skep419
No show, all go!
I'm using the better voodoo lifters And 1/2 turn of preload
https://m.summitracing.com/parts/LUN-71977-16
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Super tuning car runs good shooting for great
- Thread starter skep419
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I'm using the better voodoo lifters And 1/2 turn of preload
https://m.summitracing.com/parts/LUN-71977-16
nm9stheham
Well-Known Member
1/2 turn seems a bit small.... if the adjusters are 24 tunrs per inch, then 1/2 turn is just .020". I'd be doing an full turn and maybe a touch more to be in the .040-.050" range.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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FWIW
My Hughes are at 1/2T. Most of them have held that for a few years. I never kept track of which,if any ,require more frequent adjustment, than any other. I rather readjust one now and then, then encounter pump up on a missed shift. In ten years, I have only adjusted them twice that I can recall. That's about 60,000 or more miles.But there are one or two that have been ticking for a number of oil changes now,lol. maybe three.
I even tried a quarter turn, but that didn't work out for me.
As long as the lifters have HD retainers....................and the springs are adequate..............IDK, I can only say what works for me.
My Hughes are at 1/2T. Most of them have held that for a few years. I never kept track of which,if any ,require more frequent adjustment, than any other. I rather readjust one now and then, then encounter pump up on a missed shift. In ten years, I have only adjusted them twice that I can recall. That's about 60,000 or more miles.But there are one or two that have been ticking for a number of oil changes now,lol. maybe three.
I even tried a quarter turn, but that didn't work out for me.
As long as the lifters have HD retainers....................and the springs are adequate..............IDK, I can only say what works for me.
skep419
No show, all go!
I drove around with the vacuum gauge hooked to ported vacuum. It wasn't steady at all. At cruise throttle it would drop to zero.
I backed off the secondary idle speed screw and opened the primary slightly. It helped a little bit it still doesn't react like the manifold vacuum port.
With the timing light connected I couldn't get any advancement out of the ported vacuum port.
Almost like it only pulls vacuum under load.
Any ideas on what could be wrong?
My understanding is once the throttle blades open it should be pulling the same vacuum as full manifold vacuum.
I backed off the secondary idle speed screw and opened the primary slightly. It helped a little bit it still doesn't react like the manifold vacuum port.
With the timing light connected I couldn't get any advancement out of the ported vacuum port.
Almost like it only pulls vacuum under load.
Any ideas on what could be wrong?
My understanding is once the throttle blades open it should be pulling the same vacuum as full manifold vacuum.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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The sparkport requires the throttle blades to pass by it to relay the vacuum to the Vcan. Then for a time, the signal strength will increase, and eventually it will decrease. It may or may not ever match intake vacuum exactly.
With the car in Neutra/Park and the gauge plumbed in, slowly rev up the engine to say 4500 and watch the gauge. You should see the vacuum rise, but you may not see it peak on account of it doesn't take a lot of throttle opening to hit 4500.
A better solution is to put it in 2nd or even third, and slowly accelerate the car.
In direct at 65 the throttle may not be open far enough to activate the port. I have had to lower the pick-up point on several carbs over the years,including a couple of Holleys.
The problem is often that the engine is too powerful, and/or the rear gears are too easy, and then the carb is barely open at cruising speed.
With the car in Neutra/Park and the gauge plumbed in, slowly rev up the engine to say 4500 and watch the gauge. You should see the vacuum rise, but you may not see it peak on account of it doesn't take a lot of throttle opening to hit 4500.
A better solution is to put it in 2nd or even third, and slowly accelerate the car.
In direct at 65 the throttle may not be open far enough to activate the port. I have had to lower the pick-up point on several carbs over the years,including a couple of Holleys.
The problem is often that the engine is too powerful, and/or the rear gears are too easy, and then the carb is barely open at cruising speed.
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skep419
No show, all go!
So I need more transfer slot exposed?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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No, the Transfers have got nothing to do with it.
If you know that the spark-port actually works, by roadtesting it in first or second, but there is little to no signal at cruising speed, then the sparkport will have to be lowered in the bore, to activate it earlier. But most Vcans can be activated to the fullest with as little as 7 to 10 inches vacuum.
