The Triumph Dolomite Club - Discussion Forum

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PostPosted: Tue Jan 08, 2019 9:53 pm 
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Location: north of France
Good evening ,
as the ones who read the restoration project section know , i plan to race with my 78 sprint in some french rallyes .
first need is to rebuild engine , and need some help for a few questions .

-considering workshop manal ,it seems that there are high compression and low compression engines , how can i identify mine considering i find no Numbers on the head and on the block ?

-where can i find parts to modify the steering rack , in order to do a "quick-rack" ?


Laurent


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PostPosted: Wed Jan 09, 2019 2:23 pm 
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Hello Laurent,

Normally, the engine number should say "HE" at the end, which stands for High Compression. But as far is I know there are no (LE) Low Compression Sprint engines, so consider your engine as High Compression. :D

For the "quick rack" steering, the company Jigsaw Racing did a special pinion a couple of years ago (read this thread). I can't find it now, but they are still trading, so you can ask them directly:

Jigsawracingservices.com
+44 (0) 1536 400 300
enquiries@jigsawracingservices.com

Hope this helps :wink:

_________________
Ronald
Club Triumph Holland - Dolomite Registrar




www.triumphowners.com/tahitisprint


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PostPosted: Thu Jan 10, 2019 10:49 pm 
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Some Triumph Toledos came fitted with the pinion that can be used in a Sprint rack to produce a 'Quickrack'. Standard is 3.75 turns lock to lock, quickrack is 3.25. Otherwise as Ronald says try Jigsaw.

While your engine is undoubtably a Sprint high compression one as they all were. However, for racing you may want to increase the compression further depending on how much power you want. Most older engines get some way along that path depending on how many times the head has been skimmed and how much has been taken off in total. You can also achieve this by ordering special forged pistons with a partially raised top. I assume you will be using a STR139 cam or something equally wild. Given the valve clearances of only 8/9 thou, a skimmed head and the valves protruding further, you will need to measure the gap between fully open valve and the piston crown cutouts. I certainly had to make mine deeper to avoid touching. From memory we allowed a 3 thou clearance when cold.

I know Cambridge Motorsport in the UK have experience with special pistons for Sprints. I didn't use them (ordered direct from USA) and stuck to flat top pistons, but with deeper cutouts.

Geoff


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PostPosted: Sat Jan 12, 2019 5:21 pm 
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Hi Laurent, Good question. I was reading the early 1850 workshop manual just now and in the General Specification section it lists the steering turns lock-to-lock as …
3 - Earlier models.
3 3/4 - Later models.
3 1/2 - nominal 1975 onwards.

So it looks like 3 different rack and pinions.

The 1850 Parts book July 1973 gives 4 listings for the pinion.
( 2 types but no ratios listed )
307522 RHS
307523 LHS

TKC0462 RHS ( Rimmers list this )
TKC0463 LHS

The later parts book just list the pinion as NSS.

https://rimmerbros.com/Item--i-TKC462

…. which is given as a Toledo pinion ???

Why are the LHS and RHS pinions different but the rack itself is the same ?

Tony.


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PostPosted: Sun Jan 13, 2019 1:05 pm 
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Location: Over here...can't you see me?
It is the pinion from a 1300 fwd that is required for a full 'quick rack' which gives I believe 2.75 turns. Our reconditioners tell me they have made them in the past. I have a NOS fwd rack here, which just needs the shorter Dolomite track rods fitting to make a 'quick rack' but it is RHD.

The rack bars are the same Tony, as they are straight cut; the pinion skews onto it at an angle, therefore LHD needs to be the mirror image.


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