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MG MGB Technical - CROSS MEMBER CLEARANCE TO BOTTOM PULLEY

The engine in my 79 MGB seems to sit high in the engine bay, which causes the air filter to come in contact the hood (bonnet). Curious to know what is a "correct" clearance from the top of the cross member to the bottom of the crank shaft pulley? Mine is approximately 1-3/4".

Cheers

Gary
79 MGB
gary hansen

Gary, Not sure if there is an exact measurement, but 1 3/4" is a big gap. If your air filters are hitting the bonnet, the whole engine could be too high, and that is an engine mount issue. Either the rubber elements are the usual rubbish items and are too thick, or the chassis mounts are wrong. This could be down to a deformed chassis or inaccurately positioned replacements brackets. It could be that the engine is not mounted horizontally, in other words it is twisted, leaving the air filters higher.
Allan Reeling

Allan. IIRC, the rubber mounts have offset bolts on oppostie faces. I'm thinking the mounts were incorrectly installed in the first place, thus creating a high engine position. I have looked at other MGB's and their crossmember gap appear to be half of mine.

The carburetor is a DGEV Weber (with a 7mm heat spacer to retard fuel vaporization) on top of a Pierce intake manifold and Peco header exhaust. So, that combo adds to the height of the engine. I have seen similar configurations with no clearance issues.

Cheers

Gary
79 MGB
gary hansen

Gary, I suspect you are right. The circular engine mounts used on rubber bumper cars and V8s have the screw thread offset. Correctly mounted the screw should be in the low position. If yours are rotated 180 degrees to the upper position, the engine will sit too high.
Mike Howlett

The stud that goes through the chassis bracket should indeed be in the lower position. But if it were in the upper position the engine would sit _lower_ than it should, not higher. In fact given the Vee angle of the mounts and brackets I wouldn't be surprised if you couldn't even get both studs in the slots if they were upside down. Ignore the arrow which is indicating something else.

paulh4

Gary,
The circular mounts used on later B's were, as stated, also used on the V8. But on the V8 these are often supplied in two different thicknesses. It's worth checking to see if you or PO has been supplied with two of the thicker V8 mounts, which i think were 30mm thick. (Memory!!!!)
Allan Reeling

Gary,

See the photo for a "pair" of engine mounts that I once received. This might relate to what Allan said about the V-8 mounts.

Also, I think the Weber downdraft is pretty close to the hood even without a spacer.

Charley

C R Huff

To all, many thanks.

Charley: the engine mounts you show are THE ones I bought when the engine was rebuilt. And yes it is rather crowded at the top.

Allan: The "compressed" thickness of the mounts are approximately +/- 1-1/8" each.

Paul: Given the angle of the mounting, I follow what you are saying. I am wondering if the mounts are incorrect for my car due to carburetor set up(?)

I was able earlier last year to loosen the mounts, drive them down (item 18 on your attachment) to a slightly lower postion and retighten. This helped until I added the 7mm heat spacer under the carburetor.

Are there an alternative engine mounts and/or shims for the 79 MGB's? Having been in the parts biz for many years, part applications change within model years as per V.I.N. and production date.

Again, thank you

Cheers

Gary
79 MGB
gary hansen

The Parts Catalogue quotes the same BHH1621 mounts for both sides throughout rubber bumper production.

There are also RV8 mounts, one of which is thinner than the other, but I don't know the thickness of either. On that the exhaust exits through the inner wings and doesn't tend to clout them or the rack shaft as on factory V8.

See http://www.v8register.net/FilesRV8WN/RV8NOTE324%20engine%20mounts%20orientation%20080410.pdf which discusses both the thin mount and the correct position of the stud putting the engine in the higher position.

paulh4

Paul: Thanks for the website info. I found a fellow, Clive Wheatley,and sent him an email asking if he can send some part details of the thick vs. thin mounts, and if the thin mounts would be applicable.

Will post when or if he can share some technical info with these mounts.

Cheers

Gary
79 MGB
gary hansen

Gary,

The point of the photo I posted is that the "pair" of engine mounts are different heights. So, you might have a pair of the taller ones and could gain some room if you got the shorter.

Charley
C R Huff

FWIW, if they were bought as a pair and are different heights the only way you would get two of the shorter ones would be if the supplier was prepared to go through their stock measuring them. Not knowing either of the heights of yours, one wouldn't even be able to say what heights one was looking for, and could end up with two the same as one already has. Even taking the existing ones off and measuring them may not help, as despite being apparently too high they may still have compressed a little.

But on another tack, does Gary have the location plates under the chassis mounts? These are square with an off-set hole, and the hole is supposed to be in the lower of the two possible positions when fitted. This can only be done if the stud is towards the lower end of the slot in the chassis bracket. If the studs are too high and you can't get the location plates fitted that way round, then the engine will be higher than it should be, and this can happen if the rubber mount is too thick.

The converse is that the stud shouldn't be right at the bottom of the slot either, as that puts the mount in shear instead of compression. This can happen if the rubber mount is too thin. One or more spacer plates immediately above the chassis bracket may be required to achieve a clearance but still allow the location plate to be correctly fitted.


paulh4

OK... Been away for a bit.

Charley: reviewed your pix of the motor mounts and measured the height of both right and left sides. The right side measures approx. +/- 1" and the left side measures +/- 1-1/4", (I stand corrected on my previous measurement).

Paul: Thanks for the V8 register website. Page nbr. RV8NOTE324 regarding the "high" and "low" measurement of engine mounts. 2nd paragraph comment by Peter Garton from Clive Wheatley's website reads: "the thin mount goes on the LEFT and the thick mount goes on the RIGHT."
In short, the mounts are "handed".

It seems the mounts in my car have been crossed, the left mount is on the right and vice-versa.

Cheers

Gary
79 MGB

gary hansen

Don't forget you are LHD :o)

Were there any measurements for the thick and thin? I was under the impression that there was more than 1/4" difference. Email Clive Wheatley.
paulh4

Paul: The measurement I took is with the engine still in the car. The rubber on the right side is 1" and the left is 1-1/4". Also, the comment I quoted from Clive's website was from someone in Germany. This doesn't necessarily prove his car is LHD.

I did email Clive and did not get a response, so I emailed Nigel Petch at mgbhive.co/uk. Sandra responded confirming the mounts are "handed".



Cheers

Gary
79 MGB
gary hansen

(I think you missed the smiley ...)
paulh4

No, I got it LOL. :>{D

Cheers

Gary
79 MGB
gary hansen

Just spoken to Clive. He says the off-side or steering side (RHD) for the RV8 is the same as for the MGB, and he mentioned '3 or 4mm' for the other side. They certainly aren't that thin, so I think he must have meant 3 or 4mm thinner, which would be about your 1/4".

My comment about RHD and LHD was actually tongue in cheek, but seeing as how it is common with factory V8s to add a spacer to the steering side to stop the exhaust manifold hitting the steering rack, maybe on an LHD the mounts _should_ be the other way round. But then again, as the twist of the engine under acceleration tends to compress the right-hand mount and lift the left-hand up, maybe on an LHD car you could get away with thinner mounts both sides.
paulh4

This thread was discussed between 26/05/2018 and 11/06/2018

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