Warts and all GT40 Australia #48

Peter Delaney

GT40s Supporter
Hi Pete, nice bit of detective work !

The 8-Stack looks the part, & (IMHO) goes better than most other setups - BUT - synchronising the butterflies seems to be the price we pay. Perfect one month, crappy the next (for no apparent reason) !!

I had/have similar problems & settled on getting my Autronic tuning expert to check/adjust this every couple of months. I have watched him do it a couple of times, so I will be buying one of those "tennis-ball" vacuum gauges that plop into the trumpets & will have a go at doing it myself.

The problem only seems to show up at small throttle openings - after thinking about this, it figures - tiny variations between stacks equate to significant % differences at closed/near-closed throttle, but at WOT, the differences are almost irrelevant.

Kind Regards,

Peter D.
 

Pete McCluskey.

Lifetime Supporter
Hi Peter, how have you been keeping? Tennis ball vacuum gauges? I'm not sure what you mean. But sounds something like we used to balance S.U. Carby's.
 

Peter Delaney

GT40s Supporter
Hi Pete - I'm doing ok - I have retired !!!! (Should have done it ages ago) ! With the markets going as they are, GT40 bits to be sorted out, seriously getting into the Vette rebuild, model yachts, travel planning with Karen, etc, I have no idea how I had any time for work !!

The "tennis-ball vacuum gauges" I referred to are spherical & about the size of of a tennis ball (surprise). They have a conical rubber sealing ring at the bottom so that they will fit & seal into almost any size trumpet, etc, and supposedly offer very little resistance to air flow. The vacuum pressure is simply read off a scale on a rotating drum inside the clear plastic casing of the unit.

Whether they give a really accurate reading of the vacuum is probably not all that important - the beauty of the approach is that you can very quickly swap them from one trumpet to the other - just drop it on. Any air flow resistance is probably irrelevant as you are introducing the same resistance to each trumpet being measured - as long as they all give the same reading, all is synchronised.

My tuning guru does a full synchro adjustment at idle (800 rpm), then puts a shim under each idle stop-screw to lift revs to about 1500rpm, adjusts again, then goes back to idle & does it again. After that exercise, all spits & coughs are gone. With a bit of practice, it all takes about 15-20 mins - but needs to be done every couple of months.

If you are interested, I can find out the brand name/model of the "tennis-ball" gauge & let you know (I need to buy one anyway).

All the best to you & Di

Kind Regards,

Peter D.
 

Pete McCluskey.

Lifetime Supporter
Retired Bewdy,:pepper: sounds like you have plenty to keep you busy. I have been toying with the idea myself, but wonder what I would do to occupy my time. Not only that, Di gets sick of me over a weekend.:eek: Maybe I will ask David Morton if I can be his assistant and follow F1.

The gauge sounds like a great idea, I would appreciate the brand and where I can purchase one. Much simpler and less expensive than the Dyno.
I agree that as long as the restriction to airflow is constant it should not matter, given you are not altering the fuel/air map.
 

Peter Delaney

GT40s Supporter
Hi Pete - I am sorry that I can't provide the details of the "tennis ball" vacuum gauge - apparently, my tuning guru borrowed it from a mate for a while, then gave it back. However, he reckons that we could track one down through a company called "Recarb" - I'll let you know if I have any success.

BTW : The last time he did a synchonisation on my car, he just used a 2' length of rubber tubing - one end in his ear, the other stuck down each trumpet & resting on the butterfly spindle. When I tried it, I could just pick out the difference between 2 mismatched throttles (but probably only because I was told there was a difference) - I think that you need years of experience to do it this way, so I'll try to find the gauges instead !

Kind Regards,

Peter D.
 
Retired Bewdy,:pepper: sounds like you have plenty to keep you busy. I have been toying with the idea myself, but wonder what I would do to occupy my time. Not only that, Di gets sick of me over a weekend.:eek: Maybe I will ask David Morton if I can be his assistant and follow F1.

The gauge sounds like a great idea, I would appreciate the brand and where I can purchase one. Much simpler and less expensive than the Dyno.
I agree that as long as the restriction to airflow is constant it should not matter, given you are not altering the fuel/air map.
Hi Pete,

Most weber agents stock these syncrometers. You can also find them on ebay. Price varies but usually around 25 to 30 USD.
 

Peter Delaney

GT40s Supporter
Pete, that's the one that I also found last night !! It looks just like the one I saw, so I'll give them a call & let you know the story / prices.

Kind Regards,

Peter D.
 

Pete McCluskey.

Lifetime Supporter
Hi Peter, there are two types shown, the BK and the SK. Which one looks most like the one your mechanic was using?
It looks like they use the BK on Ford engines.
 

