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I am going through the process of learning to tune my '70 Cutlass. It has a bit of a stutter on light acceleration that I can't seem to pinpoint. It just kind of goes bluh-blub-blub whenever I leave a red light.
I replaced the ignition items from condenser to plugs and all the usual maintenance items, set the dwell and timing, set the idle mixture following the Edelbrock video instructions, and the issue remains.
The car has a stock 455, J heads, Edelbrock manifold, and Edelbrock 1411 carb. Looking at the Edelbrock website, I see the 1411 is a 780cfm, which seems like a bit more carb than needed- thoughts on that?
I don't see a fuel filter anywhere, which can't be good.
I wondered if I should try different metering & jet setups to see if that helps. The carb might need a good cleaning also, no way to know how long it's been and if there's no fuel filter...
I have a compression tester and plan to do that test soon.
Today I took a vacuum reading that I will try to post, the car seems to be making about 19 inches of vacuum at idle, but the needle was wagging between 18 and 19 pretty regularly.
Any thoughts or advice on the carb and vacuum reading?
What is your dwell and timing set to? Check by your fuel pump to see if there is an inline filter. There is no filter in an Edelbrock carb similar to whats in a Rochester.
Nice! Thank you! An animation is worth a thousand words! I have scenario 4 for sure, and also either 7 or 11.
Eric, dwell is 28, timing is 12 degrees BTDC. There is no fuel filter on the fuel line.
I came across another interesting problem. I'm not exactly sure what year the engine is, but it has the 369 021 casting number, which I believe means it is a 70-72 block, but it has J heads which I think are newer. I set the gap on the plugs at .030, but I saw in another GM repair guide that the gap recommendation is larger in some of the following years. I think for the last year for the 455 it was as high as .080. So I think I may regap the plugs and see if it knocks out the slight wag in the vacuum reading. if so, that would mean it was scenario 11 I am having.
I had been told by a local mechanic that he thought I might have a blown head gasket around a water jacket, but that would show on the vacuum reading if so, wouldn't it?
Actually, in looking at scenario 11 again, I don't think that's my issue, my vacuum reading was not mediocre, it was 19"Hg with a slight downward wag, sort of pulsing down 1-2"Hg
Try getting your dwell to 30 then set your timing to 12 with vacuum advance disconnected and rpm @ 1100, then drop it down to 650 in drive. The bigger spark plug gaps are for an HEI distributor. You need to ad a fuel filter.
Oh, right, that makes sense about the gap and the HEI. I read that also about setting the timing at 1100 so I did that yesterday. I need to fix the E brake before dropping it down into drive though
So if ol blue has been being driven around with no fuel filter on it for who knows how long, could it be that my stuttering issue is due to a contaminant in the carb? If so, what specifically in the carb is most likely to have been affected? I have an Edelbrock 1411. I've wondered if that carb is too much for a stock motor.
The AVS series from Edelbrock is great and very tune-able carb, without disassembly. But Id pull the horn and inspect for any debris and clean accordingly. As Eric said it needs a in-line filter between the pump and carb. Ebrock has a nice aluminum log style filter that accepts a standard GM in-carb style cartridge. Use better quality non ethanol rated fuel line. The NAPA, United, Federated etc have the better stuff (as a rule). Purchase the Ebrock rod, jet, spring kit for the 1411. Then go to Edelbrocks tech site(or call them) and get the tuning chart. Study it good as it can be hard to interpret at first. You should be able to dial out the stumble. Make sure the centrifugal advance is in good shape...springs not stretched and rusted, advance mechanism operates smoothly etc...Also make sure there is zero vacuum leaks as this will null the tuning.
Last edited by droldsmorland; October 7th, 2016 at 09:50 AM.
OK, thanks! The car has a rubber fuel hose going from where someone hacked the original metal line, about halfway from the pump to the carb. Maybe I should look at a replacement fuel line and replace the hack job metal/rubber line while I'm adding the fuel filter.
Edelbrock has a pretty good video on YouTube showing how to use that kit, think I will look at that metering/jet kit too. Not sure how to choose jets but as you said I could call and talk to the folks at Edelbrock.
Funny you mention fire, I've wondered before if this car had an engine bay fire at some point. The paint on the brake booster is peeled, the a/c insulation is melted on the engine side, and the tank for the wipers back by the distributor looks heat damaged.
Eric I'll try moving that lever to the lower hole tonight, that should be simple to try.
OK, thanks! The car has a rubber fuel hose going from where someone hacked the original metal line, about halfway from the pump to the carb. Maybe I should look at a replacement fuel line and replace the hack job metal/rubber line while I'm adding the fuel filter.
There is no replacement line for your setup with the Edelbrock carb. Use rubber fuel injection hose and use an inline fuel filter
Edelbrock has a pretty good video on YouTube showing how to use that kit, think I will look at that metering/jet kit too. Not sure how to choose jets but as you said I could call and talk to the folks at Edelbrock.
If you don't have instructions for your carb, you can down load some form Jeggs/ Summit, or Edelbrock.
