Kiwi scratchbuilt
- Thread starter Russ Noble
- Start date
Well there was quite a bit happening on Friday's practice session and race day Saturday, so I will do seperate posts for each.
Investigation during the week revealed that the fuel pressure problem was not so much a problem with fuel delivery but more the setup of my surge tank. In actual fact the bypass on the regulator passes very little fuel when the bypass is in action. (Completely the reverse of the situation causing the high oil pressure from the oil pump!) I had a -3 bleed in the top of the surge tank and this was almost passing more fuel than the bypass. This caused the low fuel pressure but the actual fuel volume delivered to the carb appeared to be more than adequate. However I removed the surge tank in case it was a problem.
My rev counter problem http://www.gt40s.com/forum/gt40-tech-fueling-electrics-engine-cooling/29894-problem-tacho-dying.html which I posted in the electrical section I hoped was cured by changing the input wires to the tach.
And the problem with hitting the brake pedal when going for the clutch I decided could be cured by about a three inch a 'wing' mounted on the brake pedal to stop my clutch foot from getting over on to it.
So Friday practice was the try out for the mods and now that the fuel pressure and tacho issues had been addressed I was hoping for the motor to pull sweetly up to the redline. Well the fuel pressure was good and the tacho was reading correctly but the motor would still not rev over 4500 at full throttle at which point the tacho would die completely. I now think this is indicating a problem with the MSD quitting, rather than a problem with the tach.
However practice was cut short after abot five laps, but best lap of the day was 1:44 compared to 1:50 on the Tuesday. This compares to my best TR7V8 time at 1:42.8 and Ross' times of 1:38 and the class lap record of 1:29.5
The practice session ended when the handling deteriorated rapidly and the left rear wheel assumed an excess toe in condition. From a cursory look, it wasn't immediately obvious what the problem was, except that it was serious, so I decided to go back to the workshop where we could investigate it properly.
The upshot of it was that the upright had distorted, apparently due to the loads induced under braking. It appears the 1.6 mm panel plate is too light for the job so we had to remove the upright, cut out the damaged and distorted sections, set it up in the jig again and rebuild it, this time using 3mm plate. Of course the opposite upright would also be prone to the same problem, so we beefed that one up as well. Also the 'wing' on the brake pedal was less than satisfactory and in the heat of the moment just plain didn't work, and got flattened by my left foot, so as a quick stop gap measure for race day, I ran a length of 30x5 flat alloy bar the length of the footwell between the two pedals.
From early afternoon to just after midnight, about twelve hours solid work for Lim and myself. Finally got to bed about 2am ready to get up at 6 to load up and get out to the track for race day. Haven't had time to retorque the heads yet!
Investigation during the week revealed that the fuel pressure problem was not so much a problem with fuel delivery but more the setup of my surge tank. In actual fact the bypass on the regulator passes very little fuel when the bypass is in action. (Completely the reverse of the situation causing the high oil pressure from the oil pump!) I had a -3 bleed in the top of the surge tank and this was almost passing more fuel than the bypass. This caused the low fuel pressure but the actual fuel volume delivered to the carb appeared to be more than adequate. However I removed the surge tank in case it was a problem.
My rev counter problem http://www.gt40s.com/forum/gt40-tech-fueling-electrics-engine-cooling/29894-problem-tacho-dying.html which I posted in the electrical section I hoped was cured by changing the input wires to the tach.
And the problem with hitting the brake pedal when going for the clutch I decided could be cured by about a three inch a 'wing' mounted on the brake pedal to stop my clutch foot from getting over on to it.
So Friday practice was the try out for the mods and now that the fuel pressure and tacho issues had been addressed I was hoping for the motor to pull sweetly up to the redline. Well the fuel pressure was good and the tacho was reading correctly but the motor would still not rev over 4500 at full throttle at which point the tacho would die completely. I now think this is indicating a problem with the MSD quitting, rather than a problem with the tach.
