Pelican Parts Forums

Pelican Parts Forums (http://forums.pelicanparts.com/)
-   911 / 930 Turbo & Super Charging Forum (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/)
-   -   Connecting rods balanced (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/800923-connecting-rods-balanced.html)

JFairman 03-12-2014 03:07 PM

Connecting rods balanced
 
It was raining earlier today so cleaning more parts and other stuff outdoors wasn't happening so I balanced my rods down to 1/10 of a gram indoors in my kitchen. 2 or 3 weeks ago I balanced the piston and wristpin assemblies down to 1/10 of a gram so now these parts are ready to go back in.

It's supposed to be nice out tomorrow so it should be a good day to install the rods and maybe the pistons and cylinders too.
The motor is in the car with the back way up on jackstands and the back of the motor lowered down about a foot on to a jackstand.

I still have to port match the intake manifold holes from 32mm to 40mm. Once I do that and finish cleaning all the old hardened sealant off the cam towers there are some small parts to paint black and then it's time to put this thing back together.

I have a used KEP stage one pressure plate I got around 6 years ago I may install too. Now is the time to do it but I havn't decided yet because the Sachs clutch in it now works really well.
You can see where I carefully removed material from the rods to balance them in these pics.
I put in new rod bearings after cleaning them with brake clean and compressed air.. now they're ready to go back in.
http://forums.pelicanparts.com/uploa...1394665394.jpg
http://forums.pelicanparts.com/uploa...1394665405.jpg

DSPTurtle 03-12-2014 04:03 PM

Nice work. I'm curious though, did you balance big and small end or just overall weight? Should spin smooth as a baby's bottom!

RennSport911rsa 03-12-2014 04:03 PM

what are you using for your scale?

what level is the crank being balanced to?

did you also balance the front pulley and the clutch/flywheel? Pays big dividends as well in terms of overall smoothness and efficiency

JFairman 03-12-2014 04:49 PM

Quote:

Originally Posted by DSPTurtle (Post 7958577)
Nice work. I'm curious though, did you balance big and small end or just overall weight? Should spin smooth as a baby's bottom!

Thanks! I tried setting up a funky end for end balancing rig but I couldn't get any consistancy with how I was trying to do it so I ditched that set up and just balanced them overall to the exact same weight on my triple beam scale.
They were all within 2 grams of each other to start with so I didn't remove a lot. Most of what I removed was from the squared off edges where the rod and cap come together. You can see that area is shiny and rounded off now. I used a 6" DA made for doing body work. I locked down the 6" pad so it spun like a grinder and I used sticky back 320 grit sandpaper spinning around 15,000 rpm to do this.
In the past I've done entire rods in my old BMW's and polished them to a mirror finish and spent many hours doing it but I didn't want to do all that to these. I guess I did them in around 4 hours.
A week ago I had the best automotive machine shop in town resize the big ends, they were out of round and they installed my new wrist pin bushings and honed them to fit my new wristpins for the right oil clearance.

Here's my funky end for end rig on top of my refrigerator I tried first that didn't work. Too much friction and inconsistant. Maybe hanging one end of the rod from string would work but I decided to just weigh them overall and that would be good enough for my street car.http://forums.pelicanparts.com/uploa...1394671299.jpg

This is how I positioned them on the scale to weigh them overall. Kevin Jeanette gave me the picture on the wall in the background back when I worked for him at Gunnar Porsche in the mid eightee's

http://forums.pelicanparts.com/uploa...1394671450.jpg

Here's the new pistons and wrist pin assemblies that all weigh the same now after i removed material from the ends of the wristpins. I didn't do anything to the new pistons. The new cylinders are in the box.

http://forums.pelicanparts.com/uploa...1394671559.jpg

JFairman 03-12-2014 04:59 PM

Quote:

Originally Posted by RennSport911rsa (Post 7958578)
what are you using for your scale?

what level is the crank being balanced to?

did you also balance the front pulley and the clutch/flywheel? Pays big dividends as well in terms of overall smoothness and efficiency

The scale is an old Ohaus triple beam I've had for around 25 years. I just had to turn off the ceiling fan to have it work consistant and accurate:)
The motor, crank, and all the other stuff you mentioned are still in the car so they are what they are. I'm on a budget and have more time than money so this is how I'm doing it.
I bought all the parts 6 or 7 years ago when I had more $ and I found them for sale on the classifieds here for really good prices.

DSPTurtle 03-12-2014 05:10 PM

Jim, when can I take you to lunch? I wanna hear some Gunnar stories! And run some ideas past you.

Tippy 03-12-2014 05:14 PM

I wished I would have just paid $100 to balance my low end.

I see you tried moment weight, but it didn't work out?

JFairman 03-12-2014 05:40 PM

Quote:

Originally Posted by DSPTurtle (Post 7958690)
Jim, when can I take you to lunch? I wanna hear some Gunnar stories! And run some ideas past you.

That sounds like fun, anytime I guess. I'm in West Palm. I was working in the body shop most of the time and running errands and stuff when I was at Gunnar in the mid eightee's.

Chinook 03-14-2014 09:56 PM

Triple beam madness
 
Ya Jim I've been down the triple beam road. It took awhile. Very accurate once set up. I rigged up a definitive point or fulcrum that the big end rested on on the scale platform and a stationary pivot on the small end and got very consistant repeatability. With patience the triple beam is very precise. 1/10 of gram is way way more than many race shops balance to. Myself, I wouldn't balance unless I could accomplish rotating as well as static weight. Digital scale is the way but the ol triple beam was around. Let's see now, what was it that I used to use that triple beam for anyway............?

Gary

Tippy 10-13-2017 02:28 PM

I can vouch for the repeatability of doing moment-weight; it ain't happening.

You need to hold both ends on concentric fixtures from what I've seen online. Placing one end on the scale platen and the other end on a spindle just doesn't seem to work.

Bummer.

Ken911 10-13-2017 06:40 PM

Quote:

Originally Posted by Chinook (Post 7962339)
Ya Jim I've been down the triple beam road. It took awhile. Very accurate once set up. I rigged up a definitive point or fulcrum that the big end rested on on the scale platform and a stationary pivot on the small end and got very consistant repeatability. With patience the triple beam is very precise. 1/10 of gram is way way more than many race shops balance to. Myself, I wouldn't balance unless I could accomplish rotating as well as static weight. Digital scale is the way but the ol triple beam was around. Let's see now, what was it that I used to use that triple beam for anyway............?

Gary

yeah make sure all the powder residue is off first

proffighter 10-16-2017 02:44 AM

Hmmm I love that DIY spirit!!! Nice work


All times are GMT -8. The time now is 09:40 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website


DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.