Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 06-01-2016, 08:55 PM   #1
dean from bozeman
Senior Member
 
dean from bozeman's Avatar
 
Join Date: May 2010
Location: Bozeman, Montana
Posts: 902
Default Rebuilder out of business and I know why

For years I had wanted to restore several Model A's. So when I had the chance I had an engine rebuilt by a man who at the time had a good reputation. Well as time went on there were other priorities and the engine wasn't used.

Fast forward to last Fall: A Model A that I had needed an engine so I put that rebuilt one in. It took some doing but we did get it going and it ran fine...that is until we turned it off. When that happened we couldn't get it restarted until it almost totally cooled down.

We measured the bore and the pistons. There was less the .002 clearance. The pistons were .030 over. They were replaced with .020 pistons and the engine ran well until it was turned off. The same problem. It had to totally cool down before it could be restarted. It was better than before (less time to restart it) but still not right.

Now I must say that going to a .020 piston, I thought it would be best to put the .030 rings back in so it wouldn't be too sloppy.

We checked the clearance on the center main and it was less than .002.

When the engine was rebuilt the man said that he had built it "tight" so that when it finally broke in it would be a fine engine for a long time. Naive me. I wondered why a guy wouldn't build it to be at its best from the get go. But I figured he knew what he was talking about.

Engine rebuilders live hours from me. So I can't just drive over and talk to them...yet. So I "drove" to Fordbarn and want to get your ideas first. Any ideas, suggestions, experiences are welcomed and appreciated.

Thanks.
Dean
dean from bozeman is offline   Reply With Quote
Old 06-01-2016, 09:11 PM   #2
ronn
Senior Member
 
Join Date: Feb 2011
Posts: 3,696
Default Re: Rebuilder out of business and I know why

Just a thought........... synthetic oil keeps motors looser then reg oil- the reason I know is my buddy used to work on school buses and they often came in bone dry and never froze. I would try a 20 weight............. for break in.
ronn is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 06-01-2016, 10:10 PM   #3
700rpm
Senior Member
 
700rpm's Avatar
 
Join Date: May 2010
Location: Portland, Oregon
Posts: 5,260
Default Re: Rebuilder out of business and I know why

Dean, are you asking for the name(s) of rebuilder(s) we trust? Do you want to take the engine to somebody and make it right?
__________________
Ray Horton, Beaver Chapter, MAFCA, Portland, OR


As you go through life, keep your eye on the donut, not the hole.
700rpm is offline   Reply With Quote
Old 06-01-2016, 10:23 PM   #4
C26Pinelake
BANNED
 
Join Date: May 2010
Location: Michigan / Ontario border, Sarnia, Ontario. 50 miles from Detroit and 150 from Toronto.
Posts: 5,800
Default Re: Rebuilder out of business and I know why

how many years from time it was a rebuilt until you installed it. How many years ago was it rebuilt ? Wayne
C26Pinelake is offline   Reply With Quote
Old 06-01-2016, 10:45 PM   #5
J Franklin
Senior Member
 
J Franklin's Avatar
 
Join Date: May 2010
Location: oregon
Posts: 4,013
Default Re: Rebuilder out of business and I know why

I would not be worried about .002 on the bearings, but those undersize pistons should cause a bit of slap.Maybe try 5-30 oil for a few thousand miles.
J Franklin is online now   Reply With Quote
Old 06-01-2016, 11:06 PM   #6
40 Deluxe
Senior Member
 
Join Date: May 2010
Location: now Kuna, Idaho
Posts: 3,094
Default Re: Rebuilder out of business and I know why

Need more info. Is the engine seized and unable to be turned over after shutdown? Or does it crank OK but just doesn't fire up? Any unusual noises, leaks or blow-by while it is running? Does it run smoothly? Does it have normal power? Those .020" pistons are going to be sloppy no matter what rings you used. Rings do not take any slop out of a piston! What is the ring gap set at? What did the cylinder walls look like after the initial teardown? Any scoring or scuffing? If so, near the top of the cylinder, or near the bottom?
40 Deluxe is offline   Reply With Quote
Old 06-01-2016, 11:08 PM   #7
larrys40
Senior Member
 
Join Date: May 2010
Location: St Charles , Missouri
Posts: 1,689
Default Re: Rebuilder out of business and I know why

Probably Herm and James Rogers may comment but I would first make sure you measured the bore accurately with a high quality bore gauge and compared to the pistons. a .002 clearance should be fine, if less then it was probably too tight.
My druthers would be to NOT run undersize pistons but to disassemble and hone the block to the proper piston fit... then reassemble with new rings.

