|
 |
|
|
|
02-25-2010, 06:30 AM
|
#16 | |
|
Registered User
2003 TJ Wrangler
|
jayscj7, if it still runs with the idle mixture screws all the way in, you,re power valve may be blown. That carb should work fine for that motor, provided its properly tuned.
|
|
|
|
|
|
|
03-08-2010, 11:12 AM
|
#17 |
|
Registered User
1978 CJ5
|
Jeephammer. . . from your reply . . .
KEEP IN MIND... If you are running a GM HEI distributor, the vacuum advance is much 'Faster' and adds more advance to the timing curve. Many times (most times actually) you will find the timing is too much for the engine at PTC when you try to accelerate a little for traffic or keep speed up on hills... If the power valve is correctly sized for the PTC vacuum signal, And you get a 'Hesitation' or in extreme cases, 'Pinging' or 'Spark Knock' when trying to accelerate slowly during PTC, Then you have too much ignition timing for the engine load, RPM and fuel mixture. The only way to 'Fix' this problme is by using the CORRECT vacuum advance source (Spark Ported Vacuum), And by adjusting the vacuum advance to work with the vacuum signal being used (adjustable vacuum canister on the distributor), In extreme cases, you will have to limit the amount of advance the vacuum canister can apply to the ignition curve... So. . .Yep. . .I have the off brand HEI. I noticed that by backing off my timing just a bit at a time and going for a short drive that perhaps this stumble issue is too much timing. Being that I have no timing light, I marked my location to start with ~8 as set with a light when I first started this motor after rebuild. The carb. . The manifold idle vac reads 14" power valve 75. So I beleive the power valve opens at vacuum below 7.5" . . .correct? You mentioned that I should set power valve based on PTC vac reading to -1.5 to 3 depending on driving preference. But when I crack the throttle when crusing my vac drops to practically zero. Did I miss understand or? Disty. . . .Ported vacuum line is used. So now moved to heaviest springs, lighter weights and backed off the timing seems to be best settings to. Down side, harder start when warm and still have a little stumble in fourth and OD (NV4500) when crusing low RPM and I crack the throttle, vac drops to near zero and bingo we stumble, and see it go leaner with the analyzer but sure is less with a little less timing. Next questions. . . Can/how do I adjust for less total mech advance? Can/how do I adjust the vac for later or less as well. Or am I opening a crappy can of worms here. Should I just suck it up and toss the HEI disty and go with the MSD 6 box and a new disty that will run with the MSD?
__________________
78 304-CJ5 |
|
|
|
|
03-08-2010, 12:50 PM
|
#18 | |||||||||
|
Running On Empty...
1973 CJ5
|
Quote:
You want the power valve to stay closed at PTC. When you tip into the throttle, or go up a hill, whatever, You want the power valve to open and add fuel for the extra load on the engine. When you are at PTC, you want the power valve CLOSED, Main Jets only, so you get the best fuel mileage, BUT, You don't want the engine to 'Lug' without extra fuel when the engine loads up. *IF* your PTC MANIFOLD vacuum signal is at about 9 In.Hg., you want the power valve to open at about 7 In.Hg. so when you tip into the throttle to get a little more speed or go up a hill, the power valve opens and adds the extra fuel. The vacuum rating on the power valve is the CLOSING point, it CLOSES at 7 In.Hg., and opens below 7 In.Hg. in my example. You are cruising, you are holding 9 In.Hg., the power valve is closed, You go up a hill, lug the engine, or tip into the throttle, The vacuum will drop quickly, and the power valve will add fuel for the load the engine is seeing. Quote:
Quote:
Quote:
Vacuum BELOW the closing point, and you are getting extra fuel. Quote:
When the vacuum drops, that means the engine is being loaded, and when loaded, the power valve is supposed to open and add extra fuel. Quote:
The engine RPM hasn't changed yet, so you will still have the same amount of centrifugal timing, the only thing changing is the vacuum advance. *IF* you have TUNED your vacuum advance correctly, You will have the most advance during PTC you can run without 'Spark Knock'... And it *SHOULD* drop a bunch of advance when you tip into the throttle. Heavily loaded engines should have LESS timing advance when heavily loaded. The idea of the vacuum advance is to 'Sense' engine load via the vacuum, and to add/subtract advance as the engine loads heavier and becomes less loaded... Quote:
