Engine Stumbling

[Jon Green]

Hi Guy's,

 

Is some of you will know I fitted a unleaded injection head and FR33 cam to my 2lt 2B recently. Yetserday I took the car to the tuners and had an hour on the rolling road.

 

The good news was that it got 120Bhp at the wheels. Unfortunately the engine seems to have a problem between 2000 - 3000 rpm where it faulters in 3 and 4 the gear.

 

Could this be due to not having a modified dissy? Any suggestiond!

 

Cheers,

 

Jon

[Guest vacinc]

does the engine miss, when cold ? in 3rd and 4th

[Guest salty_monk]

It shouldn't be to do with the dizzy, I had the same set with modified dizzy, now similar without. Difference is primarily that the power is much more urgent with the modified dizzy.

 

It could be timing or that your dizzy is knackered with sloppy bearing or a worn out vac advance system (what carb do you have??)

 

Tuner should have been able to get rid of the hiccup.... you're doing well to get 120bhp out of a 2l unless you had the tyre pumped up to 40 psi... I got 100 at the wheels out of the same setup (with a Dgas) with modded dizzy & Bob got 116 at the wheels with a stage 3 big valve head & 40's.

 

We used the same tuner so maybe our rolling road is just stingy on the figures!!

[Jon Green]

Im running on twin dellorto 40's and the tyre pressures are about 20psi

 

It's not really a missfire... it's more like Kangaroo petrol at low revs.

 

There was one other thing... the tuners could't get the tickover revs down any lower than 1100 rpm which I thought was rather odd.

 

They did suggest that I should change my o rings - carbs to manifold ones to the solid rubber bonded to metal type as I may be getting an air leak.

[Guest salty_monk]

Are you sure they know what they are doing? Lumpier cam requires higher tickover... recommended for yours is around 1100 I believe, Kent don't give any figures for tickover on their site but recommended for my Piper 285 was 1100 from memory & your FR33 is slightly lumpier than that.

 

Have a check on Piper's website.

 

Dan

[Guest robin]

i have a similar specced engine. its a 2.0 injection converted to 32/36 dgav carb with fr33 cam and 4-1 exhaust. it has a really lumpy idle and tends to stall at anything less than 1000 rpm. so i keep it at 1100 rpm. does anyone know if at idle there should be a small trickle of fuel coming from the accelerator pump jets cos mine does and wondered if an over rich mixture wont help the idle?

[Guest salty_monk]

They don't trickle on my DGAS, guess something is worn....

 

Dan

[Jon Green]

Could it be possible that my cam timing is out by a little? The tuners reconed that it it must be pretty close if as im getting such good BHP at the top end..... but is the cam timing more sensitive at lower revs?

 

Should I be getting my hands on a proper spinnie depth gauge and rechecking the cam timing?

[Big Jim]

You've done the thing that everyone does, bolted twin carbs on it, fitted a fast cam, then you're dissapointed because it runs like a bag of poo!

Get your dizzy sorted, reset the ignition timing like it should be (not 8º BTDC) then get it tuned, (and buy your shares in Shell or BP!)

[Guest hypermick]

Always a difficult one. As Jim says all too often a bag of goodies doesnt necessarily make a good engine.

 

You need to know whether the drivewheel timing on the cam needs altering. The best thing to do is get hold of a Burton vernier adjustable cam wheel. They come up on EBay most of the time,. However, unless youre able to do it competently DONT mess with the settings on it until you have all the info and then only proceed with total caution since MR Pistons and the Valve sisters have a habit of getting closer than they should (not a successful marriage if it all goes wrong !). Check with the manufacturer who made the cam and dont forget to tell them the rest of the mods info too.

 

Im also doubtful about the tuning shop youre using. For them to have a hiccup between 2-3k revs suggests that the main jets may be a trifle out,. or the advance curve is totally wrong for your set up,............ unless the cam really is that wild in which case................................................................................................................................................................................................. !

 

Look out for the cost of the fuel.

 

Best of luck

[Jon Green]

Jim, are you saying to get the dizzy modified as per the NW rhocar?

 

I do have a DGAS that I can fit to check if it's a carb problem.

[Big Jim]

Jim, are you saying to get the dizzy modified as per the NW rhocar?

 

I do have a DGAS that I can fit to check if it's a carb problem.

John, first of all sticking a DGAS onto won't cure anything. you need to put each and every piece of the puzzle together to make it work correctly,

 

Go to Dave Andrews site. http://hometown.aol.com/dvandrews/ and do some reading.

 

You need to work out the angle of dangle of your camshaft then the advance curve that it needs, this all needs to be set up BEFORE you can start messing about with ANY carb setting, DGAS or twins.

Now you can either mess about with the dizzy yourself, by seeing how it's taken apart on our site, or you can pay to have your's reconditioned and setup for you (there's even a link to that man on our site too!)

 

As I've said before, I've not a lot of faith in most (I'm sure there's a good one or two somewhere!) these rolling road tuners, they are looking for maximum power, how many times do you ever use maximum power?? very rarely! only when the red mist comes down and you give it some stick! what you really need is a nice DRIVEABLE powerband, very few actually know how to set it up like that, and with a Pinto running "ordinary" iginition, there's not an awfull lot you can do!

To really be able to tweek it properly, you'll need mapable ignition.

 

Now when you've finally got it running the best that can be got out of it (and that's not very good under 2200 rpm, due to the cam you've chosen) be prepared for a fuel comsumption UNDER 20 mpg with twin carbs.

[Jon Green]

Thanks Jim,

 

Just read Daves artical on modifying the dizzy. A job for the weekend!

 

I'll let you know how I get on.

[Guest salty_monk]

looking for maximum power, how many times do you ever use maximum power?? very rarely!

 

Quite often when you're under 50...

 

 

I agree with Jim it's hard to find a good tuner & those that are good with mapped ignition are not always as good with carbs.... best to go to one that's recommended. Sanspeed did a reasonable job on mine but too far away from you...

 

Dan

[Big Jim]

Quite often when you're under 50...

 

 

Dan

I seem to remember when one "under 50" recently managed to find full throttle, he put it through a hawthorn hedge!

a simple miss-calculation on the E/A fraction no doubt