Ok from my last post you know that I now can set the timing.. the problem is that we have messed so much with the carb that it is running rich.. what is the best way to "zero" out a carb to a general setting.. the carb is a holley 4B 700cfm Double pumper. Should I turn the idle screw all the way in and back it out 3 turns like you would with an original carb?
Clearification: Not the idle mixture screws located on the bowls of the carb.. I mean the idle set screw .. I think...
[ 04. September 2002, 09:41 AM: Message edited by: zleviticus ]
Posted by Steve da Wrench (Member # 1301) on :
First, pitch the Holley carb in the scrap bin..........
but, if you dont want to do that, then GENTLY bottom out the mixture screws, then back them out approx 2 or 2.5 turns. Start the car, and set them for the best vacuum reading, on the lean side.
Glad I could help on your other problem!
BTW, set your initial timing at approx 10 or 12 degrees initial, just watch for pinging.
[ 04. September 2002, 09:53 AM: Message edited by: Steve da Wrench ]
Posted by zleviticus (Member # 1648) on :
why do you not like holley or mallory.. what do you recommend.. demon? Edelbroch? We have an edel on the mustang and I must say it is a piece of crap... I have never had problems with my holleys... other than the one time i bought one and the bowl gasket leaked out of the box... other than that I love mine...
Now does the idle speed of the car need to be set before you mess with the mixture screws?
Also I have a crappy original style dampner with two lines on it.. ione more prominent than the other.. when setting the timing which do I go by? I assume the larger one and the smaller one will coincide with zero on the timing marks at 8 deg BTDC.... I have not measured the difference to be sure though....
I currently am set at around 10 deg BTDC with a idle speed of around 800 rpm but it doe snot want to stay running that well and looks to be running rich... the carb is factory set as far a s air/fuel mixture... do you think I really need to reset the mixture or just mess with the idle speed and timing a little more to get the right combination...
I do need to see what the vaccuum is on the carb but setting the timing and messing with all the gauges is just so hard to do with only one person... I wish I had some friends.. LOL
Posted by 2002Z4CSS (Member # 1393) on :
quote:Originally posted by zleviticus: why do you not like holley or mallory.. what do you recommend.. demon? Edelbroch? We have an edel on the mustang and I must say it is a piece of crap... I have never had problems with my holleys... other than the one time i bought one and the bowl gasket leaked out of the box... other than that I love mine...
Now does the idle speed of the car need to be set before you mess with the mixture screws?
Also I have a crappy original style dampner with two lines on it.. ione more prominent than the other.. when setting the timing which do I go by? I assume the larger one and the smaller one will coincide with zero on the timing marks at 8 deg BTDC.... I have not measured the difference to be sure though....
I currently am set at around 10 deg BTDC with a idle speed of around 800 rpm but it doe snot want to stay running that well and looks to be running rich... the carb is factory set as far a s air/fuel mixture... do you think I really need to reset the mixture or just mess with the idle speed and timing a little more to get the right combination...
I do need to see what the vaccuum is on the carb but setting the timing and messing with all the gauges is just so hard to do with only one person... I wish I had some friends.. LOL
If you do not know which mark on the balancer is the correct one,but the #1 clyinder in tdc compression stroke and the piston all the way to the top. You can feel it with a thin screwdriver when it is at tdc.A mark on the balancer should line up with the timing pointer at or very close to the zero mark. use a paint marker or crayon to mark the balancer groove.
Posted by Z28-SORR (Member # 1565) on :
zleviticus
Some of what you have said is a bit confusing. So lets get real basic.
First, most chevy's have a single machined groove that runs all the way across the harmonic balancer at TDC. Clean this groove and mark it with something bright. I use white paint. All the other timing marks should be on the timing pointer attached to the timing chain cover. The pointer usually has a deep "V" at 0 degrees several shorter ones at 1 to 2 degree increments and then a medium one at 10 degrees.
Second, 800rpm is a bit high to be setting your timing. Normally done around 500 or 600 hundered rpm. depending on the Cam. you'r using. If your Mallory has a vacuum advance make sure you've remove it and plugged the line. 8 to 10 degrees is a good starting point for most small block Chevy's. However total advance is more important for peak power.
OK, now that the timing is done. There are three critical ajustments on your Holley for idle. Float level, idle speed, and idle mixture screws.
First, check that the float level is exactly at the bottom of the sight hole. Set it check it, then check it again.
Second, set your initial 2 to 2.5 out on the idle mixture screws, two, one on each side of the metering block.
