1987 318 Tuning with Summit Carb
- Thread starter sarguy01
- Start date
-
sarguy01
Well-Known Member
That's good feedback. I'm sure it's probably my lack of experience with this style of carb and possibly another issue that's contributing, like a weak ignition or something.
sarguy01
Well-Known Member
Question. Anyone know what these jets or restrictors are? Are these for the accelerator pump? They are in the primary side only.
They sure look like fuel restrictors. Have you tried calling Summit and asking who makes them? I think it might be Holley, but I really don't know. If you can get someone at Summit that will actually tell you, you could call them and maybe get more information.
sarguy01
Well-Known Member
- Joined
- Dec 31, 2005
- Messages
- 8,738
- Reaction score
- 4,684
Find a Crane Hi-6 and PS-92 coil and never look back. Daytona also do a good ignition box.
Daytona Sensors Ignition
- Joined
- Dec 31, 2005
- Messages
- 8,738
- Reaction score
- 4,684
Air restrictors if they are exposed to the surrounding atmosphere.
sarguy01
Well-Known Member
I didn't see anything Crane or Daytona. Picked up a 6A for cheap and a new Blaster coil.
- Joined
- Dec 31, 2005
- Messages
- 8,738
- Reaction score
- 4,684
Which one?
sarguy01
Well-Known Member
Update. It was the ignition. I checked voltage at the battery and alternator, it was fine. I then pulled the Orange box and threw in an MSD-6A and new Blaster coil I got for a pretty good deal. Ran pretty well with the Eddy that's still on there. I'm not sure whatever combination of jets and rods is in there but it needs work. However, I'm pulling the Eddy and going back to the new Summit. I'm starting the Summit as it came from the box, so the .043 air bleeds. I'm not sure if the Orange box wasn't getting a good ground or if it was failing, but I wasn't going to mess around with the cheap Orange boxes anymore.
I believe the other bleed jets are actually the accelerator pump fuel restrictors. I'll confirm by filling the bowl on the bench and moving the throttle.
I picked up a set of numbered drills for cheap as well. So I'll take some measurements before I put the Summit carb back on.
I believe the other bleed jets are actually the accelerator pump fuel restrictors. I'll confirm by filling the bowl on the bench and moving the throttle.
I picked up a set of numbered drills for cheap as well. So I'll take some measurements before I put the Summit carb back on.
sarguy01
Well-Known Member
Blaster II.
- Joined
- Dec 31, 2005
- Messages
- 8,738
- Reaction score
- 4,684
I replaced what you just bought MSD 6 and Blaster 2 with a Crane and it was much much better.
If the MSD HVC is compatible with the 6A use it but its not cheap.
- Joined
- Dec 31, 2005
- Messages
- 8,738
- Reaction score
- 4,684
Keep us posted!
Sarguy,
Did you read post #46. I pointed out the Idle Feed Restrictions [ idle fuel jets ]. They are a fuel jet [ not an air bleed ] because it is immersed in the fuel in the fuel bowl. As I also said earlier, the 046 could be a misprint, which is why numbered drills are reqd to properly test the orifice size.
The two jets circled in red are probably the main air bleed or idle bleed. Do you have a drawing that shows what they are? No mention of them in the spec chart in post #25. It is also possible that they are the economizer jets, which controls off idle & low speed cruise calibration. Often in the 0.042-0.060" range.
Did you read post #46. I pointed out the Idle Feed Restrictions [ idle fuel jets ]. They are a fuel jet [ not an air bleed ] because it is immersed in the fuel in the fuel bowl. As I also said earlier, the 046 could be a misprint, which is why numbered drills are reqd to properly test the orifice size.
The two jets circled in red are probably the main air bleed or idle bleed. Do you have a drawing that shows what they are? No mention of them in the spec chart in post #25. It is also possible that they are the economizer jets, which controls off idle & low speed cruise calibration. Often in the 0.042-0.060" range.
6*of timing, good luck with that.
Set it at 12-14, lower the idle speed back down and readjust the carb mix screws. You may need to dive into the distributor to limit total.
Set it at 12-14, lower the idle speed back down and readjust the carb mix screws. You may need to dive into the distributor to limit total.
Good to see you back in the saddle! Hope you're feelin' better.
sarguy01
Well-Known Member
Yes, I read it. The idle fuel restrictions (The inner brass tubes) are approx. .053 based on a number drill set. The screw in air bleeds circled in the pic measure at .043. These are what I ran at .039, .043, and was going to run at .046, but never actually tried .046.
In the parts diagram for the Summit and the Holley 4010, there are no bleeds shown in the picture, which is frustrating.
But, now that the ignition is sorted, I put the Summit carb back to .043 idle air bleeds, which is what it came with. I then reset the transfer slot and idle mixture screws. Getting ready to bolt it back on. The only thing I didn't change back to the out of the box config was the main and primary jets. It came with 68 / 73, and I put in 66 / 71, guessing that the 318 might not need that much fuel. However, jets are an quick change.
sarguy01
Well-Known Member
Yep, it was me trying to figure out a carb's tuning when a weak ignition was the problem. It did not like 6 degrees. Now that the ignition is good, I have the timing set back up at 12. I have a limiter plate in the dizzy set to 18 max, so I might bump the timing up to 14 and see how it reacts. I also recurved the Proform dizzy as it came with a lightning fast curve. Still might need to fine tune the curve.
