Setting Driveline Angle - LS1 Swap with a 21st Century Subframe

[Mkelcy]

I'm in the process of mocking up the LS1 in my 21st Century Street Machine subframe for my project '68 Camaro. The subframe is out of the car on a stand. I'm using AutoKraft LS1 mounts, and the transmission crossmember that came with the frame. With the AutoKraft LS1 mounts swapped (passenger side on driver's side and driver's side on passenger side) my front to rear distance looks pretty good and so far as I can tell with careful measurement/eyeballing I should have the engine about an inch or so away from the firewall.

That said, using the cross-member with a poly transmission mount results in about zero degrees driveline angle and sticks the collectors of the 21st Century headers halfway into the passenger compartment, as well as aiming them directly into the cross-member.


I've determined that a 4 degree downward angle pretty much solves my header to floor issues, leaves the oil pan higher than the front crossmember and allows room for the exhaust to go under the transmission crossmember. I'll have to revise the transmission crossmember by dropping the center section by about 2.375".

So, is 4 degrees too much? When the car's aligned should I set the rear pinion angle to 4 degrees as well, or should I set it to something less so it'll be more nearly 4 degrees under acceleration?

Steve Rupp and Payton King - did you have any cross-member issues with your 21st Century subs? I'm somewhat astonished that I need to make such a dramatic change to the cross-member and would suspect the headers, except that the drivetrain is virtually parallel to the subframe with the unaltered transmission cross member and the poly mount in place. Any thoughts?

[Lance-W]

I believe when I was doing mine the magic number was 3 degrees. I'm using a factory subframe so it's not the same but I just ended up making a custom crossmember after I figured out where it needed to be. If you decide to go that way we can make one fairly easy. Plus from the way your picture looks the cross member is going to be right in the way of the exhaust. If you make a custom one it'll solve that too.

[Mkelcy]

I believe when I was doing mine the magic number was 3 degrees. I'm using a factory subframe so it's not the same but I just ended up making a custom crossmember after I figured out where it needed to be. If you decide to go that way we can make one fairly easy. Plus from the way your picture looks the cross member is going to be right in the way of the exhaust. If you make a custom one it'll solve that too.

Yes, the way it sits right now there's no way to route the exhaust even half way decently. I'm not sure I'd trust my welding skills to do the cross member, but I'd be happy to supply the beer if that was an offer

[Lance-W]

Yes, the way it sits right now there's no way to route the exhaust even half way decently. I'm not sure I'd trust my welding skills to do the cross member, but I'd be happy to supply the beer if that was an offer

Beer will work

[Mkelcy]

Beer will work

Cool.

[Payton King]

Snap me some pics of the motor mounts you are using they should be the short style used on a 67. Also what is the clearence of the pan to the rack up front? My oil pan is is paralle with the front cross member and level. Yes the angle is 0 when compared to the sub frame.

Steve ran into some problems, but I did not...of course they installed mine and built the cross member at the shop.

[Mkelcy]

Snap me some pics of the motor mounts you are using they should be the short style used on a 67. Also what is the clearence of the pan to the rack up front? My oil pan is is paralle with the front cross member and level. Yes the angle is 0 when compared to the sub frame.

Steve ran into some problems, but I did not...of course they installed mine and built the cross member at the shop.

Thanks. I'll take some picures.

[Vegas69]

Cross member looks to flat. Take some radius steel and make some notches for exhaust. I'd go with 3 degrees if you have tunnel clearance.

[Payton King]

the clearence from my pan to the rack is 1/8 to 1/4 of an inch. It sits close. The mounting plates on the block for the motor mounts....21st did there's out of 1/4 steel and used the short mounts. I think the depth is 1 11/16 compared to the new mounts that are 2 1/16. Most of the aftermarket block mounts out of aluminum are 1/2 thick. The rear mount for mock up was a stock rubber mount. The stock LS rubber mount is shorter than the one you have. Although mine is at 0 degrees because I am running the same mount you have in the picture, with the correct rear mount you should have about 1 to 1.5 degrees down running front to back.

I am guessing that the motor is too high in the car along with this other stuff.

I would make sure the front mounts are correct and lower the rear cross member. You may check around and see if you can find a shorter rear mount.

I also have about 2.5 inches from motor to firewall.

[silver69camaro]

Motor angle can up to 20* until oiling problems occur. In other words, put it wherever you want and adjust the pinion angle to fit.

[Vegas69]

Motor angle can up to 20* until oiling problems occur. In other words, put it wherever you want and adjust the pinion angle to fit.

Ouch....what about his u joint working angles.

[Mkelcy]

I put the oil pan back on the engine (don't ask) and installed the rack. It looks like I have good clearance for the stock F-body oil pan everywhere but for one of the lines on the rack:


The line isn't pinched, but I don't like the way it's bent. I'll either reroute it away from the pan or try to raise the engine slightly; but I don't think I can go any lower with the engine. I don't think the AutoKraft pan I have will fit with the engine this low, but I'm not sure I need it.

