. As mentioned above, you can check for any unusual wear on the bottom cover plate. If it's not scored you are probably good to go. The only specification I have found for checking them is that the clearance between the bottom of the gears and the cover plate should be .002-.006", which can be checked with plastigage. You should replace the relief spring with a quality new one when re-using a pump. Pretty basic stuff.

[Tim Ayers]

https://www.fordbarn.com/forum/showt...cleaning+block

Read my comments in this thread about what you can do at home prior to block cleaning.

[jayvee34]

Barnes and Noble book sellers: Rebuilding the Famous Flathead by Ron Bishop.
A great and informative book with pictures.

[Desoto291Hemi]

19fordy ,
I think he was referring to the tube that goes from the tappet chamber up to the bottom of the intake .
That tube can become damaged while removing,,,if not handled correctly.
I inserted a large screwdriver handle in the tube,,,,,while holding the steel screwdriver part in my hand,,,I started a circular motion with the driver .
It worked the tube loose,,,,,and not a bit of damage to it .
That tube is in the block pretty tight from the factory,,,,,for over 70 years .
It will come right out though,,,,with some gentle attention.

Tommy

[FortyNiner]

In addition to the book by Ron Bishop, this one was very helpful for my rebuild project: https://books.google.com/books/about...dir=0&gboemv=1

[50MercMetalHead]

Desoto291 is right, that's the tube I was referring to. I will try to get it out how you say, it has a couple flat spots like someone used a vise-grips on it, so I was going to just replace it, but I could try to straighten it if I can get it out without making it worse.

I've got my main caps numbered and direction indicated, and I've got all my parts organized well for when it's ready to reassemble. I'll open up the oil pump sometime this week and see how it looks.

I've done some reading on the links you guys have sent and I will look into the books suggested, I appreciate the info. Ford Barn and VanPelt's site have been my two main sources of info so far, a lot of what I know about flatheads has come from these two sites, so a big thanks to the folk around here.

[V8COOPMAN]

Originally Posted by 50MercMetalHead

I’ve managed to get down to just the block and I’m about ready to send it off to the machine shop to get acid dipped and to have new cam bearings installed, the only removable thing left is the crank breather/road draft tube that runs from the crankcase to the intake via the lifter valley. Im not really able to get the tube out without wrecking it, and it was already really misshapen from whoever rebuilt it last, so does anybody have a source for finding a replacement? I know it’s just a plain old 1-5/16” tube from other posts here, but I haven’t had much luck looking for a replacement.

Originally Posted by 19Fordy

Here's your oil fill tube.
https://www.ebay.com/sch/i.html?_fro...+tube&_sacat=0

I believe this internal tube for an 8BA that goes in the front of the valve chamber is what he's looking for. DD







...

[50MercMetalHead]

Originally Posted by V8COOPMAN

I believe this internal tube for an 8BA that goes in the front of the valve chamber is what he's looking for. DD.

Yep, that’s the one I meant.

[Desoto291Hemi]

50Merc ,
If the tube is deformed,,,,you can reshape it,,,,they are reasonably soft .
Just try to get her out,,,use something similar to the Same ID,,,,it will come right out .

Tommy

[glennpm]

Wrong thread