Front Motor Mount

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csingletary01
Posts: 73
Joined: November 29th, 2009, 2:00 pm

Front Motor Mount

Post by csingletary01 »

I have a 1965 Autodynamics Mark IIb that I vintage race. My front motor mount is a 3/4" square tube that spans the engine bay and bolts on tab under engine. Last weekend it broke in middle of tube. Anyone have any photos of their front mounts? When I restored this car I tryed to keep it as original as possible and it had stock VW Midmounts and stock VW rear trans mount. I built the front mount to help stiffen the frame. I think the rubber allowed enough flex to break front mount. I am going to build solid mounts to replace the rubber. This Vee has 13 logbooks and I have raced 10 weekends in last 20 months since I fully restored. Just looking for some ideas on a front mount.
brian
Posts: 1348
Joined: June 26th, 2006, 12:31 pm

Re: Front Motor Mount

Post by brian »

I know there have been zillions of cars with front engine mounts and many recommend keeping the bolt loose to prevent engine binding. Many years ago, during testing of an aircraft conversion of a vw motor, we learned that thermal expansion on an anchored motor would cause binding on a dyno. I would suggest looking for other places to firm up your chassis. Over the top braces work much better. Having the tranny hang out the back without bracing causes issues as well. Many older chassis had bracing over the top of the tranny to prevent movement. The LYnx had mounts on both the bottom and top of the bell housing to steady the drivetrain.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
problemchild
Posts: 901
Joined: June 25th, 2006, 9:34 am

Re: Front Motor Mount

Post by problemchild »

brian wrote:I know there have been zillions of cars with front engine mounts and many recommend keeping the bolt loose to prevent engine binding. Many years ago, during testing of an aircraft conversion of a vw motor, we learned that thermal expansion on an anchored motor would cause binding on a dyno. I would suggest looking for other places to firm up your chassis. Over the top braces work much better. Having the tranny hang out the back without bracing causes issues as well. Many older chassis had bracing over the top of the tranny to prevent movement. The LYnx had mounts on both the bottom and top of the bell housing to steady the drivetrain.
That is a myth. BS from the 80s that sold a bunch of FVs. Great theory though. I've seen engines (from a front engine mount FV) come apart with 20 weekends on it with bearings that looked perfect. There could not have been any "binding". Maybe some other application engines have that problem, but not VWAC and certainly no reason to butcher a classic car.

BTW, I once answered a newspaper ad for an old chevy and bought a mint 58 Corvette for $200 from an old lady's barn.
Greg Rice
"Happy 50th Birthday"
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