With the engine set at a 3 degree angle, the headers are almost perfectly parallel with the subframe:

So it looks I'll be taking Lance up on his offer to help build a new cross member with more drop to accommodate the transmission mount and more arch on both sides for the exhaust.

I'll take some measurements after I've got it mocked up in the body to confirm that the 3 degrees works for the exhaust, etc.

Payton, thanks for your measurements and comments; it's nice to hear from someone who has the same subframe. The rest of the 21st Century piece is so nice, and so well thought out, that I was wondering what I was doing wrong to have the transmission cross-member so far off.

Lance, I'll be talking to you no later than the next Cruise the Crest.

[DEIGuy38]

Have you tried to talk to Steve with Bad Penny. He has the 21st Century sub in his car?

[Lance-W]

Lance, I'll be talking to you no later than the next Cruise the Crest.

No sweat bud. We're outta here for the weekend and riding in the desert. We'll make a plan next week or on the Crest run.

[98ssnova]

I would think that if you left it at zero it would hit the trans tunnel. And 20* seems a little to steep for me what about getting a taller engine mount?

[Payton King]

No need to re-route that line on the rack. Once you bring the rear down it will clear line that you pictured.

The stock LS1 rear mount has 1 stud in the center and the mount you have has two...or you could use bolts...so unless you drill a center hole in the crossmember you cannot use that mount.

You may want to check with Prothane and see if they make a chevy style trans mount that is 1 inch instead of 2. You could always make your own. I would make a new cross member myself, but not until the subrame and motor is installed.

Going back and looking at the pics, the mounting pad on that tricky Viper trans may be slighly different than a stock T56.

On a seperate note, I have been in contact with the same guy that Steve used to valve up his Bilstiens. I should be getting a set soon. What are using for a shock and spring rate?

[Mkelcy]

No need to re-route that line on the rack. Once you bring the rear down it will clear line that you pictured.

The stock LS1 rear mount has 1 stud in the center and the mount you have has two...or you could use bolts...so unless you drill a center hole in the crossmember you cannot use that mount.

You may want to check with Prothane and see if they make a chevy style trans mount that is 1 inch instead of 2. You could always make your own. I would make a new cross member myself, but not until the subrame and motor is installed.

Going back and looking at the pics, the mounting pad on that tricky Viper trans may be slighly different than a stock T56.

On a seperate note, I have been in contact with the same guy that Steve used to valve up his Bilstiens. I should be getting a set soon. What are using for a shock and spring rate?

I should have clarified what the picture shows. I took the transmission mount out, so the rear of the transmission has been dropped about 1.75" (the thickness of the transmission mount) and is sitting directly on the crossmember. The picture of the rack and oil pan is with 3 degrees of down angle on the engine/transmission.

I'll put the subframe on the car, see where everything falls and decide on leaving the mounts where they are and re-routing the line on the rack, or getting mounting plates that raise the engine. I kind of like the idea of the engine being as low as practical, so it's going to be, as they say, a "game time decision."

As for shocks and springs, my car's still a way from being on the road. That said, I'll start with some single adjustable QA1's and 550lb springs I had sitting around on the front and 225-250's on the rear with some double adjustable M2's I ordered from AFCO. I gave the shock guru at AFCO the details on the car and they custom valved a set for me. (I was (and am) too ignorant of what I need to give them any direction.) Both sets of shocks are rebuildable and revalvable (if needed), so maybe I can get the Pozzi's to thrash the car once I get it on the road and get some good suspension input.

I don't know how directly the rear end setup of Steve's car is going to relate to ours, because (as I understand it) his upper cross-member is lower than stock because of prior modifications to the car. If that's correct, the angle at which the suspension is working is likely going to be different from his car to ours and the spring and shock valving rates may be affected.

[CarlC]

LS eh? Nice.

[Mkelcy]

LS eh? Nice.

Don't tell anyone, but I found a pretty decent deal on a NIB 376/480 LS3 with the ECU, wiring harness, etc. kit. The engine in the picture will be up on Craig's List once I get done with my mockup.

[Payton King]

of the way my pan sits in relation to the front cross member so you can see if the motor is indeed to low. I would not want my oil pan lower than the front cross member just from a damage standpoint on that cast pan.

I am guess that you will need to raise your tunnel a bit to get it to clear the transmission.

I started out with an AFCO street rod shock and 350 lbs springs. I have DSE leafs and koni's in the back. Rode like a Caddy, but a little to floaty. Went to a 450 lbs up front and it feels great. With the new Bilstiens I may be running 500 lbs. Eventually I will be changing the leafs out...but admittedly, they are working pretty darn good.

Looking forward watching yours come together.

If you need to get a power steering pump, get it from Turn One and tell them you are running a Mustang II rack. If you already have a pump, call them and get a flow reducer. It takes about 2 minutes to pull the old one out and put the new one in. Makes all the difference in the world on the way your steering feels. Best $35 I have spent.