The Stovebolt Site Forums The Shop Area The HiPo Shop V8 Installation Question

Before I weld in the new motor mounts and the transmission mount on the crossmember can anyone advise what the preferred front to back pitch of the SBC engine should be? I have it sitting at 5 degrees now on a level floor but the frame is bare with the exception of the cab shell. Still have the under bed gas tank and bed to install. If I raise the transmission more to reduce the current angle I will have to modify the floor of the cab for clearance (no big deal). What is the optimum angle for the engine and trans? Thanks for the help.

1954 1/2 ton

I was always told to shoot for 2-3deg. pinion angle.

I could be wrong - but if you set your motor level (according to measurement taken on top of intake manifold) then you'll get soemthing close to the desired pinion angle.

Further - if your vehicle is not at ride height - or proportinate to it - then your measurements will be incorrect when you actually put the rest of it together.

On my 59 when the motor is level, the tranny is darn close (highly technical measurement ) to the cab.

Anyone else know more about this?

- Ryan

Thanks Ryan. My understanding is the pinion angle is a related but separate issue. The differential yoke centerline and the transmission output shaft centerline should be set up parallel. From there you push the differential downward 2-3 degrees further to set pinion angle. I could be wrong and as my wife often reminds me I am but the engine/trans angle is what I am needing now. It has to do with oil draining/flow I believe. If you find out definately that it is 2-3 degrees for the engine please let me know. Thanks again.

Sounds like you know more than I.

I've been told to keep the motor level (as measured on the top of the intake) when at ride height or as close to it as possible. This would make your carb level - which I belive was the whole point made to me when installing the motor.

I'm sure someone on here has more experience though!
- Ryan

By the way - I agree with your analysis of pinion angle.

- Ryan

I agree with Ryan in measuring this angle as close to the ride stance as possible. Otherwise you'll be adjusting all over again. This can be a catch-22, as you need to assemble to get to ride stance. Adjust, repeat; adjust, repeat...

On the driveline, isn't there concern about some travel under power? Keep that tranny off the floor/firewall and give yourself some play!

If were me, I would find a vehicle with the same drive train you are using that is still in it original position. Jack the vehicle up to where the frame is level and measure the angle. Then jack the frame up on your vehicle to level and set engine to the same angle. It's the angle in relation to the frame that matters not to the ground isn't it?
That's what I think anyway'
Scott

Although I understand the need for the truck to be at ride height when setting this angle, at this time it is not feasible to fully assemble the truck to achieve a fully loaded stance. I can pre-load the rear suspension to simulate ride height (I will assume about an inch for a full 18 gal tank plus bed,fenders,dog,wife,etc) but what I need is the preferred angle of the engine/trans. I do not think it is a direct relation to the frame but rather to the ground. Also, since both the engine and trans are hard mounted there should not be any or minimal vertical movement under load so floor clearance is planned to be .5". Has anyone installed a 350 SBC with a TH350 that can give me a angle reading off their valve covers?

The angle of the motor/tranny is the natural angle set when the top of the motor is level (0 deg). I checked my el camino last night - it came stock with a small block. The top of the intake is parallel with the ground (0 deg). This position allows the oil to flow to the pickup point in the pan and keeps the carb level - as it should be (or so I would assume - or it wouldn't be that way stock!).

I understand about preloading - I had to account for the amount of weight that the cab and body panels added when installing my motor as well.

Don't forget, you can still adjust the motor slightly (very slightly) once it's bolted down. The motor mounts provide a small amount of flex - so to speak.

I can measure tonight off of the valve covers on the el camino.. do you need me to do that? You can also call you FLAPS and they should be able to tell you the same thing.

- Ryan

Ryan, It would not hurt to get your angle if you think about it. Thanks.

I'm not understanding something here. Why does the engine angle matter to the ground? The angles need to corrospond from engine/trans. to rear diff. People change ride height all the time with tires or lift kits or heavy loads and so on. The important angles are still the same. Are you only going to drive on level ground? I'm probably wrong but what else is new?
Scott

Scott, it's best if the carburetor sits level on level ground, so that variations in attitude of the carb average out over the long run. The intake manifold has an angle built into it, which makes the engine sit down in the rear at that angle. Then the differential should be rotated to that angle or a little more, so the u-joints are working in the same plane under typical load.

