Mike, Have you tried advancing distributor with engine running ( past 15-16 dg )?? If engine rpm smooths out , maybe a problem with harmonic balancer phase. Wouldnt take but a few minutes to try that .
Any carb Gods out there?
- Thread starter Tic's60
- Start date
Good thought! If I go to advanced it drops the rpms and dies, if I retard it back some it smooths out.
I played with it allot today and found if I retarded it it would smooth out some speed up and I could take a turn more out on the Carter idle screw.
Vacuum went up about .5 inches and then started to drop so I stopped at the highest point - tunning by vacuum!
As a matter of fact I set it there and then tried the holley again, which is still on it cause I am tired of removing carbs, and got the same thing.
I am pulling the vacuum readings from the manifold not the carb as well.
FYI- The motor was balanced with the harmonic, crank flywheel and pressure plate. It has a crank oil stripper (those are a PIA to cut), windage tray and baffled pan :-) That was another 3 or 4 weeks of top rammon noodle lunches
If I cannot figure it out with all of these great hints and tips I will take and pull the intake and redo everything on the top end gasket wise and borrow a buddies Holley HP and see if that changes anything.
That's all I can do start from point a and go to point b and triple check everything. Hey it's hot rodding right!! That's why we love it!! All these cool puzzles....
OK, more good info on the timing. Retarded it and it liked that.
Was your cam degreed or just installed out of the box?
Just noticed you said the cam was set by 30 yr builder. OK that answers that, I guess. I was concerned if it had been properly degreed, because the valve to piston clearance for that grind is ever so critical and ever so close. Hate to see a bent valve from the get go due to improper installation. If you have the time, run a compression check on all cylinders.
Was your cam degreed or just installed out of the box?
Just noticed you said the cam was set by 30 yr builder. OK that answers that, I guess. I was concerned if it had been properly degreed, because the valve to piston clearance for that grind is ever so critical and ever so close. Hate to see a bent valve from the get go due to improper installation. If you have the time, run a compression check on all cylinders.
You've mentioned that it keeps running rich. I had a 396 with almost the same set-up as you. And close to the same problem. Balanced, blueprinted, 10.75:1, closed chamber heads with .225/ .188 valves. Holley 800 double pumper, 610 lift cam, blah blah blah. To make mine idle AND perform, I went to 70 primaries and 102 secondaries. Also ran about 12 initial degrees timing, and around 950 RPM. On the Holley, sometimes you have to piddle with it, A LOT!! But in all honesty, it seems you have a metering block or metering block gasket problem. The power valve can cause similar probs, but you've probably already addressed that. And you've already checked all the most common things. However, 5 inches vacuum seems a bit low. Oh, I know the manufacturer says it's plenty, but my ex-best-friend had problems with an Isky and he was positive the cam was the problem. The guy he talked to on the phone said the vacuum was fine. After several calls, many replaced parts, and not being satisfied with the conversations with Isky, he removed the Isky, installed a Comp Cams unit (which I really don't care for). All, repeat ALL, his problems went away. Now don't misunderstand. That doesn't mean your cam is defective. But his was. If you are intent on running the Holley, which in this case is probably the better choice, try another known good unit. Borrow one, or something. As the police say, "It will eliminate it as a suspect",and tell you whether or not to find the problem in the carb or focus on the cam. By the way, how much fuel pressure are you running?
Degreed and putty was used.
You need to get an adjustable timing pointer to avoid confusion. You said the throttle blades were cracked 1/8" ? If they are you will run rich at idle and yes it will die. At 1/8" you are past the idle circut and are pulling fuel from the off idle or main metering circut. The idle mixture screw adds air to the fuel at idle speed, you said your idle air bleed screws were turned out 1.5 turns, try this, turn the idle bleed screws out 3.5 turns or more and at the same time bump the timing at idle up to 18/20 dgs. Now try backing off the curb idle screw and close up the throttle blades to get back into the idle circut,,damn, I wish I were there, I love a good challange.
Do this instead
Don't drill the primary blades. Just open the secondary for added air.
http://store.summitracing.com/partd...63-2&N=700+4294925239+400990+115&autoview=sku
Don't drill the primary blades. Just open the secondary for added air.
http://store.summitracing.com/partd...63-2&N=700+4294925239+400990+115&autoview=sku
I had the same problem with a sbc. Check the vacuum, divide it by 2 and that is the size power valve you should use.
