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Mk2 Engine Rebuild going into a Mk1 GT6 by a novice!


AidanT

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3 minutes ago, AidanT said:

Quick question 

Should the bottom cog just slide off? Mine seem to not want to go further than this  or does it need a little more persuasion??

 

 

20201227_135503.jpg

More persuasion.  You're at the end of the Woodruff key, which is probably raised a little bit stopping it from coming off.  With a bit more effort the key will shift position slightly (the groove is 'C' shaped usually) and the sprocket will come off.

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1 hour ago, Roger K said:

Interested to know how that is more accurate than using a dial gauge?

Both systems work but rotating the crank clockwise and anticlockwise to a dead stop and taking the middle of the two readings seems easier than trying to rotate the crank while watching the dial gauge and seeing where the dwell point is. 

I've recently seen the piston stop method used in two engine shops I've visited. 

Iain 

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It's really odd, I took all the followers out in order, and gave them a clean on the outside. I will check tomorrow that specific follower but they all looked in really good condition with smooth bums!!

Is it possible the engines PO just fitted followers to an old cam??

Does a re- grind involve adding metal back and grinding back to the std profile??

Aidan

Looks like new it will have to be esp re angelfires other comment. 

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4 hours ago, Roger K said:

Interested to know how that is more accurate than using a dial gauge?

As the piston approaches TDC, the distance it moves per degree of rotation gets less, until it stops, and reverses direction.   At TDC, there may be several degrees during which it doesn't move at all.  So where is TDC?     See my article on "Equal Lift on Overlap" on Sideways for a full description of the piston stop method.

PS I'm sitting on the northbound M6 and have been for 45 mins while they scraped some bodies off the tarmac ahead, or something.    Online ETA for "normal service" is in one hours time.   What are they doing, having the bloody PM there and then? I shall need to get out and have a per soon!

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15 minutes ago, JohnD said:

As the piston approaches TDC, the distance it moves per degree of rotation gets less, until it stops, and reverses direction.   At TDC, there may be several degrees during which it doesn't move at all.  So where is TDC?     See my article on "Equal Lift on Overlap" on Sideways for a full description of the piston stop method.

PS I'm sitting on the northbound M6 and have been for 45 mins while they scraped some bodies off the tarmac ahead, or something.    Online ETA for "normal service" is in one hours time.   What are they doing, having the bloody PM there and then? I shall need to get out and have a per soon!

True, there is a substantial rotation where the piston appears to sit still, but the crank moves quite a bit, in relation to the small adjustments available to the cam teeth, that is.

Junctions 28 29 and 30 are all closed at present due to collisions. Might be the same one, just with very long skid marks.

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54 minutes ago, JohnD said:

As the piston approaches TDC, the distance it moves per degree of rotation gets less, until it stops, and reverses direction.   At TDC, there may be several degrees during which it doesn't move at all.  So where is TDC?     See my article on "Equal Lift on Overlap" on Sideways for a full description of the piston stop method.

PS I'm sitting on the northbound M6 and have been for 45 mins while they scraped some bodies off the tarmac ahead, or something.    Online ETA for "normal service" is in one hours time.   What are they doing, having the bloody PM there and then? I shall need to get out and have a per soon!

The correct method for using a dial gauge is to set the dial gauge before tdc at an arbitrary position, well 'on the ramp', and note the reading.  Move the crank over until it reads exactly the same amount on the other side.  Halve the value and set your pointer there - that is tdc.  You will never get a decent result trying to read tdc directly off the dial gauge.  Much easier, and more reproducible, than using piston stops in my experience, although of course that is a perfectly valid method.

It's also the only way I know to get peak position on a cam lobe, as well.

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you can make a piston stop from a bit of timber and a screw 

cheap effective and repeatable results unless you make it from plasticine or knicker elastic

any home made stop will arrest the piston accurately enough .

we are not on rocket science just simple good known mechanical observance of some simple basic facts , 

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17 minutes ago, Anglefire said:

Odd - worked for me - but it is the PDF download - try this Camshafts | www.newman-cams.com (newman-cams.com) and follow Triumph link

Thanks 

The ph1 looks to be my best bet for new then but will give them a call - i guess mine's for the bin as it's at the top of the lobe? 