Intake attitude doesn't matter on fuel-injected engines. On my LT1, there is no angle built into the intake. Still, the basic layout of front engine-rear drive vehicles tends to stay the same, so the engine needs to be down a bit in the rear to get the trans clear of the cab floor.

I wonder about the importance of matching u-joint angles, though. The common wisdom is that the joints won't wear properly and will cause vibration if they aren't running in close to the same plane, and that the bearings will brinnel if they don't have enough angle, but I've been looking at trucks with two-piece drivelines lately. There does not appear to be any effort to follow the "rules" in the trucks I've noticed. One medium duty truck (single rear axle) I checked out in a parking lot the other day looked to be as straight as a string from the trans through two drivelines to the rear end. I haven't heard that big rigs are prone to u-joint failure.

Any truck mechanics aboard who care to comment?

Joe

I dont know if this will but here is a sight that explains how to set up your diff and tranny.I just went through all this with my 54 3100
www.iedls.com

There is your answer, get your truck as close to running heights as you can fake and level the carb flange. The carb is almost always level, no matter who's motor. Some of the older ***** had a lot of motor angle and the intakes were a wedge to compensate.

Larry

Ha!

I just realized that this forum will not let you spell "Found On the Road Dead". Cool.

Later.........................................Larry

So I was somewhat right in my first post without even knowing it. If you go to an all original vehicle, the numbers should be similar to your numbers. Sorry about the mix-up, but it wouldn't be very easy to set your engine angles without a more complete truck if you go by the ground in my eyes. I've done V-8 swaps in AD trucks but they were complete trucks. I just put the engine in, bolted to bellhousing, sat it on a floor jack with the cross member loose in the frame, took the measurements to center, added a few degrees for the wieght of the engine. Made the marks in the frame, drilled and bolted.
That's how I did it,
Scott

Thanks for all the replies to this issue. From this point I will set the ride height, get to 0 degrees on the carb mounting flange and set the trans mount on the crossmember. Wife just went on the 8 minute workout diet so I may have to wait await before I weld it tight. I guess I can always feed the dog more to compensate for whatever my wife looses.

Houston54 is right. In other words, the transmission output shaft and the pinion shaft in the rear end need to be parallel to each other. In practice, this is impossible to maintain at all times, due to varying loads and engine torque. Loads will make the rear end squat, which changes the relationship. Also, torque from acceleration will do the same- plus make the axle housing twist up.

So, by nosing the pinion shaft down 2-3 degrees, some of this will average out, but you will never maintain a precise angle.

It's all a compromise....

the engine/trans angle depends on the way you will use the truck for drag racing every now and the (like i do ) you will want the front of the engine down a couple of degrees so the gas in the carb stays off the back side of the float bowl i did this with the osition of the cross member in the frame as for the pinion angle i used some spring shims between the spring and the perch any high pro catalog will have these also depending on what trans cross member you use there can be some flexibility built in my 51 with the small block runs down the road great and also races pretty good

Joe,

You're right, truck drivelines are a "wierd science" all unto themselves. I'm just apprenticing right now and haven't started the "school" part of it yet, so I don't have any real specifics I can share with y'all yet .

One thing to think about is the driveline "wrap" or "movement" as mentioned above...You should see how the rear diffs in an FD120 tractor twist around starting from a stop with no trailer on! Just imagine how much more they'll move when the truck is loaded!

I believe (from my admittedly limited experience) that the big trucks are designed to have this much driveline movement to help reduce breakage of u-joints and other such "hard parts." The hanger bearings are usually suspended in quite flexible rubber mount bushings, just for this purpose.

BTW, the level carb for fuel theory is the one I've always heard as Gospel from both "car guys" and in automotive trade school...sounds like a winner to me.

Hope this helps.

Regards,
Wannabe