Pinking under load!

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clive
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Re: Pinking under load!

Post by clive »

You've got rain??? It's over six weeks since we've had any.
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Re: Pinking under load!

Post by CobStang »

As an aside those glass fuel filters are a known cause of many fires, they crack and leak fuel !!
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John H
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Re: Pinking under load!

Post by John H »

Yes I can imagine...I have placed mine on a foam bed and tied it down so it doesn't move....but I hear you!
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John H
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Re: Pinking under load!

Post by John H »

So latest on the pinking.......moved to 32 Deg BTDC at 3000 without vacuum. Pinking is improved but still there. On discussion with Roadcraft they normally feed vacuum with permanent supply off carb, where it was, and mentioned as Karl did above using weaker springs in the distributer mechanical advance..... So I will try - once the rain has stopped Clive, at 31 with and without vacuum if I can get it to 31. He is also saying that less than 34 is likely to reduce power.....so I get very confused!
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peterc
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Re: Pinking under load!

Post by peterc »

Surely weaker springs in the dizzy only lowers the revs at which you reach the max advance. This confirmed by Karl’s comment that his gets to max advance at 2700 rpm.
Getting to much advance too early will only encourage pinking. If Roadcraft think it should be 34degrees max advance and you have backed off to 30/31 then what else is causing the pinking?
Wrong jetting in the carb? Running too lean?
I know mine is Rover engine not a Ford but same principles apply. I don’t have the records but believe max advance was 32 at 3500. They advised that a vacuum advance was more for economy and not usually used on performance engines. None the less I kept it fitted but was advised to fit a control valve on the vac line. This slows the effect of the vacuum but is free flowing towards the dizzy thus allowing the advance to reduce easily when you throttle off. Basically dampening the effects of the vac advance to avoid dramatic changes in timing due to full throttle conditions.
This maybe unique to the Rover engine set up but if you are getting pinking under hard throttle then maybe the vacuum is advancing the ignition timing too quickly.
Having been on the rolling road the engine builder then advised the ignition setting needed at idle with the vac line blocked. 12 degrees compared to a standard Rover at 6.
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Re: Pinking under load!

Post by Karl »

John, I don?t know what carb you use. On a standard Holley there is a timed vacuum source to which the distributor needs to be connected. Also, if you have a vacuum operated second stage try with the weakest spring available (if I remember correct it is marked white). Also you need to check if your fuel pressure stays high enough. On a Holley you can also easily take off the fuel bowls and check the jets.
Difficult to check the opening of the second stage on the carb under load, I only could see it good on the rolling road when accelerating in fourth or fifth gear. Running the ehgine with no load will not open the second stage.
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peterc
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Re: Pinking under load!

Post by peterc »

Hi John,
Just another thought.
What fuel was the engine designed for. E.g. what is the compression ratio.
Over 10.5: 1 and you would probably need premium.
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clive
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Re: Pinking under load!

Post by clive »

John,

I know it is getting close to your Le Mans trip and you might be getting anxious about your engine issues. One person I can recommend to consult is Mike Stewart at Errol Airfield. He is highly regarded among the racing fraternity especially those using old school engines.

http://www.mikestewartperformanceengine ... dex_1.html
Cheers, Clive.

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John H
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Re: Pinking under load!

Post by John H »

Thanks guys of all the input. I have a few things to try this weekend. Clive thanks for the tip I will reach out to him next week if I can't sort this weekend.
Peter - yes I have premium 99 in the tank right now so should be good. Roadcraft did say just disconnect vacuum as for economy more than function!
Karl - I have asked the Roadcraft for the weaker springs.....

I will let you know...cheers John
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Re: Pinking under load!

Post by 289 Baz »

Timing depends on many things, as a base line, I run mine at 40 deg max advance on standard pump fuel, it only pink's when out acceleraing a Jag 'F' type up hill 4th gear from 1500 rpm at full throttle, I have Scat all steel bottom end, high silicon forged pistons high flow GT40 heads oh yes I also run weber carbs. Don't try this at home.
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