However practice was cut short after abot five laps, but best lap of the day was 1:44 compared to 1:50 on the Tuesday. This compares to my best TR7V8 time at 1:42.8 and Ross' times of 1:38 and the class lap record of 1:29.5
The practice session ended when the handling deteriorated rapidly and the left rear wheel assumed an excess toe in condition. From a cursory look, it wasn't immediately obvious what the problem was, except that it was serious, so I decided to go back to the workshop where we could investigate it properly.
The upshot of it was that the upright had distorted, apparently due to the loads induced under braking. It appears the 1.6 mm panel plate is too light for the job so we had to remove the upright, cut out the damaged and distorted sections, set it up in the jig again and rebuild it, this time using 3mm plate. Of course the opposite upright would also be prone to the same problem, so we beefed that one up as well. Also the 'wing' on the brake pedal was less than satisfactory and in the heat of the moment just plain didn't work, and got flattened by my left foot, so as a quick stop gap measure for race day, I ran a length of 30x5 flat alloy bar the length of the footwell between the two pedals.
From early afternoon to just after midnight, about twelve hours solid work for Lim and myself. Finally got to bed about 2am ready to get up at 6 to load up and get out to the track for race day. Haven't had time to retorque the heads yet!
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Was your MSD new or did you buy it SH, if so it might have been modded for 4 or 6 cyl in which case the rev limit will be 75% or 50% of the value on the chip, sent you an email with installation data etc.
Check with 3000 test chip against rev counter readout. OR remove chip altogether although ***********NOT recommended in your current state of heightened agitation.****
Check with 3000 test chip against rev counter readout. OR remove chip altogether although ***********NOT recommended in your current state of heightened agitation.****
MSD was new Jac Mac, so I've got all the installation instructions but thanks for the email. Since I've only done about 25 laps since we've had it on the track I was still running with a 6000 chip in the limiter but at Leons suggestion swapped that out for the 8000 but this had no effect.
When it misses at 4500, if I lift off and and put my foot down again gradually it will recover and rev quite a bit higher. If I feed the throttle in gradually it will rev through the 4500 without missing. But if I have my boot hard up it, it just suddenly hits a brick wall and bucks and misses and won't go any faster. In fact it's that violent that if it happened on corner exit it would cause a spin!
The O2 sensor indicates a rich condition, 11:1 or possibly richer, right through the rev range at WOT, but the tail pipes show a light grey. Haven't checked the plugs yet. I don't think its a mixture issue coz its strong to 4500 then instantly and violently nothing and the rev counter dies. I'm seriouly thinking of throwing the MSD away. I've got a Crane XR700 that was good on the TR7V8 with an optical trigger, I think I'll check and see if it is compatible with the magnetic set up. I went with the MSD because it had a built in rev limiter which the Crane did not and I do succomb to the red mist from time to time! The last instance of red mist of course caused the unfortunate demise of the TR7V8 engine and resulted in this sentence of five years hard labour for the GT40 project!~
When it misses at 4500, if I lift off and and put my foot down again gradually it will recover and rev quite a bit higher. If I feed the throttle in gradually it will rev through the 4500 without missing. But if I have my boot hard up it, it just suddenly hits a brick wall and bucks and misses and won't go any faster. In fact it's that violent that if it happened on corner exit it would cause a spin!
The O2 sensor indicates a rich condition, 11:1 or possibly richer, right through the rev range at WOT, but the tail pipes show a light grey. Haven't checked the plugs yet. I don't think its a mixture issue coz its strong to 4500 then instantly and violently nothing and the rev counter dies. I'm seriouly thinking of throwing the MSD away. I've got a Crane XR700 that was good on the TR7V8 with an optical trigger, I think I'll check and see if it is compatible with the magnetic set up. I went with the MSD because it had a built in rev limiter which the Crane did not and I do succomb to the red mist from time to time! The last instance of red mist of course caused the unfortunate demise of the TR7V8 engine and resulted in this sentence of five years hard labour for the GT40 project!~
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Have you run it up thru RPM with timing light attached to see if ign curve is within spec @ what point ignition breaks down, also chuck the 3k chip in to check limiter function while doing so. I know I sent you the data where some folk were wiring MSD incorrectly which causes the ignition to fire off the wrong side (trailing) of the trigger & causes all sorts of timing issues.
