The Jalopy Journal
Discussion in 'Traditional Hot Rods' started by Smart62, Jul 22, 2021.
I will measure from the surface of the trans output and double check it off the engine block.
It seems to be quite usual to use a hurst mount on the SBC at the front and chassis engineering plate at the back in centre of crossmember but this is what is giving me the engine being high at the front. 5 degrees from level. Anyone from Chassis engineering out there who can comment?
The diagrams in Tman's post (#23) pretty well say it all. You want the output shaft of the trans and the pinion shaft parallel with each other no matter how much they are offset from each other.
The one that says NOT that says high strain bad vibration is what half the spit and whittle club will claim that you have to do to compensate for pinion rise (axle housing twist) when you have hard acceleration. That same bunch has been claiming that for at least 60 years that I know of and they are usually the ones puking U joints on the starting line at the drags or in a street race.
I think chassis engineering is gone , kaput , out of business
What’s problematic is (unjoint working angle) with drive shaft pitch is if the trans is down to the rear, and then your drive shaft headed up to the rear. This happens on lowered cars.
5* down on the trans works in lifted trucks.
Zero works in lowered cars where the pinion has more ground clearance than the trans.
Then if you’re looking at an open hood hot Rod setting on 4* chassis rake and the engine is set at 3* then you’re looking at 7* included angle at the firewall. To me it’s not visually appealing.
Do you have anything positive to offer this discussion ?
Curious why it’s problematic for the drive shaft to head uphill, if the angles are correct does it know which way it’s going?
If you are starting with engine/trans down 3* how much can the driveshaft run up hill before the ujoint is out of operating angle specs ?
If the engine is at 3 the driveshaft should be zero. If the engine is at 2 the DS can be 1 up hill, and so on.
If the engine is 3* down the driveshaft can be up to 6* down
If the layout of the car dictates an up hill drive shaft then the engine should be less than 3* down
Do you? I cannot seem to find many instance where you actually do.
You mostly belittle people, and you won't even pay for an Alliance membership. Can't you find some other place to troll?
I pay to be here. You don't.
Yes that makes sense, but a blanket statement that it can’t run up hill to the rear ended is incorrect, as I said if the angles are correct it doesn’t know the difference.
This question will always come up. Searches will not give a fella the exact answer they are looking for. That’s most likely due to the fact they don’t have a lot of experience doing it.
So OP asked about his set up with a Hurst mount. His set up gives home a 5 degree angle. That’s his concern, just a bit different than “how to set angles”. Help the brother out, been some good info so far and hopefully he’ll get what he needs.
If you're unable to see the irony in your statement .....WOW!!
I have a 327 SBC with small dizzy in a ‘40 Deluxe.
Frame has 2 dgr. stance, engine 3 dgr, 5 in all engine vs frame. Just clears firewall.
Jag rear same angle as engine.
Came with Hurst front motor mounts, it sat higher, but still cleared firewall. Now has side mounts.
It must be possible to make a larger ‘valley’ or cutout in firewall and retaining original look, but it should be possible. Tight fit though.
Good luck on the project!
Not so sure this is good advise, many intakes are set up to be 3 degrees with a level carb but not all. I would double check off the back of the trans to be sure.
Check out this web page from Spicer. You can enter your drive train angles and it calculates universal joint operating angles. It allows you to do " what ifs" and decide what things you can change and by how much. https://spicerparts.com/calculators/driveline-operating-angle-calculator
On the OPs question to Chassis Eng. , IIRC the Hurst mount will set the front of the sbc higher than the C.E. bolt in mounts; I modified mine (avatar) to drop the engine about 5/16 in. while raising the rear of the trans about 5/8 in. to help me get good universal joint operating angles. I think I got them to 2 1/2 deg.
I didn’t make a blanket statement.
Every 3 to 6 months!
I was referring to your previous comment before you edited it that it’s problematic if it runs up hill, I was simply asking why that was, I understand perfectly how to set them up. Before you added the pertinent clarification it was a blanket statement. It really doesn’t matter because the information is now there.
I'm sure happy I understand how all this stuff needs to be, and try not to get into these discussions because they always turn into a shit-show. I do need to point out that the "W configuration" is valid. The diagram below is from the Spicer web site. I think they know most of what there is to know about u-joints.
May want to note that your diagram has a slip yoke IN the driveshaft, that makes a difference but may cornfuse some folks. It works differently than a slip yoke at the output shaft.
Nothing edited was there beforehand
If you have a smart phone, Just download the TREMEC toolbox app. It will make more sense to you.
Lets mention one more thing that ALWAYS comes up in this discussion. ENGINE ANGLE. Many folks think they should be measuringoff of the carb pad. That really has nothing to do with this. The angle of the back of the block AND Transmission output WILL be parallel. That is why most of these charts show measuring off the tailshaft for a good visual.
So this is a different discussion, but when using front engine mounts you should use mid mounts at the bell housing. If using a crossmember mount at the rear of the trans you should be using side mounts on the engine. Maybe you need to rethink your engine/trans mounting scheme, that may just take care of your engine angle.
The imaginary line through the transmission output shaft, and the imaginary line through the pinion shaft should (with a few exceptions) be parallel when viewed from the side, and from above.
The angles made between those two imaginary lines, and the imaginary line through the driveshaft, should have the same absolute-value (with a few exceptions), when viewed from the side, and should be set to the minimum (as close to a straight line) that best-construction-practices allow.
Pinion offset is fine, however, for each joint degree, when viewed from above, induced by the offset, decreases the permissible angles, when viewed from the side.
No up, no down. No convergent angles meeting at the center of the Earth. No perception problems.
Thanks Everyone! Amazing input and help.
Here' some pics so you can see where I am at.
All just mocked up so far at one possible ride height with running boards to view ride level.
I wanted to keep the front end traditional as you can see. Hurst will have donut mounts when I have worked out all the angles etc. Back end will use ladder bars.
Frame seen here slightly higher at the back. - Frame to ground at back end is 15 1/2 inches. Engine sits at 4.5 degrees from horizontal. Axle input shaft is about 13inches off the ground with diameter 28 inch tyres. (depends on compression of tyre.) Trans output shaft is 12 inches off the ground here. Front end is about as low as it will go I think. - Not sure how much gap there will be between front axle and frame when all the weight is on which may make it lower. This is my first project... as you can see not an acceptable set up so far, but moving forward bit by bit..
another pic from front. Hurst Mount sat resting on cross member. Could modify mount to get a bit lower.
As the front height of the engine is limited by the cross member I guess everyone with an SBC and solid front axle and any type of engine mount will have similar problems to solve. Let me know anyone if you have successfully solved it on your 35-40 Ford. Cheers
That's Pretty Clear thanks
Separate names with a comma.