Kiwi scratchbuilt
- Thread starter Russ Noble
- Start date
It's still there! 
I tested last Tues, tried new cap and rotor, direct feed from the battery, disconnected tacho. The miss is still there. Had to curtail the test session early, so didn't get to try the seperate battery setup.
Kevin, I'll keep your dizzie for later, got your email too. Thanks.
Now I am beginning to wonder if I am actually dealing with TWO problems that just happen to be occuring at the same time..... ie I have a rev counter problem that is happening at the same time as the miss but is in no way related to it. It may have been giving me a bum steer, making me think I was looking at an electrical problem when in fact it may be something totally different.
Right now I am tending to think it is the carb just going miles too rich, as indicated by the lambda, BUT the plugs and the pipes look fine. So it is with some trepidation and great care that I am going to try leaner jets.
The carb was a secondhand Barry Grant with removable venturis that I got off ebay. It was fitted with really lean mains, 74/80 as opposed to the listed standard setup of 78/86. I thought the vendor had just taken the opportunity to get rid of some unwanted lean jets so I fitted some 78/86s. But maybe this particular carb works with the leaner jets that it came with? Hmmm.... you try to do things right and cover all the bases, who knows? I'll find out on Tuesday.
In the meantime I'm also making adjustments to suspension settings and brake bias, and pedal/foot position, and refining a whole lot of other wee stuff. At least I seem to be heading in the right direction with the non-motor stuff!
During the last test session I also managed to set up the incar lap time display which will be very handy, and this Tuesday, if I have time, I hope also to have a go at setting up the incar video. It would be nice to have that recording for the Club Race Day Dec 13.
Anyway, roll on Tuesday! Fingers crossed.....
Action pic from Levels Raceway at Timaru a couple of weeks ago.
I tested last Tues, tried new cap and rotor, direct feed from the battery, disconnected tacho. The miss is still there. Had to curtail the test session early, so didn't get to try the seperate battery setup.Kevin, I'll keep your dizzie for later, got your email too. Thanks.
Now I am beginning to wonder if I am actually dealing with TWO problems that just happen to be occuring at the same time..... ie I have a rev counter problem that is happening at the same time as the miss but is in no way related to it. It may have been giving me a bum steer, making me think I was looking at an electrical problem when in fact it may be something totally different.
Right now I am tending to think it is the carb just going miles too rich, as indicated by the lambda, BUT the plugs and the pipes look fine. So it is with some trepidation and great care that I am going to try leaner jets.
The carb was a secondhand Barry Grant with removable venturis that I got off ebay. It was fitted with really lean mains, 74/80 as opposed to the listed standard setup of 78/86. I thought the vendor had just taken the opportunity to get rid of some unwanted lean jets so I fitted some 78/86s. But maybe this particular carb works with the leaner jets that it came with? Hmmm.... you try to do things right and cover all the bases, who knows? I'll find out on Tuesday.
In the meantime I'm also making adjustments to suspension settings and brake bias, and pedal/foot position, and refining a whole lot of other wee stuff. At least I seem to be heading in the right direction with the non-motor stuff!
During the last test session I also managed to set up the incar lap time display which will be very handy, and this Tuesday, if I have time, I hope also to have a go at setting up the incar video. It would be nice to have that recording for the Club Race Day Dec 13.
Anyway, roll on Tuesday! Fingers crossed.....
Action pic from Levels Raceway at Timaru a couple of weeks ago.
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Russ: Does it miss under cornering? Some of the Holley carbs on oval track applications use a special float. We had a Ford 2 barrel simular to a holley that would run really lean on one cylinder bank because of fuel sloshing up the side of the float bowl. If the fuel is sloshing it could possibly be shutting off the needle valve early. Something to check Was the carb a drag race carb?
Kevin.
Yeah, its pretty full on trying to get it sorted. Many things that I thought could possibly have been a problem, have not. Some things that I never even considered have unexpectedly given me major grief. Like the missfire frinstance! It is all go trying to turn this bundle of nuts and bolts into a competitive race car. I WILL get there though! If I don't have the motor gremlins sorted in the next few days it WILL be going on a chassis dyno.
Should be out at the track in 12 hours time, it is is really persisting down at present! I guess I have to do my wet setup at some time, it may as well be tomorrow! Could be interesting......
Dave.
No, corners are fine, except for a propensity to swap ends! But I'm working on that. Carb is a BG Race Demon RS General Competition. Seems to be a nice piece. But what would I know.....?
I will most likely post the results of tomorrows test session this time tomorrow night. Fingers (and everything else) crossed again.
Yeah, its pretty full on trying to get it sorted. Many things that I thought could possibly have been a problem, have not. Some things that I never even considered have unexpectedly given me major grief. Like the missfire frinstance! It is all go trying to turn this bundle of nuts and bolts into a competitive race car. I WILL get there though! If I don't have the motor gremlins sorted in the next few days it WILL be going on a chassis dyno.
Should be out at the track in 12 hours time, it is is really persisting down at present! I guess I have to do my wet setup at some time, it may as well be tomorrow! Could be interesting......
Dave.
No, corners are fine, except for a propensity to swap ends! But I'm working on that. Carb is a BG Race Demon RS General Competition. Seems to be a nice piece. But what would I know.....?
I will most likely post the results of tomorrows test session this time tomorrow night. Fingers (and everything else) crossed again.
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Gidday Russ,
assuming that the power valve restrictions in both metering blocks have not been drilled oversize, and that you have an operable primary power valve and a power valve plug in the secondaries, you should be in the general ballpark with 72s in the front and 80s in the back possibly + a few sizes. At least that's where I used to end up more often than not with the variety of 750DPs I ran on my SBC. If you have a power valve in both ends, then 72s each end possibly + a few sizes.
I assume the BG carb has adjustable air bleeds fitted to the top of the main body - make sure the main air bleeds are all present and are not blocked. If they are blocked or way too small you will trend rich as RPM rises.
I know that an MSD 6AL will fire a mixture as rich as AFR = 9 using plug gaps of 0.45, so you'd have to be ULTRA rich to be extinguishing spark. A lean misfire will read rich because raw fuel will be in the exhaust - so check it's not fuel delivery, and I assume you ruled out spark scatter.
Have you completely ruled out the tach by disconnecting it and everything associated with it?
Keep at it - you'll nail it!
Cheers, Andrew
assuming that the power valve restrictions in both metering blocks have not been drilled oversize, and that you have an operable primary power valve and a power valve plug in the secondaries, you should be in the general ballpark with 72s in the front and 80s in the back possibly + a few sizes. At least that's where I used to end up more often than not with the variety of 750DPs I ran on my SBC. If you have a power valve in both ends, then 72s each end possibly + a few sizes.
I assume the BG carb has adjustable air bleeds fitted to the top of the main body - make sure the main air bleeds are all present and are not blocked. If they are blocked or way too small you will trend rich as RPM rises.
I know that an MSD 6AL will fire a mixture as rich as AFR = 9 using plug gaps of 0.45, so you'd have to be ULTRA rich to be extinguishing spark. A lean misfire will read rich because raw fuel will be in the exhaust - so check it's not fuel delivery, and I assume you ruled out spark scatter.
Have you completely ruled out the tach by disconnecting it and everything associated with it?
Keep at it - you'll nail it!
Cheers, Andrew
Well, I was hoping to report that the Tuesday session was a success.
But it wasn't. I am still chasing that elusive miss, but I have now got the suspension settings etc in the ballpark. With the motor the way it is, there is no point in doing any more on that front until the motor is right, as more power and revs and using different gears will change everything. So off to the dyno shop for some plug in diagnostics as soon as possible.
Bit of a bummer getting the run around with a simple miss... And times running out....
But it wasn't. I am still chasing that elusive miss, but I have now got the suspension settings etc in the ballpark. With the motor the way it is, there is no point in doing any more on that front until the motor is right, as more power and revs and using different gears will change everything. So off to the dyno shop for some plug in diagnostics as soon as possible.
Bit of a bummer getting the run around with a simple miss...
And times running out....Russ,
It's a bit of a long shot but have you checked the distributor gear and bushing or bearing on the end of the shaft. I have heard of them going bad and having too much play. This will throw everything out. You could try another distributor and see what happens.
Dave
It's a bit of a long shot but have you checked the distributor gear and bushing or bearing on the end of the shaft. I have heard of them going bad and having too much play. This will throw everything out. You could try another distributor and see what happens.
Dave
Good luck with the dyno session Russ, and by the way, what I said above was bollocks - any kind of major misfire reads lean on the WB02 due to the large amount of oxygen in the exhaust that has not been used in combustion.
Cheers, Andrew
Thanks for the suggestion Dave, I had it out earlier in the piece and all that is good.
Andrew, yes I knew any miss showed up as a lean reading so no problem. I checked fuel delivery back in early November at the start of all this and removed the surge tank which was bleeding off all the pressure. Plenty of fuel delivery and thats confirmed by the dash mounted fuel pressure gauge.
Dyno guy, who was highly recommended, is coming round at the weekend to check he has some adaptors for the wheel hubs. Should be on the dyno early next week.
Andrew, yes I knew any miss showed up as a lean reading so no problem. I checked fuel delivery back in early November at the start of all this and removed the surge tank which was bleeding off all the pressure. Plenty of fuel delivery and thats confirmed by the dash mounted fuel pressure gauge.
Dyno guy, who was highly recommended, is coming round at the weekend to check he has some adaptors for the wheel hubs. Should be on the dyno early next week.
Right on both counts KB!
Lim worked until 2 this morning to get the adaptors and nuts done. We are racing this Sunday so time is critical. We are booked and ready to go on the dyno tomorrow. Hopefully we can find the problem. And more hopefully cure it....
So in the pics. The guys dyno drive that we have to adapt up to is top left. Alongside that are the two adaptors that Lim has machined.
The next row down are the final locking nuts and spanner that we (Lim!) had to make. Bottom row is the first set of locking nuts that we made before we had access to the dyno drive. The hex nuts were too large to fit inside it.
Should have pics tomorrow of the whole lot assembled and in action. I hope we can cure the problem and also be able to take advantage of the opportunity to optimise all the settings at the same time.
Lim worked until 2 this morning to get the adaptors and nuts done. We are racing this Sunday so time is critical. We are booked and ready to go on the dyno tomorrow. Hopefully we can find the problem. And more hopefully cure it....
So in the pics. The guys dyno drive that we have to adapt up to is top left. Alongside that are the two adaptors that Lim has machined.
The next row down are the final locking nuts and spanner that we (Lim!) had to make. Bottom row is the first set of locking nuts that we made before we had access to the dyno drive. The hex nuts were too large to fit inside it.
Should have pics tomorrow of the whole lot assembled and in action. I hope we can cure the problem and also be able to take advantage of the opportunity to optimise all the settings at the same time.
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Not only that, he's also got another interesting and complex project lined up. Which is why he's so anal at getting perfect castings for the GT40. They are just a trial run before he attempts something much more difficult and involved.....
Nah. It's not luck, it's good management! I started him off on small seemingly harmless doses of motor racing but now the euphoric highs have got him and he's just like the rest of us with a fully fledged addiction!!
He took the day off work today to be at the dyno session too!
Well I fell on my feet with the dyno operator! He came up through drag racing in his younger days so really knew his way round four barrel carbs then went to Europe and was a spanner man for F2. Absolutely top notch! For any local guys, I highly recommennd Gary at P.A.D Racing.
The miss that I have been looking for never actually manifested itself on the dyno though, however there were three variables. I fitted a new set of plugs the night before, the motor was running a lot hotter than at the track, the rear clip was not in place. So it will be interesting to see how it goes on Sunday!
Had a bit of drama on the first few pulls which were each prematurely terminated when the oil pressure dropped to 25psi at WOT at high revs! That's a worry! Tried to visualise what in the motor or oil system could be causing this problem but to no avail. Added another couple of litres of oil and cranked up the relief valve to see if it would make any difference, but no. Getting this thing up and running is revealing one problem after another....It must end soon...!
Could it be the gauge? In days gone by I have clutched to this straw only to find that the motor concerned is invariably well and truly poked! Worth a try though, fitted a mechanical gauge and instantly got 75psi at WOT. Instant relief.
So the dyno program back on full song! Gary rejetted the carb a few times, drilled out a few passage ways in the metering block and eventually got a consistent AF ratio all the way through the rev range. Then we played with the spark and found 30° gave the best results. 2° either side producing a small intermitent misfire.
So a fairly full on day, all day on the dyno. I really learnt a lot and would never have been able to achieve these results left to my own devices track testing. So all good.
First pic is Lims adaptors all bolted up
Second pic, the whole setup and Gary on a mission.
Third and 4th pics with additional mufflers which were used for all but the last few pulls and blower ducting to the oil cooler.
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Russ
Good to see the miss is gone
Dyno is allways a good place to do diagnostics. I have heard many critcs say they can do better without but I have always felt it is the best place to start. The other thing is you see directly the effect of any small change.
Once you have a bench mark, it is easy to go one jet size richer to or leaner to got a desired result e.g. getting it to pull out of corners better etc.
Also it comes down to dyno guy knowing what he is doing. As without that you are still fumbling.
Unfortunately cars are not like jetboats where you effectively have a Dyno in the back???
Russ. You forgot to give the best bit of info . How many neddies do yu have tied up ???
I'd be keen to look at your power curve ???
Have you had the driver on the dyno too? He probably is the most importamt part!!!!
Look after him as well!!!!
Best of luck for the weekend.
regards
Kevin B
Good to see the miss is gone
Dyno is allways a good place to do diagnostics. I have heard many critcs say they can do better without but I have always felt it is the best place to start. The other thing is you see directly the effect of any small change.
Once you have a bench mark, it is easy to go one jet size richer to or leaner to got a desired result e.g. getting it to pull out of corners better etc.
Also it comes down to dyno guy knowing what he is doing. As without that you are still fumbling.
Unfortunately cars are not like jetboats where you effectively have a Dyno in the back???
Russ. You forgot to give the best bit of info . How many neddies do yu have tied up ???
I'd be keen to look at your power curve ???
Have you had the driver on the dyno too? He probably is the most importamt part!!!!
Look after him as well!!!!
Best of luck for the weekend.
regards
Kevin B
Kevin, as you pointed out the dyno is good for diagnostics. But, as someone said, we don't race dynos.
So I wasn't particularly perturbed that we couldn't get peak hp figures. We appear to have comfortably over 500 hp but we couldn't run it to full revs in 4th as the speed was too fast for the dyno. Anyway I was more interested in the comparisons between the various graphs from pull to pull. The aim was to get the A/F consistent at 12.5 through the range and then optimise the advance which we did. It doesn't sound much, but it took all day...
There wasn't much point in getting any print outs as I was happy with what we achieved, and the proof of the pudding will lie in the track results! But the data will still be on his computer if needed for any future comparisons.
Dyno the driver? The driver's having a night off tonight! A bit of R & R, much better than getting wound up on a dyno!!
I've still got a small list of things I want to do to the car before Sunday, as there always is...! But not too much pressure this time.
So I wasn't particularly perturbed that we couldn't get peak hp figures. We appear to have comfortably over 500 hp but we couldn't run it to full revs in 4th as the speed was too fast for the dyno. Anyway I was more interested in the comparisons between the various graphs from pull to pull. The aim was to get the A/F consistent at 12.5 through the range and then optimise the advance which we did. It doesn't sound much, but it took all day...
There wasn't much point in getting any print outs as I was happy with what we achieved, and the proof of the pudding will lie in the track results! But the data will still be on his computer if needed for any future comparisons.
Dyno the driver? The driver's having a night off tonight! A bit of R & R, much better than getting wound up on a dyno!!
I've still got a small list of things I want to do to the car before Sunday, as there always is...! But not too much pressure this time.
It's all good! The miss has gone! epper:
Had a good day at the track. Got a 5th, a second, and a win! In that order. Best lap time was a 1:36.9 No problems with the car, we just put fuel in it and I refined the brake bias after the first race. I'll do a quick report on the Racetrack sub forum, but not tonight, I need an early night.
Fives years solid slog by myself and all my helpers has finally culminated in a troublefree and successful race meeting. My thanks to all the guys who have helped me over this time, particularly Lim who was there today too to enjoy the moment.
This week I will pull the engine and trans out for a fairly superficial check over, also so I can have a good look around the rear chassis where there have been a few issues which I will detail later. Also strip all four uprights and check that all is well with the bearings and the fabrication. Then there will be some settling down races on 8th Jan at the F5000 Wigram Revival meeting before three fairly full on consecutive weekends in Feb for the SFOS
epper:Had a good day at the track. Got a 5th, a second, and a win! In that order. Best lap time was a 1:36.9 No problems with the car, we just put fuel in it and I refined the brake bias after the first race. I'll do a quick report on the Racetrack sub forum, but not tonight, I need an early night.
Fives years solid slog by myself and all my helpers has finally culminated in a troublefree and successful race meeting. My thanks to all the guys who have helped me over this time, particularly Lim who was there today too to enjoy the moment.
This week I will pull the engine and trans out for a fairly superficial check over, also so I can have a good look around the rear chassis where there have been a few issues which I will detail later. Also strip all four uprights and check that all is well with the bearings and the fabrication. Then there will be some settling down races on 8th Jan at the F5000 Wigram Revival meeting before three fairly full on consecutive weekends in Feb for the SFOS
