Interesting bore dimensions

[GB SISSON]

I have been sorting through some of my blocks I have stored up. I would like to build an engine without the aid of a machine shop. I have 2 good 8ba candidates but haven't had time to do all the testing on them. Of these, one is .030 over and has an older crack, stitched and sleeved that is tight and there is no ridge whatsoever. The other is .040 over but has an intake valve seat that is staked in place, so will want to address that.. My starret dial type bore gauge shows no taper, no out of round, no issues on either block. My question on this Christmas eve is this.
The .040 block, which I prefer as I have six nice .040 pistons measures 3.225 at the top on all 8 cylinders and at about 1/4" down they measure 3.212 . In my research it seems like that is normal procedure on a re-bore and the rest would be left to the honing process. I have a set of Hasting rings at .040 and at 1" down they show .005-.006 end gap. These merc pistons are currently a tight fit, but they will fit in with encouragement. To me it sounds like a good situation. I have a good hone and my Sioux valve surfacer is all dialed in and a B&D and a Van Dorn seat grinder. There are no visible cracks, but after Christmas I will mag and pressure test. Tell me if I'm missing something on the bore diagnosis. And Merry Christmas, one and all!

[cadillac512]

Gary, do you mean the cyls measure 3.221 rather than the 3.212 you posted? Even at 3.221 you'll have .006+ to hone, and that's a lot to try to keep straight unless a rigid hone and a lot of care is taken. Merry Christmas!


Terry

[Kube]

Originally Posted by GB SISSON

I have been sorting through some of my blocks I have stored up. I would like to build an engine without the aid of a machine shop. I have 2 good 8ba candidates but haven't had time to do all the testing on them. Of these, one is .030 over and has an older crack, stitched and sleeved that is tight and there is no ridge whatsoever. The other is .040 over but has an intake valve seat that is staked in place, so will want to address that.. My starret dial type bore gauge shows no taper, no out of round, no issues on either block. My question on this Christmas eve is this.
The .040 block, which I prefer as I have six nice .040 pistons measures 3.225 at the top on all 8 cylinders and at about 1/4" down they measure 3.212 . In my research it seems like that is normal procedure on a re-bore and the rest would be left to the honing process. I have a set of Hasting rings at .040 and at 1" down they show .005-.006 end gap. These merc pistons are currently a tight fit, but they will fit in with encouragement. To me it sounds like a good situation. I have a good hone and my Sioux valve surfacer is all dialed in and a B&D and a Van Dorn seat grinder. There are no visible cracks, but after Christmas I will mag and pressure test. Tell me if I'm missing something on the bore diagnosis. And Merry Christmas, one and all!

This was a fairly common way of "rebuilding" at minimal cost and effort.
I would never consider doing what you are contemplating.
I'm from the old school teachings of "do it once, do it correctly".

[Ol' Ron]

Saving money can be quite expensive.
Gramps

[GB SISSON]

I completely understand what you are all saying here. The best engine will be one with a trip to the machine shop and all new parts installed. That is just plain how it's done in this day and age. I get that with no dispute. But I also stand firm that I have overhauled (not rebuilt) an estimated eight flathead V8s without a visit to a machine shop and have never experienced even the slightest problem. I have followed the ones I have sold and they continue to give good service. This includes the one I built using teflon buttons I made on a router jig to replace the circlips for the wrist pins. I owe this success to the fact that I strictly adhere to all of the procedures outlined by the Ford Motor Company's publication (well, maybe not the teflon buttons) on repairing the v8 to good servicable 'not new' condition. I use new valves, rings and bearings. Most engines I have done in the past may have had a slight ridge which I remove with my ridge reamer. My question today comes from the fact that this .040 block has zero ridge and the bore is concentric and straight, yet measures smaller, not bigger than at the top. If that proves to be a problem, I will use the .030 8ba and come up with 8 new pistons.

[Bored&Stroked]

Sponsored Links (Register now to hide all advertisements)

Any competent machine shops will tell you that you don't use a hone (even a rigid stone hone) to take out that amount of taper in a bore. You're talking about .013 of taper (or incorrectly bored) in those cylinders - this is NOT how boring is done.

A good boring bar will hold a consistent diameter the length of the bore. The hone is used to tune the final clearance and to prepare the bore surface for the type of rings you're planning on running.

If it was mine, I'd have it rebored/honed for .060 pistons/rings.

[big job]

Originally Posted by Bored&Stroked

Any competent machine shops will tell you that you don't use a hone (even a rigid stone hone) to take out that amount of taper in a bore. You're talking about .013 of taper (or incorrectly bored) in those cylinders - this is NOT how boring is done.

A good boring bar will hold a consistent diameter the length of the bore. The hone is used to tune the final clearance and to prepare the bore surface for the type of rings you're planning on running.

If it was mine, I'd have it rebored/honed for .060 pistons/rings.

Well said I could not agree more..........

[GB SISSON]

Thanks all! I now know this block is not suitable for an 'in house' overhaul. I will look into the other ten and maybe find something.

