'76 engine not centered to frame
Thread Starter
Pro
Joined: Mar 2007
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From: Fallbrook CA
'76 engine not centered to frame
OK Guys,
I'm doing a frame off with an LS6 upgrade. I was working on the transmission crossmember today and noticed that my whole eng/trans combo was shifted to the passenger side approximitly .75". I remembered before I pulled the 350 out that I thought it was odd that the crank HB bolt was not in line with the hole in the center of the frame (see pic). Are my factory motor mounts off or is the engine supposed to be offset to the passenger side slightly????
TIA....gp
http://s187.photobucket.com/albums/x...t=DSC03713.jpg
I'm doing a frame off with an LS6 upgrade. I was working on the transmission crossmember today and noticed that my whole eng/trans combo was shifted to the passenger side approximitly .75". I remembered before I pulled the 350 out that I thought it was odd that the crank HB bolt was not in line with the hole in the center of the frame (see pic). Are my factory motor mounts off or is the engine supposed to be offset to the passenger side slightly????
TIA....gp
http://s187.photobucket.com/albums/x...t=DSC03713.jpg
Thread Starter
Pro
Joined: Mar 2007
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From: Fallbrook CA
I guess everybody knew that but me. My 4 spd auto transmission is longer than the old TH 350 so the drive shaft angle is greater now. Unless of course the diff. is offset 1" also but it appears to be center.
The point is that if the motor is offset 1" to the passenger side and the differential is on center, you have a drive shaft angle. This angle is greatly amplified with the shorter shaft. I just wanted to confirm this before I made the bracket.
The point is that if the motor is offset 1" to the passenger side and the differential is on center, you have a drive shaft angle. This angle is greatly amplified with the shorter shaft. I just wanted to confirm this before I made the bracket.
Last edited by palamesa; Jul 21, 2007 at 10:50 AM.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
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From: Graceland in a Not Correctly Restored Stingray
That difference in offset isn't a problem. Fact is, u-joints need a small amount of angle in the driveshaft to function properly. For that reason, your diff points at an equal but opposite angle than your engine when viewed from the side.
Wouldn't be a bad idea to check those angles while you're at it. Here's a recent thread that is very informative about the subject of pinion angle.
http://forums.corvetteforum.com/show....php?t=1741084
Wouldn't be a bad idea to check those angles while you're at it. Here's a recent thread that is very informative about the subject of pinion angle.
http://forums.corvetteforum.com/show....php?t=1741084
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Melting Slicks
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From: Beringen
Team Owner
Joined: Oct 2004
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From: Springfield MO
St. Jude Donor '07
That wasn't criticism...it was just an observation that the old thread went back and forth for a long time, while coming to a very simple conclusion - the factory offset the engine a bit.
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Joined: Mar 2007
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From: Fallbrook CA
I've been out working on my alignment all morning. Time for lunch and an update.
Yea...The engine/trans combo is offset 1" to the passenger side as everybody knows. The reason why is still up for debate I guess but it doesn't really matter to me right now. The Diff. is on center so there is an left/right angle going from the trans to the diff. Both shafts are parallel to each other so it shouldn't be a problem. As far as up/dn, I have a down angle on the tail shaft and my pinion is also pointing down. I'm a little confused about the other thread about shimming the diff. to get the pinion pointing up. If you shim the front mount, it will point the pinion down. Looks like the way to do it is shim the back or put a thinner bushing in the front.
http://s187.photobucket.com/albums/x...t=DSC04103.jpg
http://s187.photobucket.com/albums/x...t=DSC04101.jpg
Yea...The engine/trans combo is offset 1" to the passenger side as everybody knows. The reason why is still up for debate I guess but it doesn't really matter to me right now. The Diff. is on center so there is an left/right angle going from the trans to the diff. Both shafts are parallel to each other so it shouldn't be a problem. As far as up/dn, I have a down angle on the tail shaft and my pinion is also pointing down. I'm a little confused about the other thread about shimming the diff. to get the pinion pointing up. If you shim the front mount, it will point the pinion down. Looks like the way to do it is shim the back or put a thinner bushing in the front.
http://s187.photobucket.com/albums/x...t=DSC04103.jpg
http://s187.photobucket.com/albums/x...t=DSC04101.jpg
Last edited by palamesa; Jul 21, 2007 at 05:57 PM. Reason: Pics
Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
I had always heard it was offset as a counter to the driver's weight being on the left side of CG. One of those Zora things, unofficially, for the track.
