Friends, First off, hope you are weathering the Covid storm well! I’ve been working on setting a Y Block into a 1935 chassis for the purpose of making a shop truck. I have the chassis set up such that the axles are bearing the weight of the chassis, engine and transmission. I have the axles set so that they are at a distance from the floor to coincide with the big and little tires I plan to use. The engine has been offset about 3/8 inch to the right both in the front and in back keeping the driveline parallel to the chassis centerline. The sketch shows the distance from the floor to points at the bottom of the chassis for both a stock truck-Avatar as it sits now (numbers below the chassis) and the project chassis (numbers above the chassis in the sketch) as it sits sans body etc. There is a picture showing the angle at the carburetor as very close to zero in the mock up (I realize I took the picture at a bit of an angle) and there is a picture showing the angle at the tail shaft (between 3-4 degrees down front to rear) and have a few of questions and seek advice on them as well as likely some things I didn’t think of: Based on the various threads out there, please weigh in on this: Do I have a proper drive line angle for the engine and transmission? If not, what needs to change? Given the angles noted above, what is likely to change with the addition of the cab, bed etc.? How much more deflection or drop can I expect from the chassis with the addition of full sheet metal? Will this change be similar front and back? Not sure what to think as the front is pretty loaded with the engine in place, but have to think the cab (kind of towards the center of the chassis), hood and front fenders weigh more than the bed in the rear. With the addition of the cab, body and full sheet metal etc. am I correct to think the angle change between the carburetor mount and the tail shaft will stay the same, however I guess depending upon the answer to #2 above, the carburetor mount may not stay at level? Can you suggest how much weight I should add in the front and rear of the chassis to get an idea of the answer to question 2 above? What say you all? Any insight and advice welcome and thank you in advance for your help! Pete
I am tired of this topic but I will mention that carb angle is not always the same as crank centerline. Yours looks to be high in the back compared to the head deck in the above photo. Use the deck under that valve cover for your measurement and I think you will see it matches the angle at the trans output.
go to Tremec toolbox app . Put the app on your smartphone and it will find the angles for you and give you the skinny.
What Kiwi 4d said x2 I've used it twice. Bandit Billy's advice is spot on too. Do not set your rear axle angle until the vehicle is at ride height with the body, etc installed. When I installed the last rear axle assembly in my 38 Chevy I had the car on jack stands with the springs relaxed when I set the rear end up. What was I thinking Later I made my own wedge shaped lowering blocks to compensate for my stupidity.
This, if the yoke is machined square and not sloppy in the tailshaft, is closer to your crank centerlines angle. Best to use the face of the crankshaft damper as a reference for actual crank angle. If the crank snout is known not to be bent. Trust but verify all components. Crankshaft angle should be the same angle as tailshaft. Depends on how much rpm the shaft will be turning, you can get away with higher angles with lower rpms, less angle at higher rpms. This is difference of angles, not individual. Look at any commercial multi-piece drive shaftshaft truck and some will have what appear to be extreme angles but function properly due to correct phasing and difference of angles. If you know the weight of the components, bed/cab/fenders/hood/seat/gas/tank/coolant/gas/oil/driver/etc, you can get a pretty decent estimate of what and where the weight needs to be distributed over the axles. Anything that is split between the front and rear(such as cab) the total weight of the components can be divided in percentage of the weight that is to be placed over that axle to load it correctly. This will get you fairly close to where you will need to be. If the body panels are not available, you can use plywood sheets bolted to the frame(same size) to simulate the bed and cab stiffness. Being the intake is bolted to the engine, and the transmission is bolted to the engine, those two angles will never change. As for the carb being perfectly level fore/aft, that is not much of a concern. You don't want the carb to be rolled(left/right) as that can affect running condition moreso than pitch. You have to weigh components and load the chassis/suspension so it will be at correct ride height. Including driver weight, cars don't drive themselves. If wheels/tires are not available cutout some plywood discs and install those, that would allow the suspension to be loaded while not binding up and make the chassis easier to move around. https://spicerparts.com/anglemaster/measuring-angles https://spicerparts.com/calculators/driveline-operating-angle-calculator https://spicerparts.com/calculators/driveshaft-safe-operating-rpm-calculator Spicer has several articles on driveline angles, U-joint tech, and how to set them up.
