Holley 830dp woes
Thread Starter
Instructor
Joined: Sep 2007
Posts: 218
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From: Tonbridge, Kent
I was thinking whether I had a little bit of a blonde moment when I was trying to tune the carb the other day. When I set up the carb the before start up, I set all the idle mixture screws out 1.5 turns. When I started the car I said it was running at about 1400rpm. If this was running that lean with the additional holes in the butterflies, could I not of made it rich by just keep on screwing the idle mixture screws out until the revs dropped off again? What is the maximum turns you could screw them out without causing other problems.
Problem is I had an argument with a whinging neighbour crying about the noise of my Car, an not being able to read in peace. So I wasn’t thinking logically at the time.
Problem is I had an argument with a whinging neighbour crying about the noise of my Car, an not being able to read in peace. So I wasn’t thinking logically at the time.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
I was thinking whether I had a little bit of a blonde moment when I was trying to tune the carb the other day. When I set up the carb the before start up, I set all the idle mixture screws out 1.5 turns. When I started the car I said it was running at about 1400rpm. If this was running that lean with the additional holes in the butterflies, could I not of made it rich by just keep on screwing the idle mixture screws out until the revs dropped off again? What is the maximum turns you could screw them out without causing other problems.
Problem is I had an argument with a whinging neighbour crying about the noise of my Car, an not being able to read in peace. So I wasn’t thinking logically at the time.
Problem is I had an argument with a whinging neighbour crying about the noise of my Car, an not being able to read in peace. So I wasn’t thinking logically at the time.
Solder up the holes and reinstall it.....there is simply too much leak.
I also believe your vacuum at idle should be much higher than 7”. More like 11”. But if you can’t get the idle circuit correct due to there being holes in the plates then you will never see a correct reading.....
Jebby
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Instructor
Joined: Sep 2007
Posts: 218
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From: Tonbridge, Kent
Well soldered up the holes in the butterflies set the both pri and sec blades to show about 25 thou of the transfer slot and she fired up nicely with no problems except for a sticking TV Cable which has been I problem for a while. You can see it i in the video I’m trying to upload. Tv cable is adjusted correctly before you ask, it just needs a little coaxing to retract fully. A job for another day. Still need to do some more fine tuning. This video was taken about 1 minute after it fired up after I had adjusted the primary float level. Set the float levels before I fitted the bowls taking the center line of the float just a couple of millimetres below the sight window. Got the secondary bowl spot on but I was just too high on the primary’s. Fitted the 6.5hg PV’S back in waiting for a test drive once it stops raining.
Jebby by I can’t get the idle above 9hg unless it is idling above 1200rpm still at 7hg in drive, and 650rpm.
Jebby by I can’t get the idle above 9hg unless it is idling above 1200rpm still at 7hg in drive, and 650rpm.
Last edited by knodty; Apr 17, 2020 at 01:18 PM.
Race Director
Joined: May 2006
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Well soldered up the holes in the butterflies set the both pri and sec blades to show about 25 thou of the transfer slot and she fired up nicely with no problems except for a sticking TV Cable which has been I problem for a while. You can see it i in the video I’m trying to upload. Tv cable is adjusted correctly before you ask, it just needs a little coaxing to retract fully. A job for another day. Still need to do some more fine tuning. This video was taken about 1 minute after it fired up after I had adjusted the primary float level. Set the float levels before I fitted the bowls taking the center line of the float just a couple of millimetres below the sight window. Got the secondary bowl spot on but I was just too high on the primary’s. Fitted the 6.5hg PV’S back in waiting for a test drive once it stops raining.
Jebby by I can’t get the idle above 9hg unless it is idling above 1200rpm still at 7hg in drive, and 650rpm.
Jebby by I can’t get the idle above 9hg unless it is idling above 1200rpm still at 7hg in drive, and 650rpm.
Your description above makes no mention if you readjusted the mixture screws after setting the float levels?
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
I went through something similar with a proform 850 mech secondary last year.
Two things came up:
#1 Secondary rod linkage was bent ever so slightly that if you backed out the curb idle screw all the way, it would pull on the secondary from the see-saw motion. The car would not shut off because the secondarys were slightly cracked open.
#2 I failed to properly seat the gaskets at the idle mixture screws, causing a slight vacuum leak. Change those little donuts and seat them real good.
Two things came up:
#1 Secondary rod linkage was bent ever so slightly that if you backed out the curb idle screw all the way, it would pull on the secondary from the see-saw motion. The car would not shut off because the secondarys were slightly cracked open.
#2 I failed to properly seat the gaskets at the idle mixture screws, causing a slight vacuum leak. Change those little donuts and seat them real good.
Thread Starter
Instructor
Joined: Sep 2007
Posts: 218
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From: Tonbridge, Kent
Last edited by knodty; Apr 17, 2020 at 02:44 PM.
