21 stud deck height, gasket thickness, etc. questions.

The stroke on #1 throw is 3.743. That's measured with 2 different starrett depth mics and checked with a B&S dial caliper. I could drag out other measuring methods but I'm confident in these tools, they get calibrated and get used daily. I have a 6" travel Starrett dial indicator but I don't think that's as accurate as depth mics and it would take a while to set up.



So the stroke is .007 short. That accounts for only .0035 of deck height.
 
The double slinger rear main, would be a '38 crank, I believe. It should be the same as the '37 but, with 2.499 mains, instead of 2.399. Maybe someone could verify that?

Edit:
The second slinger is what the rope seal replaced, as I remember.
 

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I went back an reviewed both the 59AB and 8BA prints - they both show 10.445 - 10.450. So maybe it is different (not by much), though that earlier print doesn't show a manufacturing tolerance . . . so we don't know the low and high end of the range. It would not surprise me if all blocks were supposed to be the same . . . within a range of tolerances.

On the crank, as Frank mentioned the first slinger is the rear thrust surface and I guess also a slinger and the second one is the actual oil slinger that rides inside the pot-metal rear main seal-plate pieces. Some folks will remove the second slinger (on the crank grinder) and put in a later type rope seal. (And use the later pot-metal seal plate - or whatever you call it).

Also on the later crank, obviously the mains are different sizes from your 36 or so crank. I have no idea as to if there are any counterweight or other "fitment" issues if one was going to rework the mains and run the later crank.

I've not built early 21 stud engines, so I can't recommend exactly what the process is - though I've seen some custom seal plates/work done on the rear main caps to handle it.
 
Also, given the dimensions that Frank showed (the lower deck height), this would put the piston crown further up or out of the bore as compared to a later block (if there is truly .008 to .013 deck height differences).

Just wanted to make sure we're all thinking the same.
 
Thanks Frank. I can't read much on that print, but I do see the 10.437 deck height.


I'm making an assumption about the the piston compression height by assuming the pistons I have are close to nominal, since they are all the same within .005. Are there any prints in existence for those pistons, to know what they are intended to be from Ford?


Cutting the deck to 10.437 and making the stroke 3.7500 would still leave my pistons .036 below the block deck.
Adding .020 to the stroke would still make it .026.



Looks like without custom pistons the fix is to profile the heads. At least I can do that here.
How deep can I make valve reliefs in stock ford heads?
 
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Just to let yah know, I have called Ross directly and they will move the piston pin for a fair price - just not sure they make 221 sized pistons.
 
As I said, in my first post, if you use a crank, with the 2.139 rod journal, you can offset grind and adjust the stroke, for any deck clearance you need.

MY intent is to offset the crank to give .020, above the deck and the std Victor, .060 head gasket.

The increased stroke, also gives a higher CR.
 
frnkeore said:
As I said, in my first post, if you use a crank, with the 2.139 rod journal, you can offset grind and adjust the stroke, for any deck clearance you need.

MY intent is to offset the crank to give .020, above the deck and the std Victor, .060 head gasket.

The increased stroke, also gives a higher CR.
Click to expand...


There's no 2.139 crank that drops into a 36LB. At least that's my understanding. I was going to do that to fix a 37 block that has .015 oversize saddles, convert it to 59a bearings and put a 4.125 offset ground Merc crank in it. But that conversion is not real simple and not in the cards for this motor.
 
So, your saying that there is more to it than grinding the mains to 2.399 and using the later seal?

If I need to know, because that is what I intend to do with my '37 block.
 
Frank, With the 2.449 [std] journaled cranks, the front and centre main journals, whilst being.100" larger in dia than the 36 LB crank, are shorter....so, when you whittle them down to 2.399", you'll also need to widen them so they will indeed drop into the 36 block. Then you need to put a spacer behind the crank timing gear in order it will line up with the camgear. The snout of the larger crank is also longer and larger dia, so use later pulley or machine to suit the 36 crank.
 
