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Took the car out today for a run after new clutch / points/ timing. I am getting a flatspot in 4th gear then the car eventually gets through it, same in 3 rd but not as bad. The car is a 1380 and was set up with the dwell angle and timing light. The timing should be bang on which makes me think its not getting enough fuel at those points, is there anything i can do or check to establish whats up? Iv not touched the carb. Just the timing. Iv tried retarfing, advancing in between runs but nothing noticeably different either way.....any ideas?

So whats it timing set to and whats the full spec of the motor ?

1380 cc , Hif44 , no idea what camshaft , and a slightly lightened flywheel to my knowledge. Big valve head not sure of the sizes.

4 years ago it was running 88bhp with a hif38 , the carb is the only change since then . {timing was out that day as well }

The ignition timing was done with the dwell angle I think it was 10 thou feeler. {new points} Lucas 59d

The timing at idle 1000rpm {vac pipe removed and plugged} is advanced 8 degrees,
The timing at idle 1000rpm with vac pipe connected is advanced about 22 degrees .

The plugs are new and up and down the dual carriageway testing is all they have done and look a bit grey no sign of brown.
Before the timing and new points etc. the old plugs were pretty coked up .

don't know if this is relevant but when I rev the engine and the rev counter rises... if I let off it drops right down to zero and sticks at zero {new tacho so could be a fault}....If I put the clutch in at 60 the engine will turn off ...... but at idle the revs are fine .

??
black plug is from before timing {old plug} light plug is now after timing and abit of running

Theres not enough timing, set it to 16 degrees at 1200rpms. But when you drive it listen out for any sign of pinking and don't give it full throttle under load just yet.
The other thing I say looking at the pic's, is check and adjust your valve clearances.

thanks for the reply smiffy

What signs will I be looking for to tell me to adjust ? I previously sat at about 25mph in 3rd and slightly applied handbrake to check for pinking etc but my method obviously isn't efficient when I took it to a descent speed....
After looking into things a bit more a lot of people say a rolling road but I'd rather try and get it better myself first .

I wouldn't go by certain timing figures in degrees etc . Firstly I would set the tappets , then a compression test to see if all the cylinders are relatively the same . You'll be flogging a dead horse if one or two of the cylinders are down . A gunston colour tune to set the mixture . As for timing , if it's got a non standard cam set the revs at 3 to 4 thousand rpm , then swing the dizzy left or right till the revs reach a peak . Then lock up the dizzy . .... Ken

swifty wrote:I wouldn't go by certain timing figures in degrees etc . Firstly I would set the tappets , then a compression test to see if all the cylinders are relatively the same . You'll be flogging a dead horse if one or two of the cylinders are down . A gunston colour tune to set the mixture . As for timing , if it's got a non standard cam set the revs at 3 to 4 thousand rpm , then swing the dizzy left or right till the revs reach a peak . Then lock up the dizzy . .... Ken

with vac hose connected ? or disconnected ?
Iv heard similar to that but when it reaches peak , drop it off 250rpm for some reason ?
The neighbours are gonna flip at 4000 rpm surely on the road under load this wouldn't be accurate ?

Iv heard so many , and tried so many ways

mk1mini wrote:thanks for the reply smiffy

What signs will I be looking for to tell me to adjust ? I previously sat at about 25mph in 3rd and slightly applied handbrake to check for pinking etc but my method obviously isn't efficient when I took it to a descent speed....
After looking into things a bit more a lot of people say a rolling road but I'd rather try and get it better myself first .

What you need to do is find a long straight road up a gradual incline (hill). Now drive up the road in third gear accelerating steadily, while listening out for any signs of detonation/pinking. Which sounds like a small stone placed in a can and rattled, if you hear this immediately get off the throttle. Pull over and retard the ignition a couple of degree's, then repeat until you can get right through the rev range without any sign of pinking.

What needle have you got fitted to the carb ?