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Thread Starter
Instructor
Joined: Sep 2007
Posts: 218
Likes: 7
From: Tonbridge, Kent
Thread Starter
Instructor
Joined: Sep 2007
Posts: 218
Likes: 7
From: Tonbridge, Kent
Finally found my correct cam I fitted all those years ago. Not that it makes much difference to what diagnosis you all gave me.
Thanks
Peter
https://www.summitracing.com/parts/SUM-K1302#
Thanks
Peter
https://www.summitracing.com/parts/SUM-K1302#
Thread Starter
Instructor
Joined: Sep 2007
Posts: 218
Likes: 7
From: Tonbridge, Kent
It comes off the pcv valve and connects into a 4 way tee piece which connects to the manifold, brake servo, and the vacuum for the lights.
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Instructor
Joined: Sep 2007
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From: Tonbridge, Kent
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,095
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From: Marlton NJ
I'm with Jebby. The vacuum is to low. Check your gauge with another gauge to be sure. My cam is that same size as yours 228/238 @.050" and I have 15 inches at 850. You won't get that much vac 'cause I have a fast-ramp one , you don't. But it's still too low. Yes it should like around 16-18 initial, as long as you stay under 36.
What's the C.R.?
I see a vac can. Do you have it hooked up? It'll idle better. And give you more vac to boot. But you'll probably need an adjustable one and a vacuum advance limiter to like 10 degrees on that.
And there is no way you need the holes with that cam, mine doesn't.
The idle mixture screws should be able to give you both a lean roll-off and a rich roll-off. Best mixture and highest vac in the middle. If it doesn't do that I'm leaning toward an unidentified vac leak.
I just checked my Dyno run. It made 15.8" vac at 880 rpm. They had the advance "locked" at 35 even at idle with their distrib not mine. It liked it! I'll run the 18 initial plus 10 vac adv.
Yours sounds awesome BTW! (Mine had 6 foot tall dyno mufflers on it)
What's the C.R.?
I see a vac can. Do you have it hooked up? It'll idle better. And give you more vac to boot. But you'll probably need an adjustable one and a vacuum advance limiter to like 10 degrees on that.
And there is no way you need the holes with that cam, mine doesn't.
The idle mixture screws should be able to give you both a lean roll-off and a rich roll-off. Best mixture and highest vac in the middle. If it doesn't do that I'm leaning toward an unidentified vac leak.
I just checked my Dyno run. It made 15.8" vac at 880 rpm. They had the advance "locked" at 35 even at idle with their distrib not mine. It liked it! I'll run the 18 initial plus 10 vac adv.
Yours sounds awesome BTW! (Mine had 6 foot tall dyno mufflers on it)
Last edited by leigh1322; May 5, 2020 at 07:16 PM.
Thread Starter
Instructor
Joined: Sep 2007
Posts: 218
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From: Tonbridge, Kent
I'm with Jebby. The vacuum is to low. Check your gauge with another gauge to be sure. My cam is that same size as yours 228/238 @.050" and I have 15 inches at 850. You won't get that much vac 'cause I have a fast-ramp one , you don't. But it's still too low. Yes it should like around 16-18 initial, as long as you stay under 36.
What's the C.R.?
I see a vac can. Do you have it hooked up? It'll idle better. And give you more vac to boot. But you'll probably need an adjustable one and a vacuum advance limiter to like 10 degrees on that.
And there is no way you need the holes with that cam, mine doesn't.
The idle mixture screws should be able to give you both a lean roll-off and a rich roll-off. Best mixture and highest vac in the middle. If it doesn't do that I'm leaning toward an unidentified vac leak.
I just checked my Dyno run. It made 15.8" vac at 880 rpm. They had the advance "locked" at 35 even at idle with their distrib not mine. It liked it! I'll run the 18 initial plus 10 vac adv.
Yours sounds awesome BTW! (Mine had 6 foot tall dyno mufflers on it)
What's the C.R.?
I see a vac can. Do you have it hooked up? It'll idle better. And give you more vac to boot. But you'll probably need an adjustable one and a vacuum advance limiter to like 10 degrees on that.
And there is no way you need the holes with that cam, mine doesn't.
The idle mixture screws should be able to give you both a lean roll-off and a rich roll-off. Best mixture and highest vac in the middle. If it doesn't do that I'm leaning toward an unidentified vac leak.
I just checked my Dyno run. It made 15.8" vac at 880 rpm. They had the advance "locked" at 35 even at idle with their distrib not mine. It liked it! I'll run the 18 initial plus 10 vac adv.
Yours sounds awesome BTW! (Mine had 6 foot tall dyno mufflers on it)
I checked my mityvac pump with my 2no 6.5 HG Power valves. And they opened dead on 6.5hg so I think it is reading OK. I will check the vacuum just at the manifold to see if I get any different readings there? My 74 has a vacuum tank built into the front of the car. I will check if that is leaking also. Think this was only fitted to 74’s, I think.
