Engine Mounts for 350/TH400 - Team Camaro Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools Display Modes
post #1 of 7 (permalink) Old Sep 16th, 05, 05:48 AM Thread Starter
 
Join Date: Oct 2004
Posts: 52
Engine Mounts for 350/TH400

What are the correct engine mounts for 68 Coupe, SB350 with TH400 transmission? I nelieve I have a tailshaft driveshaft angle problem and think it is being caused by engine angle. I have a 68 GM TH400 crossmember so the backend hopefully is where it should be. I know the crossmember off centers the driveshaft and wonder since the TH400 only came with BB's did their mounts do something to compensate for the off centering. And more importantly did BB mounts make the driveshaft angle correct.

Do you think having what I believe are 68 GM SB 350 engine mounts on a new GM 350 HO crate engine with a TH400 tranmission will result in the proper tranny tailshaft/driveshaft angle?
68SS96GS is offline  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old Sep 16th, 05, 06:47 AM
Senior Tech
 
Join Date: May 2004
Location: Southeast PA
Posts: 8,303
Re: Engine Mounts for 350/TH400

Where the big blocks are different is in the engine mount towers that bolt to the frame. These are staggered to offset the big block toward the passenger side about an inch, and the trans crossmember has about the same.

The mounts on the engine block itself aren't offset.

I think when everything is offset, the driveshaft angle is fine because it's really not that much offset. Yours sounds like the tailshaft could actually be angled toward the passenger side (crooked to the passenger side), so your driveshaft is not only seeing a trans that is offset 1", but cocked away from the pinion centerline.

I'm just chiming in because I have BB knowledge. I did drive a 350/TH400 67 in high school, and there were no driveshaft issues, but I did not do the conversion and can't recall what crossmember it had.

Eric
69 'vert project big block/TKO 600 RR
68 'vert driver RS clone -- gone!
Eric Kammerer is offline  
post #3 of 7 (permalink) Old Sep 16th, 05, 11:24 AM
Senior Tech
Ed
 
Join Date: Sep 2004
Location: Hello Wisconsin!
Posts: 363
Re: Engine Mounts for 350/TH400

Eric is right, your tranny output is pointed to the pass side at an angle which could be causing your vibration.

The turbo 400 crossmember tranny mount pad is offset to the pass side by approx. 1" to match the offset of the big block motor mounts as only a BB received a turbo 400 in 1st gens.

Try unbolting your tranny at the crossmember and side the tailshaft over to the the drivers side so you can run 1 bolt thru the driver's side hole on the crossmember into the pass side hole in the tranny mount (I hope that made sense) and take it for a test spin. The distance between the two mount holes is approx. 1" and should simulate your engine/tranny/rear end being in a straight line. Hopefully that eliminated your vibration. You may be fine, but I do not recommend you leave it that way. The right way to do it is to cut the tranny mount pad off your crossmemeber and have it reweled back on approx 1" to the drivers side so you can use both bolts on the tranny mount.
freezined is offline  
 
post #4 of 7 (permalink) Old Sep 16th, 05, 06:00 PM Thread Starter
 
Join Date: Oct 2004
Posts: 52
Re: Engine Mounts for 350/TH400

I like the idea of moving the tranny over one tranny mount bolt hole.

Not only am I wondering about the angle left and right but up and down too.
68SS96GS is offline  
post #5 of 7 (permalink) Old Sep 18th, 05, 08:09 PM
Senior Tech
Ed
 
Join Date: Sep 2004
Location: Hello Wisconsin!
Posts: 363
Re: Engine Mounts for 350/TH400

Good question on the vertical relationship of the crankshaft centerline between big block and small block, that's one I don't have an answer for, hopefully someone here will chime in and help us out.

If nothing else have the pad welded lower and shim the mount up to get your straight line, I wouldn't expect the difference to be greater than 1/2", and would bet it's within a 1/4". Maybe someone out there has a manual crossmember for SB and BB and can lay them on a flat surface to measure the difference.
freezined is offline  
post #6 of 7 (permalink) Old Sep 24th, 05, 05:49 PM
Senior Tech
Ed
 
Join Date: Sep 2004
Location: Hello Wisconsin!
Posts: 363
Re: Engine Mounts for 350/TH400

I just happened to be able to compare the height difference between a SB and BB manual crossmember today at the Jefferson swap meet, granted this was just eyeballing it, but if anything the SB trany mounting pad sits lower than the BB. The difference is within a 1/4", probably within an 1/8". It you vibration goes away after moring the trany over, just have it welded at the same level.
freezined is offline  
post #7 of 7 (permalink) Old Sep 25th, 05, 05:29 AM Thread Starter
 
Join Date: Oct 2004
Posts: 52
Re: Engine Mounts for 350/TH400

Checking angles and changing position this week!! The car has been parked becuase it is no fun to drive on the highway, especially after 2 years of work and tons o money.

Does anyone know what the stock working angles of the tranny and rear end are?

Thanks again for all your help, I'll be sure to post the results this week.
68SS96GS is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
WHY KEEP ENGINE RPMS under 7000rpm grumpyvette Performance 50 Oct 4th, 05 10:39 AM
Small block - Frame backets / engine mounts - Revisited HwyStarJoe Engine 3 Sep 7th, 05 05:19 PM
engine mounts for P/S and Header Leburks69SS Camaro Tech 1 Dec 16th, 04 10:29 AM
Replace Engine Frame Mounts 69ss350 Engine 1 Sep 4th, 03 07:57 AM
EBAY or Build Balboni Performance 16 Jun 3rd, 03 11:16 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome