Help! Dual RPR (IDF) Tuning problem

I have just switched from a pair of Weber ICT's to a pair of RPR (IDF's) on a type 1 1600 DP engine.

Upon setting them up I have the idle set at the recommended idle speed and balanced, the idle jets are 52 and the engine idles smoothly with 1 1/2 turns out on mixture screw.

The mains are 120 and air 200.

Readings appear to be within OK on my gas analyzer.

On the road test the car accelerates reasonable but not crisp, however when turning a corner and presented with a climb it dies immediately, running on two cylinder (1&2) it now would appear. Stop, select 1st - take off and run up to 4,000RPM gets you up the hill. Changing up a gear earlier results in death.

Now back in the workshop, I wound in the mixture screw on each cylinder until the engine misses. Cylinders 1 & 2 (RH Carby) works a treat. Cylinders 3&4 (LH Carby) when wound all the way in makes no difference?

To me this represents a problem with the idle circuit on the LH Carby? I have removed the jets, cleaned them out and same for the carby.

Any suggestions thoroughly appreciated.

What size chokes are in the carbs.

28mm

Have tried them with both an SVDA Distributor that I was using with my ICT's without a problem and a 009 Distributor I had previously used.

The engine has done 3,000 since a total rebuild. Still 1600cc, port and polished heads, standard valve size, moderate cam with 1:1.25 rockers,, light flywheel. C/W crank, fully balanced.

Was running very well with the ICT's just running out of a little steam on the long Tasmanian hills. Thought that the IDF'type carbies would cure this problem.

Using the long offset CBPerf manifolds.

landfall wrote:Upon setting them up I have the idle set at the recommended idle speed and balanced, the idle jets are 52 and the engine idles smoothly with 1 1/2 turns out on mixture screw.

The mains are 120 and air 200.

Personally, I reckon you need 32 chokes.
That is based on my experience, AC.net and others.
But what ever works

landfall wrote:Now back in the workshop, I wound in the mixture screw on each cylinder until the engine misses. Cylinders 1 & 2 (RH Carby) works a treat. Cylinders 3&4 (LH Carby) when wound all the way in makes no difference?

To me this represents a problem with the idle circuit on the LH Carby? I have removed the jets, cleaned them out and same for the carby.

Correct - reckon there is a boogie in the LH carby
Maybe water?

What happens when you pull #3 or #4 plug wire?

What colour are #3 or #4 plugs?

You DEFINITELY got them balanced?
Did you use a synchrometer?
or just your ear?

I have balanced them with and without the linkages connected using a snail type balancer.

Idle is perfect with and without the linkages hooked up.

Giving it a quick rev. from idle without any load it picks up without hesitation. Goes up our short and very steep (read MT Everest) driveway without a hitch. On the road, as I stated, turn a corner in second gear and go to accelerate up a hill and die, back to first and accelerate but do not change to second too early or the same dying.

Back in the workshop with engine at operating temp. any adjustments on LH carby idle mixture screws, either in or out is a waste of time.

Suspect dodgy carby, but would like to explore all avenues first.

Thanks for your replies so far.

Could it be a fuel blockage on that side.getting enough fuel at idle but not with more revs??
If not maybe get them ultra sonic cleaned if all else fails.can't hurt and it's cheap
I remember always chasing fantom issues with Webber's,well not always but it was a pain in the ring
Fabo

Anything is possible.

Thinking it through tonight I will swap sides tomorrow to eliminate any other possibilities other than the carby.

Fuel blockage doesn't make sense as the idle is perfect, cannot get cylinders 3&4 to misfire. I would think that when I close the mixture screws at idle the cylinder should misfire.

I will however recheck everything again tomorrow.

As for getting them ultrasonically cleaned, even if someone did that sort of work in Hobart, I would not be prepared to have it done. These are new carbies out of the box and I paid RP extra to set them up and jet them.

Once I have determined if it's my adjustment at fault or it is a dud carby, I will return it.

I'm hoping someone can come up with something I have missed out on checking.

They can be such a pain when they want hey...is the accelerator jet adjusted right

First step anyone should take with carb problems is make sure the float level is correct,
and fuel pressure not too high.

No point playing with jetting and venturis unless these things are correct first.

Floats often get maladjusted in shipping.

