Technical Mounting an engine off center?

I’m working an install of a GMC 302 with a 4-71 blower in a ’37 Chevy. The blower hangs off the drivers side of the engine and uses a very long snout which places the blower pulley about where the driver’s side headlight is. To make this work, my thought is to re-mount the headlights lower on the front nose and then cut an opening in the nose allowing the blower pulley to stick out a bit where the driver’s side headlight originally was. To minimize the cutting, it would be great if I could move the engine a little to the p***enger’s side. I know manufacturers often did this in the 60’s and 70’s to fit big blocks V8s into smaller cars.
Ok so my question is how much can I offset the engine and keep smooth drive shaft rotation? The engine would remain parallel in the frame.
Another thought….I have read that you can also angle an engine 2-3 degrees which I’m not so sure about. So if I did this, and kept the transmission tail shaft centered, I think the blower pulley would move about 2” towards the p***enger’s side.
Moving the front of the engine 1”-2”, or more, would help a lot.
Thoughts? Thanks!

 

you want the engine parallel to the frame (viewed from the top), and usually the nose of the engine is up 3-4 degrees relative to the frame (viewed from the side). It's fine to scoot the whole engine over to the side a few inches, just make sure to move the front and back an equal amount.

beware there may be other clearance issues if you move it too far

 

Later model Corvettes, Mustangs, Thunderbirds had the engine offset to p***enger side from factory and as Jim states, as long as drivetrain centreline is parallel to car centreline there should should not be any issues. Last thing you want is strange drive train harmonics.

 

61 to 66 ford pickups had about 4 inches of offset....post pictures!....good luck!


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1967-69 Camaros as well, had offset on the big blocks. I don't think the trans mount was any different in either direction. 1" on the engine if I remember .

 

Most full-size vans have offset engines, too. Well worn territory. As has been mentioned, 3-degrees nose-up, parallel with the ch***is centerline.

 

my 37 as pictured in the avatar has an inline 292 offset about 1-1/2" to the right

 

mopars did it for years!

 

All 60s 70s Mopars are offset. Usually 2 1/2 inches. The weight of the battery, the steering box and the fact mopar found out in studies that 90% of the time cars have only the driver in them con tribute to this design. Tis really funny when a non-mopar guy builds one and spents forever putting the motor dead centre. Looks funny to us right away.
don

 

Yep, and the guys putting 318's in 52's are still doing it. When you're adjusting the nose-up/nose-down, check the angle of the pinion on the rear-end... you want it parallel (not on the same plane, but parallel). If you set the engine angle first, you may have to use angled shims on the rear leaf springs.

 

It has been my experience that the most over rated critical angles are drive shaft related. That is the reason for U joints. They say, (the people that think they know) , the angles should be the same at both ends,, not to exceed 15 degrees,, etc. etc. If this is the case a Monster Truck should not move, and never hold up to 600hp.
Just look under one and see all the "this won't work ideas under there". There are limits to everything , you just don't know until you try.

 

I know this is a dumb question, and might even be thread jacking, but here goes; if ones frame got a rake, going down hill to the front, does you still put it 3-4 degres up from level. And the match drive train flanges?

Sorry for the dumb question, and thraet jacking.

 

Monster trucks don't need to drive down the highway at 70 mph without vibrating, and check out how many use constant velocity joints. In your case Volvo, I would be more concerned about leveling the carb (if it has one) at normal ride height than following the 3-4 degree rule.

 

Volvobrink, it is the relationship of the crank centerline to the pinion centerline that matters and that the U-joints are operating at a slight angle. (for highway use, 2 to 5 degrees is the best. (the only reason pinion and crank aren't set dead level is to get the rear of trans and driveshaft low and out of the p***enger compartment)
And Babyearl, take that monster truck out and run it down the highway for 100,000 miles and see what happens to the U-joints. There are trade-offs!

 

You are remarkably off-the-mark. Driveshaft angles, driveshaft movement, u-joint cycling, etc. are all a function of physics, the laws of which you ignore at your peril.

I don't think I know. I know.

