The Triumph Dolomite Club - Discussion Forum

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PostPosted: Tue Feb 07, 2017 10:27 am 
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I can't do any bodywork at the moment and I want to make some space in the workshop so I'm going to reassemble the engine and overhaul the gearbox. Then they can both be wrapped up and go into storage to get them out of the way.

Plus it'll give me something to do in the evenings when I'm bored!

Jeroen, you put ARP studs and rod bolts in your 1850 when you were rebuilding it. Given what I have done to the engine with the balancing etc is it worth me doing the same?


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PostPosted: Tue Feb 07, 2017 12:05 pm 
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I used new rods and these came with new bolts and nuts but they are original, not ARP. If you want to use ARP bolts on the rods then you might find it tricky to fit them. Chances are your rods have only been tightened once when the engine was built. I know mine for sure had been used at least twice, once when new and once when the big end bearings were changed. I therefore figured I'd be happy not using them again. The cost of a set of new rods c/w the bolts and nuts was cheaper than buying a set of ARP bolts alone.

I plan to use new head studs rather than re-use my old ones as I'm unsure of how many times they've been used and stretched. They aren't a 'proper' stretch bolt like you get on some modern engines. For example K series engine studs are use once then bin. I'm not sure I trust the repro studs, though that said I cannot see ARP listing the studs for the Sprint. I would be interested in a set if they do exist. I assume they are different from the TR7 which they do list.

In extremes of performance I'd want to use ARP bolts and studs as they are a known and very high quality but depending on how you plan to use the car then you may find original parts absolutely fine. If you're running your engine flat out all the time then the forces generated will be much higher than a road car, especially if it has significantly more power than standard.

For example we build various engines at work with more than twice the power of standard. The rebuilds are expensive and so you want to minimise the risk of damage by fitting good quality studs and bolts etc. That said even in racing engines we hardly ever see situations where the rod or main cap bolt has given up and broken, ARP fitted or not. All the engines we build here are fitted with ARP but they are 90% race engines. I'm not an engine builder by trade but have a good idea of what goes on in the workshop from speaking to my colleagues and looking at the dismantled engines lying around.

ARP bolts, nuts and studs etc. will not on their own give your engine more power, though they may aid reliability if you do want significantly more power. I would say they would be a questionable fit on a standard or even a fast road car, though as I say I would prefer to use their head studs if they are available because I don't know the history of my existing ones.

Your engine your choice though!

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1980 Dolomite Sprint project using brand new shell
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PostPosted: Tue Feb 07, 2017 2:31 pm 
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Head bolts and studs I would use used standard ones. Checking the re-torque will tell you if they move much more each time. If after 2 retorques (3 in total including the original toque) they keep moving you could then decide to change for new by removing one at a time.

If you use ARP rod studs and nuts you may want to check the concentricity of the big end bore when they are torqued up as it may be a higher value and the rods originally would be finish honed whilst torqued up. Re-check rod weights but I'd imagine they wont vary much.

Tony

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PostPosted: Wed Feb 08, 2017 11:29 pm 
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Bolts and studs for the critical parts i like to replace by new and when then i use ARP. The old ones are old and history unknown. The head is not a very critical part but I run my engines at a high compression ratio as possible because the fuel I use has 108 octane and like to have it torqued ok. I only retorque once after the first heat up and cool down and that's it.

For the main bearings I experienced some problems. As the studs are slightly thicker than std the holes in the mainbearing caps have to be drilled somewhat larger. There are some pictures in a post.

viewtopic.php?f=4&t=28355&start=30

The block part where the main bearing bolts are in is the weakest part of the engine. When torgueing the best is to torque a nut on a stud than a bolt into the weakest part.

Used rod bolts i replace and when using new rods i use the new original ones already fitted.

Jeroen

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PostPosted: Thu Feb 09, 2017 4:27 pm 
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Joined: Wed Jul 04, 2007 11:27 am
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Thanks Mark and Tony, I know they wont give more power but I am trying to build the engine as it was intended so this is something I was interested in.
Quote:
For the main bearings I experienced some problems. As the studs are slightly thicker than std the holes in the mainbearing caps have to be drilled somewhat larger. There are some pictures in a post.

viewtopic.php?f=4&t=28355&start=30
Thanks Jeroen, yes, thats the thread I have been following and was referring to.

I will go ARP for the reasons that you mentioned, not the head though, I don't think they do them for a Sprint head anyway.

Can I double check the ARP part numbers with you?
Rods - 206-6006
Block studs - 206-5404

Ta


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