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I am putting a 454 into a 66 Chevelle.It has SBC pads in the frame and from what I gather they will work fine.My concern is with the engine side.What mounts work???I am trying to keep as much hood clearance as possible??Do the SBC mounts put the engine lower in the cradle than the BBC mounts???Thanks for any help

Kevin
 

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Re: Motor mounts HEPL !

Search is your friend but, here are the small block frame mounts I took out of my 66 El Camino and the correct Big block frame mounts I put in. the engine will sit too high with the small block mounts. About 3/4 inch too high if my memory serves me right.
I believe what Dean said is correct for 68 up.

Old small block


New big block...much shorter
 

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Discussion Starter #3
68-72 shows the same frame pads bb and sb
65-67 shows different for the sb and bb BUT the only difference is a brace in the mount.???


The engine side shows different for the sb and bb 66-67

Can I use a sb on the engine for a 66,and will it sit the motor lower in the frame?? or will the bb on the engine sit the motor lower in the frame.I want as much hood clearance as I can get.Thanks again

Kevin
 

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A lot of people say no difference. All I can tell you is that with the old small block frame mounts the steering shaft wouldn't clear the header. When I put in the BB frame mounts it cleared them. The engine sat lower in the frame.
 

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Discussion Starter #5
A lot of people say no difference. All I can tell you is that with the old small block frame mounts the steering shaft wouldn't clear the header. When I put in the BB frame mounts it cleared them. The engine sat lower in the frame.[/QUO

I am only concerned with the actual motor mount(bolts to motor),I already have the frame mounts in the car,BUT have to buy the engine mounts.I know once I get the motor sitting in the frame things change.Just looking to see what motor mounts SHOULD be the best to try first.Thanks

Kevin
 

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Discussion Starter #6
Re: Motor mounts HEPL !

Search is your friend but, here are the small block frame mounts I took out of my 66 El Camino and the correct Big block frame mounts I put in. the engine will sit too high with the small block mounts. About 3/4 inch too high if my memory serves me right.
I believe what Dean said is correct for 68 up.

Old small block


New big block...much shorter
Dave in the photo the big block mounts look like they kick up at the mounting pad making them taller than the small block ones,oh but my eyes are old ;).Thanks for the help

Kevin
 

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I was all over the board when I had this same question. I finally bucked up and ordered them. I sat them side by side and it was about 3/4" difference. Give or take an 1/8"
Like I said My steering shaft problem went away when I changed it over. Got mine off ebay about $65 I think. There is a thread in here...I couldn't find it....that has a pic of them side by side. The BB is much shorter.

 

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Discussion Starter #8
Thanks Dave muchly appreciated.I too searched and did not find anything.

Kevin:beers:
 

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I never knew that, I guess I have the dreaded 307 mounts. I guess that's why I have to take the louisville slugger to the drivers header!!! Next time I have the engine out I guess I will look into swapping stands.
 

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Wow. I think I'm having a moment of clarity. This is why my driver side header hits the steering shaft. My 72 was born with a 307.....it must still have the 307 mounts.
 

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66 Chevelle SS396 & 66 Chevelle 327 Convertible.
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68-72 shows the same frame pads bb and sb
65-67 shows different for the sb and bb BUT the only difference is a brace in the mount.???


The engine side shows different for the sb and bb 66-67

Can I use a sb on the engine for a 66,and will it sit the motor lower in the frame?? or will the bb on the engine sit the motor lower in the frame.I want as much hood clearance as I can get.Thanks again

Kevin
Both the SB and BB 66 frame brackets as they are called sit at the same height. The 66 BB mounts are a little different and the 66BB engine mounts were different with more rubber and thicker rubber, thus the top is designed a little differentin the 66 frame bracket and there is a another bend in the frame bracket to make it stronger.

You can use either; However if you want to used the later saftey designed engine mount you must use the BB frame bracket. Looks like some miss information in previous post. I would use the BB frame bracket.
 

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I have 66. i put a bb in it. i installed the frame mounts and motor mounts. a place called luttys has either the frame or motor mounts very reasonable. the other mount was cheaper elsewhere. it way more economical to split the purchase. if you plan on re-doing the a-arms now is a good time to do the frame mount install while the a-arm is off.

jim
 

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SB and BB mount pads in 1966 are indeed different animals, both in final engine height, but especially in fore/aft placement. You can get either motor to initially fit in the bay, but there are subtle but significant differences which will cause you headaches if you pick the wrong pad.

