Changing Holley, canīt tune it.
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From: Odder Jylland
Changing Holley, canīt tune it.
350.
Bigger Cam
Torker II manifold.
High compression.
So first I changed the distrubitor with HEI.
Endplay: 0.012
Total timing: 36° at 2800 Rpm
Base timing: 17
The old carb ran very well with this.
So now to the problems with the new Holley 670 Street Avenger..
First I changede the power valve, and the jet size acording to Lars´s advise.
Bench set the idle.
Set the float level.
Hooked up so I could read the vacuum, so I could adjust the mixture screws. But I only get around 7 In.Hg?!?!?
When I try to adjust the mixture srews there are none vacuum or Rpm change. It just dies when the mixture screws are to far in.
Everything is pluged, exept the vacuum canister.
Don´t know what vacuum reading I had before changing the carb.
Any advise?
Read all paper about tuning and timing, so I was ready to do this tuning myself. Have prepared it for about 3 months. Know I cant get anyting to work.....
350.
Bigger Cam
Torker II manifold.
High compression.
Holle 670 Street Avenger.
Wisp
Bigger Cam
Torker II manifold.
High compression.
So first I changed the distrubitor with HEI.
Endplay: 0.012
Total timing: 36° at 2800 Rpm
Base timing: 17
The old carb ran very well with this.
So now to the problems with the new Holley 670 Street Avenger..
First I changede the power valve, and the jet size acording to Lars´s advise.
Bench set the idle.
Set the float level.
Hooked up so I could read the vacuum, so I could adjust the mixture screws. But I only get around 7 In.Hg?!?!?
When I try to adjust the mixture srews there are none vacuum or Rpm change. It just dies when the mixture screws are to far in.
Everything is pluged, exept the vacuum canister.
Don´t know what vacuum reading I had before changing the carb.
Any advise?
Read all paper about tuning and timing, so I was ready to do this tuning myself. Have prepared it for about 3 months. Know I cant get anyting to work.....
350.
Bigger Cam
Torker II manifold.
High compression.
Holle 670 Street Avenger.
Wisp
Last edited by Wisp; Apr 4, 2007 at 02:32 AM.
Pro
Joined: Mar 2002
Posts: 511
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From: St. Louis MO
how big is a bigger cam. You may need more intial advance to get the vacuum signal up. However then starting may become an issue. There's a lot of trade offs with bigger and bigger cams that create less and less vacuum.
I switched to a bigger cam over the winter as well. If it wasn't for the Megasquirt computer controlling my timing only, I'd never get this thing to idel and start at the same time. I'm running 24 deg at 800 rpms in gear with 3inhg vacuum. But to start it I have a 400 rpm cell in my computer which is set at a starter freindly 13 degrees adv. Its basically acting like a start retard box.
I switched to a bigger cam over the winter as well. If it wasn't for the Megasquirt computer controlling my timing only, I'd never get this thing to idel and start at the same time. I'm running 24 deg at 800 rpms in gear with 3inhg vacuum. But to start it I have a 400 rpm cell in my computer which is set at a starter freindly 13 degrees adv. Its basically acting like a start retard box.
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From: Odder Jylland
Have no idea want kind of cam I have installed. And Iīm sick of it.... Bought the car a year ago, from a guy in the US.... In the papers it just say "Satuday Night Special Cam".... And thatīs it.
But If I cant find more vacuum, then I really need a Vacuum canister thats pullingin the mid 5 In. Hg area? Or?
Wisp
But If I cant find more vacuum, then I really need a Vacuum canister thats pullingin the mid 5 In. Hg area? Or?
Wisp
how big is a bigger cam. You may need more intial advance to get the vacuum signal up. However then starting may become an issue. There's a lot of trade offs with bigger and bigger cams that create less and less vacuum.
I switched to a bigger cam over the winter as well. If it wasn't for the Megasquirt computer controlling my timing only, I'd never get this thing to idel and start at the same time. I'm running 24 deg at 800 rpms in gear with 3inhg vacuum. But to start it I have a 400 rpm cell in my computer which is set at a starter freindly 13 degrees adv. Its basically acting like a start retard box.
