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+--- Thread: Query about gearing... (/showthread.php?tid=4913)
RE: Query about gearing... - Stuart Giles - 06-09-2020
Is this a newly built motor? if it is and everything else checks out OK, it being maxed out at low revs could be caused by the cam timing being advanced. I have dealt with two A7 motors in the past where despite having the dots lined up by the engine builder, the cam timing was out, presumably because the timing gears hadn't originally been a pair. The inlet valve shouldn't be off the seat at TDC. If your head puts the plughole over the bore you can check this by taking off the tappet chest cover.
![[Image: 39854797775_c62695b08f_n.jpg]](https://live.staticflickr.com/4792/39854797775_c62695b08f_n.jpg)
Making an offset woodruffe key will fix the problem
![[Image: 50311806481_88a3d433e5_z.jpg]](https://live.staticflickr.com/65535/50311806481_88a3d433e5_z.jpg)
RE: Query about gearing... - Charles P - 06-09-2020
(06-09-2020, 02:04 PM)Howard Wright Wrote: PS I’d ditch the air filter.
That at would be my first elimination test, and then I'd try simply swinging the distributor whilst wearing a stout glove
c
RE: Query about gearing... - "Slack Alice" Simon - 06-09-2020
I have similar problems with two different engines in the Tourer.
Putting those aside for the moment, I have been reminded of the engine I used for a JoGLE run, which didn't want to perform as it should.
I had treated it to a re-ground crank and re-metalled big ends.
Eventually,somewhere near Edinburgh, I found one big end tighter than it should be.
A thin silver paper shim solved the problem.
I think the problem on one of the Tourer engines is excessive friction caused by patent oil control rings.
The lesson is: a little extra friction somewhere can make an engine feel sluggish.
RE: Query about gearing... - Steve Jones - 06-09-2020
(06-09-2020, 05:57 PM)Charles P Wrote:That's it, Charles. I once tried a simple carb trumpet with a mesh to keep the bricks out. Strangled the thing like you can't imagine. Still think it will revolve around timing be it ignition or cam. Timing gears dotted incorrectly aren't unknown as are timing gears assembled a tooth out. Yes, there are many more complicated things that can cause problems but this is a fundamental problem and the issue will.be equally fundamental. Simple things first.(06-09-2020, 02:04 PM)Howard Wright Wrote: PS I’d ditch the air filter.
That at would be my first elimination test, and then I'd try simply swinging the distributor whilst wearing a stout glove
s
ce
Steve
RE: Query about gearing... - Charles P - 06-09-2020
An upside of the low compression head is that it's so easy to find TDC and then check valve timing with a feeler gauge checking when the follower starts to move.
The only dismantling needed is the tappet cover and the flywheel cover or starter motor.
C
RE: Query about gearing... - Duncan Grimmond - 06-09-2020
The pic was of the previous car with standard head and SU downdraught . I'll post one of the current setup.
RE: Query about gearing... - Duncan Grimmond - 07-09-2020
This is the current car, I’ll try it without the air filter
RE: Query about gearing... - Bob Culver - 07-09-2020
Does the auto advance work? in the right direction? Air cleaners do markedly richen carbs with externally vented bowls, but would have to be choke like rich to affect performance so much. A gross cam error does seem plausible
RE: Query about gearing... - Duncan Grimmond - 07-09-2020
Removing the air filter made hardly any difference. I've reset the timing to as far advanced as possible to the point where it stumbles and backed it a fraction, it pulls well through the gears up to 32 in third but into top and its screaming its nuts off at 48 mph. I feel it may have a low ratio top gear but as I have nothing to compare it with I'm now stuck. Is it likely to have been built for trials? Lack of top speed would not be much of a problem unless you wanted to drive to the trial in which case you'd need to set off the day before!
RE: Query about gearing... - Reckless Rat - 07-09-2020
It can't have a low ratio top gear because top is always 1:1 as it's straight through the box. It's possible that you've got a 5.625 diff/pinion set-up, perhaps for a van/sports (8/45). With a lightweight special you should be able to get away with the 4.9 diff from the earlier cars (9/44). The LWB axles are usually 5.25 (8/42).