bumpy
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| posted on 18/5/14 at 01:28 PM |
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Suggestions for a sluggish engine
I have a fibreglass kit car running a 2 litre pinto engine with road going GT cam and 32/36 Weber. All other parts are standard.
I am increasingly getting the feeling that the engine is pretty sluggish. Most laymen look at it and remark "that should go well with a 2 litre
engine", I'm no mad arse driver, but I remain unimpressed by the acceleration. I'm sure my 1.4 Astra saloon does much better.
Any suggestions?
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owelly
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| posted on 18/5/14 at 01:47 PM |
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Give the car a full service including all consumables. ie. New plugs and points. Check the timing and emissions. If you still think it's not
playing ball, you'll have to have it tuned to make sure everything is doing what it should!
http://www.ppcmag.co.uk
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rusty nuts
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| posted on 18/5/14 at 01:49 PM |
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Check the auto advance mechanism in the distributor hasn't partially seized, very common on Bosch distributors , check for correct dwell angle
,ignition timing, valve clearances and for full throttle any of which will lose power
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19sac65
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| posted on 18/5/14 at 02:06 PM |
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Has it always been like this or sudden
Is the cam timing correct,tappets not too tight
If so - as already advised , dont try and tune up old parts
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bumpy
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| posted on 18/5/14 at 02:30 PM |
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The engine has only done 2500 from a rebuild, but it stood unstarted with all ancillaries for 10 years in a car being built by a total of 3 previous
owners over that period.
It was sluggish when first started and after 2000 miles the head gasket blew. I suspect in its history someone forgot the last torquing of the head
when it was first fired up.
Anyway, the head and valves were in good order as were the pistons and bores. I have replaced the cam belt, done the ignition timing, tuned the carb
(air screw) to give a nice golden colour on the plugs and changed the ignition leads. But, nothing seems to make a difference to the sluggishness.
Thanks for the extra things I can check. I think I will also get someone else to drive the car as there's a slim chance its going about as good
as it should.
The only symptoms I have of poor set up is a an occasional running-on of the engine when I turn it off, and an erratic tickover that refuses to tick
over at less than about 900 rpm.
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mark chandler
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| posted on 18/5/14 at 02:52 PM |
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A pinto in good condition will idle smoothly at very low rpm, if you have the cam belt out by a tooth it will do what you describe.
In the ideal world you want to get an adjustable timing pulley and set the camshaft with around 5 degrees advance.
Regards Mark
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ian locostzx9rc2
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| posted on 18/5/14 at 03:52 PM |
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I agree full service check vac advance on distributor is working poss check cambelt isn't isn't a tooth out poss clean out carb and
finally check second choke is opening on full throttle....
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gremlin1234
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| posted on 18/5/14 at 03:55 PM |
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quote:
done the ignition timing,
what settings have you used for the timing?
the original settings would be for leaded 4 star. modern fuel is quite different.
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ian locostzx9rc2
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| posted on 18/5/14 at 03:58 PM |
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I would say 5 to 8 deg before tdc as a starting point.
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jacko
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| posted on 18/5/14 at 04:22 PM |
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And when you get it running better get your self a lighter flywheel it will make the engine rev quicker
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bumpy
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| posted on 18/5/14 at 04:52 PM |
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quote:
Originally posted by ian locostzx9rc2
I would say 5 to 8 deg before tdc as a starting point.
Ignition set at 8 deg before TDC
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19sac65
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| posted on 18/5/14 at 04:53 PM |
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Ime sure pintos are timed vac pipe off
If your setting it with pipe on itll be very retarded
You can check if dizzys advancing by pointing timing gun at the marks and connect/disconnect the pipe to see if the mark moves
It should go well,although ille be amazed if the carbs not holding it back now its been cammed
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alfas
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| posted on 19/5/14 at 10:43 PM |
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if the car feels sluggish it doesnt matter if you set it 8 degrees or 10 or with vacuum connected or not.
you can try setting it to 12 or 14 BTDC....but i doubt anything will happen:
as the engine was rebuilt in the past, its likely that the headgasket face on the head was machined, maybe also the block.
so you will never get the valve timing correctly set without a vernier pulley. even a standard engine would profit from it.
i would start to play arround with valve timing. check again the valve clearances
als very important:
if your diff ratio is too high (e.g. a 3.54), plus large wheels this will kill all acceleration.
please tell us the diff ratio, the wheel-size and tyre size?