Smiffy wrote:

mk1mini wrote:thanks for the reply smiffy

What signs will I be looking for to tell me to adjust ? I previously sat at about 25mph in 3rd and slightly applied handbrake to check for pinking etc but my method obviously isn't efficient when I took it to a descent speed....
After looking into things a bit more a lot of people say a rolling road but I'd rather try and get it better myself first .

What you need to do is find a long straight road up a gradual incline (hill). Now drive up the road in third gear accelerating steadily, while listening out for any signs of detonation/pinking. Which sounds like a small stone placed in a can and rattled, if you hear this immediately get off the throttle. Pull over and retard the ignition a couple of degree's, then repeat until you can get right through the rev range without any sign of pinking.

What needle have you got fitted to the carb ?

hi smiffy , The needle was modified about 4 years ago and there was no code on it at that time , in fact I don't think iv adjusted the carb in any way since then as it has always performed well . would I be better to perform the test you described and then when happy set the mixture with the gunson colour tune afterwards ?

Forget the color tune, set the timing 16 degrees. Then only turning the mixture adjustment screw, in & out until find the point at which the idle is the highest. Then test it as I described earlier.

Ok, so at the previously stated 4000rpm, 16 degrees with vac disconnected? Thanks for everyone's patience with me on this!

mk1mini wrote:Ok, so at the previously stated 4000rpm, 16 degrees with vac disconnected? Thanks for everyone's patience with me on this!

Well no this is what I said:

Smiffy wrote:Theres not enough timing, set it to 16 degrees at 1200rpms. But when you drive it listen out for any sign of pinking and don't give it full throttle under load just yet.

Yes with the vac disconnected.

swifty wrote:I wouldn't go by certain timing figures in degrees etc . Firstly I would set the tappets , then a compression test to see if all the cylinders are relatively the same . You'll be flogging a dead horse if one or two of the cylinders are down . A gunston colour tune to set the mixture . As for timing , if it's got a non standard cam set the revs at 3 to 4 thousand rpm , then swing the dizzy left or right till the revs reach a peak . Then lock up the dizzy . .... Ken

This is one way I'd suggest, it's much safer than trying to set it at lower RPMs, although I'd suggest using a timing light and set it to 30 degrees, vac disconnected.

Has the dissy been curved to suit the engine?

Also, the pic of the plugs, it appears that your mixture is quite rich at lower revs / idle.

Spider wrote:This is one way I'd suggest, it's much safer than trying to set it at lower RPMs, although I'd suggest using a timing light and set it to 30 degrees, vac disconnected.

Has the dissy been curved to suit the engine?

Also, the pic of the plugs, it appears that your mixture is quite rich at lower revs / idle.

Trouble with this is, it's likely to pink in the mid range with small throttle openings. If you want to start at the top end, start with 28 degrees at 3500rpms.

Probably obvious but have you checked for air leaks at the carb and is the dash pot oil okay.

Iv recently topped up the carb and removed a vac gauge from inside the car. The vac pipe carb spacer is still there but blocked off . It will probably be the weekend until i can get out to do the timing but im sure ill get it eventually. Ran great last year and iv maybe changed to many thing in that time to diagnose whats up. Ie, inline fuel filter change, clutch, points, removed a vac gauge, all of which could be causing these problems but im sute its timing.

Just one thought, none of the 1275 cc plus engines I've had has used a vacuum advance distributor, if you can borrow a non vac unit or have one built to have an advance curve to suit the engine then hopefully that will eliminate the timing as a cause of the fault. I'm now running a CSI distributor in my 1275, looks like an S dizzy apart from having 2 wires coming out of it

FWIW:

An engine making 88BHP is doing quite well, especially on a HIF38 carb.
Was this on a rolling road, or an engine dyno?

It doesn't really matter, it is either quite a good output or a very good output...

The chances are that unless the curve in the distributor has been made
especially for this engine, it will be wrong. Bear in mind that the traditional
"curve" is basically generated by weights and two sets of springs and in
reality the "curve" is really two angled lines, then a flat line.

