|
Sponsored Links (Register now to hide all advertisements) |
|
|
Thread Tools | Display Modes |
08-09-2021, 02:44 PM | #1 |
Junior Member
Join Date: Aug 2021
Location: Winterthur, Switzerland
Posts: 12
|
Engine overhaul options/decision
Hello
I'm new to the barn and just started a A project. I dismantled the for at least 25 Years sleeping engine. Head pulled.jpg Two oil rings where broken and one compression ring has gone during the removing. After cleaning (the cylinder surfaces felt smooth again) I mesured the cylinder an piston diamters. Engine bore mesurements.jpg With my simple understanding I'm not sure which oversized pistons are in. Should be the 0.06 in, right? What treatment would be recommended in this case? Could a new honing and new ring sets work out or is a borint to the next oversized piston diameter a must? Engine bore original and play.jpg Btw is the piston play of 0.002 in to 0.007 in correct? Thanks a lot for any reply Last edited by Tobias; 08-09-2021 at 02:49 PM. |
08-09-2021, 03:04 PM | #2 |
Senior Member
Join Date: May 2010
Location: Between Seattle & Tacoma
Posts: 2,351
|
Re: Engine overhaul options/decision
You probably want to take it to your machine shop. They can accurately gauge the taper in the cylinder, and tell you what size pistons to get. I would not reuse the old pistons.
|
Sponsored Links (Register now to hide all advertisements) |
|
08-09-2021, 06:58 PM | #3 |
Senior Member
Join Date: Jan 2012
Location: Western North Carolina
Posts: 3,815
|
Re: Engine overhaul options/decision
If I read your measurements correctly it looks like you have from 0.017 to 0.024 inch clearance between the pistons and the cylinders. I think the clearance is supposed to be 0.002 to 0.004 inch if my memory serves me. In any case, new pistons are needed.
How is the rest of the engine? Bearings?, Piston pins?, Camshaft? etc.? I would probably take it somewhere to get it rebuilt.
__________________
A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
08-09-2021, 07:05 PM | #4 |
Senior Member
Join Date: Mar 2012
Location: Ohio
Posts: 1,915
|
Re: Engine overhaul options/decision
Using a SAE, and not a metric micrometer, right?
|
08-09-2021, 10:09 PM | #5 |
Senior Member
Join Date: Aug 2020
Posts: 235
|
Re: Engine overhaul options/decision
If it were my engine.....hone it and new rings and replace the valve springs. Half the springs were compressed for 25 years and they will not recover..
|
08-09-2021, 11:34 PM | #6 | |
Senior Member
Join Date: May 2010
Location: PASADENA, CA
Posts: 1,881
|
Re: Engine overhaul options/decision
Sponsored Links (Register now to hide all advertisements)
Quote:
There is about .004-.005 taper in the bores which is not bad for these old engines. If the bearings look good, hone the cylinders and lap the valves if that is all they will need or grind the valves and seats if necessary. This engine will run just fine for many more miles. be sure to change the timing gear if it is a fiber gear and look at the cam. If you want the engine to be absolutely like new, then re-bore the cylinders, new pistons, valves cam and bearings etc. but for how most of use our Model A's. I think it will work just fine to work with what you have. My opinion, Chris W. |
|
08-09-2021, 11:36 PM | #7 |
Senior Member
Join Date: May 2010
Location: PASADENA, CA
Posts: 1,881
|
Re: Engine overhaul options/decision
By the way,
Your current engine has been over-bored by 0.060 inches which is a very common size. Chris W. |
08-10-2021, 11:28 AM | #8 |
Senior Member
Join Date: Jun 2010
Location: Temecula, CA
Posts: 4,066
|
Re: Engine overhaul options/decision
Minimum piston-to-wall clearance should be .003" with modern piston and the way we drive. For stock engines I bore to .003" then hone another .0005". On performance engines I allow more clearance.
|
08-10-2021, 02:38 PM | #9 |
Senior Member
Join Date: Aug 2016
Location: West Virginia
Posts: 430
|
Re: Engine overhaul options/decision
If you have any machine work done I would highly recommend using a shop with experience on model A engines that is recommended by other A owners. I would also recommend requiring the shop to magna-flux and test for cracks before doing anything.
I have a nightmare story with my engine that is still unresolved over a year later. |
08-10-2021, 03:21 PM | #10 |
Senior Member
Join Date: Feb 2011
Location: NNNNNNNNJJJJJJJJJJ
Posts: 6,758
|
Re: Engine overhaul options/decision
buy a fresh engine and install....... yes you will have to ship it.
|
08-10-2021, 05:09 PM | #11 |
Junior Member
Join Date: Aug 2021
Location: Winterthur, Switzerland
Posts: 12
|
Re: Engine overhaul options/decision
Thanks for all the feed back.
I'll definitely contact a machine shop. Unfortunately there are not many arround the corner with Model A engine experience. @nkaminar, Yes the clearence of up to 0.024 inch is way too much according to the red book p 1-128. In general the bearings, piston pins and camshaft look great. The old oil was homogeneous and had absolutely no chips or cooling liquid in it. So far I found two more irregularities. The main oil line from pump shaft to chamber reservoir looks not good Main oil line.jpg. It seems as parts from the iron cast has vanished. The piston 3 babbitt bearing has lost a part of the surface Piston 3 rod bearing surface.jpg. I'm not sure how concerning the first one is? Definitely need to solve the rod bearing. @Gene F, I used a metric micrometer an calculated the inches @jerrytocci, good point, I'll keep that in mind @CWPASADENA, do you think there is a chance to go on with the excessive piston cylinder clearence? If I conclude right then the compression will not build up as good and the oil consumption can increase. |
08-10-2021, 06:02 PM | #12 |
Senior Member
Join Date: May 2010
Location: Oregon
Posts: 5,946
|
Re: Engine overhaul options/decision
If you know no machinists with model A knowledge, find a machinist that knows his job and is careful and takes pride in his work.
|
Thread Tools | |
Display Modes | |
|
|
Sponsored Links (Register now to hide all advertisements) |
|