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Post by Gordon Harrower on Jun 13, 2014 2:24:17 GMT
My 3-Litre currently has P4 gears in the manual gearbox because that's all that was available when I rebuilt it. It works fine, but acceleration is slow. I've read that Rover made a series of changes to the manual gearbox to improve acceleration, but it's not clear when the changes were made. I've been given a Mk IA parts car, and I'm wondering if its gearbox is comparable to the Mk II one. It has the short gearshift. Basically, I want to know if it's worth the work of making the swap, or if I'd be better off waiting for a Mk II 'box to come along.
Thanks,
Gordon.
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Post by Ken Nelson on Jun 29, 2014 21:32:10 GMT
I'll be curious to hear any replies Gordon, because I have the 4-spd manual gearbox with od in my 3 litre coupe, and I find it to be slower than I would have expected for a 6 cylinder engine. It appears that my car takes it time getting up to speed, and that it doesn't like to cruise at much more than 75 mph, even though the engine seems to run fine. I suspect that this is just the norm for this version? Ken
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Post by enigmas on Jun 29, 2014 23:30:38 GMT
Ken a friend of mine now deceased used to own a 3 litre MK3 automatic. The car was mechanically perfect but slow due to the autobox. He fitted a toyota supra 5 speed gearbox through his own clever engineering skills. He was in his early 70s at the time. This transformed the car and I can attest to the transformation as I drove it. He retained the 3.5 diff. It had excellent pick-up through the gears and high speed cruising. He would drive it from Victoria to Queensland most years to visit family. I'd say that there is something wrong with your engine and a thorough diagnostic check would be advisable.
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Post by Ken Nelson on Jun 30, 2014 0:27:21 GMT
The engine and carb have been rebuilt, but I could check compression and timing again I suppose. It starts easily and runs smoothly. I recall that one of the reasons for needing a V8 for the car was the decreased performance of the 6 cylinder. Still, I've never driven another Rover, so I'll check a bit further. A modern 5 speed transmission would make a big difference I'd think also.
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fred1
Rover Rookie
Posts: 8
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Post by fred1 on Jun 30, 2014 0:35:16 GMT
Yes rover did change the manual gear box ratio on the MK2, raising second and third gear ratios, as further information might be of help in understanding your query.
Early rover 3liters developed 115 BHP gross 108 BHP net, Later cars with the introduction of the westlake head developed 134 BHP gross 121 BHP net, the 110 P4 BHP increased from 93 BHP to 123 BHP, interesting to note the P4 Rover as a result of being fitted with the westlake head developed more BHP than the early 3 Litre rovers.
3 Litre ratios early Rover 108 BHP, 1st 14.56, 2nd 8.785, 3rd 5.923, 4th 4.3 ( 3.35 overdrive )
Later 3 litre 121 BHP, 1st 14.52, 2nd 8.11, 3rd 5.48, 4th 4.3 ( 3.35 overdrive)
I haven't got the figures to hand for the P4 gear ratios.
Hope it,s help full
Allan
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fred1
Rover Rookie
Posts: 8
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Post by fred1 on Jun 30, 2014 1:57:18 GMT
Just an after thought here have you thought about sourcing a westlake head!
Allan
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Post by enigmas on Jun 30, 2014 2:48:38 GMT
Ken if it's struggling to reach 75mph something is wrong, especially with a manual car. I'd check the compression of each cyl first, then the ignition timing (too retarded) then check the centrifugal advance mechanism. If that's locked-up/seized the car will idle and rev perfectly whilst stationary, but won't pull the skin of a rice custard when driven. Check each plug lead for an open circuit with a multi meter as well, especially if they're old carbon core leads. My friends MK3 ran the standard 3.5 ratio diff with the 5 speed, so the overdrive would have jumped the gearing to 3.1 or less in fifth. This was a standard though mechanically sound car. No issues.
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Post by Ken Nelson on Jun 30, 2014 12:46:23 GMT
Very good point about the vacuum advance. I've never checked that and that could perhaps be a source of slow acceleration so I will do so with the compression and timing check. The car will get up to 75 and cruise there, just takes its time and doesn't seem too interested in heading much further up on the speedometer. My car is a 1966 with the Mk IIC engine so I believe that has the Westlake head on it? Ken
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Post by johnwp5bcoupe on Jun 30, 2014 16:25:33 GMT
Very good point about the vacuum advance. I've never checked that and that could perhaps be a source of slow acceleration so I will do so with the compression and timing check. The car will get up to 75 and cruise there, just takes its time and doesn't seem too interested in heading much further up on the speedometer. My car is a 1966 with the Mk IIC engine so I believe that has the Westlake head on it? Ken Have you checked the butterfly is fully open? just a thought Ken sorry if I am asking a silly question
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Post by Phil Nottingham on Jun 30, 2014 17:14:42 GMT
Our Mk2 Coupe auto which has a de-tuned manual engine has no problem accelerating up to the legal limit as also our P4 100 (manual) with its 2.6 Litre engine and without the Westlake head yours will have.
Note the 26D Dizzy has a nylon cush drive which can slip under load when it degrades
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Post by Ken Nelson on Jul 5, 2014 0:14:37 GMT
For a followup on my 3 litre engine performance-it doesn't seem to be a problem with the gear ratio's since it seems to have adequate torque in all gears and can dawdle in 4th around a corner if need be w/o stalling. The ignition advance seems to work, the plugs are all clean and a nice tan color, and the compression in all 6 cylinders is 170 lbs. Haven't gotten to recheck timing yet, but John's "silly question" seems the answer. When the accelerator is fully floored, the butterfly valve is not fully open! Seems to have another 1/8th to 1/4th of travel left in it! So I now need to recheck the throttle pedal and linkage adjustments as the likely problem. My throttle pedal has rotted and torn off its rubber floor mounting so is reattached with duct tape at the base, hence likely a big part of the problem. Glad there is nothing wrong with the engine though. The 3 litre specs I looked up for time from 0-50 mph are given as 10 sec, and that seems about right (may try timing myself with a stop watch). Any one know how to get a new throttle pedal to bolt properly to floor? Ken
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Post by enigmas on Jul 5, 2014 3:36:53 GMT
That's an interesting method of repair. Has it been like that for very long?
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Post by johnwp5bcoupe on Jul 5, 2014 5:30:43 GMT
For a followup on my 3 litre engine performance-it doesn't seem to be a problem with the gear ratio's since it seems to have adequate torque in all gears and can dawdle in 4th around a corner if need be w/o stalling. The ignition advance seems to work, the plugs are all clean and a nice tan color, and the compression in all 6 cylinders is 170 lbs. Haven't gotten to recheck timing yet, but John's "silly question" seems the answer. When the accelerator is fully floored, the butterfly valve is not fully open! Seems to have another 1/8th to 1/4th of travel left in it! So I now need to recheck the throttle pedal and linkage adjustments as the likely problem. My throttle pedal has rotted and torn off its rubber floor mounting so is reattached with duct tape at the base, hence likely a big part of the problem. Glad there is nothing wrong with the engine though. The 3 litre specs I looked up for time from 0-50 mph are given as 10 sec, and that seems about right (may try timing myself with a stop watch). Any one know how to get a new throttle pedal to bolt properly to floor? Ken Drop David Green an email Ken he may have a Pedal?
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Post by Phil Nottingham on Jul 5, 2014 6:29:17 GMT
Well it certainly would not help! Mind you I rarely use full throttle. I think the acceleration of our Coupe as brisk and was quite fast for the time but not as fast as the P5B of course!
It could still hold its own in modern traffic but understeer on fast corners was more than modern FWD cars and on X plies it was really bad
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