It's been a few years since I did that, so I don't recall what I did on the Holleys, but it was a little more difficult than on any other type of carb.
So it is the sparkport that has to be lowered.
But there is another part to this story.
If your T-port is not properly synced, or if you are one of those guys that likes his timing all in by 2500, then you will also get this kind of result.
By running so much centrifugal timing, the engine makes a lot of lowspeed torque, with or without the pedal down. So the port doesn't get activated.Sometimes less is more. With a big Vcan like 22*, you only need about 22* mechanical to total 44*,to maximize economy, so instead of having 20 initial, and 32 at 2500, sometimes slowing things to 14 initial, and 34 at 3400 is the hot ticket.
But above all, the T-port needs to be synced up first, and left alone after that.
If you know that the spark-port actually works, by roadtesting it in first or second, but there is little to no signal at cruising speed, then the sparkport will have to be lowered in the bore, to activate it earlier. But most Vcans can be activated to the fullest with as little as 7 to 10 inches vacuum.
It's been a few years since I did that, so I don't recall what I did on the Holleys, but it was a little more difficult than on any other type of carb.
So it is the sparkport that has to be lowered.
But there is another part to this story.
If your T-port is not properly synced, or if you are one of those guys that likes his timing all in by 2500, then you will also get this kind of result.
By running so much centrifugal timing, the engine makes a lot of lowspeed torque, with or without the pedal down. So the port doesn't get activated.Sometimes less is more. With a big Vcan like 22*, you only need about 22* mechanical to total 44*,to maximize economy, so instead of having 20 initial, and 32 at 2500, sometimes slowing things to 14 initial, and 34 at 3400 is the hot ticket.
But above all, the T-port needs to be synced up first, and left alone after that.
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rmchrgr
Skate And Destroy
That's pretty high, almost seems too high but I could be wrong.
Where was the cam installed Skep? Lunati says its supposed to be in at 106.
skep419
No show, all go!
Honestly I had a friend help me out and I have no idea. I'm going to ask him today at work. I assume it's correct. But anything is possible.
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rmchrgr
Skate And Destroy
Well, that could be something to think about there. Unless there is a reason to move it one way or another, it should be installed per the cam card specs.
Also, I didn't see you mention any timing specs, so forgive me if you did. If not, can you tell us what the timing is set at? For this combo, I would think something around 16-18 initial with 34-36 total, "all in" by 2,500 or so. As always, timing is set with V.A. disconnected.
I believe these are the two areas you should be concerned with. If the cam was installed right, then start looking at the timing to dial it in.
Also, I didn't see you mention any timing specs, so forgive me if you did. If not, can you tell us what the timing is set at? For this combo, I would think something around 16-18 initial with 34-36 total, "all in" by 2,500 or so. As always, timing is set with V.A. disconnected.
I believe these are the two areas you should be concerned with. If the cam was installed right, then start looking at the timing to dial it in.
skep419
No show, all go!
It was installed straight up. I learned a lot this morning. Aka asked questions till it made sense. 20 -34 total
skep419
No show, all go!
How do you guys go about checking cylinder pressure. I took out all the plugs and turned it over until it read the highest.
rmchrgr
Skate And Destroy
Did your 'friend' degree the cam and have it wind up straight up or did he just 'line up the dots' and call it a day? If that's the case and it wound up being installed somewhere other than what the cam card calls for, well there's your answer.
If it had 4 degrees advance built in it could possibly have been installed correctly by lining up the dots but you would have no way of knowing that unless you degreed it.
I am betting that's your issue here and why you have so much vacuum at cruise. If it was way off, you'd probably be breaking stuff but I bet it's just not optimized. Most likely you will be fighting an uphill tuning battle until you degree it.
I could be wrong though so try to find out exactly what the guy did.
Cylinder pressure is checked by removing the plugs, threading in the compression gauge and cranking the motor 4 revolutions (4 strokes) then reading the highest number. Remember to disconnect the fuel and coil.
skep419
No show, all go!
rmchrgr
Skate And Destroy
That's good. I didn't mean to imply things were not done right, just trying to help figure out how deep you might need to go to get your answer.