I switched to a bigger cam over the winter as well. If it wasn't for the Megasquirt computer controlling my timing only, I'd never get this thing to idel and start at the same time. I'm running 24 deg at 800 rpms in gear with 3inhg vacuum. But to start it I have a 400 rpm cell in my computer which is set at a starter freindly 13 degrees adv. Its basically acting like a start retard box.
Thread Starter
Instructor
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From: Odder Jylland
Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
Are you using manifold or ported vacuum?
I've got a big cam and tried Lars method. I could not get a stable enough idle to get the idle screws to work.
I changed to ported (no vacuum to the distributor at idle) and it settled down the idle enough to get it idling nicely at 600rpm with only abot 7" of vacuum.
I've got a big cam and tried Lars method. I could not get a stable enough idle to get the idle screws to work.
I changed to ported (no vacuum to the distributor at idle) and it settled down the idle enough to get it idling nicely at 600rpm with only abot 7" of vacuum.
Thread Starter
Instructor
Joined: Aug 2006
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From: Odder Jylland
Hey...
I have only tried ported vacuum becourse I wanted a smooth idle. Have thought of trying ported vacuum instead. I will try tonight...
How did you set you mixture screws? I have read that when you have the highest vacuum reading you mixture screws a set correct. But I cant see any diffrence in the vacuum reading...
I have only tried ported vacuum becourse I wanted a smooth idle. Have thought of trying ported vacuum instead. I will try tonight...
How did you set you mixture screws? I have read that when you have the highest vacuum reading you mixture screws a set correct. But I cant see any diffrence in the vacuum reading...
Are you using manifold or ported vacuum?
I've got a big cam and tried Lars method. I could not get a stable enough idle to get the idle screws to work.
I changed to ported (no vacuum to the distributor at idle) and it settled down the idle enough to get it idling nicely at 600rpm with only abot 7" of vacuum.
I've got a big cam and tried Lars method. I could not get a stable enough idle to get the idle screws to work.
I changed to ported (no vacuum to the distributor at idle) and it settled down the idle enough to get it idling nicely at 600rpm with only abot 7" of vacuum.
Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
So which is the vacuum advance connected to now, ported (carb) or manifold (manifold)?
With light springs and a faster advance, the manifold vacuum would not stabilize. It started pulling the vacuum advance in too early and would not stabilize.
Going to the ported (carb, no vacuum at idle) the idle would settle down and I was able to tune to most vacuum at about 600rpm.
With light springs and a faster advance, the manifold vacuum would not stabilize. It started pulling the vacuum advance in too early and would not stabilize.
Going to the ported (carb, no vacuum at idle) the idle would settle down and I was able to tune to most vacuum at about 600rpm.
Hey...
I have only tried ported vacuum becourse I wanted a smooth idle. Have thought of trying ported vacuum instead. I will try tonight...
How did you set you mixture screws? I have read that when you have the highest vacuum reading you mixture screws a set correct. But I cant see any diffrence in the vacuum reading...
I have only tried ported vacuum becourse I wanted a smooth idle. Have thought of trying ported vacuum instead. I will try tonight...
How did you set you mixture screws? I have read that when you have the highest vacuum reading you mixture screws a set correct. But I cant see any diffrence in the vacuum reading...
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Thread Starter
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Joined: Aug 2006
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From: Odder Jylland
Sorry for the mixup.....
Itīs connected to FULL MANIFOLD VACUUM.
Right now I have trouble with the vacuum canister not working in the 7 In.Hg area.....
So If I connect it to ported vacuum, the vacuum canister will only come into play under light load. So I just have to hope the idle wont be to rough with ported vacuum....
But I was hoping that I could bring my vacuum up instead..
Wisp
Itīs connected to FULL MANIFOLD VACUUM.
Right now I have trouble with the vacuum canister not working in the 7 In.Hg area.....
So If I connect it to ported vacuum, the vacuum canister will only come into play under light load. So I just have to hope the idle wont be to rough with ported vacuum....
But I was hoping that I could bring my vacuum up instead..
Wisp
So which is the vacuum advance connected to now, ported (carb) or manifold (manifold)?