All this talk of backing the timing off until the engine stops pinking is fine,
but in reality, what you end up with is an engine which is retarded EVERYWHERE
except the point where the pinking was just tuned out, where it will be just about
correct.

So the way to go is to get a distributor made with a tailored curve. You could buy
an "off the shelf" one like I did, based on the spec of the engine. My spec years
ago, 1380, 'S' type head, 286 cam, LCB, etc suggested an Aldon "Yellow", so I
got one and ran it like that for several years thinking that I had the right dizzy.

When I finally got round to having my first rolling road session at Aldon, they
found that the "Yellow" was a mile out, and so was their "Red", but "Red" was
closer and they built me a dizzy based on "Red". The difference on the road
was phenomenal and I was severely p!ssed off that I had not dyno'd the engine
before!

Again, even with a custom mechanical dizzy, we still have the problem where
it can only generate 3 straight lines for a curve. What we really need is some
kind of programmable device, such as the 123Tune, or MegaJolt.

"Flat spots", in my experience, are generally carb-related, not timing related...
Carb springs and a lack of oil on the dashpot can make a lot of difference as well.

As for "ColourTune": Yes, I do have one that I bought years ago... Unless you
have had a needle selected for your exact spec, this will be useless. It will tell you
how your mixture is burning at tickover, under no load AND NO MORE.

My 1380 was running an HS6 with an SZ needle and a Yellow spring.

Here is a tool which will compare pretty much any needle, fixed or swing...
If you don't know what the needle is, measure it. The spreadsheet will tell you
what it thinks the needle is.

http://mk1-performance-conversions.co.u ... l_carb.htm

EDIT: The website seems to be playing up:
I am sure Mark is on the case!


EDIT:EDIT: Mark has fixed it already - Well Done!



Good Luck!

Ian

Hi thanks for the reply, the car was dyno'd in 2007 and carb, exhaust and things have changed since then. I was just stating the power output approx. Im reluctant in changing to a fancy dizzy as the car has ran fine for 4 years , I understand what you are saying though. I think it will be a case of adjusting the timing correctly through trial and error with the previous instructions. Iv not had a chance to get out to it yet but i will keep everyone posted, the feedback and help has been excellent.

mk1mini wrote:Im reluctant in changing to a fancy dizzy as the car has ran fine for 4 years

This was pretty much what I thought, but for 10 years with my 1380...

When I did finally get the dizzy sorted out, the difference was instantly noticeable.
As an added bonus, I also picked up an extra 5mpg.

Subsequent to that, much more recently, I got a 123/Tune which is a fantastic piece
of kit. The beauty of this is that providing you don't change from 'A' to 'A+' or the
other way round, you can use it on any specifcation you like, just connect up the
laptop, and off you go!

As an example, I changed an engine form 1380 to 1480, cam 286 to 276,
CR 11.7 to a too high 13:1 (Same Head). I found that I needed to back off the
timing by a massive 8 degrees, mostly due to the CR, I suspect....
Using the old-fashioned method of just swinging the dizzy round to cure the problem
would have left me with virtually no advance and very poor performance at the
bottom end.

Another comment was made about the engine pinking at light load in the midrange...
Engines normally tend to pink in the midrange generally in the area where most
torque is being produced, and this will be happening if you have your foot down....
If this is happening under light load, there is WAY TOO MUCH advance at this RPM.
If an engine is going to pink/detonate, it will be at wide-open-throttle, or at least
getting on that way. If it happens at anything less, the timing should be retarded
immediately or else your engine may be not long for this life.

Back to carbs and the Needles spreadsheet I linked to before, you say that
the needle has been "modified". If this involves it having had a flat filed down it,
the spreadsheet will be able to calculate this back as round again so you can
start off with a known profile in your tuning efforts. If you want further details
on how it will do this, go here:

viewtopic.php?f=3&t=6239

... and post a reply!

Reading back through the posts, I would be more concerned about the engine
cutting out at 60 if you press the clutch...

Ian