So you said in regards to the timing, "It comes in fast and I'd like to get aggressive with the vacuum advance if I could find the right can."
Have you tried backing down the initial to 16 and see if its what you're looking for? I do think you may have a little too much initial timing for V.A. to be truly effective here, it makes your window very small to get it right. If you had like 10-14 it might work better.
So you said in regards to the timing, "It comes in fast and I'd like to get aggressive with the vacuum advance if I could find the right can."
Have you tried backing down the initial to 16 and see if its what you're looking for? I do think you may have a little too much initial timing for V.A. to be truly effective here, it makes your window very small to get it right. If you had like 10-14 it might work better.
skep419
No show, all go!
That's the plan for tonight. Back off the initial and see what happens. probably going to order a set of springs too.
I'm not 100% "how the spark-port actually works" I have this base plate
accept for the ports come out the front (not sure why its different in the picture).
From the sounds of it I'm going to have to make small adjustments take it for a ride......repeat..... for the rest of the year until its just right.
I'm not 100% "how the spark-port actually works" I have this base plate
accept for the ports come out the front (not sure why its different in the picture).
From the sounds of it I'm going to have to make small adjustments take it for a ride......repeat..... for the rest of the year until its just right.
rmchrgr
Skate And Destroy
Yeah it's adjust, drive repeat.
Just one point - if your advance comes in quick like you say, adding extra timing might not be what you want under certain load situations; WOT doesn't matter since vacuum drops to zero but maybe under light or normal acceleration when the RPMS are relatively low and you still have a decent vacuum signal. Obviously keep the vacuum gauge attached while doing this.
I still think 21-24" at cruise is too high. Think about it - an engine like yours is probably going to idle at 15-17" and that's with the throttle closed. The more you open the throttle, the more vacuum drops until you reach cruise rpm and the engine does not require the power to overcome inertia.
Put a vacuum gauge on both of those ports in the baseplate to see how they behave, one is for ported I think? They connect to different things.
Just one point - if your advance comes in quick like you say, adding extra timing might not be what you want under certain load situations; WOT doesn't matter since vacuum drops to zero but maybe under light or normal acceleration when the RPMS are relatively low and you still have a decent vacuum signal. Obviously keep the vacuum gauge attached while doing this.
I still think 21-24" at cruise is too high. Think about it - an engine like yours is probably going to idle at 15-17" and that's with the throttle closed. The more you open the throttle, the more vacuum drops until you reach cruise rpm and the engine does not require the power to overcome inertia.
Put a vacuum gauge on both of those ports in the baseplate to see how they behave, one is for ported I think? They connect to different things.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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rmchgr
With a stock type teener I do see what you are saying. They have little to no reversion,so the manifold vacuum will be very high at idle and will hang there for a few hundred rpm before beginning to decrease,gently but continuously.
-But with performance cams, I find that the low idle-vacuum increases as rpm rises to the point where the reversion (due to the late closing intake valve),ends. For streeters(all I know), this is usually somewhere in the 1800 to 2200 area. Then,with no load on the engine,it will hang there, a good long way. I gear my car to run hiway at just above the no-load vacuum peak.
My 367 with a 230 cam,for instance, idles around 11inches, and with no load, the vacuum increases to around 22inches at 2200(24*timing), and IIRC it hangs there for at least 1000 rpm.
Now this data is subject to change somewhat with changes in timing, but it is not drastic. I think the cid/cr and chamber seal have the biggest effects on the size of this Vacuum number, and the ICA probably determines where it peaks,rpm wise. That's me thinking tho.
With a stock type teener I do see what you are saying. They have little to no reversion,so the manifold vacuum will be very high at idle and will hang there for a few hundred rpm before beginning to decrease,gently but continuously.
-But with performance cams, I find that the low idle-vacuum increases as rpm rises to the point where the reversion (due to the late closing intake valve),ends. For streeters(all I know), this is usually somewhere in the 1800 to 2200 area. Then,with no load on the engine,it will hang there, a good long way. I gear my car to run hiway at just above the no-load vacuum peak.
