1940 v8 engine rebuid

[Robin 47 ford pickup]

Hi guys , what is the biggest piston I can use in a 1940 V8 (91A?) std bore engine with bad bore corrosion without breaking into the water jacket?
Is there a gain to go to 8BA crank and rods if they will fit ? any help would be great . For any of you Aussies on this forum who would be the best people to use in Melbourne to do any machine work on this engine ?
cheers Robin

[JSeery]

Only way to really tell is to have the cylinder walls sonic tested. There is no way to tell where the cores were in the original casting without testing. You should also have the block pressure tested before putting any money into it.

[deuce_roadster]

JSeery beat me to it, you also don't know how much rust has diminished the casting, what he said x3.

[Kube]

You've been offered great and very accurate advice. I've bored a number of these and blown through a cylinder wall with as little as +.030". One I did about 35 years ago went a full +.155 with no issues. I recall I had That engine is in a friends car and still runs beautifully to this day.

[Seth Swoboda]

I'm just throwing this thought out here...You can use an 8BA crankshaft and rods, however the 8BA rods are larger on the big end of the rod than then say 21A rods that would be used in a 1940, 221 cubic inch engine. So the big end of the 8BA rods will not fit through the bore of the 221 engine unless you bored the block out to 239 cubic inches.

If you used the 8BA rods and lets say hypothetically your standard bore cleaned up at .060 over, you would have to install the rod and piston assembly through the bottom of the cylinder bore since the 8BA rod will not fit through the smaller cylinder bore.

Using an 8BA crankshaft and connecting rods will work but when it comes to engine assembly it would be a lot of work to get the rod assembly installed. The rod journals on the 8BA are bigger than the 221 crankshaft, the main bearing size is the same.

Where am I going wrong here?

[flatjack9]

Sponsored Links (Register now to hide all advertisements)

Nothing wrong.

[Robin 47 ford pickup]

ok guys thanks , the cylinders on this engine are pretty bad so the 239 CID pistons maybe the option if the walls are thick enough . I have all 8BA parts available . only going this way because the engine # is stamped on the chassis and I am trying to keep this thing as original as possible .
cheers Robin

[Ken/Alabama]

Never seen the engine with a number to match the frame number. But the transmission is stamped with the matching number on the pad on the top close to the bell housing on the engine that matches the frame. Your engine should go to 3 3/16 though without a problem.

[Robin 47 ford pickup]

The engine number is stamped on the chassis , not a match to the frame number . So your telling me that a 1940 block will bore out to 3-3/16? thats 1/8 overbore . how much meat would be left in the wall of the bore at a guess? it would solve my rusted bored problem an std 3-3/16 pistons are they easy come by??
cheers Robin
sorry guys just being careful here

[Phil Gillespie]

Originally Posted by Robin 47 ford pickup

The engine number is stamped on the chassis , not a match to the frame number . So your telling me that a 1940 block will bore out to 3-3/16? thats 1/8 overbore . how much meat would be left in the wall of the bore at a guess? it would solve my rusted bored problem an std 3-3/16 pistons are they easy come by??
cheers Robin
sorry guys just being careful here

I am in a similar situation at present. My block is 3 1/16 plus 80 thou over.
Presently being cleaned and then to be Ultrasonic to assess bore wall thickness with a view to go to 3 3/16. Better to have it checked first rather than go at it blind and hope for the best.
Phil NZ

[Ken/Alabama]

Originally Posted by Robin 47 ford pickup

The engine number is stamped on the chassis , not a match to the frame number . So your telling me that a 1940 block will bore out to 3-3/16? thats 1/8 overbore . how much meat would be left in the wall of the bore at a guess? it would solve my rusted bored problem an std 3-3/16 pistons are they easy come by??
cheers Robin
sorry guys just being careful here

Yes, 1/8" overbore shouldn't be a problem on a 40 block. Have done it many times. Remember at 1/8" that's only 1/16" into the cylinder wall. 3 3/16 std pistons are easy to come by.

[Bored&Stroked]

As a few have said . . . it "should". This doesn't mean it will.

You should have the block cleaned, then magged first. If it passes the mag test, then have them sonic test the cylinder walls - should really measure every bore in about 9 - 12 places . . . recording all the information as such. Based on this, you'll have a pretty good idea as to IF you can bore it .125, if any of the cylinders need to be "moved" a bit to account for core shift, etc.. Given the costs of rebuilding these engines (and the time and $$$ involved), it is always a good idea to do these preliminary steps before you start buying parts and making plans. If you get it to a 3 3/16 bore, then all the rods will fit . . . so that problem goes away.

Also, since you mentioned a lot of rust in the bores - it is a really good idea (once you know the block will meet your requirements) to have the block baked, blasted and even chemically cleaned to get all the rust, casting sand and other crap out of the water jackets. This is an important step if you want to have a cool running flathead. Don't skip it!

Good Luck!
B&S

[Seth Swoboda]

If authenticity is not a worry here, then why not just find a suitable 59A or 8BA block to use and avoid all the other issues or potential problems?

[JSeery]

Robin, how about posting a photo of the engine/chassis numbers you referenced? Most of us have never seen or heard of this before, would be interesting to see.

[Robin 47 ford pickup]

Ok , I am going to sand blast the rusty bores to get a better idea how bad they are . this engine is out of the 3 door ute on another post of mine Ex army so I want to keep as many original parts as possible , thanks for the help so far guys. the crank and rods are really good out this engine if anyone is interested in them . Anyone got a pair of alloy heads to fit this engine the originals are rotted away. I think the whole truck was under water at some stage as the gearbox was full of water as well