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bumpy
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| posted on 20/5/14 at 07:55 AM |
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quote:
Originally posted by alfas
if the car feels sluggish it doesnt matter if you set it 8 degrees or 10 or with vacuum connected or not.
you can try setting it to 12 or 14 BTDC....but i doubt anything will happen:
as the engine was rebuilt in the past, its likely that the headgasket face on the head was machined, maybe also the block.
so you will never get the valve timing correctly set without a vernier pulley. even a standard engine would profit from it.
i would start to play arround with valve timing. check again the valve clearances
als very important:
if your diff ratio is too high (e.g. a 3.54), plus large wheels this will kill all acceleration.
please tell us the diff ratio, the wheel-size and tyre size?
I will get the details of the diff/wheels later.
Interesting what you say about the valve timing. Is it documented somewhere how you set up with a vernier pulley. I would worry about getting it wrong
and hitting the valves with the pistons. Do you just target the standard valve timing (but more accurately) or do you target a different setting for
each cam shaft.
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alfas
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| posted on 20/5/14 at 04:23 PM |
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a standard or slightly uprated pinto will not have valve piston contact, even if the cambelt would break
[Edited on 20/5/14 by alfas]
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bumpy
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| posted on 7/9/15 at 09:22 PM |
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UPDATE
This topic has moved on a bit since last I posted.
The engine has now been returned to a standard camshaft, so everything including the distributor, carb, camshaft, exhaust is nominally standard.
But, the sluggish behaviour still exists, even in first and second gears.
If the timing is set at 8 deg BTDC at tickover with vacuum disconnected, the car starts fine, ticks over well but has very little power when
accelerating, even when 'buzzing' at about 3000 rpm.
If the ign timing is increased a few degrees, the tickover speeds up and remains smooth, and the acceleration begins to pep up a bit.
BUT, at the position where the performance is satisfactory (but not startling) the engine becomes very difficult to turn over when starting. It has
all the symptoms of over advanced ignition with it appearing that the battery hardly has enough power to spin it over.
The vac advance retard is operating and the mechanical bob weights seem OK. Where do I go from here?
[Edited on 7/9/15 by bumpy]
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bumpy
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| posted on 7/9/15 at 09:25 PM |
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quote:
Originally posted by alfas
if your diff ratio is too high (e.g. a 3.54), plus large wheels this will kill all acceleration.
please tell us the diff ratio, the wheel-size and tyre size?
I have a type 9 gearbox, 3.62 diff and 17 inch wheels with low profile tyres. At 70 mph in fifth gear I am pulling just 2500 rpm, so don't
expect it to be pulling away well under those conditions.
[Edited on 7/9/15 by bumpy]
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adithorp
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| posted on 7/9/15 at 09:41 PM |
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Sounds overgeared.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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alfas
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| posted on 7/9/15 at 10:00 PM |
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quote:
Originally posted by bumpy
quote:
Originally posted by alfas
if your diff ratio is too high (e.g. a 3.54), plus large wheels this will kill all acceleration.
please tell us the diff ratio, the wheel-size and tyre size?
I have a type 9 gearbox, 3.62 diff and 17 inch wheels with low profile tyres. At 70 mph in fifth gear I am pulling just 2500 rpm, so don't
expect it to be pulling away well under those conditions.
[Edited on 7/9/15 by bumpy]
what i estimated months ago: diff-ratio & those monster wheels will kill all acceleration.
so all you have done until know, was a bit of waste of time.
you can re-fit the original camshaft and try to source 13inch wheels with tyres (the total diamter of the new wheels needs to be remarkably smaller
than the actual ones)
what size tyres are fitted now?
