I've just dropped the freshly rebult 351w into my '54. Problem us that I think I set it a tad too high and now I have a small interference problem between the driveshaft and frame crossmember.

I guess that my question is how far can I tilt the engine down in the back without affecting the way the engine will run? (BTW 600cfm carb)

I built the mounts with about a 3 degree tilt but it looks like I'll need about 6 to clear the cross member.

Any suggestions?

Thanks
Mike

 

I would think a few degrees tilt will be OK. When we used to run straight axle gassers made out of tri 5 Chevys the angle was down a bit but never had a problem.

 

Do you have a front sump pan? When I got my 351W it came with front sump pan, and it was sitting to high with my MII front x-member. I got a dual sump pan like on 302's in Mustangs and it sits way lower now. I'd change pans if cutting off your mounts isn't a problem and moving and rewelding them...

 

If you tilt the engine down, how is the angle on the drive shaft affected?

 

If the tranny output is level but higher than the rear end then the U joints will be working pretty hard unless the rear end is angled up to minimize the angles. Imagine the letter Z.

If the tranny is still high but is pointing down there will be less of an angle (within reason that is) and maybe it wont be necessary to angle the rear.

A delta of +/- 3 degrees is considered the limit with the vehicle sitting at ride height; that means one U joint is running at a 3 degree down angle and the other 3 degrees up. Above that the joint wear gets excessive; it will work but joint replacement will be frequent. Rough roads will aggrave the situation.

 

Ya, it can be a huge pain when making up some motor mounts and your trying to get your motor straight and level and tilted right. Took me and a couple of guys to finally get mine right.

 

Can you lower the motor mounts to make up the difference?

 

I'm way to far to move engine mounts. Frames already been painted. The reason that I set it higher than normal probably is that most of the time engines get lost in these big engine bays. Mine site nice and high... I was always under the impression, from both books and Mr Niolons site, that as long as the diff angle matched the output shaft angle everything would be just peachy with u-joint angles. Is this not correct? In other words, if my tranny was dipped 3 degrees down, the diff needs to be pointed up 3 degrees to keep everything in phase.

It really wouldn't bother me to move the crossmember back to get some more clearance. I would just need to find another place to mount the original style emergency brake mount.

Also, my 351w has a rear sump..... no clearance problems with the k-frame.


Thanks all
Mike

 

Mike,
If you read John's article and followed those guidelines, everything should work out. I have read several articles on the internet and in magazines, and they are all very similar.

The only other thing some of the articles discuss is the type of rear suspension. A 4 bar is built to be adjustable and also to maintain the angle under acceleration and braking. The leaf springs (especially if some leaves have been removed) will "wrap" under acceleration and "dive" under braking. One of the leaf spring articles that I read suggested reducing the pinion angle 2-3 degrees so that when torque is applied, the axle wraps and the pinion angle and transmission output shaft angle are the same again. The hard part is deciding how much offset your ride will require.

Good Luck,

 

<b>...that as long as the diff angle matched the output shaft angle everything would be just peachy with u-joint angles. Is this not correct? In other words, if my tranny was dipped 3 degrees down, the diff needs to be pointed up 3 degrees to keep everything in phase. </b>

That is correct. Starting off with a zero angle difference between both ends you now allow the rear to move either way during driving but hopefully not exceeding the 3 degrees.

The 3 degree rule is broken all the time by 4 wheelers but many I know either carry spare driveshafts or get towed a lot.
Some of the mountain backwoods trails around Northern New England can be quite brutal.