partial engine drop to replace throttle bellcrank bushings on CIS engine?

brian-80SC · 05-07-2008, 08:30 AM

Hello everyone,

The bushings for the throttle bellcrank on the top of my CIS engine have disintegrated and need replacement. Can anyone advise how to get access to this area for this repair?

If I I want to avoid disturbing the CIS (since it is running well despite having many older parts), is a partial engine drop the right way to go?

I couldn't find dedicated information on doing only a partial drop. Any suggestions for what to leave alone relative to the full drop (I have Wayne's books and the Bentley manual for this) would be greatly appreciated!

I am a little intimidated by the engine drop process, and any other tips or encouragement would be welcome too!!

Thanks!!
Brian

Howard M · 05-07-2008, 08:53 AM

I performed this very task on my '76 911S (original 2.7L engine) last winter. I also did the bellcrank bushings on the driver's side of the trans. Neither one required a partial engine drop in my case. That being said, both jobs were a pain but very do-able, especially if you have long fingers! You might find, as I did, that the available brass bushings did not fit very well and required some minor machining. Available plastic bushings might fit better. Lube everything thoroughly and make sure that you get full throttle plate opening with a full accelerator pedal when you are done. Adjust cable as necessary to achieve full throttle.

Porsche-O-Phile · Porsche-O-Phile's Garage

You should be able to get to that without dropping the engine. Take the snorkel off the air box and disconnect the stuff going to the air box on the driver's side of the engine bay. You should be able to get at it. Three 13mm bolts (I think, they might be 14mm) is all it takes to remove it.

Well, that and the springs/linkages. At your discretion you might find it easier to take the throttle body & decel. valve assembly off the CIS since it's on that side too, although I found it to not be that much in the way - you can work around it.

Mike Andrew · 05-07-2008, 08:59 AM

I just replaced mine with the engine out and don't think that a partial drop will do you much good as they are at the back and on top. By doing a partial drop, I don't think that you will gain anything as the motor will just be lower and you still need access. I think that if you remove all the heater plumbing, and airbox cover you can get to them but it will be tight and your back will probably hurt from leaning in over the engine.

brian-80SC · 05-07-2008, 09:34 AM

Thanks Howard, Jeff and Mike. I'm glad to hear this should be doable without a drop. I've got some plastic bushings on hand from Pelican, so I hope to give it a go this afternoon.

Thanks again!

brian-80SC · 05-07-2008, 09:37 AM

Quote:

Originally Posted by Howard M

make sure that you get full throttle plate opening with a full accelerator pedal when you are done. Adjust cable as necessary to achieve full throttle.

Howard, could you or anyone else elaborate on this? I imagine I want to make sure the pedal can actuate the throttle plate through its entire range of movement (i.e. the maximum range available through direct operation of the throttle plate by hand). Should it go essentially to the hard stop?

bkreigsr · 05-07-2008, 10:15 AM

http://www.pelicanparts.com/techarticles/911_partial_engine_drop/911_partial_engine_drop.htm

brian-80SC · 05-07-2008, 10:51 AM

Quote:

Originally Posted by bkreigsr

http://www.pelicanparts.com/techarticles/911_partial_engine_drop/911_partial_engine_drop.htm

Thanks - I missed this one when scanning the other tech articles!

Howard M · 05-07-2008, 11:42 AM

Regarding full throttle adjustment: The "stop" should be at the accelerator pedal, not the throttle plate. If the throttle plate is not fully open at the stop, adjust it at the transmission bell crank. While there, look at those bushings, too.

fred cook · fred cook's Garage

If your engine still has all of the stock brackets,etc you should find that there is a support bracket held on by the throttle console nut closest to the front of the car. It supports some of the hoses/fuel lines that cross in that area. Once you get the linkage disconnected and the 3 nuts and washers off and accounted for (don't drop anything!) you should be able to lift the support bracket about 1/2" and move it out of the way. Also, there is a throttle return spring that hooks on one of the intake pipes and on the throttle bellcrank. Be certain that you take a good look at where it hooks. Then the throttle console should simply lift off the engine. As mentioned earlier, the space is somewhat tight and some extra care is needed while putting the washers and nuts back in place. This is not a terrible job, but it does require some patience. Good luck!

porsche930dude · porsche930dude's Garage

Just wondering how did you determine your bushings are shot when the bellcrank is so hard to get at and see?

brian-80SC · 04:38 PM

Quote:

Originally Posted by Howard M

Regarding full throttle adjustment: The "stop" should be at the accelerator pedal, not the throttle plate. If the throttle plate is not fully open at the stop, adjust it at the transmission bell crank. While there, look at those bushings, too.

Makes sense, thanks for the elaboration.

Quote:

Originally Posted by fred cook

If your engine still has all of the stock brackets,etc you should find that there is a support bracket held on by the throttle console nut closest to the front of the car. It supports some of the hoses/fuel lines that cross in that area. Once you get the linkage disconnected and the 3 nuts and washers off and accounted for (don't drop anything!) you should be able to lift the support bracket about 1/2" and move it out of the way. Also, there is a throttle return spring that hooks on one of the intake pipes and on the throttle bellcrank. Be certain that you take a good look at where it hooks. Then the throttle console should simply lift off the engine. As mentioned earlier, the space is somewhat tight and some extra care is needed while putting the washers and nuts back in place. This is not a terrible job, but it does require some patience. Good luck!

Thanks Fred. I ran out of time today, so I'm going to review the diagrams and photos in Wayne's and the Bentley manuals to see if I can get a clear mental picture of what I need to be disconnecting and removing since it will be hard to see what I am doing with my hands in the way! I'll report back when I finally get in there, as I'm sure I'll have some more questions!

MBAtarga · 05-07-2008, 04:39 PM

I did this on my 83, as part of replacing the engine thermostat o-ring and pressure switch. I don't know how anyone with an SC can replace those bushings without a partial drop!

brian-80SC · 05-07-2008, 04:46 PM

Quote:

Originally Posted by porsche930dude

Just wondering how did you determine your bushings are shot when the bellcrank is so hard to get at and see?

I initially suspected the bushings were missing from the large amount (5 mm) of lateral and vertical play I felt in the bellcrank when pushing and pulling on it with my fingers. Using just the right viewing angle, I then inspected the driver's side end of the bellcrank and it looked to me like the bushing part was missing when compared to the PET diagram for the bellcrank. I understand from reading threads here that this has been known to happen with other folk's cars too.

brian-80SC · 05-07-2008, 04:52 PM

Quote:

Originally Posted by MBAtarga

I did this on my 83, as part of replacing the engine thermostat o-ring and pressure switch. I don't know how anyone with an SC can replace those bushings without a partial drop!

That was my impression also from reading other threads here. But based on the suggestions above I'm going to give it a shot. When I finally make time (this weekend hopefully) I'll report back on my experience...