With light springs and a faster advance, the manifold vacuum would not stabilize. It started pulling the vacuum advance in too early and would not stabilize.
Going to the ported (carb, no vacuum at idle) the idle would settle down and I was able to tune to most vacuum at about 600rpm.
With light springs and a faster advance, the manifold vacuum would not stabilize. It started pulling the vacuum advance in too early and would not stabilize.
Going to the ported (carb, no vacuum at idle) the idle would settle down and I was able to tune to most vacuum at about 600rpm.
Melting Slicks
Joined: Aug 2003
Posts: 2,135
Likes: 2
From: Dayton Oh
Here's my setup on my 355.
First I've verified my timing is correct. I'm 36* all in at 2500RPM. Hooked to manifold vacuum, I'm at 18* at 850RPM idle.
Recently I installed full length headers, true duals with an x-pipe. So I rejetted my 670 SA. Primaries are now 68's instead of the original 65's.
Resetting the idle was not scientific but worked out OK. I ran the idle screws all in (clockwise) and then back out 1 1/2 turns as a starting point. The engine ran like crap. I then adjusted the idle speed screw until I achieved @900 RPM. I couldn't get a lower idle.
I then started turning BOTH idle mixtures screws 1/4 out (counter clockwise) listening to the engine increasing RPM and idle smoothing out. For each 1/4 turn of BOTH screws, I kept reseting the idle as close to 850RPM as I could get.
Eventually, I achived a very smooth idle at 850RPM. This is where I stopped, popped a top and called it a day.
First I've verified my timing is correct. I'm 36* all in at 2500RPM. Hooked to manifold vacuum, I'm at 18* at 850RPM idle.
Recently I installed full length headers, true duals with an x-pipe. So I rejetted my 670 SA. Primaries are now 68's instead of the original 65's.
Resetting the idle was not scientific but worked out OK. I ran the idle screws all in (clockwise) and then back out 1 1/2 turns as a starting point. The engine ran like crap. I then adjusted the idle speed screw until I achieved @900 RPM. I couldn't get a lower idle.
I then started turning BOTH idle mixtures screws 1/4 out (counter clockwise) listening to the engine increasing RPM and idle smoothing out. For each 1/4 turn of BOTH screws, I kept reseting the idle as close to 850RPM as I could get.
Eventually, I achived a very smooth idle at 850RPM. This is where I stopped, popped a top and called it a day.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Is the initial timing the reading you are getting with the vacuum advance removed (no vacuum to the distributor)? If you did not remove the vacuum advance, reset your timing. Also check for vacuum leaks in the carb.
For your vacuum to be that low at idle with no problems, your cam would have to be running around 240 degrees duration with an LSA or around 108 degrees. I'm assuming that high compression means around 10:1.
For your vacuum to be that low at idle with no problems, your cam would have to be running around 240 degrees duration with an LSA or around 108 degrees. I'm assuming that high compression means around 10:1.
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From: Odder Jylland
Hello again....
The timing is set with the vacuum canister plugged.
This is what i´m running:
http://store.summitracing.com/partde...1&autoview=sku
Dont know anything about cams...
I just cant get the mixture screws to have any effect compared to vacuum or RPM. I don´t se or hear any difference when I turn the mixture screws
Thought of a vacuum leak, but everything is plugged, exept the vacuum canister...
Wisp
The timing is set with the vacuum canister plugged.
This is what i´m running:
http://store.summitracing.com/partde...1&autoview=sku
Dont know anything about cams...
I just cant get the mixture screws to have any effect compared to vacuum or RPM. I don´t se or hear any difference when I turn the mixture screws
Thought of a vacuum leak, but everything is plugged, exept the vacuum canister...
Wisp
Is the initial timing the reading you are getting with the vacuum advance removed (no vacuum to the distributor)? If you did not remove the vacuum advance, reset your timing. Also check for vacuum leaks in the carb.
For your vacuum to be that low at idle with no problems, your cam would have to be running around 240 degrees duration with an LSA or around 108 degrees. I'm assuming that high compression means around 10:1.
