Ok as some of you may know, I am having an issue with my 383 stroker stuttering at light cruise anywhere from 1500-1900 RPM. Everything that I have read, and everyone that I talked to says that it was stemming from a lean condition. I have been playing around with the carb for the last week or so now richening it up to the point that I am now at the richest most point on the calibration graph. So I then turned my attention on to the ignition. I found that I had full advance(36 degrees) at 1700 RPM so I changed the springs to slow the advance down. It got a little better, but is still there none the less. Anyway, I am my wits end with this but still I press on. I decided to take a look at my spark plugs so I pulled them out on Sunday. As you can see, the ground strap electrode is gray, not the healthy tan that you'd expect. You can also see what looks like soot collecting at the base of the plug near the center electrode as well as the first two threads of the plug itself. If I had to guess, I'd say that these were on thier way to being carbon fouled. Double checking the plugs showed the gap stayed the same when I set it which brings me to a question. I am using a full MSD ignition. I have a 6AL box, Blaster Pro HVC coil, MSD Street Pro Billet distributor, and 8.5mm wires. Currently I have my gap set at .042. MSD recommends anywhere from .050-.060 gap for engines up to 10:1 compression. Do you think widening up my gap to .050 would do anything good???? I mean, I have never ever ran a plug with that much gap before, and don't think that it would be a good idea. What do you guys think???

I am not seeing any white

On most EFI motors that Ive worked on, the ground electrode is usually bare, probably from the leaner fuel calibration. My 350 runs at 15:1 in closed loop during cruising, and there is almost no deposits at all. Porcelin is bone white, and the ground electrode is clean. The motor may still be lean during cruise (although theres still alot of deposits on the center electrode), or it may be some other issue, such as varying AFRs or some ignition problem. Whats the heat range on the plug? How is it when you give it some throttle in that area? Does it still hesitate/stumble, or immediatly improve? do you have a wideband O2 available?

As for the timing, where does full advance come in now? Maybe try bringing it all in by 3200 RPM so theres not so much timing during light cruise.

This was my second attemt at making a post in the tech/general engine forum, but for some reason none of my posts show up there. Is something up with the site?? Anyway, I had to do an advanced search for my username to find this post, and I wanted to post a reply so you guys don't think I'm ignoring you or anything or purposly double posted.

There have been some issues with the boards not properly updating/showing threads. The admin is aware of this, I believe, so somebody should be working on it.

Dimented-Sorry bout the long response time. I guess the site was having some issues. I still can't access the home page at www.thirdgen.org. It comes up as a screen that reads database error. And when I create a new thread and someone posts in it, I can't read their post until I press the post button, pretty weird. Anyway to answer your questions....

Im not sure exactly what the heat range of the plug is. It is an NGK V Power FR4 if that helps.

If it is stuttering at steady cruise and I tip into the gas, the stutter goes away until I resume the steady cruise. Since my last post, I cleaned out my plugs, widened the gap to .050 and reinstalled them. I have been driving on them for a few days now, and I'd like to pull them again to see what they look like.

As for the timing, I now have 1 heavy silver and 1 light silver springs. The base timing is 13 degrees, and I have 32 degrees all in at 2500 RPM. The only option that I have left is to go with the 2 heavy but I really don't think that the engine wants that. it seems to run much better with a lighter spring in the D.

Unfortunately, I don't have any type of air fuel ratio monitoring equipment which is proving to be quite bothersome. At least if Iknow my A/F, I could tune the fuel mixtures right and then work from there. I can tell you this though. I can get the stutter to happen in 3rd gear. Funny thing is that it occurs at the same throttle angle(but at a higher rpm) when it does it in 4th or 5th. Let's say that I am cruising at light throttle in 4th gear at 35 MPH, probably around 1700 RPM. If I keep my foot in the same position but down shift into 3rd, the RPMs would go up to about 2500-2700 RPM, but the stutter will still be there. That leads me to believe that either...