Thanks,

Using a Holley fuel pressure regulator with gauge set at 2.5psi

Float level checked when I checked out the carby on bench before fitting.

Before removing it today I will be checking everything again and spraying some carby cleaner throughout.

Also check that the shitty choke extra fuel valves are shut , as have had experience with these on another set of chinese IDF's .
You'll have to remove the float bowl top / carby top to get to them and as you'll soon see they are a crap design at best with the only thing holding them shut is the spring pushing against the gasket and as they have a low pressure compresion spring holding these choke fuel valves shut it takes very little inperfection in the gasket etc for these to dribble fuel into the throats and upsetting the idle circut supplied fuel

try spaying a HEAP of WD40 down the idle jet

It was easy with jet doctors on Dells cause the hole is on the top

Thanks,

I have gone through the whole procedure again today, adjusting float level to recommended 10mm, ran like a dog. Readjusted them again after talking to Rod using his method (he had set them before delivery) and it ran better, but still the idle mixture problem.

Checked timing, spark plugs, etc.

Car is almost driveable, lacks low down pulling power. Makes more induction noise than action when placed under heavy load, light throttle gets a response on the flat or downhill.

Seems to idle OK could be smoother, but sounds like 4 cyls. Simply cannot get any response from the LH carby.

Rod suggests that the 40's are too big for the 1600 engine, but I have been reading on various forums that a lot of people are getting good results from them.

The dead idle circuit still worries me. How can I tune and jet the carbies when I can't get a starting point?

landfall wrote:Rod suggests that the 40's are too big for the 1600 engine, but I have been reading on various forums that a lot of people are getting good results from them

What rubbish 😜
I am VERY surprised he would say that.
I will say, again, if anything, IMO, with 28's, they are jetted too small.
I have run stock 1600's with 32's and made good power

It is definitely both circuits dead on 3&4?

The circuits are free?
You have taken the mixture screws out and can hear air when you blow through them?

Try swapping the mixture screws over to the other carb.

Definitely no air leaks?

Plugs are a good colour?

You 100% sure the butterfly cam the bump stops rest against are not too tight or loose.
I have seen them not return properly throwing out the tune

Hi and thanks for the reply bizarre.

First let me say that I am also surprised at the "too big" response, but in all fairness to Rod he said that he is going to sleep on the problem tonight and contact me tomorrow with his thoughts.

During my many tries today I increased the idle speed to 1050RPM from 850RPM. On the snail gauge this increased the reading from 3.5 to 5. this was suggested by Rod.

I also disconnected all linkages and had the car idling with the carbies operating independently - balanced. The mixture screws on the suspect carby made no difference.

On the road test the car ran at 3000RPM on the freeway with light throttle OK, load it up and I got plenty of noise but not much action. Using a lighter throttle and acceleration was possible, albeit slowly.

Running the ICT's the car is much more responsive so it's not an engine or ignition problem.

Ken

Bizarre,

Both circuits are dead.

Plugs very slightly sooted, more like a dusting, was able to simply wipe them clean.

Can hear air.

Rod has suggested advancing timing by 2 degrees, will try this tomorrow.

Thanks for the replies.

Quote " however when turning a corner and presented with a climb it dies immediately"
What does your A/F meter read when it dies? and at what RPM?

Just read the last post. Quote "load it up and I got plenty of noise but not much action"
Again, what does the A/F meter read at that time?

Dave

Sorry Dave I do not have A/F meter readings on the road.

RPM on corner would be around 1500-1800.

From sound I would guess air speed non existent, car sounds like it wants to go but has run out of breadth.

Where I am heading with my questions is identifying what is happening around transition to the main jet.
With a A/F meter, you can see easily if it is a fuel problem, because there either is or isn't any fuel to burn due to the main jet not coming in/on,
which is why you get QUOTE 'From sound I would guess air speed non existent, car sounds like it wants to go but has run out of breadth" Air speed is there but no fuel!
It's all about main, air correction jet and emulsion tubes and the correct combination. Much easier if you can read the A/F ratio to guide your changes.
It is a common problem I have seen with big carbies on little engines, but it can be fixed. I'll try to explain a little more later tonight.
Dave

Appreciate your thoughts and input Dave.

I played around with it quite a bit today, small adjustments including swapping the SVDA Distributor for an 094 mechanical advance unit. Advanced timing two degrees at the suggestion of RP.

Some things worked and not others. I basically have two test circuits. The first involves a left turn at a round about and up a steep hill, this is the one that does all the damage. Initially I was having to stop about fifty to one hundred metres around the corner, select first and try again. After considerale mucking about today I was able to stay in second but no acceleration.

Second circuit is freeway with a long hill, once again from a round about. With the ICT's I could go up that hill at 70>80kph in third. Presently I can barely manage 50KPH.

Talked to Rod this afternoon and he is going to send me another carby and some idle jets.

It has us both stumped, it idles smooth, accelerates OK under light load and goes good on the freeway. But as he says, when I stamp on the accelerator it should rocket away, not go to sleep.

Ken

Drop the fuel pressure down to 1.5- 2psi, maybe flooding carbs, fouling plugs. I run my IDF's at 1.5psi on my 2054cc. Have you checked that the throttle plates open evenly and are at the same position when fully opened? Out of sync carbs can cause your symptoms, check your linkage isn't bent or getting caught up anywhere.

shokwave2 wrote:Drop the fuel pressure down to 1.5- 2psi, maybe flooding carbs, fouling plugs. I run my IDF's at 1.5psi on my 2054cc. Have you checked that the throttle plates open evenly and are at the same position when fully opened? Out of sync carbs can cause your symptoms, check your linkage isn't bent or getting caught up anywhere.

Talked to Rod this afternoon and that is a;lso the pressure he recommended. currently I am running 3psi and the first thing on my list for tomorrow is to reduce it to 1.5>2psi.

Have checked the linkages and syc. all good.

Received a much better pair of extra return springs in the mail today, will also fit them tomorrow.

Appreciate all the suggestions and am working my way through them that I may have overlooked.

Feel like I am progressing, on Saturday I wasn't game to get too far away from home😂 I am now planning on going on the car clubs 350km rally on Sunday with this set up.

Cheers

Can o ask if you have a stock fuel pump or an electric one?

No problem, it's stock.

Check the sealing of the top plate of the carb to the body.

Check the float action is free on its axle when not perfectly straight as if in the car.

Have had both these problems cause the cornering and hill issues you describe.

What happens on level ground when WOT?

^^^^ correct, it could be binding float. And yes the carbies can be too large if your engine combo is inefficient and lazy.
What exact heads and work, exact cam specs, c/r, etc etc.

Had a big day today, took the carbs/mainfolds off, removed plugs and checked everything.

Considering the engine has done 3,000km I did not expect any alarm bells. Plugs on 1&2 cyl a nice grey and dry, 3&4 a light soot and dry.
Compression OK all cyls.

Manifolds sealing OK at head and carby. Cleaned suspect carby with carby cleaner, checked passage ways for blockages and float level (again) checked butterfly's and put it back together.

Checked all spark plug leads and electrical connections.

Tomorrow I will complete reassembly, hopefully start it up and rebalance carbies, check timing, adjust carbies and hope that problem side is no longer a problem.

Rod rang me this morning and to be on the safe side he is going to post a replacement carby to me today. Can't complain about the service or the amount of support he has given.

On that note, thanks to everybody here, you have given me plenty to go on with. Beats the hell out of becoming frustrated on my own.

So tomorrow you are swapping carby sides? You still havent told us about the engine combo, what is, it top secret stuff?

fish26 wrote:You still havent told us about the engine combo,

landfall wrote:The engine has done 3,000 since a total rebuild. Still 1600cc, port and polished heads, standard valve size, moderate cam with 1:1.25 rockers,, light flywheel. C/W crank, fully balanced.

Using the long offset CBPerf manifolds.

You aint reading the whole story Benito 😊

Bizarre wrote:

fish26 wrote:You still havent told us about the engine combo,

landfall wrote:The engine has done 3,000 since a total rebuild. Still 1600cc, port and polished heads, standard valve size, moderate cam with 1:1.25 rockers,, light flywheel. C/W crank, fully balanced.

Using the long offset CBPerf manifolds.

You aint reading the whole story Benito 😊

Shoulda gone to Specsavers.

I'd like to thank everyone for their input.