Jeep/Motorcraft factory distributors are adjustable, but HEI's don't have total centrifugal advance limiters you can adjust. You would have to take the distributor completely apart, and weld up part of the centrifugal advance limiting slot. You CAN add heavier springs/lighter weights to keep the advance from coming 'IN' too soon, Or you can take some of the 'Initial' advance out to reduce the total advance.[/quote] Quote:
Takes more vacuum to get it to move, which delays the advance at lower vacuum levels (Like when the engine is heavily loaded). You *CAN* build a limiter for the vacuum advance pretty easily that will limit the total vacuum advance that can apply to the total. It's not very hard, and you will need a large washer with small hole or a dime to drill a hole in... Quote:
The Jeep/Motorcraft is more adjustable than the HEI, Doesn't have the problems that come with an HEI, And the problems they do have can be corrected with 'Tune Up' parts from the local discount parts store (Cap, rotor, plug wires, IE: TeamRush Upgrade) Jeep/Motorcraft distributor will come with the correct advance curve and correct vacuum advance for your engine. You are VERY close to working the 'Issues' out on yours, but if you didn't test the distributor gear for being hardened before you put that HEI in your engine, You may wind up taking your engine apart anyway. The 'Cheap' HEI's have a nasty habit of eating up the camshaft gears and wearing out oil pumps really quickly... What I would do is go back through all the 'Tuning' steps for the Holley, make sure your initial advance is about correct, and tune from there... You just get to start over again & again if you keep switching things...
__________________
REMEMBER, 'Free' internet information is worth EXACTLY what you paid for it! LINK:Dual Battery Diagrams & Explanations. LINK:Winch, Welding, 'Lend Power' Project, LINK:Water Proofing Ignition, Hubs, Ect., LINK:BSERK's Winch Plate, LINK:AMC V-8 Front Cover Recondition, LINK:How An Ignition Works, LINK:Ignition Swaps '77 Older Jeeps, LINK:'78-'90 Jeep Ignition Upgrades, |
|||||||||
|
|
|
|
03-08-2010, 05:38 PM
|
#19 |
|
Registered User
1978 CJ5
|
Jeephammer. . .can't say enough. . .but thanks again for your willingness to share and document your knowledge.
Well. . .you are telling me what I was slowly figuring out on my own. The HEI is not really meant for my motor and while I might be able to force it to work. It is still a cheap GM setup that with the hard gear issue it has got to go. Don't wish to ruin my new cam just yet. So now I go butter up the wife so I can now spend another $500 on top of the pile I just dumped to rebuild motor, clutch and tranny. The good news it will run great for many moons when I am finished. So. MSD pro billet disty, ~$260 MSD 6x Ign. module, ~$170 MSD wires, ~$90 MSD coil, ~40 And 4 hours or so installing and making it look nice. Now I have to push out the D44/D30 with 4.27s I was eyeballin. My 3.54s are just a bit higher than I want.
__________________
78 304-CJ5 |
|
|
|
|
03-08-2010, 10:50 PM
|
#20 |
|
Registered User
1978 CJ5
|
Went out and looked around and came up with my old stock motorcraft distributor. Looks like I need to study the Team rush modification. Just might save me a few hundred bucks.
__________________
78 304-CJ5 |
|
|
|
|
03-09-2010, 08:59 AM
|
#21 | |
|
Running On Empty...
1973 CJ5
|
Quote:
You are VERY close with your current HEI, and ALL new distributors need to be fine tuned. If you went with the MSD unit, it's really more than you need. You aren't racing, you aren't going to sustain RPMs above 5,000 and you are never going to flash yours up to 7,500, So you don't need double roller bearings and all the other stuff. It's a waste of money unless you REALLY WANT IT.... Then is still a waste of money, but you feel better about it!  evil:Cap upgrade, MSD version, http://www.summitracing.com/parts/MSD-8414/ You already have plug wires for the HEI, and they work on the MSD cap system. Ignition module is $25 if you go with an HEI style module, Or a CDI module will boost your spark energy by $500+ Percent... And do it for around $150. Something you can't say about an HEI, it's still a single fire, pretty weak spark. ---------------------------- Remember to check that vacuum source from the carb! Make sure you aren't getting way too much vacuum at idle to start with!