[GB SISSON]

I have some breaking news on this subject... While it's kind of embarrasing to admit here I was not using the telescopic gauge correctly. In my mind I thought that rolling the locked gauge over center in the bore would give me a false reading so I tried to hold it as close to center as possible, then locked it and slowly withdrew it. I decided to remeasure these two blocks with that flawed method and sure enough, got inconsistent results. Duh. So I went to Youtube and searched use of telescopic gauge. Sure enough four videos in a row locking the pin at a cocked position and rolling it over center. The .040 block is still too big to hone, but it is very consistent. The top bit above the rings is 3.225-3.227 and a ring has a gap of .006 +_ and the bores are quite even at 3.220-3.221. The new .040 rings will insert down into the bores 1" before the gap closes completely and they stop. I then went and got the sunnen hone kit that my stepson had given me a few years back.... I suppose I could give it a shot if I was desperate, but I don't want to set this fresh ground 4" crank into a home shop experiment. Besides, it's for the woodie. I turned my attention (and telescopic gauge) to the .030 block that had also showed no ridge. That measures very well as though it had been bored and honed. I bought it mostly apart at Portland with no history. That will go back together as is with it's ford crank and numbered pistons. The third block I went for needs a bore, but dangit, you will like this one. Details at eleven.....

PS, told ya there was an ugly valve seat.

[petehoovie]

Originally Posted by GB SISSON

PS, told ya there was an ugly valve seat.

[GB SISSON]

Thank you Pete!
This is block 3. Above the ridge it is 3.187. Just got off the phone with the machine shop. I will mag and pressure test first.

[petehoovie]

Originally Posted by GB SISSON

Thank you Pete!
This is block 3. Above the ridge it is 3.187. Just got off the phone with the machine shop. I will mag and pressure test first.

[GB SISSON]

And cleaned up for further inspection with a nylon bristle cup brush. Thinking that nasty groove is from a circlip popping out. Guessing will need sleeve. Pete... yer workin' overtime

[petehoovie]

Originally Posted by GB SISSON

And cleaned up for further inspection with a nylon bristle cup brush. Thinking that nasty groove is from a circlip popping out. Guessing will need sleeve. Pete... yer workin' overtime

[38 coupe]

That last block looks really good, other than the gouged cylinder wall. I have a friend with a Kwik-Way boring bar and have helped bore and sleeve a hole worse than that. Looks like you will have a nice engine.


With the crank and block figured out, what about the rest of the parts? What camshaft and heads are you planning to run?

[GB SISSON]

I have many pairs of 8ba type heads. I know I have at least one set of 8rt heads. I'll probably use them unless I get other feedback. I've never had much interest in aftermarket speed equipment, so it will be stock carb/load-a-matic and a stock ford cam as far as I can tell from here. Like another post currently running here, I'm most interested in low end torque. I just may step outside of my box and run dual exhausts, just because.

[tubman]

If you have to bore one out and buy pistons, you may as well go 1/8" over (3 5/16"). It won't cost much more (if anything) and, as they say, you can't beat cubic inches. With a Ford crank, that'll give you 258 ci (bigger than a stock Merc), while the Merc crank comes out to 276 ci. I've done two engines at 1/8" over with no real problems. I did have one cylinder in which a small pit showed up; the machinist said to just run it, but I decided to spend the extra $125 to sleeve it, just to be sure.) You will probably be able to get by without a sleeve in the scored cylinder; that should save at least $100. By the 8BA era, Ford had their shit together so core shift is not a problem. Just about any 8BA will go to a 3 3/8" bore, and there have been examples at 3 7/16"+.030", so you should have all the meat you need for several future rebuilds.

[GB SISSON]

Originally Posted by tubman

If you have to bore one out and buy pistons, you may as well go 1/8" over (3 5/16"). It won't cost much more (if anything) and, as they say, you can't beat cubic inches. With a Ford crank, that'll give you 258 ci (bigger than a stock Merc), while the Merc crank comes out to 276 ci. I've done two engines at 1/8" over with no real problems. I did have one cylinder in which a small pit showed up; the machinist said to just run it, but I decided to spend the extra $125 to sleeve it, just to be sure.) You will probably be able to get by without a sleeve in the scored cylinder; that should save at least $100. By the 8BA era, Ford had their shit together so core shift is not a problem. Just about any 8BA will go to a 3 3/8" bore, and there have been examples at 3 7/16"+.030", so you should have all the meat you need for several future rebuilds.

Hmmmmm, 276 huh. Good point about saving a sleeve too. Would it have more chance of overheating?

[tubman]

Originally Posted by GB SISSON

Hmmmmm, 276 huh. Good point about saving a sleeve too. Would it have more chance of overheating?

I've never had a problem. Plus, think of all the new engines with "thin-wall" cylinders (most won't even take a .60 overbore because of wall thickness) that never have problems. Just make sure the block is clean and everything else is in order. Anyway, you have the same advantage that I do; living in a cool climate.

[GB SISSON]

Originally Posted by tubman

I've never had a problem. Plus, think of all the new engines with "thin-wall" cylinders (most won't even take a .60 overbore because of wall thickness) that never have problems. Just make sure the block is clean and everything else is in order. Anyway, you have the same advantage that I do; living in a cool climate.

And after 45 years of living on this rock I have yet to be stuck in traffic, so there's always forward motion. The shop I called came highly recommended by a friend on the mainland and was recently called out by 'Uncle Buck' as one of the few flathead friendly shops left around here. They told me to call back this morning and ask for their 'senior' machinest who now leaves the shop around one in the afternoon.