A. The stutter is directly proportionate to a certain throttle opening angle or

B. It might be some type of light misfire

The reason why I never suspected a misfire in the first place is relevant. If a misfire were to ever occur, wouldn't it occur at higher engine loads? I mean at WOT there is much higher combustion chamber temperatures and pressures for the spark to overcome. In that case it would take the path of least resistance which would be out of the wire, or arcing to the headers, etc. Once I got that idea in my head, about the misfire, I began to listen to the engine when it was stuttering. It almost sounds like there is a light booming sound coming from the exhaust. Not sure exactly what it is from but it could be something. So the next thing on my list to check is to verify the firing order. If everything checks out OK then I am going to check resistance of my spark plug wires(MSD Super Conductor 8.5 mm wires) and see if they are in spec. If both of those check out, then I'm done. I have no other options left. I've exhausted them all.

first off I have my timing locked out completely at 32 degrees all the time. I have no stuttering or stumble at all from my carb. If it stumbles slightly upon tip-in while cruising then I would swap out accelerator pump cams or squirter sizes. I'm guessing you've already tried richening the idle mixture screws 1/8 turn each if 4 corner idle system to see if the "dead" spot goes away? if not that is a simple trick that worked on my old 850 holley double pumper when I would have a stumble at cruise. It really depends on how open the throttle plates are to determine which circuit the carb is running off of. But between the mixture screws and the pump cams or squirters I bet that will improve it right there. You'll never get perfect white plugs out of a carb application if you want max power as well.

xpndbl3- The stutter does not occur on tip in, it only occurs at steady cruise at light throttle. If I tip in tothe throttle, it goes away. Also, I have an Edelbrock carb, and don't have the 4 corner idling system like the Holley's do.

i would jet up a size of two and see what happens then if only cruise causes the stumble. I'm sorry i'm not too familiar with carter carbs, but I did have one for a short while, so i'd say add more fuel on the primaries and see if that clears up the stumble. Like on a holley I jet down 4 sizes from optimum to keep the primaries "lean and mean" on the street to not foul out plugs, but at the track the extra fuel is worth .2 in ET. I'd add fuel and see if that clears it up for you. Also a bigger cam might not want to be lugged down that low if you're shooting for under 2000 rpms during cruise with more duration and lift.

xpndbl3- That is just the problem, I can't *jet* up anymore than I currently am. My Edelbrock carb doens't have the same type or number of adjustments that the Holley carbs do. I am atthe richest calibration right now and can't go any richer. I'm not sure if I would call the camshaft that I have *big* but it isn't small. It is a COMP cams 288HR-10 lift .520/.540 duration 236*/242* and 110 LSA. Maybe I'm just asking too much for it on the street.

i would venture to guess that while cruising that carb would want to stay above 2200 rpm or so rather than under 1700 like I think you posted up above, will that help the situation at all? Also, I think the edelbrock cars use hangers or rods and if you're at the smallest rod I believe you can grind the point down more for more fuel flow, but I can't believe you'd be at the richest possible hanger/rod that they make for that carb.

xpndbl3-If I can get at a steady cruise speed in 4th or 5th gear at about 2200 RPM, the stutter pretty much goes away. I have noticed that the stutter is also in 3rd gear at about 2500-2700, but only if I keep the same throttle angle. For example, let's say that I am cruising in 4th gear at about 1800 RPM(about 40-45 MH) and I downshift into 3rd at the same throttle angle, I will still have the stutter. I think that it might be the carb not liking a certain throttle plate angle. However, I am in the process of fixing my #5 plug wire. I ohmed out all of my wires and found the #5 wire to have about 55,000 ohms of resistance. I am using the MSD Super Conductor wires that have 40-50 ohms per foot. This wire is smoiked. Anyway, I'm going to replace the wire and see if it does anything.

Also, here is the power and cruise mode fuel mixture calibration chart for the Edelbrock 1407 and 1410



Like I said previously, I am currently at the #17 calibration. At this point in time, I feel more inclined to remove the Edelbrock carb and install a Holley 750double pumper only because I know that it has the ability to deliver more fuel. However, I still don't want to give up on the Edelbrock just yet. If you take a look at the #1 point on the graph you sill see that the number 1 is base calibration the way it came from Edelbrock. Now, with the carb in that calibration(#1), it is designed to supply enough fuel to feed a 420HP 9.5:1 350 engine because it is part of the Edelbrock Performer RPM package. Now I on the other hand am a 500HP 10.0:1 383 engine, but the extra fuel requirements of my engine should not put me on the richest end of that graph(at least I would think). I am seriously considering going back down to calibration #13 and driving it around for a week or so and then pull the plugs yet again to see what they look like.

i've never had much luck with edelbrock carbs on performance engines. I would imagine a bigger edelbrock might have more fuel delivery availability, but it sounds like just the cruise or possibly idle circuit depending which you're on at light cruise needs to be richened more. Did you try richening the idle mixture a bit to see if that helps?

