351C Max overbore

[1973stang]

I have 2 351C blocks from 1973 mustangs that are .30 overbore, I need to do a rebuild as these came out of cars and I know little of thier mileage or history. If possible I will be able to just hone and use .30 pistons again. BUT my luck is never that good. I would like to have them sonic tested for cylinder thickness but dont know where to get it done or how much it cost. On an average 351C block is a .40 overbore usually fine? Also how would you go about checking for non obvious cracks in the block if it is already out of the car and disassembled. I didnt notice any mixed fluids when tearing them down.

Any advice or comments would be great.

 

[1973stang]

Oh and Im just looking to rebuild the best of the two.

 

[rbohm]

you can go another .010 without problems. if you need to go further then have the blocks sonic checked for core shift.

 

[1973stang]

so doing a .40 over is not out of the norm? Should I not mess with the sonic test then? I hear alot of talk about them on here.

 

[1973stang]

Should I run into over heat issues at .40 over

 

[dodgestang]

My 410 is .040 over. It runs a little warm (then again I have tiny little aluminum radiator in the my 65) but it's ok and has not overheated on me...but then again I also don't drive it when it is over 90 degrees because it has no AC and I don't get stuck in stop and go traffic.
.040 is pretty common and many places stock pistons in that size.

 

[1973stang]

Well my concern is due to the 351C having notoriously thin walls from what I have read, I could be wrong I am just wanting to cover all my bases before dumping the money into the build.

 

[shoguun]

its fine to do it but just keep in mind that the more you boar the more cooling problems your gonna have

 

[1973stang]

any advice on what I should do to correct the cooling issue? (on a college kids budget) Different waterpump? radiator from another car? its going in my 1973 mustang. Would love inexpensive fixes but I am open to all input.

 

[mach1one]

.040 is fine, my block is .060. Not really ideal but it works. We did initially having some overheating problems, but my cooling mods that fixed them are pretty basic. Stock radiator, flex fan, big oil cooler mounted in the grill opening, and water wetter. Keeps about 195-200 idling in the heat and is fine at speed. so far so good.

Eventually I'd like to get a thicker radiator but for now the setup works.

 

[rbohm]

.040 is fine, my block is .060. Not really ideal but it works. We did initially having some overheating problems, but my cooling mods that fixed them are pretty basic. Stock radiator, flex fan, big oil cooler mounted in the grill opening, and water wetter. Keeps about 195-200 idling in the heat and is fine at speed. so far so good.

Eventually I'd like to get a thicker radiator but for now the setup works.

probably the two best mods here are the large oil cooler and the water wetter. i would recommend using a largest radiator you can stuff into the compartment, either a high efficiency three core copper/brass rad, or an aluminim rad with two rows that are 1" wide each. dump the flex fan in favor of an electric fan from something like a taurus.

 

[1973stang]

I have the stock 1973 radiator now and I am on a budget, are there any larger radiators from other vehicles of the era? I don't know about buying a new aluminum unit. I will def go for the oil cooler and water wetter they seem like affordable mods.

 

[67efivert]

i had a 40 over 71 block and it cracked in number 7 wall im sure from the notorious core shift so id look into sonic testing or sleeving so u know what ur getting into

 

[1973stang]

does anyone know where I go to have sonic testing done? Is it expensive? Do average machinists have the equipment

 

[ddonaca351]

40 over isn't out of the ordinary...

Any good engine builder will know who has sonic check equip locally... ( you'll want him to tank and mag the blocks first anyhow, so you're not wasting time and money sonic checking a cracked block )

If you're worried about heating problems, that's just a good excuse to get some alloy heads or go waaayyy overkill on the cooling system.

D

Hey since I didn't see it mentioned yet, don't forget you can always go cle-vor if you have to.

 

[1973stang]

Thanks for all the help guys, Heres a quick update of where I am at. I have both blocks torn down and I am going to send them to a shop for magnaflux and a cylinder wall sonic check. It will run about $60 a block to have this done. I think I may take one in at a time so they dont do them both if the first turns out fine. ( college kid budget remember). The clevor seems cool, do they turn out decent power? Better than a traditional Cleveland? I just did a lil spot research on them after I got your response.

 

[ddonaca351]

Naw, same power... kinda a pain though cuz of special manifold or intake plates needed, etc... just thought I'd mention it, so you know ALL options, but it would probably be a "only if I have to" kinda thing.



Also might be cheaper to get both blocks done at the same time: Alott of shops have a min charge time in .5 or 1 hr blocks of time, so for him to spend an extra 15-20 min doing 2 at the same time might be cheaper than paying him to do 1, then a week later do another... just fyi.

Plus even if you dont use the second one, once its tanked and maged and sonic'd, then you get a good quality 4-6mil garbage bag, enclose the block with a healthy shot of "fogging oil" and you can flea-bay it or whatever to recoup some of your cost.

( if the block is useable, *some* shops or engine rebuilders will take it in trade against labor cost, etc... )

D