custom cam anyone?
Launching!
Joined: Oct 2006
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Before you drop a ton of money and a new cam and associated parts, check with Comp and see what they recommend as far as timing, carb size and modifications (downleg boosters, annular discharge, etc.). It may be that what you already have is good and it just needs to be optimized. Some carb and timing work and it may wake right up. You may also need to advance the cam.
I'm no expert, but I know new cams can be expensive!
I'm no expert, but I know new cams can be expensive!
Launching!
Joined: Oct 2006
Posts: 289
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Get your timing set where it wants to be (use a vacuum gage on the carb to get your best reading). When you get that sorted out, then set the idle speed and mixture for the carb set (use your vacuum gage again). With a lot of overlap, my experience is the exhaust will smell like gas. It certainl does on my IROC, even though the wideband O2 indicates the mixture is lean. Pay attention to the plugs to see if you are running way too rich at idle.
Is your problem mainly at idle or does it bog when you get on it?
Is your problem mainly at idle or does it bog when you get on it?
Launching!
Joined: Oct 2006
Posts: 289
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Some other things to consider:
1) Does adjusting the idle mixture screws have any affect on idle? If not, they may need to be enlarged (you need special bits to do this)
2) Do your primary throttle blades have small holes in them near the outside edge? If not, I have heard of guys putting holes in the plates to help the engine idle better. I have never tried this, so I would search the net and read up on it before trying it. I believe some Holley carbs come with this mod stock.
Good luck!
1) Does adjusting the idle mixture screws have any affect on idle? If not, they may need to be enlarged (you need special bits to do this)
2) Do your primary throttle blades have small holes in them near the outside edge? If not, I have heard of guys putting holes in the plates to help the engine idle better. I have never tried this, so I would search the net and read up on it before trying it. I believe some Holley carbs come with this mod stock.
Good luck!
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Thread Starter
TECH Enthusiast
Joined: Dec 2005
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Some other things to consider:
1) Does adjusting the idle mixture screws have any affect on idle? If not, they may need to be enlarged (you need special bits to do this)
2) Do your primary throttle blades have small holes in them near the outside edge? If not, I have heard of guys putting holes in the plates to help the engine idle better. I have never tried this, so I would search the net and read up on it before trying it. I believe some Holley carbs come with this mod stock.
Good luck!
1) Does adjusting the idle mixture screws have any affect on idle? If not, they may need to be enlarged (you need special bits to do this)
2) Do your primary throttle blades have small holes in them near the outside edge? If not, I have heard of guys putting holes in the plates to help the engine idle better. I have never tried this, so I would search the net and read up on it before trying it. I believe some Holley carbs come with this mod stock.
Good luck!
2) no they dont but there is a screw for adjusting the opening of the secondarys and I read somewhere that when the screw touchs the fork turn it 1/4 maybe it needs more maybe !!
ZONES the gauge is fine I have three gauges and all of them reads the same pressure Im using a new stock mechanical pump I have holley 130 GPH but it needs a regulator if I run this fuel pump without regulator the pressure ges around 9 PSI,how much PSI does a stroker needs?
Thread Starter
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ok the car now starts if you floor it twice before you hit the ignition key but as soon as the car starts it run for a while then shut off I hold the pedal while it runs is like it want to shut off it wont stay at 3K rpm when I hold the pedal it goes like 2800 then 3000 then back to 2800 rpm as soon I left my foot of the pedal it shut off right away whats now? the jets are 71/77 and the power valve 6.5/blocked is it supposed to have two power valves or only on primary and blocked on secondary's? it runs better after the rebuild but it wont stays on I hope this is small problem,another thing how hard/easy the tension of the springs for the distributor weights? I used the lightest now should I change them to harder ones?
Thread Starter
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ok the jets now 77/80 and has two power valves it revs like hell I like the response now but it hardly start now it needs timing,ZONES do you put the pistons exactly at TDC or its few degrees ATDC ? what about the mixture screws how many turns it needs? it was 1 1/2 all of them but it didnt like it like half to one turn
1.5 turns out is a starting point, i find that my cammed motors usually like 2-2.5 turns out. It is all about tuning till you find the sweet spot that the engine likes.
Launching!
Joined: Oct 2006
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What is your base timing set at? When you say it is hardly starting...is it cranking slow? How much vacuum is the engine pulling at idle (if you can get it to idle)? It sounds like you are making progress. Stick with it!
Thread Starter
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ZONES when it was 1 1/2 turn and when I turned it back to half to one or so the idle was smooth and the rpm raised a little bit so I left it as it is half turn all of them but it doesnt effect when I turn the screws in primary what should I change?
Launching!
Joined: Oct 2006
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Thanks to www.bob200.com (the site has a lot of good carb info...)
On a regular, standard idle circuit Holley, turning the idle mixture screws all the way in should kill the engine. If your idle mixture screws do not respond to adjustments, you may have several different problems. Another common cause of non-responsive idle mixture screws is having too much (more than .040 inch) of the idle transfer circuit exposed. The idle circuit allows a very small amount of finely metered fuel into the engine. By exposing the transfer circuit too much, the gross feed of fuel coming out of the transfer circuit overpowers the fine amount coming out of the idle ports. There are several ways to fix this problem:
3. Open the secondaries a bit, and close the primaries a like amount. This will allow more air in, without exposing quite so much of either primary or secondary transfer slots.
4. If opening the secondaries doesn't work, then you may have to drill small holes (1 per plate) in the primary throttle plates to allow air in while the plates cover the transfer slots. This is a trial and error procedure, so start small, about 1/16 inch. You should not have to go much larger than 3/16 inch. Drill on the side opposite of the transfer slots, to help keep this added airflow away from the idle ports and transfer slots.
From the sounds of it, your primary blades are open too far to maintain your desired idle speed. Try getting the secondarys open a little more (and close the primary side up a little). Last resort is drilling the holes in the primary blades. I am nervous to try that!
On a regular, standard idle circuit Holley, turning the idle mixture screws all the way in should kill the engine. If your idle mixture screws do not respond to adjustments, you may have several different problems. Another common cause of non-responsive idle mixture screws is having too much (more than .040 inch) of the idle transfer circuit exposed. The idle circuit allows a very small amount of finely metered fuel into the engine. By exposing the transfer circuit too much, the gross feed of fuel coming out of the transfer circuit overpowers the fine amount coming out of the idle ports. There are several ways to fix this problem:
3. Open the secondaries a bit, and close the primaries a like amount. This will allow more air in, without exposing quite so much of either primary or secondary transfer slots.
4. If opening the secondaries doesn't work, then you may have to drill small holes (1 per plate) in the primary throttle plates to allow air in while the plates cover the transfer slots. This is a trial and error procedure, so start small, about 1/16 inch. You should not have to go much larger than 3/16 inch. Drill on the side opposite of the transfer slots, to help keep this added airflow away from the idle ports and transfer slots.
From the sounds of it, your primary blades are open too far to maintain your desired idle speed. Try getting the secondarys open a little more (and close the primary side up a little). Last resort is drilling the holes in the primary blades. I am nervous to try that!