Of course checking for proper clearance on mains and rods as well.
Larry Shepard
larrys40 is offline   Reply With Quote
Old 06-01-2016, 11:17 PM   #8
John Duden
Senior Member
 
John Duden's Avatar
 
Join Date: Jun 2010
Posts: 1,839
Default Re: Rebuilder out of business and I know why

i rebuilt my john deere G, with a 6 1/8 bore and a 9 inch stroke the mainbearings and rod bearings were set at .003-.006, And that is for the 2 inch journals, now factor in heat expansion,
They recomend (for them at least) .004 per inch of bore between wall and piston, for heat expansion.
hope this may help
john
John Duden is offline   Reply With Quote
Old 06-01-2016, 11:35 PM   #9
Mark in MT
Senior Member
 
Join Date: May 2010
Location: Western MT
Posts: 202
Default Re: Rebuilder out of business and I know why

Dean: If I had to bet, I would say that the pistons are swelling up in the cylinders, causing the tightness. Aluminum expands at twice the rate of cast iron, and the pistons gets hotter than the block. I will send you a pm.
Mark Nelson
__________________
Mark in MT

Always looking for another opportunity to be wrong.
Mark in MT is offline   Reply With Quote
Old 06-01-2016, 11:48 PM   #10
aonemarine
Senior Member
 
aonemarine's Avatar
 
Join Date: Dec 2013
Location: Delaware
Posts: 252
Default Re: Rebuilder out of business and I know why

check the depth of the ring grove. if the rings are too wide for the depth of the grove when the piston expands it will wedge the rings into the cylinder wall.
aonemarine is offline   Reply With Quote
Old 06-02-2016, 02:43 AM   #11
Tom Wesenberg
Senior Member
 
Tom Wesenberg's Avatar
 
Join Date: May 2010
Location: Mpls, MN
Posts: 27,461
Default Re: Rebuilder out of business and I know why

I would do as Larry said.

John, I'm really surprised the large bore and stroke G only has a 2" journal. I'd have thought it would have used about a 3" journal.
Tom Wesenberg is offline   Reply With Quote
Old 06-02-2016, 06:15 AM   #12
harleytoprock
Senior Member
 
Join Date: Aug 2014
Posts: 438
Default Re: Rebuilder out of business and I know why

When you removed the .030 pistons, how did they look? Any scoring on pistons or rings? Did you check the .030 ring end gaps?
harleytoprock is offline   Reply With Quote
Old 06-02-2016, 06:22 AM   #13
James Rogers
Senior Member
 
James Rogers's Avatar
 
Join Date: May 2010
Location: Asheville,NC
Posts: 3,099
Default Re: Rebuilder out of business and I know why

40 Deluxe is on the right track. You are probably having a problem with expansion of the pistons tho, I have never had one seize when shut down. I have had pistons that seized or almost did while running. This most often or always happened when I used older split skirt pistons. I always hone to .004-5 for clearance using pistons available from Snyder's. This is to coincide with a ring end gap of .004 per inch of piston diameter or, .014-16. As for the .002 bearing clearance, I always set mine at .0015 -.002 so, .002 is at the top of the range and close to too loose. I have never had a problem with these practices and have many motors running happily.

Last edited by James Rogers; 06-02-2016 at 06:39 AM.
James Rogers is offline   Reply With Quote
Old 06-02-2016, 06:33 AM   #14
George Miller
Senior Member
 
George Miller's Avatar
 
Join Date: May 2010
Location: NC
Posts: 2,959
Default Re: Rebuilder out of business and I know why

The rule off thumb is .001 per inch. The bearings are good, a little on the loose side for a new engine. Pistons are to tight. You need to have the cylinders honed. You could take it to any engine shop and have it honed. Get those .020 pistons out of there it is not going to work.
George Miller is offline   Reply With Quote
Old 06-02-2016, 06:40 AM   #15
James Rogers
Senior Member
 
