Ford Y-Block Assembly Errors

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Tips for avoiding things that can bite you

By John Mummert

In disassembling Y-Block core engines, I have noted a number of common mistakes that are made during the assembly of Y-Blocks during rebuild. Take care to avoid these mistakes.

HEAD BOLTS

There appear to be two different length head bolts in a Y-Block engine-five short bolts near the spark plugs and five longer bolts under the rocker arms. It’s true that the five short bolts near the spark plugs are identical, but the five under the rockers are not the same. Two of these bolts are slightly longer and are installed at the outer ends of the head where the alignment dowels are located. Lay all 10 longer bolts (five per bank) next to each other and you should find four longer and six that are about 1/4″ shorter. Installing the longer bolts in the center three holes can cause them to bottom in the block, which can result in a blown head gasket.

HEAD GASKETS

The two head gaskets used on a Y-Block are identical. It might seem that the same face of the gasket would go against the block and the opposite face would go against the head on each side. This is not the case. What is critical is that the open coolant holes are at the back of the head and the blocked portion of the gasket is at the front. Look for the word FRONT on the gasket and place it at the front even if it looks wrong. This places one of the gaskets face up and one face down. Notice that there is a square corner at one end of the gasket. This must be at the front of the engine. This can be checked without removing the heads. If you are having overheating problems, check for these square corners at the top front corner of the head near the intake gasket.

CAM BEARINGS

If you are using a camshaft with a cross-drilled center journal, you must use 1955-early-1956 cam bearings designed for cross-drilled cams. If you are installing a cam with a grooved center journal, you must use the late 1956-1964 cam bearings. While on this subject, all new camshafts currently available for the Y-Block are made with the oil groove in the center journal too shallow. This will restrict the oil supply to the rocker arms. The groove should be made .035″ deep. Do not widen the groove.

ROCKER SHAFTS

It is amazingly simple to install the rocker arm shafts upside down on a Y-Block. The shaft stands are identical and will bolt down either way. You must be absolutely certain that the oil hole in the shaft aligns with the hole in the stand and is at the bottom when the stands are bolted down. If done improperly, no oil will get to the rockers. The best way to check for proper assembly is to look for the holes for the overflow tubes at the right hand end of each shaft. If the hole is visible with the rocker arms installed, the head it is correct.

292 & 312 MAIN CAP BOLTS

When Ford designed the 312, they made the main caps taller than the 292 cap, anticipating added load. The cap for the 312 rear main was left the 292 height to clear the rear main seal holder and the oil pan rail. This makes it possible to install any of the longer main cap bolts from the front four main caps in the rear cap, where they could bottom out during tightening. Some blocks are drilled deep enough to accept the longer bolts in the rear cap. There have been a few instances where the rear main area of a 312 cracked during assembly. Installing the incorrect bolts in the rear cap probably caused this. If any of the longer front bolts are installed at the rear, the misplaced rear bolt will be installed in a front cap where it will engage less than 1/2″ of thread.

Another problem was the incorrect torque specification of 120 lbs./ft., which was printed in all 1956 factory and many aftermarket manuals. This figure is excessive and undoubtedly caused the many of the cracked main webs in 312 blocks. Always use the later 95 lbs./ft. specification. It is also critical to check the amount of thread that will be engaged in the block. Do not use main cap bolts in any Y-Block that don’t reveal at least 7/8″ of thread when placed in the main cap. Later 292s have significantly longer main cap bolts, an indication that Ford realized this need. Care must be taken not to use bolts or studs that engage more than 1 1/8″ of threads as the oil passage to the main bearing will be blocked.

INTAKE MANIFOLD BOLTS

When installing the intake manifold, be certain not to use excessive length bolts. The intake manifold bolt holes in the head intersect the pushrod passages and too-long a bolt can hit the pushrods. Also, be certain that the bolt holes in the heads at the rear of the manifold are plugged. These are the threaded holes that are unused but are drilled through into the pushrod passage. Water, dirt and other crud can enter the engine through these holes. Use bolts with 1/2″ of thread so you don’t hit the pushrods.

LEFT- AND RIGHT-HAND HEADS

Although all Y-Block heads can be installed on either side of the block, after years of exposure to coolant the 0.906″ holes at the front of the intake surface will not accept a freeze plug. When choosing heads to rebuild, be sure you have a usable left and right. When installing heads, be sure the corroded hole is located toward the front of the engine. Be sure the hole at the rear of the head will accept a freeze plug or a temperature sender bushing. The water temperature sender bushing hole can be reamed to a larger size if need be. It is very discouraging to have two heads ready to install and find that they can’t be used as a set.

OIL GALLERY PLUGS

Remove all oil plugs and the oil filter adapter before hot-tanking the block. I’ve had the best luck by drilling out the center of the oil plug, leaving the hex. After heating the plugs with a torch, they come right out. I have never damaged a block using this method.