 

Can somebody draw some pics of "acceptable angles"
ie: motors parallel to ground (carb maybe level), rear end pinon parallels ground(input/face of u joints input shaft perpendicular to ground). But rearend can travel up/down __?___ degrees.
So if rear differential is offset to p***enger side & transmission is near center, what's difference?
Or rear differential is dead center, how far can motor be cheated to p***enger side to give some steering clearances.
ujoints don't know if they are 3 degrees right left up down?

Just went through this cheating a nailhead over to p***enger 1-2" to get starter & steering room, but rearend differential was offset anyway.

Fng question, but more I looked & thought, dumber I felt.
I guess there's probably too many variables b/w setups, but on u-joints alone, what are most setup tolerances?


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side to side offset no biggie just concern yourself with this when mounting engine: If you run carburetor the carburetor base needs to be level, if running injection it doesn't matter! from what the 4x4 guys tell me is the further away from 2 degrees you get on driveline angles just expect to change u-joints more often and experience more vibrations which doesn't mean you will but might. check out some of their extreme angles that work.

 

The carb mounting surface should be level to the earth, + or - 2-3 degrees. More then that causes problems with fuel going through the carb. If your running fuel injection, this one doesn't matter as much. You still have to keep the oil pump pickup tube submerged in oil, so keep that consideration.

U-joints are the limiting factor in determining off set. U joints have a max of 30 degrees before they bind up, and that would be in any combinations of directions. Motor/transmission centerline should be within 2-3 degrees of being parallel to the centerline of the rear axle pinion shaft. More then 2-3 degrees here runs the risk of dive shaft vibrations. Shorter driveshafts will reduce the amount, in inches, of what offset you can run. These are numbers that have been proven, over time, to be acceptable numbers, but you all can try whatever you would like. Gene

 

Someone recently posted a real good video explaining driveline physics, relating the effects of angle, etc. It was well worth a look.

 

U-joints that rotate thru the 3* angle, rotate the needles and spread the lube around.
Greater angles cause power loss with each revolution, and can induce vibration.
I always try to keep the fabrication (as built) alignment close to this value.

 

Of course the other way to do it would be to offset the entire driveshaft - frame permitting - and use an asymmetrical axle like Land Rovers have had front and rear for 66 years. Not that angling the driveshaft in the horizontal plane won't work, as everyone else has said.

 

Driveshaft angles are also dependent on length. The longer the wheelbase the less the angle so a short wheelbase car needs to be more careful figuring the engine placement and U-joint angles.

 

Offset is ok if its aligns the frame rails. Best to level the engine with the Carb pad to minimize fuel problems. That's usually tailshaft down a little. Put the carb pad at zero at ride height.

 

The C-3 Corvette does not have the engine parallel to the vehicle center line and neither do a lot of Mopars. A lot of Fords do not have centered pinions in the rear end even though most of the ones I have worked on had the motor in the middle of the vehicle. As for setting the engine with a 2-3 degree angle those who suggested using the intake manifold surface as a guide are also on the right track--the carb needs to be level and then the pinion angle needs to be set based off how the engine ends up. As several posters suggested, that is what the U-joints are for, as well as allowing the suspension to articulate.

Roo

 

The answer is yes, you can offset the engine and is/has been done many times from the OEs as stated previously, BUT, the pinion is usually offset also near or the same amount. When the engine is horizontally (top view) offset from the pinion, a compound angle is created that has to (or should be) added to any vertical (side view) angle, to arrive at an actual u-joint working angle. This applies to the common single cardon u-joints, not constant velocity.

 

I think you may have typo'd the above. The way it reads is that the engine and trans are mounted at an angle, viewed from above, and I believe that is not the case. If you meant to say the engine trans are offset to one side, but parallel to the centerline, then that is an accurate statement.

Ray

 

Picture of my buddy's old '40 Chev PU. The motor is a 292 with a 6-71 blower running (2) Holley 1150 cfm carbs. The 292 is backed by a TH350 and 4:30 Ford 9" rear end.

No engine offset, but did have to clearance the hood sides and top.

 

CV joints would make everything a whole lot simpler.

I seem to remember a packaging study Ford did ('70s? '80s?) that had the engine angled to send the driveshaft about a third of the way across the rear footwell area, using a heavily offset axle. It placed the tunnel such that two p***engers could sit comfortably on one side of it and one could sit on the other.

 

This one? Pete

 

Another one!! Pete