My 367 with a 230 cam,for instance, idles around 11inches, and with no load, the vacuum increases to around 22inches at 2200(24*timing), and IIRC it hangs there for at least 1000 rpm.
Now this data is subject to change somewhat with changes in timing, but it is not drastic. I think the cid/cr and chamber seal have the biggest effects on the size of this Vacuum number, and the ICA probably determines where it peaks,rpm wise. That's me thinking tho.
rmchrgr
Skate And Destroy
He said he has 3.91 gears so the RPMs will climb pretty quick if he is into the throttle, even with lighter acceleration. That's what gears are supposed to accomplish, right?
He didn't say what his vacuum is at idle but if I had to guess, it's probably between 13-17". At least you would hope a closed-chamber, aluminum headed 360 with a decent performance cam would be around there.
The stock, lo-po 400 in my truck with the silly long duration cam and high rise intake idles at 15" of vacuum which is actually pretty good. My initial timing is 18 degrees though which is almost double the factory setting. With a heavy vehicle, low geared trans. and 3.23 gears, it's likely why I run into issues with the V.A..
Again, if I changed the springs in the distributor to slow the advance curve it might help to dial in the V.A. but the cam is too big and it will be more of a dog than it is now. Frankly, life is too short to mess with it that much. I have a smaller cam for it but there's other projects to finish before I put it in.
One of these days I will get my Sun distributor tester up and running again and it will be easier to do but until then, no V.A.. But I digress...
I'm interested to hear about what happens when he backs off the initial. If I am right, he will have more room for the V.A. to work and the negative effects will be minimized. I would also like to hear if he tries to tune it without V.A. to see if things improve. It's a balancing act with a street car, there are no hard-fast rules to apply.
skep419
No show, all go!
Dropped the initial down to 16 last night. After adjusting idle speed screws and the accelerator pumps. Took it for a test drive. The manifold vacuum didn't change. Still at 11-12 at idle maxes out at 21 above 2200.
The ported vacuum though is now working perfect. Driving normal it peeks around 18 getting up to speed.
I took the distributor apart to change the mechanical advance. I lost the kit I bought that had plastic spacer tools to gauge it. So I'm forced to guess.
I was slightly off with a total of 32. I tested it out anyway.
Hooked up the vacuum advance with no pinging (unhooked it again but just wanted to give it a try)
It idles at 700 vacuum droppes below 5 and bogs intermentantly on take off. (Must be the power valve opening its a 6.5).
I really need to get the spring kit to test delaying the mechanical advance.
It's feels like a turbo is kicking in around 1500 rpm under light throttle take off.
The idle mixture screws are now out less than 1/2 a turn (were at 3/4 turn with more initial)
I live in a small town and work 24 miles away.
It is a street car
I appreciate all the advice.
I enjoy trying different tunes to make the car run better.
My last cam was a lost cause (way too big)
It's nice making changes and actually seeing/feeling results.
The ported vacuum though is now working perfect. Driving normal it peeks around 18 getting up to speed.
I took the distributor apart to change the mechanical advance. I lost the kit I bought that had plastic spacer tools to gauge it. So I'm forced to guess.
I was slightly off with a total of 32. I tested it out anyway.
Hooked up the vacuum advance with no pinging (unhooked it again but just wanted to give it a try)
It idles at 700 vacuum droppes below 5 and bogs intermentantly on take off. (Must be the power valve opening its a 6.5).
I really need to get the spring kit to test delaying the mechanical advance.
It's feels like a turbo is kicking in around 1500 rpm under light throttle take off.
The idle mixture screws are now out less than 1/2 a turn (were at 3/4 turn with more initial)
I live in a small town and work 24 miles away.
It is a street car
I appreciate all the advice.
I enjoy trying different tunes to make the car run better.
My last cam was a lost cause (way too big)
It's nice making changes and actually seeing/feeling results.
rmchrgr
Skate And Destroy
Sounds like you're on the right track.