Jac Mac, it is wired correctly. I will try your suggestions
Dave, it's 12v the alt charges at just below 15v. Thanks for the thought though!
Kevin, I take your point but I have heaps of other things to fine tune too, like suspension, brakes, driver! So at this point track testing is my preferred option.
When I read on Ron's thread that he has fitted two MSD units to his T70 so he just has to flick a switch if/when one fails, and now that I have found many guys believe MSD is an acronym for My Spark Disappears, I tend to think it's the last thing I need in my car. I will give it one more try and if its still no good the whole lot is going to hit the rubbish bin!
Anyway race day Saturday was full of promise with great weather a 40 minute practice, 20 minutes qualifying, and a 15 lapper. So with the rebuilt uprights and other mods done overnight I was raring to go. About ten minutes into the practice, apart from the miss the car was feeling good, my clutch foot was behaving itself, and then suddenly I had a couple of spins. Suspecting a puncture I made my way back to the pits and noticed the water temp had climbed quite high, so I switched on the electric pump and it started to come back down.
Back in the pits a look over the car revealed a thrown waterpump/alternator belt and the pump pulley hard up against the bulkhead in fact it had formed a sizable indentation in the bulkhead panel. This had obviously caused the motor to rapidly overheat, overfilling the catch tank which then threw water over the right rear tyre causing the spins. I noticed too that the right rear wheel was also missing it's spinner!!!! Interesting times. The wheel had moved so that it almost cleared the pin drives then had locked itself up onto the centre locator. We couldn't budge it. (Still can't, time for a bigger hammer!) Between that and the waterpump, there was no way I was going to make the race. There was also a minor issue with the rear muffler mount, this had completely destroyed itself. Another item that needs beefing up.
I said somewhere way back in the build thread that I preferred to build things light and then strengthen any items that failed. It being much easier to do this than to subsequently try to lighten up a car that is built too heavy. So I willingly accept these small hiccups.
Although I only did half a dozen laps on race day, I was very pleased with the way the car is shaping up. It sits nicely and flows with the track, even though we haven't played with the suspension or brake settings yet. It's a bit twitchy down the main straight and into the left hander off it, but it's very controlable and I'm sure once I dial a bit of stability into it, it will be magic! Best lap this time out was 1:40. I can't wait to get rid of that bloody miss!
Some pics from the weekend. Last one is that pesky water catchtank. That will have to be relocated behind the rear wheel!
Dave, it's 12v the alt charges at just below 15v. Thanks for the thought though!
Kevin, I take your point but I have heaps of other things to fine tune too, like suspension, brakes, driver! So at this point track testing is my preferred option.
When I read on Ron's thread that he has fitted two MSD units to his T70 so he just has to flick a switch if/when one fails, and now that I have found many guys believe MSD is an acronym for My Spark Disappears, I tend to think it's the last thing I need in my car. I will give it one more try and if its still no good the whole lot is going to hit the rubbish bin!
Anyway race day Saturday was full of promise with great weather a 40 minute practice, 20 minutes qualifying, and a 15 lapper. So with the rebuilt uprights and other mods done overnight I was raring to go. About ten minutes into the practice, apart from the miss the car was feeling good, my clutch foot was behaving itself, and then suddenly I had a couple of spins. Suspecting a puncture I made my way back to the pits and noticed the water temp had climbed quite high, so I switched on the electric pump and it started to come back down.
Back in the pits a look over the car revealed a thrown waterpump/alternator belt and the pump pulley hard up against the bulkhead in fact it had formed a sizable indentation in the bulkhead panel. This had obviously caused the motor to rapidly overheat, overfilling the catch tank which then threw water over the right rear tyre causing the spins. I noticed too that the right rear wheel was also missing it's spinner!!!! Interesting times. The wheel had moved so that it almost cleared the pin drives then had locked itself up onto the centre locator. We couldn't budge it. (Still can't, time for a bigger hammer!) Between that and the waterpump, there was no way I was going to make the race. There was also a minor issue with the rear muffler mount, this had completely destroyed itself. Another item that needs beefing up.
