Team Chevelle banner
  • Hey everyone! Enter your ride HERE to be a part May's Ride of the Month Challenge!

Status
Not open for further replies.
1 - 20 of 23 Posts

·
Registered
Joined
·
27 Posts
Discussion Starter · #1 ·
What is the differance between the small block and big block frame mounts. I bought a set of big block mounts from The Parts Place and they sure don't look much differant from my original mounts. Hooker (Holley)tech help said most places sell small mounts as big block mounts and the only place to get them is from Year One. I am having trouble putting in a 396 with hooker headers.

Thanks, Maynard

------------------
 

·
Premium Member
Joined
·
5,068 Posts
350 motor mounts will work for a big block motor. Chevy was smart like that.

However, do not use the lesser 307 type mounts with a big block. You can get by with putting a 350/400 SB motor onto the 307 mounts, but NOT A big block! -been there, am doing that now! the motor sits higher in the engine bay and causes exhaust pipe - cross member issues.

------------------
71' 3880# with me. Big Block 402, TH400, 3.73 posi,
13.1sec @ 105 MPH (poor 2.1 sixty foot and rookie tuning)
--will be racing at Chevellebration 2001!--
Picture of me roasting the tires and other guy stuff
Video of me staging (smoke of course)
 

·
Registered
Joined
·
1,318 Posts
What is the difference between the 307 frame mounts and the other ones?
How can I tell which ones are on my car?
Thanks guys.
 

·
Registered
Joined
·
290 Posts
DZauto know this stuff.

I hope I'm quoting him correctly but the 307 mounts will have the engine sitting higher.

And if you use the 350 (and bigblock) frame mounts and the 307 motor mounts, you'll have it sitting a litter lower than stock.
 

·
Premium Member
Joined
·
131 Posts
Maynard, I think your problem may lie with the fact that you have Hooker Headers. They are notorius for not fitting correctly. Just my .02 worth



------------------
Rick
67ss bb
But dear, all it needs is a harmonic balancer.....
Rick's 67
 

·
Gold Founding Member
Joined
·
978 Posts
guess im missing something how can 307 /350 mounts be different

small block = small block doesnt it??

ive have also read here that small block and big block mounts ARE the same

who knows for sure??

and how can you ID what you have by looking??

------------------
Rich Baratta
Cocoa Beach, Fla
Team Chevelle #380
May 2001 Feature Car
[email protected]
www.chevelles.com/showroom/70_SS_454.jpg
 

·
Registered
Joined
·
1,318 Posts
If someone can answer this questions it would be greatelly appreciated.
It looks like the frame mounts are a PITA to change, so it would help to know what will and will not work.

Sounds like DZauto might be the guy.

Thanks.
 

·
Premium Member
Joined
·
13,692 Posts
BBMike is right...you dont want 307 mounts,but 350 mounts will work...my car had a 350 in it,and I put a 454 with Hooker headers too, the headers do hang real low,but not hard to install, I had to ding em to fit around the brake distribution block on the lower frame,and ding em to fit the upper A-arm on the pass. side....I like the headers but hate draggin 200.00 on the ground when the car is full and we're cruising


------------------
Bob West
Monett,Mo.
1972 Malibu .030 over 454
350 turbo-3.73's
[email protected] 1000ft.track
[email protected] mph 1/8th mile
 

·
Registered
Joined
·
1,318 Posts
Sorry to persist on this, but I can see it becoming a nightmare.
The question is how can you tell the difference between the 2 typs of frame mounts (307 vs everything else.)

For example, my car originaly came with 307 but when I bought it, it had a 350 in it. So are the frame mounts for the 350 and big blocks, or are they for the 307 and the 350 fit on them but a big block will not?

I have ordered the short and wide engine mounts that happen to be the same size as the ones that the 350 had on it. Is that going to work?

Thanks.
 

·
Read Only
Joined
·
589 Posts
I did the conversion from 307 to 350 and replaced the 307 mounts with 350/454 ones. Yes, its a pain. If I remember correctly, the 307 mounts were 1/4 inch higher. There's an old post back in 99 from someone that used 307 mounts on a stout SB and broke them. The 350/454 motor mounts are of the interlocking type, while the 307 are not. It is also not advisable to mix 307 frame mounts with 350/454 motor mounts. It can be done, but it requires alot of leveraging. This is based on previous old posts from 99 & 00. I'm at work, but I still have the 307 mounts in a cabinet at home and can measure them if you want.

------------------
Tino #28 Gold
72 Malibu 350-300,700R4
83 Grand Prix LJ 305
 

·
Registered
Joined
·
1,318 Posts
Thanks Tino.
If you could measure them I would really appreciate it.
I am totaly confused on this subject, and if I can figure out what frame mounts are on my frame I can figure out the rest.
Thanks again for your help.
 

·
Premium Member
Joined
·
5,068 Posts
Yanni.

The previous owenr of my car swapped a 350cid motor into what was an 'originial 307' car. I assumed he put in the correct motor mounts. -WRONG- No biggy really with the SB350 motor, I could just run a 3" tall air cleaner with no problems.

-I can't tell you how to decipher between the two mounts as I didn't read up on the issue enough and shot myself in the foot!


Just buy some new frame mounts and don't try to save some labor like I did. ALSO, when you go to remove the old ones: Things go much easier if you just cut off the hold nut/bolts and buy new ones!

-Go down to the Chevy GM dealer and see if they can pull two off of the shelf and you can compare?!?!

