Projects had a hotrod shop fab new mounts for my 1956 olds with a 455 and 700r4 trans

Here is the new mounts i had a shop fab and put in my 1956 oldsmobile for my 455 and 700r4 trans...i was just kinda curious look at the bolts they used they look like a grade 5... is that aceptable? being they do this at their hot rod shop all the time im guessing...but would like to hear some feed back

 

My biggest concern is not using lock nuts on the bolts, grade 5 are pretty tough and aren't as brittle as grade 8. I seriously doubt they will see the 81,000 pounds of force needed to even stretch them. All the other work looks clean, functional and simple.

 

change them if they bother you, under ten bucks for locks, bolts and nuts and under 1/2 hour to swop them out.
i think they would be fine.

 

Bolts look fine. Personally i do not care for the flat bar for the trans mount. I know it is heavy enough material, I would have preferred a piece of angle iron or tubing. Less chance of sagging with age.

 

It all looks good but I'm not a fan of the trans cross member. I would have used tubing for that to reduce flex.

 

Id worry about the mounts flexing before id worry about the questionable bolts. They look like nice welds and smooth cuts. I see the gussets underneath I just feel like that is a heavy motor with a lot of overhang on the mounts. I would have done a more boxed in kinda mount if that makes sense. I'm sure they will function however. everyone has a new way to do something.

 

I agree, that ****** mount is apt to sag over time.

 

The through bolts look like grade-8, which is fine. The rest can be grade-5. I like to see flat & lock washers too... someone cut a corner there.

What concerns me is the amount of bow in the plates off the frame. The gusset is way too small.

The trans cross member looks a bit bush league but may hold up.

 

thats some interesting mounting for sure, wonder how your going to get that brake line out/replaced with te front clip on with it snaked in like that?

 

At first I thought the front mounts seemed to be hanging out in space, but, after looking at all the pictures, they will probably be ok. I too am concerned about that trans cross member, not crazy about the stacked tubing design. Round or larger rectangular tubing would have been my choice.

Bolts are ok, but need nylock nuts to be safe.

Don

 

I agree with everyone else, that ****** mount needs to be redesigned.

 

No split lock washers. It has been long proven that they are as bad as, or worse than no washer at-all, by NASA, no less.

Don't make me bust out the study.

Use a stover nut or a nylock.

And fix that transmission crossmember.

 

Six radial lines on the head means grade 8 (they're not brittle...), three lines means grade 5. The bolt head marked 4.8 is metric, roughly equivalent to SAE grade 2, and shouldn't be used anywhere on a car. That one I'd change, otherwise grade 5 is ok. Personally, I think the minimal extra expense of grade 8's would be cheap insurance. And I agree with gimpyshotrods on not using split lock washers. Lock nuts and Loc***e are much better.

Edit: I'd be interested to read that NASA test.

 

Strange as it seems, flat stock, like they used on the trans cross member, is actually easier to bend than hollow rectangular tubing. You would think that solid steel would have more resistance to bending than tubing, but the reverse is true.

That trans cross member really needs to go and no pro shop should have done it that way. They would have been better to use some round DOM tubing or even square or rectangular tubing. I would take this thread back to them and ask them to build you a proper cross member.........the existing one is going to sag big time, especially with the weight and torque of a 455 and transmission.

Don

 

I agree that the ****** mount should be tubing. I have never heard about the split washers being bad, please explain for me.

 

Not sure why they used those metric bolts on the engine mounts. As stated by others, Grade 5 are perfectly fine but with nylocs and washers.
The motor mounts will probably be OK but I would have liked to see them made of a little thicker material as far as they are cantilevered off the cross member. Also a gusset on each side would be better than the single one in the middle to reduce the chance of the bracket flexing at the edges. From a design point of view having the gusset the same depth all the way out is redundant and a wedge shape would look better (although not too many people will be seeing it)
I also agree with Don on the trans cross member. A piece of tubing set back a bit further to allow room for some section height with a plate welded to it to get to the correct height for the mount pad would have been better. Over the short span and due to the fact that it would have to pull the frame cross member sections together (unlikely) to bend it will most likely work OK but it is definitely not the best solution.

Roo

 

Isn't there another set of midmounts? You have the very front of the engine supported and the very tail of the ****** supported, what is supporting the bellhousing? The crankshaft?

 

Trans crossmember is fine , heavy , thick and short enough it's not gonna bend,,,it's only supporting back of drivetrain.....I've done em like this , no problems....

