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Cylinder throttle balancing


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Hi All

Managed to change the coolant and antifreeze today so another job completed.

Whilst I was there I decided to check points timing and throttle balance primarily because I recently purchased a balancing gauge.

All seemed to be good but I've noticed that cylinder 1,3,5 where all  reading 2.4 on the gauge and cylinders 2,4,6 reading ~2.0

This didn't make sense to me as I would expect each pair to be the same therefore allowing me to get all throttles the same. Dispite fiddling for some time I cant get them all exactly the same and the throttles can only be adjusted as a pair fro  what I can see. Last year I did change the original throttle linkaged for the upgraded versions by Moss or maybe it was Rimmer.  Idling is reasonable smooth at 900 rpm and timing 11°

This may have been covered but I cannot find a thread so maybe it's something I've missed.

Any ideas or just a clarification that this is the norm would be appreciated.

Scratching my head

Steve

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It is possible that the shafts have a very slight twist on them over the years thus allowing one side to be very slightly more open than the other, not that easy to rectify but it is possible.

Stuart.

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It's also possible that the spindles or their bores in the throttle bodies have worn more on one side of the TB than the other, probably the side with the link rod and operating lever.

The resulting air leaks down the spindles would upset the air flow balance from one side of the TB to the other.

Nigel

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12 hours ago, Nigel Triumph said:

It's also possible that the spindles or their bores in the throttle bodies have worn more on one side of the TB than the other, probably the side with the link rod and operating lever.

The resulting air leaks down the spindles would upset the air flow balance from one side of the TB to the other.

Nigel

Correct also and usually the spindle, One of the guys that does engineering work for me has perfected a way to make new spindles now as theyre not normally available.

Stuart.

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The volume of air at idle, is nice to have,  but is more important to crack the throttle open a bit to give say 1500rpm and then set the balance.

Usually the even numbers are the higher values as there is more wear at the operating side than the other, closed side.

Have you tried to recentralise the plates by slackening the screws and snapping shut the shaft, that can do it sometimes?

John

Edited by John L
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13 minutes ago, stuart said:

Correct also and usually the spindle, One of the guys that does engineering work for me has perfected a way to make new spindles now as theyre not normally available.

Stuart.

I fitted new spindles to the throttle bodies of my CP-series car a few years ago. It made a big difference without attending to the slight wear in the throttle bodies.

At that time, I bought the spindles from Malcolm Jones at Prestige but he has since retired. SC Parts list spindles for the CP throttle bodies but they're not cheap:

https://www.scparts.co.uk/sc_en/throttle-spindle-1-129566.html?gclid=Cj0KCQjw4dr0BRCxARIsAKUNjWQMRLxEDNmw3LyfT4bR0ep7BzLiYeYU-q87-tohZH3hQyNmXHOCf0IaApLjEALw_wcB

Nigel

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22 minutes ago, Nigel Triumph said:

At that time, I bought the spindles from Malcolm Jones at Prestige but he has since retired. SC Parts list spindles for the CP throttle bodies but they're not cheap:

Nigel

£240! Ouch that would hurt, what about asking Neil Ferguson for advice?

Andy

 

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I put the spindles in CAD and had a local supplier make them. Cost about 33 pounds per Spindle (8mm CP). Attached to the lever linkage which you can buy from Webcon.

If any interest is there, I may be able to have a batch made again. 

 

Spindles.thumb.JPG.1a6a20f1cd7a1a2f7fc716e9cad9769b.JPG

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I ordered mine from Revington, the lever was already soldered on. Good quality and I think they were around 40 pounds each.

Waldi

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CP throttle spindles seem to be readily available from the usual suspects - Rimmer, Moss, Revington at around £50.  I have just ordered some together with new discs for my CP throttle bodies as the current ones are worn and on a least one pair I have a large discrepancy between the two throttles so probably a damaged/twisted spindle.

Spindles for the CR bodies seem a bit harder to come by. My spare CR set has modified spindles from Malcolm at prestige so that they work with CP style linkage.

Chris

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Thanks for all the replies chaps

I will take a closer look at the spindles and if they look suspect I may change.

I will see what the balance is like at 1500 John, may point me in the right direction. I will also start with a fag paper gap and start from scratch just in case as I've also noticed that the bleed valve is only just cracked open for 900 rpm which makes me think the butterflies are adjusted too far open.

Steve 

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