Am unexpected cost but hey no such is life 

 

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3 minutes ago, Roger K said:

Would those in the know recommend a PH1 profile for an otherwise standard late stepped-block GT6 engine (sorry to hijack)?

The mk2/earlymk3 GT6 cam is a good all-rounder. Chris Witor also sells a hybrid cam which is worth a look. Need to compare compression ratio too. Not sure how the ph1 compares, possibly similar.

If you want a fast-road cam (beware the slippery slope!) there are plenty of candidates. 

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I've spent a fortune on fast-road components on the other cars - I want to keep the GT6 pretty well standard, as it can't compete anyway and that's not why I own it.  Essential non-changeable items for my purposes are anything external - so that's carbs, exhaust etc. which limits things quite a bit.  A nice cam that is a bit nicer than stock wouldn't hurt, though.

From what you say, Clive, I take it the earlier stock cam is better than the later one?

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https://www.chriswitor.com/cw_technical/camshaft_applications.pdf

That may help. I am certain teh mk2 GT6 cam carried over onto the rotoflex/flat topped piston mk3 as well. The earlier cam is a little "warmer" but by no means wild. As I said, Witor does this as well https://www.chriswitor.com/proddetail.php?prod=CW3021EX  but I have no idea how well it would work with the GT6 inlet. The mild extra lift can do no harm? Maybe worth a chat with him, or indeed Newman cams who I know have done hybrids.

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I believe my engine is the earlier mk2, with the better stick cam  it how can I be sure? Was their an engine number range?

Ok- answered my own question- the part is a 308778.  Is that the better of the 2 mk2 cams?

What's the best replacement per Rogers requirement as that's what I'm looking for ??

Thx

 

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19 minutes ago, AidanT said:

I believe my engine is the earlier mk2, with the better stick cam  it how can I be sure? Was their an engine number range?

Ok- answered my own question- the part is a 308778.  

What's the best replacement per Rogers requirement as that's what I'm looking for ??

Thx

 

Aidan, "best" cam is an impossible question. You need to say what for. If you want the most powerful, it won't drive on the road. 

So re-phrase teh question, saying how the car will be driven.

However, the MK2 GT6/Vit cam is a very good all-rounder. But if you like to drive a low revs, the 18-58 cam will shift the torque down the rev range a bit, but run out of puff earlier (but I note many drivers don't like hitting 5000rpm, many like to stay below 3000, so why bother with a cam that is best over these figures?)

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7 minutes ago, clive said:

Aidan, "best" cam is an impossible question. You need to say what for. If you want the most powerful, it won't drive on the road. 

So re-phrase teh question, saying how the car will be driven.

However, the MK2 GT6/Vit cam is a very good all-rounder. But if you like to drive a low revs, the 18-58 cam will shift the torque down the rev range a bit, but run out of puff earlier (but I note many drivers don't like hitting 5000rpm, many like to stay below 3000, so why bother with a cam that is best over these figures?)

Your spot on, rarely drive the car hard I would say I'm a keep it below 3k range in general but wouldn't mind a bit extra pep to get to 70 mph I have overdrive to cruise.

One of the reasons buying this engine was that the cam was said to be the best std one, so apart from the fact it's knackered and I'm now not 100% sure I have the engine with that supposed cam, that's where I'd like to get to

Aidan 

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Sounds like you are a candidate for the late mk3 GT6 cam....

I ran a 2.5S engine in my vitesse, totally std. When it got tired, I acquired a TR6 short engine, and a head, plus a piper fast road cam. Yes, it was quicker, but I always regretted not using the 25/65 cam from MK2 GT6 etc, it would have suited the car better. 

Meanwhile, I have cheated and got VVT on my spitfire. Oddly, the factory timing gives a little advance over "normal fixed" timing at sub 2k, then retards the timing by 20 degrees in the mid range, before returning to what most fixed cams are  timed to. (works only on the inlet cam, exhaust side is fixed timing) But retarding the inlet gives better mid range torque. 

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