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snapped off both motormount bolts flush on my engine block.
currently designing/modifying mounts to be able to handle the downward stress and take the load off those bolts.
this will be the 4th try.
does anybody have a photo or two showing how they did it?
as always thanks!
Billy,
The thread below, SBF Motor Mounts, shows my chassis mounts clearly, and also gives the PN for the associated OEM motor mount to link up with them. The chassis mount is a pre-fab unit from Pete & Jake's - http://www.peteandjakes.com/Catalog4.aspx?pid=548 and they work very well. Here's the link to my earlier post:
http://www.clubhotrod.com/hot-rod-ta...or-mounts.html
If you want an alternative, here's a neat kit from Paul Horton that eliminates the OEM rubber mount altogether, replacing it with simple urethane bushings.
Ford Motor Mounts, Urethane Insulated » Welder Series Inc.
I'm left questioning what you're using for bolts Billy. Assuming that your motor has 2 bolts each side that fasten the mount to the block... Were they grade 8 or 5 or???
I used mounts for a "79" F-150 pickup, then a simple rectangular box from the frame of 3/8" flat stock with a angled end at the motor side, tack welded together with all parts in place \ mocked up. Then removed to bench for final welding. Then back into car for final assembly.
Because I had access to them from work, I used Bowman "Bowmalloy" bolts. They are like equal to a grade 10 or 12 or something crazy like that. I think the block would break before the bolts but at a minimum I would've used a grade 8 bolt.
I think the real secret is to do the mockup and fitment so that there are no undue stresses so that the mount only has to carry the motor weight and torsional force, any extra stress like twisting\bending because of poor fitment will surely shorten the fasteners lifespan.
I answered your post on Hotrodders.com: ford 302 motor mounts? - Hot Rod Forum : Hotrodders Bulletin Board
I'm confused How do you break bolts with downward force. I guess I'll stick to chevys.
That one's pretty easy. With the cantilever design of the mount the downward force (weight of the engine) imparts a moment, putting the bolt in tension to one side. Under hard acceleration that tension direction switches directions on the driver's side, and increases on the passenger side.Quote:
Originally Posted by cffisher
I gotta agree with Mike, it sounds like maybe you've just got a bolt problem. I used Grade 8 bolts to bolt the mount to the block, and also as the through bolt for increased shear strength. How about some pictures of the mounts you're using now?
Generally issues when bolts are broken off flush with the hole is that the bolts are bottomed out in the hole and overtorqued trying to tighten them---already happened to this guy 4 times
You could be 100% on this one, Jerry! A bolt a bit too long is going to bottom out, leaving some "slop" for the mount to rock back & forth on acceleration, eventually snapping the head off the bolt. How about it Billy? Did you thread the bolts in w/o the mount to check the length?Quote:
Originally Posted by jerry clayton
here all the time i use nails on ford s if a nice one wood screws :)
It only takes 3/8 bolts on a chev and ford needs bigger ones--------
well what ever makes you sleep better jerry ? i was told they used bigger bolts cuz ford guy can not find a hole.....:) poor engineering quick fix bigger bolts:DQuote:
Originally Posted by jerry clayton
My 302 uses 4, 3/8" bolts..... mount to block.
the earlier failures were the steel itself cracking/splitting.Quote:
Originally Posted by jerry clayton
yes i measured the holes for depth.
i replaced the bolts with hex heads that are supposed to be a bit stronger than grade 8's
the photos will show why the previous bolts failed.
they couldnt stand up to the leverage.
http://i98.photobucket.com/albums/l2...ps7065ce01.jpg
http://i98.photobucket.com/albums/l2...psb7cda138.jpg
http://i98.photobucket.com/albums/l2...psa510e3dc.jpg
http://i98.photobucket.com/albums/l2...ps435097aa.jpg
Thanks for the pics Billy----that is a bad design on the mounts and the only way you will stop the breakage is to turn those two steel mounts into a crossmember by running a tube down and under the pan from one side to the other--
As you have it you probably have a 20to1 leverage on the bolts plus in addition to the engine weight throw in the torque from the engine plus twist of chassis----your lucky the bolts broke instead of pulling the side of the block/waterjacket open----------
you could also shorten them and weld a mount to the inside of your frame rail so the mounts didn't have so much leverage against the bolts
Gotta agree, that design just doesn't work - way too much moment arm applying torque to the bolts. If I were you I'd order either the Pete & Jake's or the Paul Horton Kit and get that support point out much closer to the engine with some healthy chassis mounts welded solid. You could also copy their design approach and cut the pieces out of some healthy plate steel yourself if you want to invest more time than money, and if you have the equipment to cut the heavy stuff. Both web sites have drawings & pics to show the details, and the Paul Horton site even has a welding video to walk through the assembly process. You also need to be sure that your boxing plate is good & strong where you weld the chassis mounts in place.
I forgot to bring the camera 'cause I wanted to snap a pic or two for you Bill... I did check the bolt size into the block and I'll stand corrected, I thought they were 3/8" but they are actually 7/16" , I didn't measure for the length but I see you've already done that.
Your engine sits alot higher in the chassis than mine but the principal is the same, the general thought needs to be triangulation if your going to come off the side of the frame. When I see your setup I sort of automatically gravitate to the crossmember setup that you can find in Speedways catalog.
Ford Weld-In Motor Mounts - Speedway Motors, America's Oldest Speed Shop also look to the bottom of that page as that is the complete crossmember with mounts that I was thinking of. If nothing else there are a couple ideas there...
Hope this helps...
since i have the shop to myself today.
i am going to try and fab up some of these
http://i98.photobucket.com/albums/l2...ps67235cc6.jpg
Those should be alot better than what you've got! If you can get the rubber mount hole closer to the block mount holes it'll be even stronger.
that bolt in the rubber dosen't look very big.1/4 or 5/16???
That's a good design, similar to Horton's but simplified another notch. That bolt through the rubber isolator only takes a tension load from torque on the driver's side, and it doesn't need to be hefty. Apart from that it's just a positioner. The bolts holding that plate to the block get some torsional load, so they're a bit more critical. Be sure your welds on the chassis side are strong, and that you have enough boxing plate meat for the load.
i forgot about this thread.
here is what i did
http://i98.photobucket.com/albums/l2...psb79db3fa.jpg
http://i98.photobucket.com/albums/l2...ps92c68020.jpg[/QUOTE]
this setup acts like a bridge abutment.
the downward pressure pushes into the inner walls of the frame.
a very strong setup.