I said somewhere way back in the build thread that I preferred to build things light and then strengthen any items that failed. It being much easier to do this than to subsequently try to lighten up a car that is built too heavy. So I willingly accept these small hiccups.
Although I only did half a dozen laps on race day, I was very pleased with the way the car is shaping up. It sits nicely and flows with the track, even though we haven't played with the suspension or brake settings yet. It's a bit twitchy down the main straight and into the left hander off it, but it's very controlable and I'm sure once I dial a bit of stability into it, it will be magic! Best lap this time out was 1:40. I can't wait to get rid of that bloody miss!
Some pics from the weekend. Last one is that pesky water catchtank. That will have to be relocated behind the rear wheel!
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It looks the Dogs Russ and I think you've done exactly the right thing, like we said earlier in the thread, if it won't break - it's too heavy and I always prefer to go that route than try to find a 1,000 places to lose an ounce and even if you do, they'll all be in the wrong place.
In my current drive (off road 4x4) I had an option to either increase power or lighten ship. I lightened ship by over 400 lbs and it is now a rocketship. Give me a light car and a 'screamer' anyday... over a barge with a barge engine... :laugh: (sorry Big Block guys)
Anyway, I used to really enjoy the 'fettling' and frankly sometimes preferred that over driving the damned scary thing. If that's all the fettling you need to do, you've done well. Hate MSD, Mallory and Accel and all those mass produced PITA's - always had problems with them - many are not fit for the (racing) purpose but are just lightweight street toys.
If you take them apart, the electronics are not even encapsulated.
Russ:
I wanted to share one thing. Double check your switches we have had new ignition switches that caused a miss in the ignition system. Also the main battery switch. I am sure you thought of this. Vibration is a major enemy of the msd boxes. All nascar cup cars have two boxes and the used parts joints around here are always chock a block with them so the teams must replace them very often.
I wanted to share one thing. Double check your switches we have had new ignition switches that caused a miss in the ignition system. Also the main battery switch. I am sure you thought of this. Vibration is a major enemy of the msd boxes. All nascar cup cars have two boxes and the used parts joints around here are always chock a block with them so the teams must replace them very often.
It will take only a few seconds of detonation to F*** the engine, best you get that misfire ironed out FIRST. Has or is it getting into a detonation state...stuffed if I know, but I would want to!
Leave the bloody catch tank where it is, consider it as an early warning to look at the temp gauge...... just after the horizon does a 360° panoramic for your viewing pleasure.
No worries Russ you'll work it out!
Some will laugh at my old school approach, but my plain old Mallory Dual Point with the lightweight spring point set works flawlessly. It didn't miss a beat on the Dyno pulls to well over 7K rpm and is inexpensive.
I know Andy's red car has gone thousands of miles with one without skipping a beat.
Plus if you want you can bypass the ballast resistor at the track for a really big spark, you just have to be willing to carry a spare set of points with you!
Some will laugh at my old school approach, but my plain old Mallory Dual Point with the lightweight spring point set works flawlessly. It didn't miss a beat on the Dyno pulls to well over 7K rpm and is inexpensive.
I know Andy's red car has gone thousands of miles with one without skipping a beat.
Plus if you want you can bypass the ballast resistor at the track for a really big spark, you just have to be willing to carry a spare set of points with you!
Russell
Car looking great - I think youre on the right track with the weight of things.
If you still have not sorted the ignitions issues pop me an email and I can lend you some gear indefinitely.
There is a basic Mallory twin point, and also a Mallory Unilite there if you want.
Since you are running dry sump you could also look at 302 distributor stuff (you dont need bigger oil pump drive ??)
I will be in Wellington next week so is no trouble to get it to you.
Let me know by friday
new email [email protected]
new cell +61 400 222 063
Car looking great - I think youre on the right track with the weight of things.
If you still have not sorted the ignitions issues pop me an email and I can lend you some gear indefinitely.
There is a basic Mallory twin point, and also a Mallory Unilite there if you want.
