The Triumph Dolomite Club - Discussion Forum

If anyone ever needs shims, I have a couple of hundred here at least! Ask...

Alun, do you have shims?

Jeroen

Yes

Thanks for all the advice, sounds good! So basically whether standard or fast road cam clearances are the same?

Yes

The 0.018' gap does large compared to other engines I have worked. other people say that a small gap gives more power.

This leads me to a couple of thoughts:
All engine manufacturers spend a lot of time and money on R & D, playing with cam shaft timing, valve lift, valve sizes and tappet clearances, helical porting etc.

So I would assume that Triumph developed the recommended tappet clearances based on research; water brake dynamometers etc.

There is also some suggestion that the Sprint was also known as the 135 and that BHP was reduced to meet insurance requirements; although other theories exist. so I wonder if the larger tappet clearances were introduced to reduce power in which case it makes sense to use the much tighter clearance.

I think it could be possible to change shims on the exhaust valves without removing the head but not possible for the inlets.

Malcolm

Yes you are right that these tappet clearances were arrived at by some thought by engineers. However step back and take a critical look at the Sprint and there are many details that don't cut the mustard and also some things that are just plain poor engineering. Which is one reason why the car never sold in huge numbers and had a poor reputation as regards reliability when compared with the Fords of the day.
People remember the Professionals for tearing around in Capri's not the BL stuff the show started with because they could not complete a days filming in one piece.
Harsh but fair

They changed manufacturer in the Profesionals,because they got a better deal off Ford.
BL were notoriously short sighted in this respect,look at the Italian job,the best deal they could get was a handfull of minis at trade price,the rest they had to buy at full price.
The other problem with BL on the Profesionals,was that different cars were sent back to them after servicing/repairs,which caused problems with the continuity of filming.
Smaller valve clearances do improve power,up to a point,but you may increase the wear on you camshaft in the long run.Its a fine line between performance and reliability.I use smaller clearances on my 4 stroke race bike engines than originally recommended,but you are hardly likely to notice the difference in performance on a road car that you will gain,so I wouldnt bother.

The slight increase in performance is a secondary advantage Tony, the prime advantage is noise reduction of the clackety clack of standard.
People make their own choices, I don't have much faith in the BL engineers after working on many different types of vehicles.
I am looking after a Toledo for a friend and frankly its only a small step up from a wheelbarrow in Automotive terms.
Sorry harsh but fair.

Yes for the noise only. Years ago i wondered why such a large gap without anything much to expand whas needed. you can even use .10 and .15 MILLIMETER but then remeasure your feeler gauges first with a micrometer. I have bought over time a lot of sets of different makes of feeler gauges and do have now a nice set from 0.04 to 1mm with the lower ones almost complete in 0.01 steps. 0.10 MILLIMETER can easily be 0.08 or 0.12. MILLIMETER using the normal available sets. So when adjusting to .15 MILLIMETER maybe you are lucky to have it .12 MILLIMETER in real. When you are absolutely sure of your measurements you can go narrower.

But not with the head on a bench. Torqueing down does tighten the play a few .01 MILLIMETERS.

Jeroen

I always thought the Sprint motor quite quiet,when compared to an Avenger

The tighter clearance, whilst I agree it's a good thing rather than the clatter of 18 THOU in a lot of OHC BL cars doesnt make a significant if any more power. Tighter means Inlet opens earlier and so does the exhaust . In effect youre ADvancing the cam timing on both Inlet and Exhaust. I dont believe tighter clearance will affect reliability one bit. If the gap is too tight for oil to get in then yes theres a problem in waiting but as long as its got oil no problem. If you have the time and inclination and a degree wheel and dial gauge check the cam timing with slack (oem ) clearances and then tighten them up and check the timing again. I'd doubt it was more than 0.75 of a DEGREE difference. In general terms on a single cam engine if you advance the cam timing (opens valve earlier and closes earlier) you gain a slight lower rpm power increase and if you retard the cam timing you will gain a bit of top end power at the expense of bottom end power.

If a cam manufacturer tells you to use a certain valve clearance, its related to the timing numbers THEY provide. If you go tighter you will have advanced the opening and that will affect the timing figure provided, may be better maybe not. It wont make much difference in the real world but I'd go for tighter and set the cam timing accordingly.

Tony

tonybsa wrote:I always thought the Sprint motor quite quiet,when compared to an Avenger

Yes I had a couple of those rattlers too . Love my 2 door back now though

Tony

tony g wrote:

tonybsa wrote:I always thought the Sprint motor quite quiet,when compared to an Avenger

Yes I had a couple of those rattlers too . Love my 2 door back now though

Tony

And an Avenger is quiet compared with the Chrysler Alpine, I actually had a trick way of setting the valve clearances on these which also involved a lower clearance than standard and a different method of setting up the relevant clearance to check! It worked though, I could get those heaps to PURR instead of clatter! They also suffered from very poor synchro on the 4 speed gearbox. I did so many of these that i could remove a gearbox, strip it and replace all 4 baulk rings, rebuild it and refit, drive in to drive out time, 75 minutes!

Steve