Hope this helps.
Brian
Hope this helps.
Brian
Ordered one as well as 2.5 PWV, PWV plugs and 86 and 88 jets. Also being anal I redid the manifold gaskets last nite after finding a small leak. No leaks anywhere now :-) Reads a stedy 6 on the vacuum gauge.
The thing runs damm good, no back fire thru the carb or run on and fires on the first turn of the key. Has a wicked wicked idle to it. Until the parts get hereI am kinda stuck.
I also tried a PVC on it that made things worse on the idle side.
I am running standard AC/DELCO plugs with 45 on the gap..should I increase with the MSD 6A? Some say yes.
When plugging the PWV will 86 or 88 be big enough?
gearhead409
Well Known Member
Tic, what did i say about having a vacuum leak? glad you found it. now get some tunning done!
The new gaskets gained me about .5 on the gauge but while I was at it I looked over the cam and rechecked the cam timing. All's good!
The MSD book says .050 .060 on the gap but that seemed a little extreme to me so I went .045. When I change plugs this week I'll nrrow the gap.
Once the break oil filter is checked this week by the machinest I still have to rebuild the Holley and wait for the new oil to get here.
I run only Brad Penn so I have to have it shipped in and I got behind on ordering some so now I am a week out. HIGH HIGH ZINC and sticky green! Made in the USA from USA oil. Real dino stuff for me
Old racers remember it as Kendall green formula. Same man still owns the formula. Enough oil plug.
Once set I gotta leave it alone though so I can ge the rest of the car done:eek:
The MSD book says .050 .060 on the gap but that seemed a little extreme to me so I went .045. When I change plugs this week I'll nrrow the gap.
Once the break oil filter is checked this week by the machinest I still have to rebuild the Holley and wait for the new oil to get here.
I run only Brad Penn so I have to have it shipped in and I got behind on ordering some so now I am a week out. HIGH HIGH ZINC and sticky green! Made in the USA from USA oil. Real dino stuff for me
Old racers remember it as Kendall green formula. Same man still owns the formula. Enough oil plug.Once set I gotta leave it alone though so I can ge the rest of the car done:eek:
Help Ignitionman !!!
Dave (ignitionman) posted a great expenation about compression and spark plug gap a while ago and I can`t seem to find it.
Dave, could you explain it again?
I got this info off the internet:
NGK:
Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.
With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.
From Gino`s Garage:
Compression ratio/forced induction: As effective compression ratio increases through engine modifications or forced induction, a colder plug using a narrower gap and higher ignition voltage is required.
I could post more but I think you get the picture.
One test would be to run the 1/4 several times and change gap size beteen runs,,, or better yet use a dyno!
As far as plugs go, IMO,,, the Bosch should be used ONLY in a car designed to use then, ie: Euro IMPORTS
Autolite ,, junk,,
Remember ,,, I smaller tipped plug should be checked more often for wear and from what I`ve heard, also the gold tip plugs,,
,,,, JMO,,,dq
Dave (ignitionman) posted a great expenation about compression and spark plug gap a while ago and I can`t seem to find it.
Dave, could you explain it again?
I got this info off the internet:
NGK:
Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.
With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.
From Gino`s Garage:
Compression ratio/forced induction: As effective compression ratio increases through engine modifications or forced induction, a colder plug using a narrower gap and higher ignition voltage is required.
I could post more but I think you get the picture.
One test would be to run the 1/4 several times and change gap size beteen runs,,, or better yet use a dyno!
As far as plugs go, IMO,,, the Bosch should be used ONLY in a car designed to use then, ie: Euro IMPORTS
Autolite ,, junk,,
Remember ,,, I smaller tipped plug should be checked more often for wear and from what I`ve heard, also the gold tip plugs,,
,,,, JMO,,,dq
No such thing as a bad plug
Just a bad selection of plug. Go here to select a plug. Get the right heat range and construction material and gap.
http://www.sparkplugs.com/
http://www.sparkplugs.com/results_app.asp?productTypeID=1&AAIA=1323425
Just a bad selection of plug. Go here to select a plug. Get the right heat range and construction material and gap.
http://www.sparkplugs.com/
http://www.sparkplugs.com/results_app.asp?productTypeID=1&AAIA=1323425