You're a better man than I. I know what I would have done to that carburetor by now. LOL
sarguy01
Well-Known Member
Haha! Well, I almost threw a chainsaw I couldn't get restarted the other day, so I know the feeling.
sarguy01
Well-Known Member
Update, for those still reading. Ignition is good. I baselined the Summit carb to out of the box specs, except for a 66 / 71 main jet. Idled pig rich and ran with mixture screws in and speed screw all the way out, and was still turning 800 RPM. So I took the .043 air bleeds and threw in the .046 air bleeds. Okay, now we are getting somewhere. Leaned it out a bit and it will die if I turn the mix screws in. Quick adjustment on those to where RPMs stopped climbing, then backed off a tad. About half a turn out each on the mix screws. Bad news. The idle speed screw is still all the way out and it's idling at 1,000 rpm.
For timing, RPM stopped climbing at 18*, so I backed it off to 16. Took it for a spin and it runs pretty good. However, it's idling at 1,000. I can turn the timing down and lower the RPM, but it would be around 12-13 degrees, and I've got the limiter plate set to 18 (with no higher option), so if I used the timing to bring the idle down I'd have a max timing advance of 30*. Not sure that's enough. Also, I can't get the idle low enough to check the timing at say, 600 rpm, to see if I've got any mechanical timing being added. So my 16 initial right now at 1,000 rpm might only be 14 initial at 600.
So, I'm tempted, and not today since I've got to pull stumps from the pond, to put in the .049 air bleeds and see if I can use the speed screw to dial fine tune the RPMs. Or, do I add wire to the idle fuel feed tubes and try to limit the amount of fuel it's getting at idle?
For timing, RPM stopped climbing at 18*, so I backed it off to 16. Took it for a spin and it runs pretty good. However, it's idling at 1,000. I can turn the timing down and lower the RPM, but it would be around 12-13 degrees, and I've got the limiter plate set to 18 (with no higher option), so if I used the timing to bring the idle down I'd have a max timing advance of 30*. Not sure that's enough. Also, I can't get the idle low enough to check the timing at say, 600 rpm, to see if I've got any mechanical timing being added. So my 16 initial right now at 1,000 rpm might only be 14 initial at 600.
So, I'm tempted, and not today since I've got to pull stumps from the pond, to put in the .049 air bleeds and see if I can use the speed screw to dial fine tune the RPMs. Or, do I add wire to the idle fuel feed tubes and try to limit the amount of fuel it's getting at idle?
The base rule... Timing FIRST!
Timing will almost always has an effect on carb setting, carb setting don't usually control timing with an idle tune up. Foundation, idle tune sets the plate for everything that stacks on top of it. As with a house, poor foundation, nothing you build on top will be optimized. JMOP, stop messing with the IFR, air bleeds until you have a stable base timing level. Reset the carb back to a baseline and start over.
If the idle timing drops when RPM is lower, the mechanical is bleeding in, Advance the distributor and turn the rpm back down until the timing is stable in park and in gear. That engine should idle smoothly at 750-800 rpm with out issue and maybe drop 50-100 in gear when it is right. You will NOT get a good tune up with the timing moving like that. The base timing should not move at all.
Yes, systems have to be functioning properly to get things running properly. That cam/engine/carb set up should be a very simple tune up. If the mix screws don't do anything to the idle speed/vac readings, you have other issues like a vac leak, dripping fuel somewhere
Last edited:
sarguy01
Well-Known Member
I checked for vac leaks. Several times. Can't find anything. My vac gauge is reading 20 at 1,000 RPM. When I dropped the idle to 800 by reducing timing, I still had 17 on the vac. I also looked down the carb while it was running and could not see fuel dripping.
How am I supposed to back the RPM down if the idle speed screw is all the way out? This is the issue I'm having. I started over, and the engine ran with the mix screws all the way in and the idle speed screw all the way out. It got better with the next step larger air bleeds. But it will still run with the mixes 1/2 turn out and the idle speed screw all the way out.
Last edited:
He told you. Kinda. If the mechanical advance in the distributor is giving some advance at idle, that could be your problem. Remove the cap and see how easy it is to turn the rotor advancing it. If it feels like you could blow on the rotor and advance it, it may need stronger springs to keep it from advancing at idle. Another possibility is that it's pulling air from somewhere (vacuum leak). One way to check for that is, while the engine is running, slowly close the choke plate. If the engine runs with the choke plate closed, or close to it, you likely have a vacuum leak.
sarguy01
Well-Known Member
Well, he explained the concept. I understand that timing comes first and how mechanical advance works. I just had the dizzy out and it doesn't not turn easy. I have a heavy spring and a medium heavy spring in it, because it came with a really fast curve.
crackedback told me to start over and set the timing first. I did do that this morning when I put the Summit carb back on. And there's no way to make it idle lower without adjusting timing, which doesn't help me set optimal timing.
I still think something is up with the carb. With the Edel, I could adjust the idle down and it would die if I turned the mix screws in. I really don't think it's a vac leak.
-