xpndbl3- Yes I have tried to richen the mixture at idle. Right from Edelbrock they said that some of the idle mixture circuit *overlaps* into the cruise section of the metering rod under extremely light throttle. Unfortunatley for me, richening the mixture at idle has no effect whatsoever.

well paul, i'm basically out of ideas for you. I do have to say that holley HP and my proform race series carbs are both nice and easily tuneable.

xpndbl3- Well, I sure do appreciate the time and help that you(and everyone else) has given. I have just come to the conclusion that this carb doesn't like me very much I can only assume that with my current engine combination(particularly the camshaft) and horsepower level that the engine just doesn't want to be at anything lower than 2300 RPM while cruising on the street. It is something that I am just going to have to live with. Not that it is a big deal or anything, I'll just have to make sure that whenever I drive the car it has to be at WOT always

have you tried changing the metering rod springs when you have the rods out. I found they are sensitive to even the smallest vacuum change. I am not 100% sure but if I recall the lighter spring may help fatten it up a little. Double check the book for sure

Below are the listed uses for Edelbrock carbs. Match your number to it's carb and that will give you a clue as to whether or not your carb can flow the fuel your engine requires. Run your plug gap up to MSD's suggested amount of
.050 and check your fuel pressure and air fuel ratio while driving to see if a weak fuel pump diaphram might be the problem. I doubt it is, but it's better to be safe than sorry. Hope this helps you get it fixed.

CARBURETOR APPLICATION GUIDELINES
General Application Use Carb Size Secondary General Displacement Cam Guide Intake Type (B) Carb Part# Calibration Kit
(CFM Rating) Type Guidelines (Duration @ .050) Reference

THUNDER SERIES AVS CARBURETORS
Mild perf. street small CID 500 cfm Adj. Velocity 225 - 327 cid Up to 220° Dual plane 1803/1804* 1486 (C)

Moderate high-performance street 650 cfm Adj. Velocity 302 - 400+ cid Up to 220° Dual plane 1805/1806* 1840

Off-road high-performance 650 cfm Adj. Velocity 283 - 460 cid Up to 220° Dual plane 1825/1826* 1842

High-performance street/light strip 800 cfm Adj. Velocity 350 - 502 cid Up to 246° Dual plane & 1812/1813* 1841

small single plane
Dual-Quad Small-Block Mild/High-Perf 500 cfm Adj. Velocity 302 - 400+ cid Up to 220° Dual Quad 1803/1804* -

Dual-Quad Big-Block Mild/High-Perf 650 cfm Adj. Velocity 400 - 502 cid Up to 246° Dual Quad 1805/1806* -

PERFORMER SERIES CARBURETORS
Stock replacement/mild perf. street. 600 cfm Velocity 305 - 350 cid Up to 200° Dual plane 1400 N/A
Calibrated for economy,50-state
legal on ’80 and prior GM only

Mild perf. street small CID & dual-quad 500 cfm Velocity 225 - 327 cid Up to 220° Dual plane & quad 1403/1404* 1486 (C)

Moderate street high performance, 600 cfm Velocity 302 - 400+ cid Up to 220° Dual plane 1405* 1479

street and towing
Mild perf. street,calibrated for economy 600 cfm Velocity 302 - 400+ cid Up to 220° Dual plane 1406* 1487

High-performance street (small CID), 750 cfm Velocity 350 - 502 cid Up to 230° Dual plane & 1407* 1480

Moderate high-perf. (big CID),towing small single plane
Mild performance street,towing, 750 cfm Velocity 350 - 502 cid Up to 230° Dual plane 1411* 1481

calibrated for economy w/performance
High-performance street/light strip 800 cfm Velocity 350 - 502 cid Up to 246°
Dual plane & 1412/1413* 1480

small single plane
Dual-Quad Small-Block Mild/High-Perf 500 cfm Velocity 302 - 400+ cid Up to 220° Dual Quad 1403/1404* -

Dual-Quad Big-Block Mild/High-Perf 600 cfm Velocity 400 - 502 cid Up to 246° Dual Quad 1405* -

(A) Use calibration kit #1485 on 4.3L 90°V6 with #2111 & #2114 manifold
(B) Adapter #2696 required for OEM spread-bore intakes
(C) Calibration requiredfor single quad applications only