The Triumph Dolomite Club - Discussion Forum

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PostPosted: Thu Apr 21, 2016 9:39 am 
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Hello!

1 st post here.

We are racing historic Dolomite Sprint here in Finland. Car is built a few year ago with all homogolated goodies including Webers, big front brakes and so on.

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We had couple issues last season, engine was overheating and syncros did not work.

Radiator is new, but might be too small. Is Spirint vs. stock radiator different?

Gearbox was rebuilt with new synchros(stock) after first race, but it did not make much improvment. We used normal mineral gear oil. Any ideas?



Regards Otto


Last edited by OttoB on Sat Aug 05, 2017 8:37 am, edited 2 times in total.

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PostPosted: Thu Apr 21, 2016 2:20 pm 
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Welcome Otto, we know all about already. :D

Jeroen

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PostPosted: Fri Apr 22, 2016 1:53 am 
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Location: Auckland, New Zealand
Yes, welcome.

My Sprint has now competed at 101 race meetings over 15 years so happy to share some experiences.

The Sprint gearbox is not the quickest changing box around and whilst I don't have trouble getting into gear at all, there is always a crunching noise when going into gear with a quick change. I've learned to live with that and found that even with this treatment, they will continue year after year without needing rebuilding. I now use a standard 'box with overdrive, but I also have a standard non overdrive, as well as an ST close ratio and they have all been the same. A 'paddle' clutch or even a smaller twin plate clutch (which will require a different flywheel) will also help minimize the drag that you will get with a standard clutch plate when trying to change quickly. I started using Castrol VMX as I have in my road car, but now use a fully synthetic Redline brand product which I feel helps a bit.

I understand the Sprint radiator is a 3 core and is thicker than the radiator frame, but the other Dolomites were 2 core and are narrower (frames are the same). Even then I have always found the Sprint cooling system is marginal when racing, especially in New Zealand summer temperatures. There are plenty of possible solutions, but what you can use will depend on what the 'classic' regulations you race under allow:
- Don't use any antifreeze / glycol, just water with a product such as 'Water wetter' than contains both corrosion inhibitors and a surfactant. Water transfers much more heat away from the engine that any glycol mix will.
- With Sprint radiator make sure all the air coming through the grill goes through the radiator core by sealing all the gaps with shaped aluminium plates and tape.
- Additional holes in the front where your JAri-Pekka sticker is let more air in
- A Porsche 944 Turbo radiator (alloy and 50% plus more surface area) is the best stock radiator that will just fit the gap - cut the existing hoses and extend with alloy tube (Dolomite petrol filler tube is the right size).
- Use an aftermarket temperature gauge that tells you what the temperature actually is.
- An oil cooler is also a good idea as it too removes heat from the engine.
- The standard water pump can cause cavitation at high revs and loss of flow. Of the three types, the six vane (but not the first version) is probably the best, but can still be a problem. A Davies Craig electric water pump is the ultimate solution, especially with the electronic controller that allows both the pump and radiator fan to continue running after the engine is switched off (both the water pump and thermostat become redundant although some modifications is required but parts are available from the club)..
- Finally a custom made header tank in the corner where the windscreen washer bottle sits. This allows the coolant level to be held above the brass nut on the thermostat cover, enough expansion volume within the system, as well as a significant increase in coolant capacity.

I can now happily race all day in temperatures in the low 30s C with the engine water temp at no more than 95C.

Hope this is of some help. Enjoy your racing!

Regards

Geoff


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PostPosted: Wed Jul 13, 2016 4:08 pm 
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Hello again

Sorry to inform you, but we have missed two first races on this summer. Honestly, some how missed pre-season over-haul and there were too many suprises.

Well, anyways engine is getting together, and gear-box is also under construction. To fix synchro problems, we have orderd these sync-rings:

http://www.wishboneclassics.com/content ... 0-tr6-stag

Have you any experience with these?

Last season we had rings from Bastuck, and they worked fine when they were new. After few laps sychros were slow to engage and there were quite much bronze flake in 'box oil.

We will use RedLine MT-90 gear oil in races. Maybe running in with simple mineral gear/engine oil, then switch to synthetics.

Do you got any experience with wishboneclassic synchros and recommendations for gear box oil?