A good way to set initial timing is with a vacuum gauge. Loosen the distributor just enough so you can turn it and hook up a vacuum gauge to the carb base plate. Start the car and with it running at idle, increase the initial to where you get the highest vacuum reading. Then, back it off one degree and lock it down. You may have to adjust your total again but it probably won't be too far off from where you are now. Then obviously you have to re-adjust your carb idle settings but again, it probably won't take much adjustment.
From what it sounds like, your bog has less to do with timing than an accelerator pump issue. Are the pump arms adjusted properly? Do you have different cams to try? There's a pump cam chart floating around that shows the delivery characteristics of the individual cams. If you only have the one cam, switch the position to see if it helps. Pump squirters can also be changed out.
Sometimes you need a longer duration cam. If you have the assortment, put the blue one in and see if the bog disappears. If it does, then start backwards with cams until it bogs again the you know where you need to be. Tuning accelerator pumps can be frustrating, more adjust, drive and repeat.
The 6.5 power valve is probably fine if your idle vacuum is over 10". You wouldn't want a 4.5, it would be dumping extra fuel. Is it blocked in the rear?
A good way to set initial timing is with a vacuum gauge. Loosen the distributor just enough so you can turn it and hook up a vacuum gauge to the carb base plate. Start the car and with it running at idle, increase the initial to where you get the highest vacuum reading. Then, back it off one degree and lock it down. You may have to adjust your total again but it probably won't be too far off from where you are now. Then obviously you have to re-adjust your carb idle settings but again, it probably won't take much adjustment.
From what it sounds like, your bog has less to do with timing than an accelerator pump issue. Are the pump arms adjusted properly? Do you have different cams to try? There's a pump cam chart floating around that shows the delivery characteristics of the individual cams. If you only have the one cam, switch the position to see if it helps. Pump squirters can also be changed out.
Sometimes you need a longer duration cam. If you have the assortment, put the blue one in and see if the bog disappears. If it does, then start backwards with cams until it bogs again the you know where you need to be. Tuning accelerator pumps can be frustrating, more adjust, drive and repeat.
The 6.5 power valve is probably fine if your idle vacuum is over 10". You wouldn't want a 4.5, it would be dumping extra fuel. Is it blocked in the rear?
skep419
No show, all go!
I do have the cam assortment. I haven't tried messing with it. I think you've got it backwards with the power valves. the 6.5 opens at 6.5 which it drops to less than that on take off adding to much fuel when the throttle blades are barely open. The 4.5 wouldn't open Intel the vacuum drops below 4.5.
It runs like a skulded dog getting after it. Doesn't bog one bit.
The accelerator pump is adjusted correctly.
I'm thinking the pump shot isn't the issue under the light tip on take off throttle situation.
I need to hook up one of those air fuel readers. I bet it would be super fat for that split second when the vacuum drops.
It runs like a skulded dog getting after it. Doesn't bog one bit.
The accelerator pump is adjusted correctly.
I'm thinking the pump shot isn't the issue under the light tip on take off throttle situation.
I need to hook up one of those air fuel readers. I bet it would be super fat for that split second when the vacuum drops.
rmchrgr
Skate And Destroy
You did say it bogs momentarily on take off, was just responding to that. I suppose I will have to respectfully disagree with your assessment, pretty sure it would be your acc. pump but hey, I could be wrong. It's easy enough to change if you want to.
With 11-12" of vacuum at idle, you are kind of in between low and normal so you could potentially try a lower number PV and see if it helps. If you go by what Holley says, divide your idle vacuum by 2 to determine your PV. It's never that simple though and you can usually get away with a higher number if everything else is OK. Again, wash, rinse, repeat.
A/F meters are good tools but you can get caught up watching them and sometimes fail to see the forest for the trees.
skep419
No show, all go!
At stop sign give it slight amount of gas. Goes from 700 to 1000rpms.holding 1000 rpm's let out clutch. Pump shot is used up well before clutch is engaged. Vacuum drops into bog zone do to load.
can slip clutch and it keeps the vacuum above bog zone.
Or dump clutch and haze tires.
Happy medium to be determined.
can slip clutch and it keeps the vacuum above bog zone.
Or dump clutch and haze tires.
Happy medium to be determined.
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