 

I share the same concern about a lack of mid mount support. You have about a 5' length between the engine mounts and the ****** tail mount (used to see it a lot on 55-57 Chevy's with only a trans tail mount and the front engine mounts under the timing chain cover).
I'd feel better about the engine mounts if they were boxed in with a gusset from the back of the mount to the frame rail. Be sure to add some brake line support clamps. Lines are running wild.

 

I will post the links when I am back at my desk.

 

Actually the 55-7 motors had a mid support for the bellhousing, they were mounted at the front of the engine, at the bellhousing and at the transmission tail. 3 point mounts.

 

http://ntrs.nasa.gov/search.jsp?R=1...009424&qs=Ntk=Do***ent-ID&Ntt=19900009424&N=0

http://hillcountryengineering.com/w...it-Lockwashers-Separating-Myth-from-Truth.pdf

 

Come now guys! Just about every V8 installation in US built vehicles has the motor /transmission package mounted via side mounts towards the front of the block and a pad on the extension housing of the transmission. Some of the newer ones have the side mounts a little further back on the block (LS Chevy for example) but most have the lugs well towards the front. Take a first gen Hemi Chrysler for example. The center of the front mount lugs is only 3" back from the front face of the block. On a small block Chevy that number is 5 1/2" and on a nail head Buick it is only 2.5". Ford put their mounts further back on the 289 series and also the big block but they are pretty much the exception. None of these installations have mid mounts as well. The OP's 455/700R4 is obviously the same and is mounted the same way that the factory did it.
In a different scenario I see quite a few drag race cars where the builder runs front and mid plates and then rigidly mounts the transmission as well. The usual result is a broken transmission (either bell housing or extension housing) or damage to the transmission mounting structure when torque twists the ch***is. And that happens in full tube frame cars as well.

Roo

 

No, the distance between the engine side mounts and trans mount is not a problem.........that is just how all Olds of those years are done. It is the Hurst style FRONT MOUNTED mounts that concern people (but my sbc in my rpu is done that way). Most modern v8's are mounted just like that, no mid mount.

As for the metric bolts, strange as it might seem, GM th350 and th400 transmissions usually have metric bolts going up into the transmission tail shaft to hold the mount on. I was just reminded of this when I mounted the th350 in my rpu a few weeks ago, the sae bolts I put in were sloppy, so I had to run out and get the proper metric bolts to hold the mount on

Don

 

About the span between the engine & trans mount, it looks the same as a stock set up the donor 455 came out of. But those bolted to a substantial front cross member, not some thin plates flapping in the breeze.

 

I'm with most people's thoughts, under engineered. Not substantial enough for the weight and torque. Gussets and plates likewise IMHO should be heavier. Insofar as transmission mount is concerned, RHS or tube would be better. You could gusset eash side with a flange (Flat bar) for additional support.

 

These bolts in the trans mount are SAE grade 5 ,
Serrated flange head. My favorite bolt for many reasons.
The crossmember has grade 5 also, however I would have chose the flanged head myself.


These dished head bolts in the motor mounts are low grade metric bolts, 4.8
Why metric?, I don't know but it doesn't make any difference nor any sence on a 1950's American car.
Why low grade?, they don't know is a good guess.
http://sizes.com/tools/bolts_metric_standards.html
http://sizes.com/tools/bolts_metric_standards.htm


I think the fabrication design set up here will give you problem free service for the life of the car. The ch***is is seeing the load as it was designed, in the front crossmember. The engine is mounted in its designed location. Both are happy could it be more artsy and have more form, sure but it's more than enough function. Form follows function.

The alternative would Have been to leave the front crossmember alone and take the mounts to the frame rails side. The side of the frame was never intended to hold a engine different than the front mount style , on the front cross member. So in this case, some kind of crossmember would need to be added under the mounts. This doesn't sound like a good idea compared to the way it was done.

The flat bar trans mount- boy I'd love to watch you guys try to bend it.
Post a video.

 

With the gusset under the front mounts they should work fine. I would rather see more gusset with like 2 at each end by the bolts and none needed in the center, but it seems the single center gusset will work. they fit the engine in the ch***is nice and with sufficient clearance for the manifolds and steering. The trans mount is plenty strong, not the most elegant design, but plenty functional. Most of the bolts are in shear, a grade 8 would be better. Only real problem is get rid of the metric bolts, and agree that nylock nuts would be better.

 

funny, on those big G.M. engines they only use two 3/4" long bolts to hold the mount to the block. i am working on a 430 buick now and the bolts to the block are the weakest link.

 

I think a front motor plate would have worked much better. That way all of the weight would be on the crossmember. I'm afraid of you hitting a big bump and your motor landing in the street. I would suggest finding a new "hotrod" shop