Br Otto


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PostPosted: Thu Jul 14, 2016 11:13 pm 
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Location: Auckland, New Zealand
Hi Otto

Not heard of Wishbone Classics before, but if they are as good as they say they are, then these synchro rings would seem to be the best that you can buy. I would be interested to hear how you get on with them. That Redline oil is the one I use.

I suppose the only other thing to look at is whether you are getting clutch drag and that is slowing down the engagement of the synchro rings? Quick gear changes rely on engine speed changing quickly so a lighter flywheel and twin plate 7.25 in clutch may be a better option? You could perhaps ask Rob at Sprintspeed for his opinion, that's where I got mine from. http://www.sprintspeed.co.uk/pages/#&panel1-3



Geoff


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PostPosted: Thu Jul 20, 2017 9:48 am 
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Hello again,

We got radiator recored with more tube area, and modified early pump impeller. Blades are shortened from inner circle, like in later design. That is to avoid cavitation. Shape of blades are better on early unit. Still, engine is running a bit hot. Geoff, you mentioned that you are running 95 C engine temp, does it stay there? What kind of t-stat you are using?

Box is working better with new sychros, but not perfect yet.

We had lots of problem with aux shafts. First we lost water pump drive and with new shaft oil pump drive broke. Is this typical for Spirint? Any ideas to avoid this happening again?

Any comments?

Regards Otto


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PostPosted: Thu Jul 20, 2017 5:49 pm 
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You can improve a lot by matching different components. Watersway's in the head don't alway's match the engine block. Also there are different engine castings wich have different inlet holes from the waterpump into the engine. Some are way too small. A 1m2 radiator won't cure that. Sorting that out you will have no overheating issue's anymore. The same as with the oil pump. The oilpump casting does not match the engine and when making it fit and have all the edges smooth the stress inside the oilpump is less. Not significant more pressure but less resistance in the oilflow resulting in less strain on the jackshaft etc etc.

Jeroen

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PostPosted: Thu Jul 20, 2017 6:10 pm 
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Hi Jeroen!

Thank you for good advice! Actually I looked that water ports in our cylinder blocks, and noticed there was difference in port area.

We tried also Evans coolant last year, but that was a big fail. It did not boil. Just overheated.

Good hint head and block coolant channel misshmatch.

Regards Otto.


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PostPosted: Thu Jul 20, 2017 6:31 pm 
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Not a sprint but 8v mismatch of waterways and oilpump.

viewtopic.php?f=4&t=28355&start=15

Enlarged waterhole inlet from the waterpump.

viewtopic.php?f=3&t=20105&start=30

Jeroen

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PostPosted: Tue Jul 25, 2017 8:34 am 
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Thanks Jeroen!

Demanding engine this 16 V, life could be easier with 2.0 Ford OHC. But this is also the charm of historic racing, most of experience racing Sprints is gone with only few brave ones that carries the torch.

As always, devil is in details. We'll do some testing and report back

Regards Otto


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PostPosted: Sat Aug 05, 2017 8:47 am 
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Thanks to hints was water pump clearance measured. It was a bit too much, and was trimmed down. Now engine is running about 90 deg C, no matter how hard it is punished. Our modified waterpump impeller seems to be working well.

There seems to be more favorable cylinder blocks for racing, is there a way to identification those from outside and what are benefits of those better blocks?

Also if interested, i can publish our fyno papers. I think we are missing few (a big stable of) ponies and like to get some comments of that.


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PostPosted: Sun Aug 06, 2017 6:34 pm 
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Most of the engineblocks are bored too deep during manufacture. The cilinderbore is then bored into the main bearing cap threads. Those engines tend to crack the webbing when using for motorsport. When you are lucky you can find one that is not bored into the the thread. Those are accidentally much stronger. Best is to find an 1850 block that is not bored too deep. That will give you some mm's extra flesh around the thread area. Make sure your machine shop does not ruin it when reboring to sprint size.

The only way to tell is taking the sump off and look visually.

Jeroen

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PostPosted: Sun Aug 13, 2017 6:10 am 
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Thanks again Jeroen!

Will look at that bore next time. Good info about that 1850 block!

Br Otto


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