__________________
REMEMBER, 'Free' internet information is worth EXACTLY what you paid for it! LINK:Dual Battery Diagrams & Explanations. LINK:Winch, Welding, 'Lend Power' Project, LINK:Water Proofing Ignition, Hubs, Ect., LINK:BSERK's Winch Plate, LINK:AMC V-8 Front Cover Recondition, LINK:How An Ignition Works, LINK:Ignition Swaps '77 Older Jeeps, LINK:'78-'90 Jeep Ignition Upgrades, |
|
|
|
|
|
03-09-2010, 07:49 PM
|
#22 |
|
Senior Member
 
1980 CJ7
|
I was able to change my jets today, put 63's in the mains and 68's in the secondaries, We'll give it a few days of driving around and see if I can tell a difference. Will changing these jets change my fuel mileage?
I think I need to change pump discharge nozzle because I have a stumble when I get on the throttle. Stock size it .028, do you have a recommendation for what size I should try next to try to get rid of this stumble? Are these hard to change? I need to check my float levels, didn't get a chance to play with it today, but I'll play with it some on Thursday. How is the accelerator pump adjusted, not the cam, but the spring with the nut on top of it? I have no idea if it has been moved from its original position or not by the PO Thanks for the advice. Last edited by TKFireman; 03-09-2010 at 08:54 PM.. |
|
|
|
03-10-2010, 08:20 AM
|
#23 | ||||
|
Running On Empty...
1973 CJ5
|
Quote:
The most mileage change you will see is with the correct size power valve for the vacuum you run at PTC. Quote:
Magnetic screw driver and long, thin needle nose pliers are a MUST! Quote:
Don't forget to do that! Fuel level is EVERYTHING to a Holley! You should adjust the inlet valve (needle & seat) to where the fuel barely creeps out the sight plug on the side of the float bowl... If you off road much, you might want to back the fuel level down about 1/8", but no more. Quote:
As long as the pump arm is in contact with the bolt head, And the pump shot starts IMMEDATELY when the linkage is moved, you don't need to mess with that adjustment. You give the engine MORE FUEL if you have a bog off the line. You do that by looking down into the carb, and seeing where the fuel shot comes from. That is the 'Shooter' (fuel discharge nozzles). There will be a screw that holds them in place... DO NOT DROP THAT SCREW! I use a magnet to make sure it doesn't get away! Once the screw is removed, you can remove the 'Shooter'... And change it to a larger version. If you have a Stumble, instead of just hesitation, you probably want to go up at least 5 shooter sizes. If you go above about a 28 shooter, then get the HOLLOW SCREW to deliver more fuel to the shooter. Holley says to wait on the hollow screw until you get to 32 or so, but I've found it helps as low as 28, so for $5, I recommend it. Increase shooter size until you get NO HESITATION, then back down one size. You shouldn't notice any hesitation with one size change, and it WILL save fuel and fouled plugs.
__________________
REMEMBER, 'Free' internet information is worth EXACTLY what you paid for it! LINK:Dual Battery Diagrams & Explanations. LINK:Winch, Welding, 'Lend Power' Project, LINK:Water Proofing Ignition, Hubs, Ect., LINK:BSERK's Winch Plate, LINK:AMC V-8 Front Cover Recondition, LINK:How An Ignition Works, LINK:Ignition Swaps '77 Older Jeeps, LINK:'78-'90 Jeep Ignition Upgrades, |
||||
|
|
|
|
03-10-2010, 09:48 AM
|
#24 |
|
Registered User
1982 CJ7
|
JeepHammer, can you come to my house?
This thread is going to come in handy. I just brought the second CJ of my life home yesterday and I noticed it's running rich. It has a chevy engine and a big holley of some sort - I don't even know which one yet. I know very little about tuning carbs, so this will be a big help for me. |
|
|
|
|
04-03-2010, 08:20 PM
|
#25 |
|
Registered User
1978 CJ5
|
JeepHammer. . .did the team Rush mod today. MSD street fire box, MSD blaster 2 coil, street fire wires. Recommended MSD ford cap and rotor on my motorcraft disty, using ported vacuum, Initial timing between 5 and 10 with vac lines off and plugged. Re-adjusted idle mixture and reset float levels, they're good. Started on first crank. . . .no more missing at all. If you drive it like you stole it it runs very nice. I thought that I have the correct power valve selected, 75 I believe, acel pump is adjusted correctly, 41 squirt nozzle. Running a holley fuel pressure regulator bouncing 4 to 5. Using the 1 input two output fuel filter correctly installed, fuel tank is vented.