For your vacuum to be that low at idle with no problems, your cam would have to be running around 240 degrees duration with an LSA or around 108 degrees. I'm assuming that high compression means around 10:1.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
This is what iīm running:
http://store.summitracing.com/partde...1&autoview=sku
Dont know anything about cams...
I just cant get the mixture screws to have any effect compared to vacuum or RPM. I donīt se or hear any difference when I turn the mixture screws
http://store.summitracing.com/partde...1&autoview=sku
Dont know anything about cams...
I just cant get the mixture screws to have any effect compared to vacuum or RPM. I donīt se or hear any difference when I turn the mixture screws
I ran a cam similar to yours before and it wouldn't idle much below 1000rpm. But I was running a tunnel ram with 2-4's and was able to close the plates enough that the idle screws were effective.
I'm running a BG race demon now and a much bigger cam. At first I couldn't get it to idle until I made sure both sets of plates were open the same, which put me below the transition circuit.
Thread Starter
Instructor
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From: Odder Jylland
Hey...
I have 0.020 visible of the transition slot at the primary side, and the same amount of air at the secundary side. Like Larsīs paper says it should.....
So what is wrong....? What happens if the jetting is of????
Running out of options here...... AND WHERE IS LARS WHEN YOU NEED HIM
Wisp
I have 0.020 visible of the transition slot at the primary side, and the same amount of air at the secundary side. Like Larsīs paper says it should.....
So what is wrong....? What happens if the jetting is of????
Running out of options here...... AND WHERE IS LARS WHEN YOU NEED HIM
Wisp
It sounds like the throttle plates are open to far and it's running on the transition circuit. I don't know anything about the SA carb, but do you have the secondary plates open the same as the primary?
I ran a cam similar to yours before and it wouldn't idle much below 1000rpm. But I was running a tunnel ram with 2-4's and was able to close the plates enough that the idle screws were effective.
I'm running a BG race demon now and a much bigger cam. At first I couldn't get it to idle until I made sure both sets of plates were open the same, which put me below the transition circuit.
I ran a cam similar to yours before and it wouldn't idle much below 1000rpm. But I was running a tunnel ram with 2-4's and was able to close the plates enough that the idle screws were effective.
I'm running a BG race demon now and a much bigger cam. At first I couldn't get it to idle until I made sure both sets of plates were open the same, which put me below the transition circuit.
Pro
Joined: Dec 2006
Posts: 665
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From: wilmington nc
if the throtal plates were open to far it wouldn"t die from turning the idle mixture screws in. When it dies from closeing a idle mixture screw your still on the idle circuit. I don"t think your going to get the reaction your looking for from the idle mixture screws with that cam. I run a 248 duration cam and yours is even larger than mine, i have 5 hg vacume, my vacume advance is hooked to manifold vacume because 5 hg at idle doesent move my timeing until the throtal is moved. useing a vacume guage to set idle mixture screws didn"t work for me either. if your jetting is off the plugs will be white or black they need to be tan.
Thread Starter
Instructor
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From: Odder Jylland
How did you then adjust your mixture screws? Donīt you mean that you vacuum canister are pluged to Ported Wacuum?
Wisp
Wisp
if the throtal plates were open to far it wouldn"t die from turning the idle mixture screws in. When it dies from closeing a idle mixture screw your still on the idle circuit. I don"t think your going to get the reaction your looking for from the idle mixture screws with that cam. I run a 248 duration cam and yours is even larger than mine, i have 5 hg vacume, my vacume advance is hooked to manifold vacume because 5 hg at idle doesent move my timeing until the throtal is moved. useing a vacume guage to set idle mixture screws didn"t work for me either. if your jetting is off the plugs will be white or black they need to be tan.
Pro
Joined: Dec 2006
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From: wilmington nc
I set mine at the only place the engine would run 1 1/2 anything less than that and it doesent run good at all. it will idle at less than 1 1/2 turns actually sounds better at 1 1/4 turns but you cant drive it there it stumbles bad. I"d start at 1 1/2 and drive it if it runs ok try going to 1 1/4 keep going in till it quits running good, then open them up 1/4 then you can start checking the plugs for color, dont worry about color at idle till you have the jets right.