Motor instal issue

[Uwon]

I'm test installing my '86 based motor into a '78 chassis. I am using a Rennline SS rear engine cross bar. My problem is that with the front motor mount bolts in place, the cross bar does not line up with the rear engine mounts. It sits about 1" further back so I have to force bend the cross bar forward to allow the rear bolts to drop into place. I tried loosening the motor mounts to give me some more wiggle room but it inly helped very little. I am concerned that it is too tight. Anybody know if there is a difference between a '78 and an '86?
Any comments and suggestions would be greatly appreciated.
Cheers....

[HawgRyder]

Is it possible to mount the cross bar backwards?
Some have the mount ends offset slightly.
Bob

[fred cook]

I believe that HawgRyder is right, it appears that the bar should be turned around (end for end). I had the same problem when I installed my newly rebuilt 3.3SS into the SC chassis. I used a motor mount console from a Carrera on my 3 liter block. Even with the crossbar mounted correctly, I still had to push/pull each end of the crossbar back towards the front of the car about 1/4" on each end. Also, don't completely tighten the tranny bolts before installing the engine mount bolts. There is about 1/8" of extra room between the tranny bolts and the sleeve in the rubber engine mounts on the tranny mount bar.

[tctnd]

Yes, that bar looks "upside down" as opposed to "backwards". Try flipping it over.

regards,
Phil

[fred cook]

Compare the new bar to the old one. The original would have had a small flange along the top edge that would point back towards the engine when bolted to the motor mount console. Also, if you look closely, you should see that the threaded tubes on each end are not welded symmetrically on the ends of the bar, but rather being slightly offset one way or the other. The spacing of the two holes for the top bolts should be a bit wider apart than the two bottom holes so the bar really can't be mounted but two ways. If the way you have it on the engine now doesn't work, just turn it "end for end" and it should fit.

[Uwon]

Thanks guys. Sorry for posting the pic sideways-it looked correct when I posted on my iPad. The original cross bar was destroyed in the crash of the '86 so I don't have anything handy to compare it to. Here is a pic of the rear cross bar. you will note that the threaded nuts are welded to the bottom of the bar ends as they should. Also, note the 90 degree edges on the bar which have to point towards the back so that the face of the bar sits right against the engine bracket (saddle). So I think that I have it the right way. However, in looking at some of the engine builds on this forum, it does appear that the Porsche cross bar mounting ends are offset further towards the front than the Rennline unit. See...
911T 2.0 engine rebuild
So I think that Fred is correct.
A bit of a disappointment with Rennline.

[iiXii]

Sorry for you trouble


What is the color of your fan ? only polished ?

[mreid]

Your bar is correct and I had a similar issue when installing my 3.6 in my 84 using the Rennline bar. In my case, the jack was pressing the tranny mount tightly against the frame and the bar was slightly warped from welding. I pulled one side into alignment and started the bolt and then the other with the tranny mounts slightly loose. I then tightened both sides until just slightly loose and removed the jack. A couple of tugs on the engine later and the engine centered. I then tightened all four bolts and have had no issues.

[Uwon]

mreid, nice motor, real nice. Those two stacks and that fan....wow.
Thanks for sharing your experience and solution. I just wonder how much side pressure ends up on the motor mounts and whether such pressure will contribute to early motor mount failure.
I'm toying with the idea of bending the bar on the bench with a block on each end and a big clamp in the middle. I only need a permanent bend of 1/2" on each side.

iixii, the fan was originally powder coated and after some 330,000 km it looked pretty pebbly. So I sandblasted it and then wet sanded it. It's all natural now but I should polish with some petroleum jelly on it for now. Some of our forum members are using some other treatment, it's name which escapes me at the moment. help anyone???

[Uwon]

Yesterday I took the plunge and decided to bend the Rennline cross bar. This SS piece is surprisingly springy. I had to use the tow hitch bar of my old rusty utility trailer to as the brace.



The starting point was an offset of 9 mm between the center and the end of the cross bar. I needed to get to an offset of 24.5 mm and in order to achieve that I had to press down on the center by close to 48 mm.



The result was a perfect. When I raised the motor the motor mount bolts slipped in without any man-handling.

For those interested you can follow my built at:

Evolution of a Carrera RST

[winders]

Wow. I wouldn't have done that. Clearly something is misaligned and that misalignment should be fixed. Bending the engine carrier is not the solution.....

Scott

[hcoles]

Originally Posted by winders

Wow. I wouldn't have done that. Clearly something is misaligned and that misalignment should be fixed. Bending the engine carrier is not the solution.....

Scott

+1, now the vertical force is not close to the area moment centroid and the "beam" will wind up. Could easily not be an issue, just saying. I guess the fore and aft offset from the engine mounting surface to the holes in the body are a key dimension and the custom mount maker would not miss it by much if any, maybe 1-2mm.

[Uwon]

I have now checked the chassis measurements including motor mounts and they are to speck within reason. First thing this morning, I had the opportunity to check another 911 with the motor just out and I checked the trani to cross bar measurements which were within 3 mm of mine. I also checked the saddle measurements with mine, particularly its depth. I did notice how flimsy an OEM cross bar is compared to the Rennline. No wonder that nobody has any trouble deflecting the OEM into place. The Rennline unit sprung back after bending which tells me that there is still lots of strength. Insofar as "vertical force" and "moment centroid" I am afraid that its well beyond my level and this dog is simply too old to learn it. But thanks anyway-Maybe in the afterlife.
I have now concluded that I have made much ado about nothing. I chalk it up to the fact that the Porsche was hand made, not perfect, and over time old parts bend and re-align and new after market parts are not quite the same as OEM.
I also think that solving the side pressure issue on the motor mount in my particular case was worth while. Cheers....

[Rennline]

Hey Guys and Gals,

We were just notified of this thread from a friend and I thought I would chime in. We have been manufacturing these engine carriers for about 9 years and have been using the same manufacturing jig from day one. Our jig for these parts utilize pins which were located using a brand new OEM engine carrier ensuring the mounting locations are all to spec.

The factory engine carrier, as well as our Rennline engine carrier allow for some flex forward and aft, and this ensures fitment in any 65-89 911 even though there is a surprising amount of variation from one car to the next. I have attached some pictures showing our engine carrier with a manufacture date of 05/13 next to the factory unit.

As always, if you have any questions, concerns, comments, etc, we greatly urge you to contact us directly at 802 892 7366. It's our customers' feedback that has helped us provide the best quality and service that we can, and without this feedback we would not be able to continuously evolve our product line into what it is today. We greatly appreciate your continued support over the years.

Tom Rittenburg
General Manager
Rennline Inc.

[Uwon]

Tom, many thanks for chiming in.