How far to bore a block?

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Model T Ford Forum: Forum 2012: How far to bore a block?
Top of pagePrevious messageNext messageBottom of page Link to this message  By steve miller- mississauga,ontario on Saturday, August 11, 2012 - 06:50 am:

Macs lists up to .060 pistons in their catalogue.
Egge lists those plus .080, .100, and .125 .
My block has rust pitting on #2. Cylinders 1, 3, & 4 will clean up at .020 . #2 can be sleeved or bore all 4 to .100 or .125
Any comments?
Thanks Steve


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren (Australia) on Saturday, August 11, 2012 - 07:19 am:

The more you bore the hotter it will run.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Richard Bennett on Saturday, August 11, 2012 - 07:22 am:

Steve, if you sleeve the one cylinder and bore to .020", your block should have two more later lives if needed. Otherwise you will go straight to it's last life without sleeving all.

Just my thoughts.

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dare - Just a little South West . on Saturday, August 11, 2012 - 07:22 am:

re sleeve back to std, a much longer life and cooler engine should be the result.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Doolittle on Saturday, August 11, 2012 - 07:28 am:

Steve- I a a pickup that is driven regularly on 100+ mile runs. It is bored .040 about 10 yrs ago. No overheating issues, not even on this summer's heat.

I might add the the radiator was re-cored at the same time because of overheating when the engine was std and stock.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Saturday, August 11, 2012 - 08:03 am:

My flathead engine that had been bored to .080 was harder to keep head gaskets on. They are not in oversizes. I have a racing block that was bored to .125 but have never used it.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Killecut on Saturday, August 11, 2012 - 08:19 am:

I have to agree with Ricks, as I have an engine bored 80 over. Getting the head gasket just right is very tricky. Also there is the increased heat issue. It can be overcome but not easily or inexpensively.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Chantrell - Adelaide, Australia on Saturday, August 11, 2012 - 09:14 am:

.060" max, otherwise sleeve & bore it back to standard...


Top of pagePrevious messageNext messageBottom of page Link to this message  By J and M Machine Co Inc on Saturday, August 11, 2012 - 10:09 am:

Steve:
I would recommend you sleeve the block on the cylinders that need it.
Every Block is different .
Just because there are pistons available to .100 doesn't mean your block will make it to that.
Since we are a machine shop I can offer you sound judgement that not all blocks have the same thickness after some 80 years.
Bearing in mind core shift, rot and other factors that play into a cast part.

Once in a while we see a block like yours that we have to sleeve and in the process the cylinder in question is thin and portions end up being paper by the time we reach the sleeve diameter.
Our point of view would be to sleeve the hole rather than take it out to the max and like others in this chat have said don't waste the block.


Top of pagePrevious messageNext messageBottom of page Link to this message  By steve miller- mississauga,ontario on Saturday, August 11, 2012 - 10:31 am:

Thanks for your input. All good points you have raised.
Allan, David and David, resleeving the block should be good for another 100 years.
Ralph and Dan, There would not be much gasket between the bores.
J&M, 45 years ago we used to bore 283's to 301. Some blocks would do it. Some wouldn't.
My block is in the hot tank right now. Goodbye babbitt.
Thanks Steve


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donnie Brown on Saturday, August 11, 2012 - 10:57 am:

Hi: Something that has not been addressed is, how are you going to use the car. Sometimes we over restore these old cars. If it will clean up at .020 and only have a few pits I would run it as is. If at .020 you have a line of pits where a ring was stuck I would sleeve the one cyl and save the rest of the engine life. For most people who drive there Ts a little bit to several hundreds miles a year. You could get by with rings only, leave the pits alone and have fun(as long as there is no line of pits around the cyl wall. If you plan on a lot of hard driving then I would recomend to sleeve the 1 cyl and re-bore to .020. I may get a lot of responce for what Im about to say, but I bought a 26 Roadster several years ago. It ran OK but was erratic. I pulled the head to check the valves and everything looked good, even had hone marks on cyl walls new .060 pistons,new valves, clean as new,while trying to set valve clearance I found the cam bearings were wore out. The previous mechanic had did something wrong (never did figure out what he did) as the cam would "walk" in the front bearing almost 1/8 inch.The cam had worn thru the babbit into the cast iron.(remember this car ran) So while Im replacing the cam bearings, and cam, I notice I can see almost all the ring on the pistons. I mic the holes and he had a .060 piston, in a .080 hole. The holes were a perfect re-bore just the wrong size pistons. Im pretty disgusted at this point so I just set the valves, checked the bottom end of motor for problems and put the head back on. I started the motor and it sounded good. I have been driving the car for about 5 years now and it uses no oil, has no noticable piston slap, does not overheat. I hand crank the car useally first or second pull. and I have about 1500 miles (or more) on it. We drive our cars quite a bit and live in the Ozarks of Ark. we have lots of hill driving. but I do agree with the others above about, just because .060 .080.125 or whatever is available does not mean we need to use them. These old motors are very forgiving and useally do not need the tolerances of the modern world, to work well. I believe that the minium we change the parts the better off we are. Good luck with the project.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Woods, Katy, Texas on Saturday, August 11, 2012 - 08:53 pm:

