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Tuning difficulties

Hi all

I'm having some trouble tuning my 202.
I've been playing with the Carby tuning a fair bit trying to get it right but just can't seem to get it right. I pull the plugs out after every few drives up the street to see how they are, and they are getting carboned up realy quickly. I pulled them out today and they were black as black can be. Not wet just black.

Thie to me meant it is runnibg rich but I have the idle mixture screws on the 350 Holley set at 2 turns out from all the way in. I don't know if that is about normal or what? When I drive it down low it's realy realy bogged down. Doesn't want to rev unless you give it a fair bit and then it revs up realy slowly until about 4000 and then revs realy cleanly. Could this mean it's fueling up? Someone suggested it had a clogged filter so I ran it without the filter today and same thing.

It hasn't been driven on any decent drives being unregistered so it could be fueling up but when I take it for laps up the street it's fine when I'm driving but when I turning around and going between 1st and reverse its really bogged down again. I try give it some big revs to clear any excess fuel out but still the same.

Is this just what big canned engines are like? Or is my tuning out like I think?

Any help/advice would be greatly appreciated.

Also I'm still leaking oil out of the rocker cover gasket. Not a huge amount but enough. I replaced the gasket because I thought it might have been damaged from being removed numerous times due to rocker problems but still leaking. I havnt tightened the nuts up to tight because it's a
Cork gasket.

Cheers
James

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Hi again James,

A few things to check...

1.) Ignition timing is spot on and you're getting a strong spark?

2.) How have you tuned it? By just accepting 2 turns out on the mixture screw or by adjusting it depending on what the engine is telling you?

3.) Have you got a manual or auto choke? Is it connected correctly and working as it should? Is it off once warmed up?

That's a bit to start with...

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Cheers,

Emu

O.H.T.C. original member

Hi Emu,

Yea seems fine to me

No I have adjusted te Carby a few times, this is the leanest I've had or because i don't know how lean you can go before doing any damage and 2 turns out seems like I shouldn't go any further (to me but this is just me being paranoid, am I able to go in further without doing damage?)

Choke is a manual choke, it's hooked up but I don't use it. Don't have a need to.

Cheers
James

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Have you been using a vacuum gauge to tune your rig?

Other wise your just guessing

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i suggest for the millionth time that you spend a copuple of hundred dollars on a dyno tune. the longer this thing runs poorly the worse the engine will be for it - rich mixtures wash oil from the bores to name but one example.

assuming the timing is close enough, you may need to change your power valve rating and the main jets may also be wrong. you really need someone experienced to look at this stuff for you, but if you insist on having a go, here is a starting point:

with a big cam, the vacuum can be so low and the throttles opened so much at idle that the standard rating power valve can actually be in operation which of course is going to give you no end of fouled plugs. idle screws may not respond if the throttles are open too far and definitely wont affect anything if the power valve is opening!!

hook up a vacuum gauge, check your vacuum at idle in neutral, again in drive. a rule of thumb for power valve selection is to halve your vacuum reading IN DRIVE...
if it has for example 15in/hg in neutral, but drops to 10 in drive, then a starting point would be a 55 power valve.

for main jets you need to start at holleys box settings, for that look up your list number and google holleys site, they have a list of standard jets, power valves, shooter sizes for most of their carbys. from there you may need to test drive to find the best size for your engine combo.

but again, i strongly suggest a dyno tune by an experienced operator.

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Thanks Ben, I know it looks as though I'm not listening to you when you say to get a dyno tune but I honestly just can't afford it at te moment. As soon as I can afford it I want to get one.

I'll continue to keep at it on my own folloqing your advise and let you know how I go.

Really appreciate you time and help.

Cheers
James

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do you have a timing light?dont use the factory timing setting at all if you have a big cam,advance it some more and see if it runs any better,the float is set correctly?

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WHAT? no gravy?

Float was set correctly when we first got it running. I'll check that Tomorow aswell, it's a pain to check because the Carby sits right above the exhaust and I don't want to leak fuel onto a hot exhaust and putting a rag there when it's running melts the rag to the exhaust. Lol

Will give it a go and report back Tomorow :)

If not something simple like float or timing will look at power valve and jet sizes.

Cheers
James

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But I would encourage you to try less, at the very least it will be a learning opportunity. I have twin strombergs on the EH. When I starting trying to figure the right balance. I started with 2 turns, very smokey, rough idling etc. i am now settled on 1 1/4 turns each carb, with some fine tuning needed.

