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Oil Pump Drive Bush


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Hello All,

I gather that late TR5 and all TR6 engines were fitted with oil pump/distributor drive bush part# 149776 and early TR5 engines fitted with part# 137978. 

My question to the learned.....is there any real difference in these parts? Are they interchangeable, if so are there any ill effects of fitting the incorrect bush?

Tanks in advance,

Richard.

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As far as I know.....The VERY early bush was a different external diameter to the later items.  These may well only have been fitted to the very first production TR250 blocks and not production TR5. - These may well have been dimensionally the same as the early T2000 & 2.5PI Mk1  but of a different material.  ie cast iron and bronze.

Chris Witor offers both types new for Tri 2000  149776RM and 128787

https://www.chriswitor.com/proddetail.php?prod=149776RM

https://www.chriswitor.com/proddetail.php?prod=126787

I never sold a different distributor drive bush for a TR5 or 6 block - always 149776 cast iron bush.

Peter W

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10 minutes ago, BlueTR3A-5EKT said:

As far as I know.....The VERY early bush was a different external diameter to the later items.  These may well only have been fitted to the very first production TR250 blocks and not production TR5. - These may well have been dimensionally the same as the early T2000 & 2.5PI Mk1  but of a different material.  ie cast iron and bronze.

Chris Witor offers both types new for Tri 2000  149776RM and 128787

https://www.chriswitor.com/proddetail.php?prod=149776RM

https://www.chriswitor.com/proddetail.php?prod=126787

I never sold a different distributor drive bush for a TR5 or 6 block - always 149776 cast iron bush.

Peter W

The smaller bush was also fitted to the early five 

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12 hours ago, BlueTR3A-5EKT said:

As far as I know.....The VERY early bush was a different external diameter to the later items.  These may well only have been fitted to the very first production TR250 blocks and not production TR5. - These may well have been dimensionally the same as the early T2000 & 2.5PI Mk1  but of a different material.  ie cast iron and bronze.

Chris Witor offers both types new for Tri 2000  149776RM and 128787

https://www.chriswitor.com/proddetail.php?prod=149776RM

https://www.chriswitor.com/proddetail.php?prod=126787

I never sold a different distributor drive bush for a TR5 or 6 block - always 149776 cast iron bush.

Peter W

Phone up CW and ask him as you will get a proper answer as to which one!

Bruce.

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I have a very early CP engine block in my TR6, I ordered a new bush from Chris Wittor, it was not the correct one as it had a larger outside diameter. I then ordered one from Revington, again the wrong, larger diameter type was supplied. I then provided dimensions and my engine number to Revington and they indicated I had a very early block, and they still had an original bush for me, which I was happy to order. 

So it is better to measure the existing bush before ordering and additionally provide an engine block number.

Waldi

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This is all very helpful to confirm the smaller diameter bush was used in TR 6 cylinder blocks, as I wrote earlier I had never supplied the smaller diameter bush over the spares counter, but was aware that the two existed in TR engines. - Now all we need is a list of engine numbers that have required the smaller diameter bush and we can perhaps point owners in the right direction.  As we all know there is no change point listed for the bush, only an acknowledgement that there are two types.

Cheers

Peter W

 

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Many thanks for the replies so far.

The main reason for my original question is an ongoing issue with lowish oil pressure at hot idle, I may be clutching at straws with my attention now being drawn to the drive bush....here's the back story.

I've covered around 5,000 miles since engine overhaul and the oil pressure has always been on the low side, several oil pumps have been tried & tested the latest fitment being one of Chris Witor's and still no improvement (I even admit to checking the tolerances myself). Various brands of oil filters have been tried, bearings checked, several PRVs have been tried, gauge calibrated, the list goes on.

When the engine block was taken to the machine shop I supplied all the parts including the oil pump drive bush, I don't recall the part number. My engine came from a TR5, the engine number is almost completely deleted due to the block face having been skimmed during the decking process, but it does appear to start CP 1????

So, back to my query, if my block is indeed a very early TR5 block and the wrong bush (supplied by me) has been fitted, could this be the cause or at least contribute to my oil pressure issue? That's if of course it's physically possible to fit the later bush (albeit poorly) to an early 5 block.

Richard.

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Hi Richard,

on my early block the later bush did not fit. So the wrong bush cannot be fitted. But I noticed my new oil pump drive shaft was a bit smaller in diameter than the old one, so there is more oil loss there.  I had to accept this.

Next I also noted my new King tri-metal bearings were thinner as expected which would lead to additional loss of oil. Glyco’s corrected that, they were a tad thicker.

Check check check.

Cheers,

Waldi

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15 hours ago, Richard71 said:

Many thanks for the replies so far.

The main reason for my original question is an ongoing issue with lowish oil pressure at hot idle, I may be clutching at straws with my attention now being drawn to the drive bush....here's the back story.

I've covered around 5,000 miles since engine overhaul and the oil pressure has always been on the low side, several oil pumps have been tried & tested the latest fitment being one of Chris Witor's and still no improvement (I even admit to checking the tolerances myself). Various brands of oil filters have been tried, bearings checked, several PRVs have been tried, gauge calibrated, the list goes on.

When the engine block was taken to the machine shop I supplied all the parts including the oil pump drive bush, I don't recall the part number. My engine came from a TR5, the engine number is almost completely deleted due to the block face having been skimmed during the decking process, but it does appear to start CP 1????

So, back to my query, if my block is indeed a very early TR5 block and the wrong bush (supplied by me) has been fitted, could this be the cause or at least contribute to my oil pressure issue? That's if of course it's physically possible to fit the later bush (albeit poorly) to an early 5 block.

Richard.

Hi Richard!

Did you check the wear on the cam shaft bearings in the block? As these play a major part in good oil pressure. The tolerances are quite tight here for wear allowance?

My engine which has only 5K on the clock since rebuild runs at 50 psi on tick over and 70+ at over 2000 RPM. Lastly did you lap in the oil relief valve and check its seating?

Bruce.

 

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