I have a late 27 block that was worn to .080 on every cylinder. I was told it was a stationary engine, not in a vehicle. Ross Lilleker, here in Texas, advised me to sleeve all the cylinders back to standard, which he did. I do believe his advise was given in my best interest, and not just to add to his machining bill.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Saturday, August 11, 2012 - 09:29 pm:

If it was my car I would bore the 3 cylinders to .020 and the bad one I would have bored to whatever was needed to clean up.
There is no need to bore the 3 cylinders out to big oversizes just to make them the same as #2.
Pistons all weigh the same.
You should have no overheating problems if you leave three at .020.
If you can not get pistons cheap enough by the each then get #2 sleeved and bore to .020.
Why spend a $100 to sleeve a cylinder when you don't have to?
I just did model A this year that had a bore grooved badly from a floating piston pin.
The other 3 bores were OK. I had the bad one sleeved and all 4 bored to .060 but if it had been my car I would have just left the good 3 at .040 and bored the bad one to whatever it took to clean up as long as it stayed below or at .080.
I had a Jag 120M many years ago with five standard pistons and one was .060.
It had a broken piston so I just bought one piston. The other five were good as new.
Does'n hurt a thing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Saturday, August 11, 2012 - 09:31 pm:

As Kerry says, "The more you bore, the hotter it will run"!
Sleeving 4 cylinders is an extra $400.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Milton,WA on Sunday, August 12, 2012 - 11:19 am:

I had picked up a rebuilt block bored to .100 over and the pistons were too large for the combustion chamber and caused interference with the head - I had to have the head machined for more clearance


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Sunday, August 12, 2012 - 11:54 am:

I never had an overheating problem at .080 over, just had to replace the head gasket one time, in western NY on the 1998 Greatrace. It didn't stop us; we just used more water one day than gas.

When I tore the engine down for inspection, we found 4 cracks in the block and 3 cracks in the Model A crank. That ended its career.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Sunday, August 12, 2012 - 11:59 am:

Quote, "The more you bore the hotter it will run."
I don't believe that, years ago I had a flathead V-8 (8BA 239 CI) bored out to .125" OS and never had a problem w/overheating.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren (Australia) on Sunday, August 12, 2012 - 05:29 pm:

Ken, no statement that it would 'over heat' just that boring a engine will run hotter, now if the cooling system is in good order, as a rule no problems or in some cases in when a vehicle is up graded for a model change, ie, engine size, same block but larger pistons, the radiator is also up graded too.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Woods, Katy, Texas on Sunday, August 12, 2012 - 08:02 pm:

Like others have said. Every block is not alike due to years of internal corrosion and shifting of the core during casting. Unless you are Superman and have X Ray vision, how thick do you know each cylinder is. I'd hate to have a valuable block, whether its original to the car or not, and find out it was ruined because i gambled and bored it too far. Over heating is just a possibility. It may not occur. boring into a crack, pin hole or casting flaw are other possibilities.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Sunday, August 12, 2012 - 08:25 pm:

Last year I had a '40 Buick block bored to .080" oversize.
I never was able to get pistons for it because all the piston companies and Buick specialists said those engines could not be driven at speed with .080 over. They said they would all overheat.
I have know of cars that never had a heating problem until the block was bored-usually quite a bit.
I did a couple in the last 30 years that were just fine with stock bore and then had to be bored a lot because of a wrist pin gouge in a cylinder. Then after the engine was rebuilt I could not even road test the car going home at night. Try to explain that to a customer.
Now a new radiator is added on the work order before the customer leaves the car-unless the radiator is only a tear or two old.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bede Cordes, New Zealand on Sunday, August 12, 2012 - 09:32 pm:

Can i ask why would a bored engine will significantly run that much hotter ? Does the increased surface area in the cylinders gained by boring result in that much more heat for the cooling system to get rid of when boring 1 or 2 sizes up ? (this a genuine question, not a shoot that man down smart comment). Cheers, bede.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Cole ---- Earth on Sunday, August 12, 2012 - 09:49 pm:

Well,Bede,I am going to ask a question to.
I relize T engines are not rocket science.if they were I would be in BIG trouble.
But I thought balance was important to some degree in a engine.So if we put a .040 piston on a crank along with 3 standards,are we not putting a unbalanced load on the weak crank?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Sunday, August 12, 2012 - 09:57 pm:

I didn't have any overheating of the .080 engine in two Greatraces.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren (Australia) on Sunday, August 12, 2012 - 10:10 pm:

Bede,
On a T I say no, vendors sell up to 60thou, not a problem, maybe a 80 is ok too, but after that as Steve has asked, the 100 and up which is not the done thing by today's rebuilds for all the reasons posted.

Mack,
Old school rebuilds for low reving engines, back in the days when you could buy just one piston and rings was done all the time, not a good idea by today's high preformance standards but in saying that and the high costs of out board motor rebuilds, you can buy and rebore just one cylinder, the new piston is balanced to the same weight as the others.


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