Installing on the wrong motor mount pads for your engine type (1965-67) will cause the engine to sit too far back or forward. NO big deal, you say? Here are some of your headaches. (most of these are SBC on BB pads, but some the other way)

1. Your clutch cross shaft rod won't work right in a manual transmission car. (either mismatch) Shaft will run crooked because the boss is out of line with the rod pivot on your block, by about 3/4" She'll never quite clutch right and you won't get the clutch stroke you need. A big PIA in 4 speed cars.
2. You will have clearance weirdnesses in various places like the distributor to firewall, especially if you put an HEI in there (SB on BB pads)
3. Your fan won't quite center up in the shroud. (either mismatch)
4. Your stock coolant lines for the transmission will run too close to your harmonic balancer if you have a big balancer BBC or a 454 (BB on SB pads)
5. Your stock and correct length driveshaft will seem to come up a skoach "too long" making it hard to install/remove. (SB on BB pads)
6. Your frame holes for your transmission crossmember won't quite line up either. (either mismatch)
7. Your OEM floor shifter rod will be off, again just a little - but maddening. (either mismatch)
8 Hood and transmission tunnel clearances will be boogered up as well, not severe, just maddening. (either mismatch, but BB on SB pads in particular for clearance height)

re: which side mounts will work. The pad mount yoke dimension is the same, and the bolt pattern on the block is the same as well, but the engine side mounts vary some in physical design. depending on the year. Mostly, it is about the safety interlock, which was not present before about 68 (working without a net here - Chevelle gurus, protect me from myself, o.k? :) BBC mounts got the safety interlock about 68 (I believe). That was after the series of infamous "Carzilla, the runaway BB Impala" incidents. In those incidents, BBC equipped Impala's massive torque and heavy car weight combined to break the left motor mount. When that happened the engine became severely displaced in the engine compartment. This rotational displacement did three things.

a) It pulled out the vacuum booster vacuum hose, rendering the brakes ineffective
b.) It pulled the rod actuated throttle on that BBC more or less wide open...
c.) It pulled the car's transmission linkage into second or low gear. In a neat economy of design, this started the WOT and now brakeless car moving, and thanks to the newly developed "safety ignition interlock" on the steering column, being locked in second or first gear made it virtually impossible to shut the car off.

The above combination apparently turned more than one BBC equipped impala into the luckless owner's very own personal guided missile.

As I remember it, there was rather a large recall on this. I believe GM's first response was to issue a piece of chain and a couple of bolts to bolt the engine to the frame. If the mount failed, the chain "caught" the engine before rotation caused the above. The second response was the "safety interlock" failsafe on the motor mount.

Nowadays, all the aftermarket V8 Chevrolet side mounts I see have the safety interlock.

One final note in this long screed. I'll try not to rant...but nowadays the aftermarket motor mounts I've seen from various "restoration houses" are made overseas. I've gotten a couple pairs which were from India and which were totally and non-functionally substandard in construction details like accuracy of holes and so forth. I would carefully examine any mount I purchase against a known OEM or good US made example before accepting it.

Quite a pain to get that motor hanging on a hoist, sitting in your perfectly restored engine bay, and not quite being able to get the long-bolt holes to line up. (Don't ask how I found this out, o.k?)

:)

just my 2C

Keith
 

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I guess my experience is different than what most have said to this point.

I have found stock original GM 1966-67 Chevelle BB & SB motor & frame stands have the same basic dimensions. The only difference between BB & SB is BB motor mounts have the safety interlock feature and the frame stands for BB have a little different design to clear the safety feature......So, you CAN'T put stock BB motor mounts on stock SB frame stands because there is no provision for clearance of the safety interlock feature....Now! don't get this mixed up with 1968 up because that is a different ball game.

I don't know about repops or aftermarket....I once used Moroso solid mounts on a BB in a 67 and they placed the engine about a half inch higher. I have a feeling reproduced stuff may use different dimensions than old originals.........
 

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Hi Papa,

I respect your position, and your lifetime premium member status. Nevertheless, I'm still going to insist with a fair degree of certainty that the fore/aft dimension of SB vs. BB motor mount stands is unique to each application.

I also stand behind my previous post noting the problems associated with mismatching the two. The difference is subtle but absolutely real. I have personally dealt with each and every problem listed in my "list of reasons why not to mix" the two styles, and can definitely trace these problems to incorrect pad / engine style mixtures.

But I wish to remain at peace with you, so I always stand ready to be corrected by hard data.

Grace and peace to you,

Keith
 

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this is the first time I've ever heard of the fore and aft difference. I'd have to see two mounts side by side or bolted together.
 

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The frame stands above are not 66-67.......They look very much like 68 up Chevelle from this angle.....The one on the left being the infamous 307 stand.

I believe the fore & aft engine position is true in first generation Camaros but not the same as Chevelle.
 

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...As I remember it, there was rather a large recall on this.... The second response was the "safety interlock" failsafe on the motor mount... Nowadays, all the aftermarket V8 Chevrolet side mounts I see have the safety interlock...
From a recent experience, do not rely on these interlocks.

...nowadays the aftermarket motor mounts I've seen from various "restoration houses" are made overseas. I've gotten a couple pairs ....which were totally and non-functionally substandard.... I would carefully examine any mount I purchase against a known OEM or good US made example before accepting it...
It will be very apparent when you run across one of the substandard mounts...much thinner metal and rubber not fully bonded to the mount.

I just installed a set of Energy Suspension motor mounts that have a different style interlock molded in the poly. So far, they have not broke like the cheap replacement did (which I returned to the store).
 
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