------------------
71' 3880# with me. Big Block 402, TH400, 3.73 posi,
13.1sec @ 105 MPH (poor 2.1 sixty foot and rookie tuning)
--will be racing at Chevellebration 2001!--
Picture of me roasting the tires and other guy stuff
Video of me staging (smoke of course)
 

·
Premium Member
Joined
·
17,553 Posts
Maynard,
all the small block mounts for your car (1967 Chevelle-from a previous post) are different than the big block mounts. The frame "tower" for a small block has one gently sloped face on the top, and three roughly 90 degree faces (relative to the top). Two of these surfaces are where the long bolt goes through and the third is toward the oil pan.

The correct big block frame tower has all four sides at 90 degrees from the top. In essence, it is notched on the oil pan side to clear the different Big Block motor mount (engine-side). This BB motor mount has a "T" shaped piece that restrains the motor in the event that the rubber fails (due to torque etc.). You could either runs a small block frame towers with the factory small block mounts on your big block (although they might not live too long) or run solid mounts from moroso, etc., that will still allow you to use the small block frame mounts...

One final note, you should really post the year etc of your car, since many things are different. All the talk here about 307, 350, lowering engine, etc... does not apply to your 1967 Chevelle. In 1967, there were NO 307 or 350 Chevelles, and the small block and big block mounts all differ.

Good luck, and remember to tell us what year your working on...

------------------
Tony
1966 SS L78 coupe
1966 SS convertible
1965 Impala convertible
1 wife that has drawn the line...
 

·
Registered
Joined
·
154 Posts
I am still a litlle confused about the 307 mounts. My car currently has a 307 in it. I am getting ready to pull the 307 and put a 350 in its place. Can I use the frame mounts that are in there now, and pull the motor mounts off the 307 and use them with the 350 block? If I do that, will the motor sit where it should?

------------------
Mark "THE DUDE" Skoch
1971 Malibu
(it's gonna be cool someday, really!)

Confucius say "Man with hand in pocket feel cocky all day"
 

·
Registered
Joined
·
290 Posts
You can use them. They do fit but the engine will sit a little bit higher.
 
G

·
Does anyone know why some big block chevelle (69) have lower frame mounting bolt holes than other big blocks. I went to a show and saw several 69 chevelle big blocks. some of them the center bolt was just about on top of the cross member and others, like mine the bolt is about 2" above the cross member. I thought this was the reason why a 3X14 air cleaner would not fit until I bought a drop base and that worked with room to spare.
 

·
Registered
Joined
·
40 Posts
I have a 69 conv. I believe it was born with a 307 3spd. (car was purchased no motor, no trans).I have a 454 4spd to go into it and it sounds like I am going to have the same problem. It looks like there are extra holes in the frame crossmember, wonder if moving the frame mounts might be the answer? The only catalogue that I found that even listed frame mounts said all v-8.
 

·
Read Only
Joined
·
589 Posts
Yanniz,
The p/n for the 350/454 frame mounts are 3980711, 3980712. The p/n for the 307 mounts are 3980707, 3980708. For the 307 mounts, the pedestal part ( that sticks up ) is at the base 2 3/4 " x 3 3/8 ". Its 1 3/4 " high. I got my frame mounts from the TC want ad section. Hope it helps.

------------------
Tino #28 Gold
72 Malibu 350-300,700R4
83 Grand Prix LJ 305
 

·
Registered
Joined
·
1,318 Posts
Thanks Tino.
Mine is mounted on the frame and I just measured it. Pretty darn close the dimensions that you gave.

Freakin great. They say big block is an easy swap in small block cars, but I can see that replacing these frame mounts is going to be anything but easy!!

I think I will just get a 175HP 350 get the darn car on the road and call it good!!

Aghhhhhh.

Here is the next question? What is the difference between these and the big block mounts. Someone mentioned 1/4" in height. Is 1/4" going to make that much difference (roockie question?) Also if for some reason something goes right by a chance
and I am able to fit the big block on the car using the existing frame mounts, is there a chance of breaking these guys? Are they not as strong as the big block frame mounts.

Last question, I promiss. How the heck to you change this. There is just no way to get inside the crossmember. Maybe if I take the lower control arms off, and then will get me all summer to get the springs back on. Just had a hell of time to get that done.

Sorry about the whinning, but any input to make see a small light and keep me going on this project, would be greatelly appreciated.

Thanks

[This message has been edited by yanniz (edited 06-05-2001).]
 

·
Premium Member
Joined
·
3,438 Posts
I know this topic has been beat to death, but I am going to disagree with the mount swap being needed. Why? Cause I have put 396/454 engines in multiple 307 cars without swapping mounts. Not one, MANY. I have never used Hooker headers, normally standard dynomax and the like, and have no problems. Done it in chevelles, camaros, and novas. NO headers issues or exhaust issues. NO problem with a HEI fitting in the chevelle, the camaros and novas needed clearancing regardless. Use the matching 307 engine mount with the 307 frame mount, as they are different than the 350. As far as the 350 mount being better because it is locking, it never made any difference to me because I can break either mount with the BB, and the engine gets a chain to hold it in place. Maybe 1/4" makes a difference with the hookers, but from what I have read they never fit without massaging anyway.

------------------
Dave (NY)
70 chevelle ss396 conv
66 chevelle ss396 hdp/conv
72 chevelle
TC member #493
Never forget Earnhardt!
 
1 - 20 of 23 Posts
Status
Not open for further replies.
Top