[Edited on 7/9/15 by alfas]
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bumpy
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| posted on 7/9/15 at 10:01 PM |
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quote:
Originally posted by adithorp
Sounds overgeared.
Thanks. A good friend of mine keeps telling me this, but why does advancing the ignition improve things?
Out of interest what revs would one expect a 2 litre engine to be pulling at 70mph?
[Edited on 7/9/15 by bumpy]
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Adamirish
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| posted on 7/9/15 at 10:04 PM |
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I have the same gearing as you, 3.62 diff, type 9 and used to have 17's. It is fitted with a 1700 x flow. The engine is tuned, around 130bhp I
would imagine and that would easily spin the rear wheels from close to tick over. I would expect that with a pinto and the extra torque(mine has none)
it should still go well. Everyone's opinion on what power is acceptable is different though.
Have you done a compression test? Does the engine Rev cleanly? Fuel pressure good? I would suggest a trip to the rolling road and get the ignition and
fuelling set up.
MK Indy 1700 Xflow
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alfas
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| posted on 7/9/15 at 10:08 PM |
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the earlier the ignition timing the better the combustion and consecutively the better your power
also fuel consumption will profit from that
my x/flow with a 4-speed box does already rev. 400rpm at 60miles with 185/60r13 and a 3,89 diff
it has around 100bhp..but acceleration is equal to my friends 120HP x/flow with bigger wheels and 3,54 diff
the cheapest tuning is a lower diff ratio and/or smaller wheels..Low gears give fast acceleration, high gears give better cruising and higher max.
speed
[Edited on 7/9/15 by alfas]
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bumpy
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| posted on 7/9/15 at 10:11 PM |
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quote:
Originally posted by alfas
quote:
Originally posted by bumpy
quote:
Originally posted by alfas
if your diff ratio is too high (e.g. a 3.54), plus large wheels this will kill all acceleration.
please tell us the diff ratio, the wheel-size and tyre size?
I have a type 9 gearbox, 3.62 diff and 17 inch wheels with low profile tyres. At 70 mph in fifth gear I am pulling just 2500 rpm, so don't
expect it to be pulling away well under those conditions.
[Edited on 7/9/15 by bumpy]
what i estimated months ago: diff-ratio & those monster wheels will kill all acceleration.
so all you have done until know, was a bit of waste of time.
you can re-fit the original camshaft and try to source 13inch wheels with tyres (the total diamter of the new wheels needs to be remarkably smaller
than the actual ones)
what size tyres are fitted now?
[Edited on 7/9/15 by alfas]
Tyre sizes are 205 50/R17
The other camshaft was giving me several other running problems and deserved to be binned 
I love my wheels and tyres, so they will be going nowhere. Is another option to change the diff?
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alfas
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| posted on 7/9/15 at 10:16 PM |
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ok, than diff needs to be changed to something around 4.4 to 4.6
dont know the nearest availble ratio for your specific diff.
is it a sierra diff?
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bumpy
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| posted on 7/9/15 at 10:18 PM |
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quote:
Originally posted by Adamirish
I have the same gearing as you, 3.62 diff, type 9 and used to have 17's. It is fitted with a 1700 x flow. The engine is tuned, around 130bhp I
would imagine and that would easily spin the rear wheels from close to tick over. I would expect that with a pinto and the extra torque(mine has none)
it should still go well. Everyone's opinion on what power is acceptable is different though.
Have you done a compression test? Does the engine Rev cleanly? Fuel pressure good? I would suggest a trip to the rolling road and get the ignition and
fuelling set up.
I don't suppose you can remember what revs it pulled at 70mph?
Compression test is fine. The engine revs cleanly when the car is stationary and there is just the hint of a stutter when accelerating hard on the
road, but that is not what I define as sluggish.
I used to own a 1600 mk 3 Cortina and that pulled pretty well, by comparison.
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