More 312 Ford Y block problems

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gn69z28
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More 312 Ford Y block problems

Post by gn69z28 »

Is it normal to see these engines with the housing bored for the cam bearings out of spec. My center bore is .0025 under the small spec and bored 4 and 5 are .001 under which would make the cam to tight. I also think they are not in align with each other. The front two seem to be on a different plane then the rear two. Is this a normal problem with these blocks and what do you do to correct this. If I put cam bearings in I'll never get the camshaft to go in.
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Re: More 312 Ford Y block problems

Post by BillK »

Machining on a lot of older engines can be pretty terrible. All you can really do is put the bearings in and scrape them till they work. I always put cam bearings in one at a time anyway. I start with the back one and make sure the cam goes in, then put in the next one and try the cam again and so forth all the way to the front. That way when you get one that is tight you know which one it is and you can work it till it fits. Chryslers seem to always have one or two that wont go.
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gn69z28
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Re: More 312 Ford Y block problems

Post by gn69z28 »

I've had to scrape bearings before. Especially on 350 Chevy's from the 70s. But on this engine the front two and the rear two aren't aligned with each other. That's going to be a lot of scraping. My concern is bearing clearance.
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Re: More 312 Ford Y block problems

Post by pdq67 »

Fwiw, Years and years ago, my wife's Uncle Mutt Hill over at Indy was into Model T's. (He's long gone)..

He poured his own main and rod babbitt bearings and bored/honed them

He even had made custom Herculoy, "T", main caps and sold them back then.

I once watched him bore/hone a T blocks mains using a homemade 5(?) foot long bar. He started at one end and the bar was long enough that he could machine them all at once so there was no coming from the front end 1/2 way, stopping and then finishing the job from the back end. Everything was in line!

Just food for thought is all.

And the old man had a souped up, period correct '23 T P/U that he drove from Indy to Moberly, MO on I-70, then north on Hwy 63 running like 70 mph. He usually had his little dog with him!!

I might be wrong, but i think the engine had an OHV head conversion (Rajo?), a bee hive oil filter, and the rest of the P/U had a 2-speed Ruckstell rear end along with tall assed Buffalo wheels.

About the only thing that wasn't period correct was his Vega steering gear box! I saw it so asked him about it and he said the stock T box was for shit compared to the new Vega box!

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Re: More 312 Ford Y block problems

Post by mag2555 »

I have seen these where not only where the Cam Bearing( s) are out of alignment to each other in a Horizontal plane, but a few of the bulk heads where off in a vertical plane also.

The result of this even if you can shave them or even pour new ones is reduced load support area supplied by the Bearing to the Cam!

This was not a big deal with the spring pressures run back then, but if your going for more it could be!
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Re: More 312 Ford Y block problems

Post by PackardV8 »

Since you're a couple of thou undersize anyway, have you considered having the cam tunnel line bored to size?
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Re: More 312 Ford Y block problems

Post by gn69z28 »

I have thought about having the tunnel line bored. But where I'm located, finding someone that's done it before to feel comfortable with doing it is the problem. Fortunately the owner of the engine understands the issue and is in no hurry.
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Re: More 312 Ford Y block problems

Post by PackardV8 »

gn69z28 wrote: Fri Sep 18, 2020 11:44 am I have thought about having the tunnel line bored. But where I'm located, finding someone that's done it before to feel comfortable with doing it is the problem. Fortunately the owner of the engine understands the issue and is in no hurry.
Doubtful you can find anyone anywhere who's recently line-bored a Y-block cam tunnel. However, larger shops bore cam tunnels on OHCs every day. It's just a slightly different setup to do a Y-block. Just make sure you give them in writing the finished ID you want.

FWIW, I had to make up a set of cam bearings for an obsolete engine by ordering the closest available from the Durabond catalog. A couple were not as tight as we wanted, but Loctite Bearing Mount took care of that.
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Re: More 312 Ford Y block problems

Post by Joe-71 »

Cam bore miss-alignment is a problem with some of the 312 blocks, but the best solution is to use a 60-66 292 block and turn the mains down on the 312 crankshaft to the 292 journal size. The later 292 blocks usually can be bored to 3.800 easily, and with a sonic check some can go to 3.860" or more. It is an easy way to slow down bearing speed heat build up, and gain a few horsepower. The 312 crankshaft can be offset ground and use 2.1 or 2.0 rod journals for more cubic inches. There are several shops still building these type of Y Block stroker engines if you are serious about a build. Joe-71
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