CR is about 10-1, with flat top pistons.
Last edited by knodty; May 6, 2020 at 06:22 AM.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,095
Likes: 4,449
From: Marlton NJ
Good move replacing the 6.5" power valves for now then. The tuning recommendation has always been unless your idle vac is at least 2.0" above that, they may not seat fully, and could dribble fuel, creating a rich condition. They feed the main booster though so I'm not sure if it would affect the idle or not?
That is a pretty healthy cam. But it is not a race cam. It is almost a hydraulic clone of the L72/L78/LS6 mechanical lifter SHP street cam.Maybe even a touch milder. Those engines do not make vacuum that low. It's got a wide adv duration but still milder than the L72. It's got slow ramps but no more than those other cams, and that's good for longevity anyway. The LC is wide at 114. I just don't get the vac that low. I suspect a big vac leak. Either hose connections, intake manifold, or carb base plate. Unplug vac connections and retest vac. Spray propane (unlit) around carb base & intake gasket etc. Does it burn oil?
Could be internal side of intake gasket. Were heads milled? etc.
It'll turn up. 7.0" vac just sounds too low. That will give a real poor signal to the carb.
What else could it be?
What kind of rich idle symptoms are you noticing?
That is a pretty healthy cam. But it is not a race cam. It is almost a hydraulic clone of the L72/L78/LS6 mechanical lifter SHP street cam.Maybe even a touch milder. Those engines do not make vacuum that low. It's got a wide adv duration but still milder than the L72. It's got slow ramps but no more than those other cams, and that's good for longevity anyway. The LC is wide at 114. I just don't get the vac that low. I suspect a big vac leak. Either hose connections, intake manifold, or carb base plate. Unplug vac connections and retest vac. Spray propane (unlit) around carb base & intake gasket etc. Does it burn oil?
Could be internal side of intake gasket. Were heads milled? etc.
It'll turn up. 7.0" vac just sounds too low. That will give a real poor signal to the carb.
What else could it be?
What kind of rich idle symptoms are you noticing?
Last edited by leigh1322; May 6, 2020 at 07:56 AM.
Thread Starter
Instructor
Joined: Sep 2007
Posts: 218
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From: Tonbridge, Kent
Good move replacing the 6.5" power valves for now then. The tuning recommendation has always been unless your idle vac is at least 2.0" above that, they may not seat fully, and could dribble fuel, creating a rich condition. They feed the main booster though so I'm not sure if it would affect the idle or not?
That is a pretty healthy cam. But it is not a race cam. It is almost a hydraulic clone of the L72/L78/LS6 mechanical lifter SHP street cam.Maybe even a touch milder. Those engines do not make vacuum that low. It's got a wide adv duration but still milder than the L72. It's got slow ramps but no more than those other cams, and that's good for longevity anyway. The LC is wide at 114. I just don't get the vac that low. I suspect a big vac leak. Either hose connections, intake manifold, or carb base plate. Unplug vac connections and retest vac. Spray propane (unlit) around carb base & intake gasket etc. Does it burn oil?
Could be internal side of intake gasket. Were heads milled? etc.
It'll turn up. 7.0" vac just sounds too low. That will give a real poor signal to the carb.
What else could it be?
What kind of rich idle symptoms are you noticing?
That is a pretty healthy cam. But it is not a race cam. It is almost a hydraulic clone of the L72/L78/LS6 mechanical lifter SHP street cam.Maybe even a touch milder. Those engines do not make vacuum that low. It's got a wide adv duration but still milder than the L72. It's got slow ramps but no more than those other cams, and that's good for longevity anyway. The LC is wide at 114. I just don't get the vac that low. I suspect a big vac leak. Either hose connections, intake manifold, or carb base plate. Unplug vac connections and retest vac. Spray propane (unlit) around carb base & intake gasket etc. Does it burn oil?
Could be internal side of intake gasket. Were heads milled? etc.
It'll turn up. 7.0" vac just sounds too low. That will give a real poor signal to the carb.
What else could it be?
What kind of rich idle symptoms are you noticing?
Last edited by knodty; May 6, 2020 at 12:33 PM.
Thread Starter
Instructor
Joined: Sep 2007
Posts: 218
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From: Tonbridge, Kent
I have it on the compression stroke as I have some white tipex in two places on the balancer, but can’t remember what degs I marked them on. 😂 doh. It was a few years ago.
Last edited by knodty; May 7, 2020 at 06:40 PM.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,095
Likes: 4,449
From: Marlton NJ
Well you could use something as simple as a straw the touches the piston & cyl wall corner. Sharpie mark. Same distance down before tdc and after tdc. TDC is exactly in the middle. That should be enough to let you decide between two white marks.
What was my name again?? LOL
What was my name again?? LOL