The motor is a fresh build, 40 over, balanced, RV cam, edelbrock performer intake, edelbrock shorty headers to a single muffler and the Holley is the 670TA. I am still fighting a lean stumble condition when running high gears low RPM and I tip in the throttle. Fuel air gage does show it going lean when I get the stumble and worse case a backfire through the intake. So after reading your notes again. . .I will put the vacuum gage back on and go for a drive. Perhaps the 75 power valve opens a little too late??? Hard to imagine that the stock motor craft distributor base has a curve that is not correct any more??? Or????
__________________
78 304-CJ5 Last edited by texasimport; 04-03-2010 at 10:32 PM.. |
|
|
|
|
04-04-2010, 06:52 PM
|
#26 |
|
Registered User
1978 CJ5
|
Jeephammer. . . . Well. . . put the vacuum gage on manifold vacuum port and when just rolling along I am getting 12/13 In. Hg. Does this seem high? And yep it drops nicely when I roll into it a little. That said it sure does seem that my power valve is opening way late then, was 7.5 Looks like I need to go all the way up to a 10.5.
__________________
78 304-CJ5 |
|
|
|
|
04-04-2010, 07:08 PM
|
#27 |
|
Senior Member
1980 CJ7
|
Texas, I put a 10.5 in mine and seems to work good, from the 6.5 stock one. But I have a idle vacuum of 20 in HG, and haven't found a good way to check it while driving down the road, need a long hose that I haven't gotten yet, but I believe earlier, Mr. Hammer said that the power valve sound be just a few in Hg under what your vacuum is at cruising speed.
|
|
|
|
|
04-05-2010, 04:30 PM
|
#28 | |
|
Registered User
1978 CJ5
|
Quote:
__________________
78 304-CJ5 Last edited by texasimport; 04-05-2010 at 06:53 PM.. |
|
|
|
|
|
04-05-2010, 06:25 PM
|
#29 |
|
Senior Member
1980 CJ7
|
it made a huge difference in mine, got rid of almost all the stumble, just need to make sure its only opening when I get on it, and not when I'm just cruising around
|
|
|
|
|
04-06-2010, 08:06 AM
|
#30 |
|
Running On Empty...
1973 CJ5
|
POWER VALVE IS NORMALLY OPEN AND FLOODING THE ENGINE WITH EXTRA FUEL...
The engine VACUUM CLOSES THE POWER VALVE. The number on the valve is the OPEN/CLOSE point. When cruising, and vacuum is HIGH, the valve is CLOSED, You don't need the extra fuel, So the valve is closed, and the fuel is from Main Jets only. When you want to speed up, you open the throttle blades a little, THE VACUUM DROPS, and you get more fuel from the power valve... ------------------------------------------ Now, If you are rolling around at relatively low RPM and you mash the throttle, You don't have enough venturi velocity to make the power valve fuel enrichment work correctly... You get raw dripping fuel instead of an atomized mixture. That's where the ACCELERATOR PUMP comes in. IT sprays a quick shot of raw fuel right on the venturi boosters and that quickly breaks up into extra droplets of fuel for a quickly opened throttle (When you stomp on it). Accelerator pumps should start pumping fuel IMMEDIATELY when the throttle is moved! This is NOT Fuel Injection, so it takes a half second for the extra fuel to reach the cylinders, So the faster your accelerator pump reacts, The sooner your engine gets extra fuel for the extra air where you opened the throttle blades quickly! There will ALWAYS be a slight bog when you open throttle quickly since this all REACTIVE fuel increases to the throttle input... Remember, it's a carb, not ported fuel injection... The carb is a LONG WAY from the cylinders, and you will get a slight delay while the fuel is traveling from carb to cylinders...
__________________
REMEMBER, 'Free' internet information is worth EXACTLY what you paid for it! LINK:Dual Battery Diagrams & Explanations. LINK:Winch, Welding, 'Lend Power' Project, LINK:Water Proofing Ignition, Hubs, Ect., LINK:BSERK's Winch Plate, LINK:AMC V-8 Front Cover Recondition, LINK:How An Ignition Works, LINK:Ignition Swaps '77 Older Jeeps, LINK:'78-'90 Jeep Ignition Upgrades, |
|
|
|
 |
| Thread Tools | |
|
|
|
«
Previous Thread
|
Next Thread
»
|
| Suggested Threads |
|
 |