Funny you mention fire, I've wondered before if this car had an engine bay fire at some point. The paint on the brake booster is peeled, the a/c insulation is melted on the engine side, and the tank for the wipers back by the distributor looks heat damaged.
Anything is possible with these old cars and carb fires were very common, especially in the winter when they got flooded because the owner could not get it started.
Eric I'll try moving that lever to the lower hole tonight, that should be simple to try.
Well fellers, I ran a compression test today. I took a look atht e plugs of course and they all looked pretty normal to me except one, the ground electrode on that one was an ash color. Compression seemed pretty consistent also, the readings were within 20lbs of each other and 4 were between 151-160.
The plugs all looked like this:
The one that looked different:
Compression readings:
I read the Edelbrock manual and they also mentioned stepping up the accelerator pump link Eric, so I did that and am going to go for a spin and see how that worked.
Also, I checked the dwell again, it was at 25 so I set it at 30, then checked the timing again, which was good, and set the gap on the plugs to .40 while I had them out. They were at .30 but a couple were below that.
The plugs need to be gapped at 30. The one plug that is different may be bad, or has a bad wire, or the wire was not connected correctly. Your #2 cylinder is a little weak, I'm assuming you did this dry. Did you also do a wet test where you squirt a bit of oil into the cylinder prior?
I did not think to do the wet test, I just warmed up the car then pulled the plugs and ran the test. I suppose I could do it again today with a teaspoon of oil in the cylinder.
I drove it to a friend's last night and unfortunately it was bogging pretty badly still. it's only with the lightest acceleration that it bogs (or stutters), but it's pretty bad when it does. There was a couple of times that I thought it would stall before it would 'catch'. It doesn't bog at all once it does 'catch' and gets going.
Otherwise it runs well but is definitely under powered.
I agree, I think it could be why the car gets up over 215 in less than 10 miles of driving. How do I fix that? Idle mixture? Change metering rods? And how do you know for sure when it's right? Am I going to have to get a rich/lean gauge and measure it at the tailpipe?
No, I guess I don't know how to check that. It's from the second cylinder on the driver's side, so it's easy to reach and the wire feels like it is seated well on the plug, I guess I can check the connection at the distributor cap, but even then I'm only confirming that it is connected. What should I do, just go get another plug and get a spark tester? I could do the old pull the wire and hold it close to the manifold but damn that shiz makes me nervous...
I would think the engine would be running rough. You can pull the wire with it idling and see if there is a change in the way the engine is running. It looked like it wasn't firing.
An inline tester was a lot cheaper so I go one of those and it looks like the electricity is getting to each plug.
When I was talking to the guy at the counter I noticed that the system called for AC Delco R45S plugs for the 455 2V and R43S for the 455 4V so I got a set of the 43s to replace the 45s I had in the car, gapped the new ones at 30 and installed them.
I also bumped the accelerator pump linkage up to the lowest hole. It gurgles, spits, and hesitates maybe a bit more severely but 'catches' at a lower rpm.
It seems to me like we're scratching more and more things off of the list of potential issues, I can't help but think it's just running lean at light acceleration and in cruise mode. That might explain the engine running hotter and hotter at cruising speeds, right? At idle the temp holds steady at 190 until I drive it around, then it climbs.
Also, when I pulled the plugs today, it was more like half of them that seem to have an ash coating on the ground electrode. That is an indication of a lean mixture, right?
What do you guys think? Next step is different metering rods? It has an Edelbrock 1411 carb.
That's a 750cfm carb, and that is plenty big for the car, when properly tuned.
It may be gunked up inside, or someone might have changed the jets inside. It may be worth taking the top off the carb and looking for debris.
Mine has a 1405 carb,( a 600cfm), and it's almost enough when jetted up a couple steps. The 750 should be way more than enough in out of the box trim. Something else is wrong here.
I thought the same thing about the carb, the calculation method I've seen for a stock 455 would be:
455 x max rpm which for me is 4500 = 2,047,500 / 3456 =592cfm carb
even if I go 5500 for max rpm which this car will never see in its current form the calc is:
455 x 5500 =2,502,500 / 3456 =724cfm
So I agree that the should be plenty of carb if someone hasn't jacked it all up. It does not have a fuel filter on it so I suppose I should clean it well.
I thought the same thing about the carb, the calculation method I've seen for a stock 455 would be:
455 x max rpm which for me is 4500 = 2,047,500 / 3456 =592cfm carb
even if I go 5500 for max rpm which this car will never see in its current form the calc is:
455 x 5500 =2,502,500 / 3456 =724cfm
So I agree that the should be plenty of carb if someone hasn't jacked it all up. It does not have a fuel filter on it so I suppose I should clean it well.
You will be hard pressed to find many 455's running well on a 600.
But I agree. Take the top cover off(it's like 10 bolts) and can be done with the carb on the car. Look into the bowls and see how dirty they are. Also consider backing the idle screws out, and cleaning those holes out. Debris likes to get stuck in in there.
I personally hate the edelbrock that's on my car, but I've been through hell and back getting it to run halfway decent.