I took all the info onboard and as I said in my previous post had a big day yesterday and finished it off today.

Whatever the problem was (and I suspect it was a little swarf in the carby) plus minor little details like ignition low voltage wires not quite tight enough on the spade terminals, fuel pressure, distributor choice, etc. The problem seems to have been resolved and now needs the help of a dyno to fine tune the whole deal.

Rod Penrose sent me a new carby yesterday afternoon at 4pm by express post and it arrived at 9.30am this morning with a selection of jets. On the phone he has urged me to keep the carby for as long as I think it needs to be here and return any unused jets. He did not ask for any payment for any of this extra service and items.
Now that's old fashioned service.

The car on this mornings test run, went like a rocket. Up a hill that I have tested on many times and the best yet was 80kph and steady with the ICT's, with these RPR IDF's 80KPH and still accelerating, backed off. (Speed limit)

Cheers

👍👍👍

well done mate

Glad you sorted out the gremlins, however we still don't know your engine combo, it must be top secret.
Baz, you wouldn't know an engine combo if it kicked you in the ass 😂

No state secret and I thought I gave enough information, but since you want to get technical, no problem.

Std 1600 Pistons and Cylinders - Mahle
69mm C/W Crank
CVP Light flywheel
CBP Ultra light cam followers
Eagle Bracket Cam 276Degree Duration Lift at cam .380" At rockers with 1:1 ratio = .417"
CBP 1.25:1 Ratio rockers - solid shaft
CBP Super H Race Rods 5.4"
MST Serpentine Belt system
MOFOCO 040 Super Street Heads Port and Polished
RPR Hideaway Exhaust System
All engine components fully balanced.
Now running RPR IDF 40mm IDF Carbs with 094 Distributor.

Using original AS41 case, with CBP Max 3 oil pump and external filter.

Well done landfall. Just goes to show when you modify something, it usually snowballs. It's great to see all the help on here and that RP stood behind his products
Cheers........Wayne

Thx landfall, i'm a sucker for technical specs. Power, reliability, driveability are all dependant on a working ENGINE COMBINATION. Vague engine specs mean nothing especially when trying to diagnose problems via social media, that's why the more information you provide, the more people are able to help out. Trust me all of the ones in the know have had massive head scratching moments, it's one of the ways to learn. Your cam looks like W100 so you should be getting good airspeed and bottom end torque with stock valved 040s unless you had the intakes polished otherwise a slight to moderate stumble may be present as it allows the fuel to fall out of suspension. Once again, im glad it got worked out, enjoy your dub.

fish26 wrote:Thx landfall, i'm a sucker for technical specs. Power, reliability, driveability are all dependant on a working ENGINE COMBINATION. Vague engine specs mean nothing especially when trying to diagnose problems via social media, that's why the more information you provide, the more people are able to help out. Trust me all of the ones in the know have had massive head scratching moments, it's one of the ways to learn. Your cam looks like W100 so you should be getting good airspeed and bottom end torque with stock valved 040s unless you had the intakes polished otherwise a slight to moderate stumble may be present as it allows the fuel to fall out of suspension. Once again, im glad it got worked out, enjoy your dub.

Slight stumble? This I still have under certain conditions.

I assumed that this can be tuned out, I did port the intake manifolds to match the head work and get some of the bumps out of the casting.

Am going to do more fine tuning today, but I can live with it if necessary because it does go as I expected it to do.

I must admit I too like specs and research. The engine specs were thoroughly talked over with CBP and MOFOCO. At the time I did not want to go big, but now wish I had.

How big are you wishing now? I ask as I still haven't built my 1776 and am agonising over a stroker crank.
Cheers.........Wayne

Hi guys

I'm curious as to what the compression ration is?

Cheers
Greg

So am i Greg,

hulbyw wrote:How big are you wishing now? I ask as I still haven't built my 1776 and am agonising over a stroker crank.
Cheers.........Wayne

Minimum 1916 but probably 2110cc. Torque is the answer IMO.

Lateral wrote:Hi guys

I'm curious as to what the compression ration is?

Cheers
Greg

8.0:1

Lateral wrote:Hi guys

I'm curious as to what the compression ration is?

Cheers
Greg

All you have to do is ask me, no use asking "Hi guys" because they haven't a clue either.

Ken