For my setup, 2 turns is far too much. welcome similar thoughts from all

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With an engine modified from original, I've always tuned by ear and usually after a few laps around the block armed with a flathead screw driver and a 9/16" spanner a very good tune is found.

Ben is spot on though....to get it done perfectly you need the sucker dyno tuned by an expert who knows Holley carbs.

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Cheers,

Emu

O.H.T.C. original member

Have you tried adjusting your idle screws while it is idling, or are you just setting them while the car is off.

As Ben has said above, your power valve is probably not right and possibly your jets.

I can sympathise with your financial position, not being able to spend on a dyno, I've been there plenty of times in my younger days, but one thing I found very helpfull in those situations was books.

When I was playing with Holley's, I went and bought a Holley book, I know, your thinking more money, but it's heaps cheaper than a dyno and gives you a much better understanding of how the carby works and how to select the right power valves, jets etc.

One other tip, I can't remember if this applies to Holley's, but I seem to recall some of the later model carby's being set up opposite to the earlier one's.

So, instead of the mixture screws all the way in being the leanest setting, on the later one's all the way in is the richest setting.

The best way to try and set your mixture screws is with the engine idling, and wind them in and out to the sweet spot by ear, or better still, by vacuum guage.

If you can't get it right like this, or it doesn't make much difference, then your power valve is not right or faulty and maybe the jet size.

You should be able to get the car to stall, or nearly stall when you go lean with the mixture screws, if it's not doing this then it doesn't matter if you lean them out totally, it still running too rich.

Also, the idle mixture screws are just that, fuel setting at idle. They don't affect your car when under throttle.

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Cheers mate,

It's idling perfectly, sits at 600 once warmed up and doesn't stall.

I will try advancing the timing a bit more and see how I go with that. Pretty sure it's for around 8 degrees at idle. If that doesn't work I'll look into the power valve and key sizes like said by you and Ben. Will try timing first but just incase it's something very simple like that.

Cheers
James

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A wise man told me when i had this same problem years ago "holleys are simple carbs, designed for wide open throttle settings. Very hard for them to respond to airflow fluctuations of hot six below 1500 rpm"
the stromberg or weber give a much better low end running engine.

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I just had 'issues' with my new 202. The cork gaskets don't like being over used... on and off too much. Mine split real quick, and thats doing up the bolts by hand. One thing I did notice was the flat section the bolts go through were not flat. I had to use a hammer and dolly to get them all straight and flat... also had to do it with the sump. Check yours with a straight edge, it'll sit much better on the gasket.

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They don't make em like they used too!

You need to contact nobody123. He sorted mine out over the phone.

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use pure cotton rag not polyester/mix,it wont melt.

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WHAT? no gravy?

Try with the mixture screws a bit further in - they only control idle and slightly above, so it won't hurt your motor. i've always found between 1 - 1 .5 turns to be the optimal range. The power valve may be the problem, but if you want to check whether or not you have a suitable power valve, you'll need a vacuum gauge. Try the mixture screws first. Set them both at 1.5 turns, and have a play with them, while it's running, ensuring both screws are moved the same amount with each adjustment. By the way, have you checked the float level? If not , that may be the problem. Also, if it's not a new carby, the diaphragm in the power valve may be perforated - that will result in the symptoms you describe. It's pointless spending money on a dyno tune if you don't have the basics sorted!

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Will try those mate.
Thanks for the help.

Yea it's a brand new Carby

Cheers
James

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i think?when you think?its bogging down and needs a big rev to clear it out its going lean not rich?

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WHAT? no gravy?

Nah, the opposite.

Bogging down is different to a lean hesitation. The hesitation you get with a shot power valve is different to the bogging down due to overfuelling.

To diagnose...if overfuelling, you should get stumbling, rough and terrible acceleration and black sh!t out the zorst.....where as if you have a lean hesitation generally you'll get a shorter stumble, maybe some pinging etc. Can diagnose with the engine off, and give the throttle a stab whilst looking down the carby. Should see a smooth stream of fuel. (won't work if bowl is empty to make sure engine has run before doing it).

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Cheers,

Emu

O.H.T.C. original member

Thanks for all the help guys, I can't realy diagnose it at the moment because the car is up in stands at the moment while I'm doing some work on the front springs.
Will update everyone once I get it down and have a fiddle. Hopefully this weekend.

Cheers
James

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