Big Healey Engine Mounts

[Dave Russell]

Need help figuring out the front Healey engine mount shimming for my BN2.

From time to time I see references to shimming the engine mounts to achieve a certain clearance between front engine mounting parts.

Never have figured out what they are talking about. What shims go where, how much clearance where, Why is it important?

The Moss catalog #AHY0408, page 7, shows item # 128 as Packing piece .048" & .036". Other references say to shim to a specified clearance, something like .025". Shim what & shim where & above all, why is this mystery clearance important?

I will be grateful if someone can explain this setup to me.
D

 

[screenprinter]

Dave,
If you don't know the answer I have to assume that this is a typical piece of British humor -
"I say Nigel, let's throw this shower in..Pull the Yanks' knickers down eh what?....That's the ticket!"

Course I may be wrong - The car may not run without this clearance, or the engine may shake itself to death - I've heard of stranger things.

I'd think if Reid doesn't know there might not be a answer available.

Bob M.

 

[Editor_Reid]

[ QUOTE ]
I'd think if Reid doesn't know there might not be a answer available.

[/ QUOTE ]

Thank you for the confidence in my knowledge of these things, but in fact I am no where near even being in Dave R's league on these matters. As I frequently tell people, I have no great mechanical knowledge myself, but I know people who do. As editor of the mag, I'm kind of a middle man between those who seek knowledge and those who have knowledge.

Therefore, in that capacity, and to answer the original question, I would recommend telephone calls to the "Technical Advisors" listed in the Austin-Healey Resource Book, published by the Austin-Healey Club USA. It's a list of professional mechanics, most of whom are Healey owners themselves, who provide free tech advice and assistance to members.

Now then, where did I put that Whitworth adjustable spanner of mine... I need it to open a small brown bottle... /ubbthreads/images/graemlins/cheers.gif

 

[John Loftus]

Dave,

The main engine mounts (132) are designed to allow the engine to move a bit relative to the frame to isolate vibration, when torque is applied and when gravity is trying to throw the engine around during driving. The upper buffers (127) are there to limit the amount of movement/damage to the main engine mounts. They keep the main rubber from being stressed too much when you launch over a bump and reconnect with the earth, during heavy torquing movement of the motor, hard cornering, etc. The "business card" gap or clearance between the buffer and main mount allows the main mount to move more freely, isolate vibration up to the point where the buffer makes contact. The shims are used to maintain a clearance when setting the mounts up and adjusted over time when the main motor mounts begin to sag.

Anyway, that's my take on it.

Cheers,
John

 

[Michael Oritt]

[ QUOTE ]
Need help figuring out the front Healey engine mount shimming for my BN2.

From time to time I see references to shimming the engine mounts to achieve a certain clearance between front engine mounting parts.

Never have figured out what they are talking about. What shims go where, how much clearance where, Why is it important?

D

[/ QUOTE ]

I'll agree with Reid that if you do not know it then it probably does not need to be known. But I recall that the Austin-Healey Concours specs state that one should be able to pass a standard business card between the mounting parts to test the clearance.

The type of business and the material used for the card were, unfortunately, unspecified....

 

[Keoke]

Dave, John's response is correct. However, since the entire assy litterly walks around I wouldn't worry too much about shimming.---Keoke /ubbthreads/images/graemlins/grin.gif

 

[Dave Russell]

[ QUOTE ]
Dave, John's response is correct. However, since the entire assy litterly walks around I wouldn't worry too much about shimming.---Keoke /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

Thank you John. I think I understand now.

Keoke,
Would you care to explain in more detail. The engine mount scheme is one of the more elaborate that I have seen. From the engineering principles involved, I would say that the engine contributes greatly to the ridgidity of the entire structure. The only time that anything "walks around" is if the structure is weakened by rust or involved in a serious collision with unrepaired damage. Adding shims makes things even more ridgid.
D

 

[Keoke]

OH! Then by all means shimm em---Keoke /ubbthreads/images/graemlins/smile.gif P.S. John says they walk around a bit too!

 

[Dave Russell]

John said "designed to allow the engine to move a bit relative to the frame to isolate vibration". I think all isolation mounts are designed to do this by definition. On the Healey, the walk around is, by design, limited to about .010". This in contrast to some mounts that let things move a whole lot more. I would call it a slight stutter rather than walking around. BTW, my mounts are tight enough that there is zero clearance & they don't even wiggle, this should be solid enough for even you. I was considering adding some more shims to get a little clearance, but you talked me out of it.
D

 

[Keoke]

Yep, You got it right now.---Keoke /ubbthreads/images/graemlins/angel.gif

 

[John Loftus]

Dave,
I think the factory engineers had good reason to build them the way they did. They continued to keep the gap through the entire production. They could be wrong but I doubt it. I'm only guessing at the logic behind the way they are set up and was hoping that someone would expand (or contradict) on my minimal understanding of the dynamics at play. This would be a good question for the 'list'. I don't follow the list right now ... just too much chatter for me but would be interested if anyone finds out more on the subject.

Cheers,
John