BLOCK DECKING

Don’t assume that since Y-Blocks have a lot of extra iron in them that the block doesn’t need to be deck surfaced, the main bearing bores align-honed or the heads surfaced. The block is around 50 years old and may have been heat-cycled over 30,000 times. Parts are bound to distort after that much use. The other enticement for bringing the pistons near flush with the deck surface is reduced risk of detonation. Many complaints of detonation have been noted with the pistons .030-.040″ in the hole and the engine is assembled with composition head gaskets.

RETORQUE THE CYLINDER HEADS

Although most modern gaskets are touted as not requiring retorquing, this extra step is still a good idea. Retorquing should be done 500-750 miles after assembly. As an alternative, the heads can be tightened, then loosened and torqued again during assembly. Y-Blocks have a large head gasket area for an engine, with 10 head bolts per bank, and this results in reduced clamping force on the gaskets.

TIMING GEAR INSTALLATION

Some people try to align the timing marks on the gears toward each other as is common on newer engines. This is bound to happen more often now as the replacement timing chains no longer have the pins marked for correct alignment with the gears. The marks on the Y-Block timing gears aim toward the oil filter side with 12 pins between them.
Hopefully these tips will avoid some grief.

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  • richardpatenaude

    Hi,I have a 56 ford 292 Y-block fordomatic. I installed a rebuilt engine and it leaked oil from the main seal from day one. I was told this is common. But after 6,000 mls it started to leak at the rear of both head gaskets, not when driving but when you shut it off and let it site. I was told that this is uncommon. All together I have put 18,000 mls on the new engine. Can I change the main seal without removing the engine and what type of main seal should I use. What can I do about the head gasket. Thank you Richard

  • richardpatenaude

    Hi,I have a 56 ford 292 Y-block fordomatic. I installed a rebuilt engine and it leaked oil from the main seal from day one. I was told this is common. But after 6,000 mls it started to leak at the rear of both head gaskets, not when driving but when you shut it off and let it site. I was told that this is uncommon. All together I have put 18,000 mls on the new engine. Can I change the main seal without removing the engine and what type of main seal should I use. What can I do about the head gasket. Thank you Richard

  • stevenscalia

    Can you tell me anything about the heads on a Y block ? some have freeze plugs and the ones i just found dont have them Thanks Steven

  • Mervross

    I HAVE AN OIL LEAK AT THE CAM PLUG. i REPLEACED THE 2 1/16 PLUG AND THE PROBLEM IS STILL AN OIL LEAK. IS THIS THE CORRECT SIZE AND IF SO DO i NEED TO USE SOME SEALER

  • Chuck Lee

    I just put another rear seal in my 312 .This time I used a seal from a Dodge 318 .I had heared it was to tight and would not work but I was at the end and did it anyway.I first went and got the diameter of the 318 crank seal aera it was 2.690 ford is 2.750 mine was already .025 small there so I went to 2.690. Then I made a plug to fit the seal aera the same size as the 318 crank,this let me fit the seal and see how it would fit it the crank was in. I then removed the two ears off the one side of the split seal ,then I had to remove about .075 to.100 off the end of one half of the other half,it took a couple of trys to get the lip to be sealing all the way around my plug that represented the crank.(the seal is just a bit big in the grooves)Once I could see it was good I installed the crank and the seal.I made sure every thing was spotless and I used a high heat rtv for the ends of the seal and the block with the rubber plugs.It has now been about 100 miles and so far not a drop. This seal is by far a better fit in the groove and this will not work in a 292 or a 272 the grooves are to small.

    Chuck Lee at clee@mts.net

  • precisionengine

    I'd suggest contacting Jody at Medina Mountain Motors…330-435-6236. He can advise you.

  • Bill Randall

    I have found on various 312 motors, a tray bolted to the front on the block, with only one 1/4″ bolt. Looks as if the tray is attempting to collect and direct returning oil towards the engagement of the timing-chain to the crank-spocket. How successful was this in your opinion, John? Why not used something like this on all Y-Block builds? What harm could occur if the “tray” is used?

  • Llkkjjfc

    The freeze (core) plugs werein the front and rear ends of the heads on 1954 and 1955 heads. A few early 1956 heads may have them. They were not there on 1956 to 1964 heads.

  • Bob Nicholas

    Hi I have a 57 Ford Fairlane 500.The engine is red but was once a blue green? Is it a 292 or 312? Cheers Bobby

  • Patpounden

     wow!!! mike-you are the guru!!i just pulled a 239 apart this afternoon,and am sure i’d make most of those mistakes!!! thank you MUCH!!!will be putting it back together next wk…and will print this page!-pat pounden

  • charles auchter

    i thought the longer head bolts, 4 of them was some kinda of wrong lenth bolts used prior to my rebuild  so i cut off the extra and made them the same lenth as the oter shorter long bolts. now should i replace them or will they be ok ? thanks for the info.

  • charles auchter

    another question i have is it ok to just replace exaust vaves and all valves seats intake and exaust so to be able to burn unleaded gas?

  • thertrevjessejackleg

    The problem with the rocker arm oiling is a turned cam bearing, not the rocker arm itself