James Rogers's Avatar
 
Join Date: May 2010
Location: Asheville,NC
Posts: 3,099
Default Re: Rebuilder out of business and I know why

George is correct. Rods 1.500 journal is .0015 and the mains are 1.625 and are .0015 also. He is also correct about the .020 pistons. A recipe for disaster.
James Rogers is offline   Reply With Quote
Old 06-02-2016, 10:35 AM   #16
Fullraceflathead
Senior Member
 
Fullraceflathead's Avatar
 
Join Date: May 2012
Location: Riverside, Ca
Posts: 922
Default Re: Rebuilder out of business and I know why

You can't run .020 size pistons in a .030 bore.
Yes it will run but the pistons are running way to lose and are cast Aluminum.
They will work harden and start cracking sooner or later.
Piston sets are still only $100.00 why risk a total failure later as that's what is going to happen?
__________________
"If I asked people what they wanted they would have said faster horses."
-Henry Ford

"Primitive technology is not a design flaw"


1928 Ford Model A Roadster Pickup
1930 Gordon Smith Air Compressor
1941 Willy's Pickup
1960 Thunderbird-For Sale
1964 Buick Riviera 2x4 425
1965 Pontiac GTO, 455 Super Duty
2004 Dodge Ram SRT-10, V-10 Viper
1977 Charger Jet Boat,460 Ford,Jacuzzi Jet
Front Engine Nostalgia Dragster,Supercharged 296 "Fullrace Flathead" Ford
Engine Build up on DVD ask
Fullraceflathead is offline   Reply With Quote
Old 06-02-2016, 10:39 AM   #17
katy
Senior Member
 
katy's Avatar
 
Join Date: Jun 2015
Location: Alberta, Canada
Posts: 2,193
Default Re: Rebuilder out of business and I know why

Quote:
It took some doing but we did get it going and it ran fine...that is until we turned it off. When that happened we couldn't get it restarted until it almost totally cooled down.
I've seen this happen a few times, it was caused by the rings end gap being too small. Rebuilder said "you don't need to check the gap on new rings, they're factory set".
THAT'S NOT TRUE, EVERY ring has to be checked in it's individual cylinder.

Quote:
What is the ring gap set at?
Quote:
Did you check the .030 ring end gaps?
Ditto on what Larrys40 said:

Quote:
My druthers would be to NOT run undersize pistons but to disassemble and hone the block to the proper piston fit... then reassemble with new rings.
__________________
Don't go away mad, just go away.
katy is offline   Reply With Quote
Old 06-02-2016, 10:50 AM   #18
James Rogers
Senior Member
 
James Rogers's Avatar
 
Join Date: May 2010
Location: Asheville,NC
Posts: 3,099
Default Re: Rebuilder out of business and I know why

Quote:
Originally Posted by katy View Post
I've seen this happen a few times, it was caused by the rings end gap being too small. Rebuilder said "you don't need to check the gap on new rings, they're factory set".
THAT'S NOT TRUE, EVERY ring has to be checked in it's individual cylinder.





Ditto on what Larrys40 said:
Ring end gap is not set by anything EXCEPT the bore of the cylinders.
James Rogers is offline   Reply With Quote
Old 06-02-2016, 11:15 AM   #19
George Miller
Senior Member
 
George Miller's Avatar
 
Join Date: May 2010
Location: NC
Posts: 2,959
Default Re: Rebuilder out of business and I know why

I agree with James .003 in the bore dia. will make much more than .003 in the end gap. Do the math.
George Miller is offline   Reply With Quote
Old 06-02-2016, 01:22 PM   #20
ursus
Senior Member
 
Join Date: May 2010
Location: Oregon
Posts: 1,050
Default Re: Rebuilder out of business and I know why

Quote:
Originally Posted by aonemarine View Post
check the depth of the ring grove. if the rings are too wide for the depth of the grove when the piston expands it will wedge the rings into the cylinder wall.
What is the minimum clearance (difference) between the depth of the ring groove and the width of the rings?

I have seen quite a bit of variation over the years, with compression groove depths of 0.160 - 0.210 inches and compression ring widths of 0.160 - 0.180 in width. I have some older Model A pistons that are labeled with a warning that they have shallow ring grooves and are not to be used with rings having a standard width, but it doesn't specify the desired ring width.
ursus is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 01:33 PM.