Pro
Joined: Nov 2002
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From: vista CA
Greg,
Making some progress there!
Is that your 'second' engine in the bay already?
When I put in my shortened driveshaft I didn't have the body off like you - really makes measuring those angles easier. I also raised my T56 up as high as I could in the tunnel (actually pounded/bent tunnel and cut a bit/rivitted in al plates) to get equal, but opposite angles to diff (if I remember correctly about 2 to 3 degrees delta. I also noticed the tranny tailshaft seemed to be offset, but never realized it was designed that way - just forged ahead and got it done. Have not noticed any driveline vibrations.
I do have an electrical angle measurement tool if you want to borrow it - let me know.
Steve
Making some progress there!
Is that your 'second' engine in the bay already? When I put in my shortened driveshaft I didn't have the body off like you - really makes measuring those angles easier. I also raised my T56 up as high as I could in the tunnel (actually pounded/bent tunnel and cut a bit/rivitted in al plates) to get equal, but opposite angles to diff (if I remember correctly about 2 to 3 degrees delta. I also noticed the tranny tailshaft seemed to be offset, but never realized it was designed that way - just forged ahead and got it done. Have not noticed any driveline vibrations.
I do have an electrical angle measurement tool if you want to borrow it - let me know.
Steve
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Joined: Mar 2007
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From: Fallbrook CA
Hey Steve....Yes, I'd love to borrow your angle finder. I did some "ROUGH" alignment yesterday to try and ballpark my angles. With my frame and transmission level (4L60E Auto), I have major tailshaft down angle. Here is a pic of a "ROUGH ANGLE" (don't want to get flamed by my good friend Pocketrocketracr). Anyway, I'll need to cheat up the rear of my tranny to try and reduce the tailshaft angle. Kinda hard with no body on. I also need to up angle my pinion. I PM'ed Keisler for input. The other thread talked about shimming the diff. but I need more clarification. If anybody out there has insight, step in.
Steve....lets get together soon and help each other out. I'll be gone next week. The kids are on summer break so I need to go out the the river and drag them around on wake boards all weekend.
Nice to hear from you....gp
http://s187.photobucket.com/albums/x...t=DSC04102.jpg
Steve....lets get together soon and help each other out. I'll be gone next week. The kids are on summer break so I need to go out the the river and drag them around on wake boards all weekend.
Nice to hear from you....gp
http://s187.photobucket.com/albums/x...t=DSC04102.jpg
Drifting
Joined: Mar 2004
Posts: 1,873
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From: Savannah Ga
A lot of cars have the engine offset for one reason or another.Could be steering linkage/box. AC config.I'm pretty sure my BB 69 Chevelle was that way and I bought it new. 396/350 4 speed.And beleive it or not it was a two door post car. I didn't know what I was buying.I know I liked the vent window and the full door frame. Another one that got away.Didn't make very many of those.Car was dark cherry red with magnim 500 wheels. I left it stock except for headers.
Racer
Joined: Oct 2006
Posts: 412
Likes: 1
From: St. John's Newfoundland
I guess everybody knew that but me. My 4 spd auto transmission is longer than the old TH 350 so the drive shaft angle is greater now. Unless of course the diff. is offset 1" also but it appears to be center.
The point is that if the motor is offset 1" to the passenger side and the differential is on center, you have a drive shaft angle. This angle is greatly amplified with the shorter shaft. I just wanted to confirm this before I made the bracket.
The point is that if the motor is offset 1" to the passenger side and the differential is on center, you have a drive shaft angle. This angle is greatly amplified with the shorter shaft. I just wanted to confirm this before I made the bracket.
Thread Starter
Pro
Joined: Mar 2007
Posts: 738
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From: Fallbrook CA
Are you sure? I don't have the drawing handy but it seams if your diff is offset, your half shafts or something would have to be different lengths to compensate or maybe the differential output shafts offset? Too dark to go out and measure but I was pretty sure it was on center.