Third, check that your idle speed is still at 500 to 600 rpm. In this configuration your engine should stall and die if both mixture screws are turn in all the way.
Finally adjust your idle mixture screws.
Hope this helps and that I haven't insulted you by being to basic.
Posted by Steve da Wrench (Member # 1301) on :
quote:Originally posted by zleviticus: why do you not like holley or mallory..
Holley and demon carbs have the same basic fuel metering system. They are fine for racing, which is running only at WOT, not part throttle cruising or acceleration. They have no provisions for setting up the cruise mixture, and so therefore they either typically run rich or lean in that area, and it creates a flat spot.
Edelbrock (or Carter) carbs are very tunable, and need to be done so. Most people have a Holley and think it runs fine. They just happen to be too rich usually, and so the person doesnt notice the poor run. Dont just install the carb. I would recommend taking it to somebody with a chassis dyno to get it tuned correctly. Short of that, do all of the tuning to the best of your abilities as per the manual that comes with the carb. Set the timing first, then the idle mix and speed, go back and reset the idle mix and speed again, then recheck timing. Then its on to setting up the primary side of the carb, and once that is done, then set up Wide Open Throttle (WOT) mixture.
The Mallory distributors have tons of misfire/poor run problems. Steve.
Posted by zleviticus (Member # 1648) on :
Z28-SORR, You did not insult my intelligence.. I am looking for answers and am I not an expert on engines by far. I have rebuilt the engine that is in the car now by myself reading book upon book upon book on how to do it and it runs great (when it is timed correctly) I am just not used to timing an engine. Nor adjusting the carb. So I appreciate any help that is given.
With that said... The dampner has a solid deep groove in it so I guess that would be the 0 degree mark. There is another smaller groove about an inch clockwise from the other if you are looking at it from the front of the car. there is where my confusion is. I have no clue why the other line is there... Also I have new chrome timing marker on the engine that was placed on it again when I rebuilt the engine a while ago. has makring both before and after TDC but I don't know which is which..LOL
As far as idle goes the books that I have read thus far for a 71 Chevy 350 with a 4B carb pushing 345 HP (which is what mine is from all the number running i did on the block It is from a 1971 police cruiser) the idle should be around 800-900 rpm... I have a slightly MOD CAM in it.. just a little more than stock for a little extra UMMPPHHH. I have tried to get it down lower but it wants to bottom out when I do...
Can you explain total advance?
I thought the total timing should be around 8 BTDC for a Chevy... (I am going to dumb it down a notch for my sake) 8 BTDC should be more counter clockwise from the zero degree mark correct?. I assume so since when i go the opposite way and try to advance the timing i sometimes will get a backfire through the carb from going to far...
As far as setting the carb.. The float levels are fine I checked those... the idle speed needs to be set but I don't know where a good starting point would be.. do I need to turn it all the way in and back it out a few turns and start from there? what is a godd setting to start with... I know that the idle setting has a lot to do with the timing... as I adjust the carb I need to readjust the timing right?
Can I test the carb's mixture using a vaccuum gauge or something?
Now the idle mixture screws, is one for the primaries and the other for the secondaries?
I hope I am not being apain and everyone is just laughing at my lack of knowledge... I can rebuild an engine no problem but I have never timed one myself or messed with the carb... LOLOLOLOL
thanks for answering all my questions... None of the people I know that live close know anything about cars...
[ 05. September 2002, 08:34 AM: Message edited by: zleviticus ]
Posted by Z28-SORR (Member # 1565) on :
At this point I think you might be better off getting one of those books you mentioned. HP Books has an excellent one on Holley Carbs, with complete, step by step, test and tune instructions. Good luck, and let us know how things turn out.
John
Posted by zleviticus (Member # 1648) on :
well fellas thanks for the help..the car is now puuurrrrring like a kitten...
the settings as as follows...
8 BTDC 1100 RPM...
anything less than these and it wants to stall out... I do have a larger than stock cam in it so 200 rpm off of stock is not that bad....
Posted by Z28-SORR (Member # 1565) on :
That's great news. Glad all's well. My 84, 383/w solid lifter cam., idles up around 1200 also. Nice pict. Say what's that other thing in the pict., got kind of an ugly horse on the front.
John
Posted by zleviticus (Member # 1648) on :
Yeh that is what I told my wife... I don't want any FORD in my garage... all ig ot to say is that I can blow its doors off so that is good enough for me.. LOL
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