Since you are running dry sump you could also look at 302 distributor stuff (you dont need bigger oil pump drive ??)
I will be in Wellington next week so is no trouble to get it to you.
Let me know by friday
new email [email protected]
new cell +61 400 222 063
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Hi Russ,
if you are still having the probs with the MSD breaking down at 4500, I can report the following based on my experience with this box and matching Dizzy on several engines:
1. I have never had a 6AL, although they will start missing at about 4-5k if the battery is going flat.
2. They light a mixture as rich as 9 to 1 AFR no problem
3. The rev limiting circuitry is quite prone to interference, and will go ape-shit if you are using solid wire core plug leads instead of spiral wound leads. This shows up as a random breakdown in ignition
4. Rule out your tach adapter by disconnecting the tach terminal and running the car with a safe chip in the MSD to see if that is the prob.
5. Some MSD dizzys seem to have a mech advance mechanism that goes unstable at certain RPM, partic if the light springs are used (i.e. swings wildly between max advance and a highly retarded position - easy to see with a timing light). If you see a lot of spark scatter at the problem RPM with a timing light then you can pinpoint whether the dizzy is the culprit by locking out the mech advance in the dizzy (very straight forward on an MSD dizzy), setting ignition to your desired total timing (say 36 - but don't use full noise under 3k) and see if it runs better. My last few laps at Ruapuna shaking down a friends 351W Cobra project had exactly this problem - would not pull nicely above mid range because timing was going everywhere until we locked out the timing - he now uses an electronic timing box in conjunction with the 6AL.
You'll be down a bit on power with an AFR of 11 but at least you won't hurt anything while you're chasing the ignition issue. Once you have that nailed 12.5 to 12.8 is the kind of zone I aim for.
Good luck with the shakedown.
Cheers, Andrew Robertson, Wellington NZ
if you are still having the probs with the MSD breaking down at 4500, I can report the following based on my experience with this box and matching Dizzy on several engines:
1. I have never had a 6AL, although they will start missing at about 4-5k if the battery is going flat.
2. They light a mixture as rich as 9 to 1 AFR no problem
3. The rev limiting circuitry is quite prone to interference, and will go ape-shit if you are using solid wire core plug leads instead of spiral wound leads. This shows up as a random breakdown in ignition
4. Rule out your tach adapter by disconnecting the tach terminal and running the car with a safe chip in the MSD to see if that is the prob.
5. Some MSD dizzys seem to have a mech advance mechanism that goes unstable at certain RPM, partic if the light springs are used (i.e. swings wildly between max advance and a highly retarded position - easy to see with a timing light). If you see a lot of spark scatter at the problem RPM with a timing light then you can pinpoint whether the dizzy is the culprit by locking out the mech advance in the dizzy (very straight forward on an MSD dizzy), setting ignition to your desired total timing (say 36 - but don't use full noise under 3k) and see if it runs better. My last few laps at Ruapuna shaking down a friends 351W Cobra project had exactly this problem - would not pull nicely above mid range because timing was going everywhere until we locked out the timing - he now uses an electronic timing box in conjunction with the 6AL.
You'll be down a bit on power with an AFR of 11 but at least you won't hurt anything while you're chasing the ignition issue. Once you have that nailed 12.5 to 12.8 is the kind of zone I aim for.
Good luck with the shakedown.
Cheers, Andrew Robertson, Wellington NZ
Well then, if you really want to, come on up and check it out Jac Mac!!! :thumbsup: I will have a look at the plugs and see how much piston is on them, but I am only on the miss for maybe half a second before I grab the next gear.
Hurtful Jac, very, very hurtful!! :laugh: However I do realise that I don't monitor the monitors, sufficiently. So plan to mount big LED idiot lights on the dash for water temp & oil pressure.
Thanks for all the suggestions guys, I have taken it all on board and will try various things. I take the point about interference and will re-route the wires as well.
Thanks for the offer Kevin, if I've still got a problem next time out then the Crane stuff out of the TR7 will be fitted. Hope alls well with you. What's happened/happening with your car?
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