A while back there was a thread on additives to replace leaded petrol, and Dizzy was querying why my Mark 1 needed an anti-knock additive but his (Mark 2 ?)didn't.
I had remembered I thought that the Mark 1 had more power than a Mark 2, but ascribed it to the wrong reason. You were right, the Mark 2's CR is higher, but according to a very authoritative article by Chris Witor in the latest Six Appeal, the Mark 1's carburation and specifically inlet manifold give it a higher torque and power.
Hence the slightly better performance from the earlier car. He even goes so far as to say that a very slightly modified 2000 can beat a standard 2500, even a PI.
Just thought I'd mention it, in case you hadn't seen the article Dizzy - can't remember which club you belonged to.
|
Cliff,
I have been a member of the Triumph 2000 Register for something like 20 years so I receive the SIXappeal magazine and I confirm that my Triumph is a MkII (2500, ex-PI). I have read Chris Witor?s article but I interpret it quite differently.
Chris points out that the original Triumph 2000 had a bit more power and torque than the early MkII, though the later MkII (1975 on) had higher power than either of the earlier engines, and almost as much torque. I accept that the original 2000 is quicker than the later ones but much of this must be due to the increased weight of the MkII cars.
I don?t think the modifications that Chris recommends for the 2000 engines could be described as ?very slight?. These include planing the block so that the pistons protrude above the top face, changing the pistons from domed to flat top, using a special head gasket, possibly overboring the block by up to 80mm, using special small end bushes, fitting a skimmed 2500 head, fitting flow profiled valves and copper bronze guides, phase correcting and stroke grinding the crankshaft, lightening the flywheel, balancing the rotating assembly, fitting reworked inlet manifold, fitting different carburettors, changing the exhaust system, fitting a 6-3-1 extractor manifold, changing the ignition system, modifying the camshaft, fitting roller rockers, fitting double valve springs, possibly changing the single chain drive to duplex drive and fitting a different ratio differential.
That?s not ?very slight modification? it?s virtually a new race-bred engine! No wonder it will outrun a 2500 and even a PI. If more ?go? is required, surely it?s simpler and much cheaper to replace the 2000 engine with the more powerful (but not as refined) 2500 engine!
|
OK, fair point! But I think he was saying that even without going to such extreme lengths a worthwhile gain could be made. Not that I'm going to try any of it, as I don't want to blow a gasket.
I was really trying to tie up the old CR point. So we still don't know why some cars seem to need octane boosters and others don't.
|
I was really trying to tie up the old CR point. So we still don't know why some cars seem to need octane boosters and others don't. >>
Yes, that continues to be a complete mystery to myself. I've been asked by the editor of SIXappeal if I would submit an article for the next issue describing the causes of valve seat recession. I wish I could include an explanation about when octane boosters are required, but I don't have a clue! Maybe that's a question for Chris Witor to have a go at.
Regarding the performance of your 2000 engine, I ran a 1965 2000 auto from 1970 until mid-1975 and was very happy with it. It wasn't a ball of fire but acceleration was adequate and cruising was relaxed and refined. The MkII 2000 auto that I used to service for a neighbour was noticeably slower, so much so that it was not very enjoyable to drive. If you are happy with your MkI 2000 as it is, then I agree that it's best to leave well alone.
|
|
|