Peter Delaney

GT40s Supporter
Pete - I spoke to Nardeck & it seems that the SK is the one for us - it has twice the resolution of the BK at the low end. The BK is fine for single or dual throats (large air flow), but with 8 throats, the SK is recommended.

BUT - Nardeck only has one BK & no SK's in stock - they have had SK's on back order for over 6 months & haven't heard a word from Webber !!!

The one remaining BK is available at cost (about $80), & the normal price for an SK is around $140.

However, there is an SK in the UK on EBay :

eBay Australia: Carburettor balancing synchrometer Weber, Dellorto SU (item 300132548195, end time 26-Jul-07 04:45:00 AEST)

Bidding is at about $60 - if you want it, go for it (I'll wait & keep trying).

Kind Regards,

Peter D.
 

Peter Delaney

GT40s Supporter
Pete - I spoke to Nardeck & they only have one BK in stock & no SK's. Unfortunately, the SK looks like the one we want - it has twice the resolution of the BK at the low end. The BK is used for 1 or 2 throats (high air flow), so with 8 throats, the SK was recommended.

BUT - Nardeck have had SK's on back-order for 6 months, & have heard nothing from Weber (not very hopeful of further supplies).

The remaining BK is on sale at cost price - under &80. The normal price for an SK is around $140.

However, there is an SK on EBay in the UK :

eBay Australia: Carburettor balancing synchrometer Weber, Dellorto SU (item 300132548195, end time 26-Jul-07 04:45:00 AEST)

Bidding is at about $60, so if you want it, go for it (I'll wait & keep looking).

Kind Regards

Peter D.
 

Peter Delaney

GT40s Supporter
Don't know what happened there - 1st post got the Page Not Found, so I retyped it & submitted again - then both of them turned up - the wonders of modern technology !!!

Kind Regards,

Peter D.
 

Pete McCluskey.

Lifetime Supporter
Thanks Peter, I dont buy stuff from Ebay any more I have been ripped off to many times, so if you want it go for it.
Thanks for your help.
 

Peter Delaney

GT40s Supporter
Thanks Pete, but I am also a bit wary of EBay purchases from O/S, so I'll keep looking for a source here in Oz.

Kind Regards,

Peter D.
 

Pete McCluskey.

Lifetime Supporter
12,500 klms covered now and all of them fun. I am always surprised by the knowledge a lot of people have about the GT40. I wonder if that is something to do with the release of the Ford GT which relied a lot on the history of the Marque for promotion.
I seem to be a magnet for the police, but they have always been very nice (touch-wood) and seem genuinely interested in the car and it's history.
There is a police station only a couple of klms from where I live so I am always very quiet and circumspect around the area.
The only worry I have had is people trying to take pictures on their mobile phones while driving next to me. They always seem to wander into my lane.:mad:
 

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Dimi Terleckyj

Lifetime Supporter
Hi Pete
I have to admit also that in the short time I have been on the road with mine I have had the same problem with other drivers and their mobile phones but I have found that a quick burst on the throttle gets me out of their way pretty quickly.
Self preservation kicks in.
Dimi
 

Peter Delaney

GT40s Supporter
Yep, defensive driving is the order of the day with these cars !! When driving ordinary cars, I assume that everyone else on the road is an idiot, but in the '40, I assume that they are blind idiots !!

When on the open road, brakes or throttle will shake off the rubber-neckers, but in heavy traffic, I keep some fingers near the horn button - triple air-horns get their attention rather quickly !!

Kind Regards,

Peter D.
 

Trevor Booth

Lifetime Supporter
Peter D,
If your throttle bodies are made correctly they will have a WOT stop. With the throttle bodies off the engine check that they are at 90º on the WOT stops. When I say 90º I mean just that -- not + or -.
With the throttle bodies on the car hold them against the WOT stops and tighten linkages etc. If everything is "correct" and you have eight cylinders all the same it should not need adjustment. But if you do the 20mm ID hose is better than the device you are speaking of. It does not take years of experience to match the sound and there is a device for replacing the human ear which is VERY accurate.
Also the hose pipe should not be poked down the throttle bore until it touches the butterfly, the hose pipe itself is then a restriction. Just think about the accuracy of placing it in exactly the same place each time. It should be held at the rim of the mouth of the trumpet and at or near 90º to the throttle bore.

Also check that each butterfly is the same in its degrees of opening ie 82º. It would not be the first time that different butterflies have been installed.

The ultra good systems have a manometer port below the throttle butterfly and the TB system runs a 100% closing 78º butterfly
 
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