RS Motorsport :: Classic Speed Restored

Cheers.

With the magnetic base I have got a loan of I am unable to fit / position it in the bellhousing without touching anything when I turn the crank.

RM posted these links on the thread I started on the other forum regarding this matter.

http://www.circletrack.com/drivetrainte ... index.html

http://www.youtube.com/watch?v=9Woh-fS3DJA

I have been able to do it this way.. but I am unsure if i am measuring it correctly. It doesn't matter where I position the magnetic base on the flywheel as it will be in the same spot the whole way round right ?

I marked four points (diagonals from the four bellhousing bolt holes) and measured the two sets of diagonal points. I got 7thou run out on the first set and 20thou ! on the second set. These values have been halved from the total gauge reading as the article instructs..

According to the article 5 thou is the maximum run out that is acceptable and I think Jim told me 7

I am going to unbolt a standard 4 speed bellhousing and have a crack at measuring it at some stage later today for a sanity check.

Here is a picture of what I am doing..

Assuming the hole is round and you should check this first.

You should be able to put a bit of nice machined [bit of] steel, maybe 5 to 8mm thick under one side of magnetic base and still have accurate measurement, with a better angle of base stem out of bell/gearbox hole.

You need to find high and lows

zero dial, somewhere/anywhere

rotate crank, watching dial, for max deflection of needle , one way. When needle reaches peak/maximum measurement, mark bellhousing.

Zero dial gauge here.

rotate bellhousing, watching dial, when it gets to other maximum, read off measurement.

this will be run-out measurement

Cheers for the replies guys.

I am going to have to do it again with a fresh mind as I checked it last night with the standard bellhousing and that was out according to my measurements aswell and I would expect the ford factory to have got it correct.

If and when I determine the amount of error what do I do about it then ? Weld up the dowel holes and have them redrilled and tapped ?? I really don't know how many people are accurate to with in 5 thou.

The bellhousing is spigoted about the gearbox just like on the standard 4 speed gearbox. Its a nice snug fit on the nose of the gearbox too.

Not wanting to add fuel to the fire Damion, but if 2 totally different bell housings are out of alignment, you would also need to consider if the block was drilled correctly.

Although the misalignment is easily fixed by machining the bellhousing spigot hole oversize but at the correct allignment,then machine up a spigot ring like aftermarket alloy wheels use,whach it in the freezer then drop it in place,problem solved. Your machinist could even machine a small lip or shoulder into the bellhousing and then the spigot to retain it once bolted together.

Well I found a better way of setting up the magnetic base and have had a few more goes at measuring the 'run out'

I have got a consistant 45thou of run out measuring it a few different ways. No deciding what to do is the problem, as everyone that I have spoken to about solving this problem doesnt want a bar of it and I don't want to get bitten by someone I don't know.

How much of an issue could 45thou possibly present ? The clamping plate on the pressure plate is easily 2.5mm larger than the clutch plate radially...

I am tempted to just stick my head in the sand and throw it back together and address the issue properly when it arises next time.. As I don't particularly like the gearbox and I am fairly certain that the clutch is not going to like the extra power that I want to make out of the engine in the future.

Might save some more $$ and go from there.

Cheers

.045" is 1.125mm which is massive, it will destroy input shaft bearings, 3rd/4th gear hub and synchro, cause clutch shudder and excessive wear...not good.

If you mark the runout at an x and y axis over the hole in the bellhousing, you should be able to get it machined oversize on its true centre, then have a reducing ring made back to the original hole size.

My guy would do it, but would probably cost the same as another bellhousing.

Cheers,

Phil.

How about just putting it together and address the prblem if it arrises.
Grab the end of the input shaft, albeit you have a bit of movement in the bearing as all boxes do. I think you are over thinking a problem which hasn't occured

It may be easier to drill the mounting holes a little oversize and move the bell housing to it's desired location an re-dowel it?

Yeah apparently the maximum allowable is 5thou run out so mine is out by a factor of 9! I will have to give it some more thought.

Moving the dowel holes is the way i initally considered, but this would mean welding up the original holes and re drilling and re tapping them.. and then I guess I would also need to have it refaced as it would probably warp with the heat that is put into it for welding.. I guess the final decision would come down to the machinist in question... To think that I will have to do this everytime I change blocks is a nightmare ! As my new block has been line bored.

Mickas, unfortunately the problem has already occured, I have had two gearbox rebuilds due to crunching syncros and several clutches... Even though the first few clutches I am fairly certain failed due to poor workmanship.. as they never even came close to holding up. I did 7000kms with the current clutch and when I pulled it out it had some wear, probably not enough to be an issue but i sent it back to be looked over regardless as it hadn't had much punishment.