I understand the "tired" part, there are a number of threads on this and I tried to read them all. Thank you for weighing in and below is a photo taken a bit ago from the valve covers--You are correct. Will do--Thank you! Mad Mike--Thank you for the links and with respect to #1 I am guessing somewhere around 2500-3000 RPM on the highway. #2: Have to try and get some weight estimates. Anybody have an idea what a pickup bed with steel pan weighs as well as a cab sans doors? The rest of the stuff, I should be able to figure. #3 Figured that with respect to engine bolted to transmission but did not think of checking at the front end of the crankshaft. Thank you for that suggestion. #4: Axles are set at tire height. Have them blocked up to match what I am planning for tires. Thank You
Thank you--Definitely trying to prevent the rear axle issue--thank you for the endorsements and pointer!
not trying to be negative,but now that you have had all this go read porknbeaner's post on over thinking. the reason i say this unless this is going to be a 200 mph racer get the rear and engine set and the small changes the sheetmetal makes won't matter. now for the positive that is going to be a hell of a shop truck. look up roothawg's thread on Lagrange produce tribute truck lot of useful info on 35/36 pu Tom
Thank you! I guess I’m trying to do the “measure it twice cut once thing“ and overthinking it too much.
Basically you need to get your chassis sitting the exact way you want it because the stance of the machine will either compliment or kill its looks. You can do a lot of measuring, but the best way is to get the actual tires and suspension in place with the engine and trans sitting in it. Doesn't matter if the engine and trans are exactly right as long as they are close to where they will be when you are done. Its very easy to be wrong if you don't put the actual components in place (wheels/tires). When you have the car actually sitting the way you want, Then look how the engine sits in relation to the firewall. Basically you want to be sure its not sitting at an odd angle. Put a level on your engines head (front to back) and see what it says. Generally about a 3 degree angle downward toward the rear. Make a temporary mount for the transmission. Cobble something crappy together and you can make a good one later. At the front of the engine make a angle iron cradle. By that I mean you bolt a couple of small angle iron pieces to the accessory mounts on the heads and they extend down like legs to the frame. Tack them in place. Your engine and trans should now be positioned exactly where you want them, and you can build mounts for the engine and trans. The rear end should be angled up slightly to be in the same 3 degree plane as the engine trans, but you do not want them to be directly in line. A string from the rear pinion on the same 3 degree angle should be parallel to the trans angle but intersect below the output of the trans. If it isn't below, then lessen the angle on the rear end. You simply want the rear end to have some room to "wrap upward" during operation as torque is applied. An engineer can calculate everything for OEM manufacturers, but they still have to test things. Doing it in your home shop, its best to use actual components rather than try to rely on getting all your calculations to be right. I'm not saying math mistakes, but simply the fact that accurate suspension measurement is often flawed and then the math is not correct.
That's cruising rpm. You will need to know your maximum rpm, engine rpm x highest transmission gear, be it 1:1 or an OD unit. Really depends on what has been, or what will be done, a mod here or there, replacement of wood with tubing or vice-versa can change the weight substantially. Might want to wait on setting the tail shaft height and pinion angle until you have the truck mostly mocked up. Don't forget fuel weight as well. Trust but verify When it comes to doing a final check of pinion angle, you don't want anything causing binding. Even with the axle housing supported at wheel height, adding weight will compress the springs and the arc of spring will move the axle housing a bit. On jack stands this will not allow the suspension to compress properly and will cause a bit of binding in the suspension. Don't you ever draw the line at infinity?
A string from the rear pinion on the same 3 degree angle should be parallel to the trans angle but intersect below the output of the trans. Should have said: parallel to the trans angle but below so the driveshaft intersects the output of the trans from below. Usually the rear is set slightly more down than the trans so as torque wraps up the rear end, the pinion is still at an angle equal to the trans. The type of traction assisting device used will affect that rear end angle. If a four link is employed, it will prevent wrap up while just leaf springs and slapper bars may need a little more angle. Good catch, the fingers don't always say what the mind meant to say. (If you want to see parallel lines intersect, stand on a railroad track and look as far down the track as you can. )
Go to you tube and bring up IMCA modified rear end movement and you won’t worry about miss alignment again. What they do and what your car does are 2 different things but it shows what a u-joint will do and live. Enjoy.
Best to set up the pinion angle after the car is nearly done and sitting level, with everything on it that will stay on it. Basically, the transmission output shaft and the pinion shaft need to be parallel to one another. For example, if the transmission output shaft is sloping 3 degrees down, the pinion angle needs to slope 3 degrees down, referencing from left to right. This will place the (pinion yoke) at 3 degrees up. Hope this helps.
Thank you all for your help, advice and suggestions! More to be done here. Hope to set the cab on the chassis soon but things move slowly so can’t fully define “soon”. Stay well and best wishes!
If I have a stock-ish intake I always set the carb flat. but here is something to think about. We have been dropping 'em in the snout and changing ride height and angles without doing a think to the engine or rear end for 5 decades for me and gawd knows how long my old man did it before I started. When we are building a dragster or a professional roundy round car we build everything to spec. Not so much our street cars. getting things set up perfect can be fun for sure. bit in my mind if you get your carb flat to start with you are probably "close enough for govment [SIC] work."
Have always used a ride height/weight and 3° angle to setup front & rear yokes. Pinion & Crank/tailshaft parallel. Never had a vibration, in 5-6 chassis. Slight angle is said to pump grease around the rollers in End Caps! (may spread wear as well!)
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