Thank you, Brian.

That's all doable, I was going to rough the mains down anyway for the crank grinder. I'll just measure the main to main distance and machine that too.
 
While the crank work will be a bit expensive, it will probably be less than a custom set of pistons. So if it was mine, I'd explore with my local machine shop (somebody who is expert on crankshaft work) - what this crank work would cost. It is very important for the quench/squish to be about .040, so an offset crank grind back to 2" rod journals would enable you to achieve the exact stroke you'll need (given the pistons you have). Let us know what you find.

Also, this approach would create the least number of "bastardized" parts (versus screwing with the heads - which I wouldn't do for multiple reasons).

BTW: If you need this type of crank work done and don't have a trustworthy local crank shop, let me know - can probably get this done for you at Fowlers in Columbus. This is where all my machine work is done and their crank guy "Dennis" is second to none. Let me know if I can help . . .

Also, I have a couple "spare" later 239 cranks - so you wouldn't have to ship or deliver one both directions. In a perfect world, I would prefer to have the short-block to mock everything up. This is the best way to prevent any potential unforeseen circumstances . . . as we all know that crap happens!
 
Thanks for the offers, Frank and Dale, you are both generous.


Dale - Why wouldn't you recommend changing the heads?
 
Yoyodyne said:
Thanks for the offers, Frank and Dale, you are both generous.


Dale - Why wouldn't you recommend changing the heads?
Click to expand...

It is just a very strange way to deal with quench issues. Also, imagine the next guy that takes the engine apart . . . would be one big "What the heck is this?" type of moment. It will make any future head work a real PITA - as you can no longer deck the head in any normal fashion.

But, it is your engine and you obviously have the skills and equipment to do such a job. And obviously it doesn't cost you anything to use this approach :D
 
Bored&Stroked said:
It is just a very strange way to deal with quench issues. Also, imagine the next guy that takes the engine apart . . . would be one big "What the heck is this?" type of moment. It will make any future head work a real PITA - as you can no longer deck the head in any normal fashion.

But, it is your engine and you obviously have the skills and equipment to do such a job. And obviously it doesn't cost you anything to use this approach :D
Click to expand...
I get that, I really do. But I gave up caring about the "weird" factor on my own stuff long ago. Iron heads are cheap, about $25 each, I can test with iron heads without much risk. Worst case, bolt stock heads on and it's a normal 36 engine. I already have the gasket pattern digitized, I could do this in a week of evenings if I needed to. I think the hardest part might be preparing the heads properly to clamp them down parallel to the table. The alternative is waiting for pistons, or waiting for a crank to be done, and nothing outsourced seems to be going quickly lately. Modifying the heads is going to be way more entertaining for me than waiting for parts would be. (When your only tool is a hammer, everything looks like nail, right?)
If I hurt a custom piston, then I'm waiting for more to be made, if I hurt a special crank, I'm in more trouble. If I hurt a head I made, I make another. If someone else is working on it they would have the same problems plus I won't be around to care.
Plus this way I can easily experiment with how close I can get the pistons to the head if I want to. I cut my engine teeth on '70s Modified eliminator SBCs that often had the pistons touching the heads at 10k+. (I don't anticipate that sort of thing to happen, but this is a what-if post, right?) :)

I'm sort of surprised this deck height issue on flat tops hasn't been discussed here before. Seems like everything else has been...

This is not a done deal yet of course, but it's how I'm leaning unless I run into something that stops me.
Thanks for the input!
 
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Would be nice to do it on a CNC - but as you mentioned, the hardest part is getting the deck surface parallel to the machine and holding the thing down. You might consider making a big plate to mount the head on - with stand-offs for some studs to set the height and make it parallel and then 4 threaded locations where you could put bolts through the spark plug holes.
 
Good thread, much valuable knowledge here!

This just show how many ways there is to correct loose factory fit.
Worst thing will be decking the block. so thin already.
 
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