I called Edelbrock on my way home tonight, got a friendly helpful guy on the phone who immediately said "You're running too lean, that carb is set up to run lean out of the box. What's your address? I'll send you the metering rods and springs you need at no charge."
Gotta like that. We'll see when they get here if that does the trick.
JPC, yours is a 350, his is a 455. That's right size carb. John make sure your getting a squirt just as the linkage is moving.
Yes, I heard it squirting when I was moving the linkage. Once those rods and springs arrive I'm going to take the top off and go ahead and give it a good cleaning, check the floats and all while I'm in there.
You might as well throw a rebuild kit in it and double check float levels.
What comes in a rebuild kit? I forgot to mention that the Ebrock guy suggested I get a little more advance, 14-16 degrees. What do you guys think about that?
JPC, yours is a 350, his is a 455. That's right size carb. John make sure your getting a squirt just as the linkage is moving.
You're absolutely right. I had left two threads open to review later, and I confused my responses between them.
But still, that 750 should be more than enough. It's gotta be gunked up, or the accelerator pump isn't working. Someone could have even changed the accelerator pump squirter nozzles too small, or made the primaries or secondaries smaller.
You've gotta take the top of the carb off in order to clean it, might as well confirm what primary and secondaries are in there, and know where you might need to go. Most likely richer.
Edelbrock sells calibration kits for each carb for around $40, that come with assorted rods, springs, jets, etc.
Depending on you vacuum at idle, you need the correct springs under the metering rods(3 minute change). I've never really noticed much of an improvement with this, but it's worth checking. They are under the two lima bean shaped covers on the top the the carb. They come out with one screw each.
The car had been running pretty well, it's still having the annoying issue with the brief sputter when accelerating from idle, but it was not stopping me from driving it and having fun. I haven't had time to take the carb apart to clean it and all, but did swap out the metering rods and springs, that made no difference at all that I could tell.
I drove the car over to my cousin's house a week ago on one of the hottest days of the year, the temp was cycling up to about 230 then back down to around 215 which was encouraging to at least see the temps going back down instead of just continuing to go up. The drive is about 30 minutes, half on the interstate so I was able to just hit a cruise speed and watch it. I made that drive again yesterday, it was a good bit cooler and the temps were fairly steady around 220.
I opened the radiator the other night and looked at the coolant level and noticed rust around the radiator cap, so I drained about a half pint or so out to look at the coolant and found it has an orange tint to it and so I put the coolant in a glass jar and could see it had quite a bit of rusty sediment in it. The coolant is fresh, about 2-3 months old, so I ordered some Evapo-Rust and plan to run that through the system and flush it again. Starting to think maybe this whole running warm issue is just that the cooling system has too much rust in it. I'm going to keep running Evapo-Rust through it until I stop seeing rusty sediment and see what difference that makes. When I let the coolant sit in the glass jar for a few days, you can clearly see the separation of coolant and the sediment collects at the bottom of the jar, so it definitely needs to be flushed in any case. I wish I could find a shop that still has a backflush machine but most places I call don't even know what I am referring to..."Sure! We have a garden hose!!"...
My big problem right now though is a problem I had once before. Last week right after I tanked up with 87 unleaded I noticed the car was running on when I shut it off, badly. I thought "well that was dumb to put 87 in it, I'll go get some 104 boost" which I did but it didn't help at all. I had added some Seafoam to the tank also, so I thought I'd just run through this tank then just go with Super with no additives and see if it keeps up.
Then last night I was driving home from my cousin's again and was cruising along on the Interstate on a beautiful, cool evening and then the car just suddenly started to lose power and started backfiring and sputtering, and badly too.
Last time that happened the distributor had worked itself loose and I was able to just turn in clockwise a bit and got it home, then set the timing and made sure the distributor lock tab was tightened down well. So I pulled over about halfway home and checked it but could not budge it. So I got off the interstate, took the back way home, all the way praying I'd make it. The car was fine at idle, a feather touch more and it would instantly try to die, but I did manage to get home.
So, this week I'll add the Evapo-Rust and try flushing the rad again, but first I am going right now to go check the timing.
Question to you guys, if it is the timing, have you guys ever heard of a distributor working itself loose like that repeatedly? I'm about ready to just replace the damn thing with an electronic swap, I'm tired of fooling with the timing, dwell etc. And my German car nut buddy is convinced my overheating problem or faulty timing advance anyway, so I could possibly kill two issues at once with a new distributor.
Last edited by mownhoj; September 18th, 2016 at 08:09 AM.
The backfiring could be a bad connection at the points or coil, a bad condenser, points loosened and dwell changed which changed timing, etc... A points distributor is the easiest to troubleshoot. On a side note, since you ran the carb with no filter, you may have gotten trash in it. Its your money if you want to buy another.
Your temps are rather hi, what thermostat are you running? Is there anything in front of the radiator blocking air flow? I would not use evaporust to flush the radiator, prestone makes a flush kit that works very well.
I wasn't thinking of buying a new carb, at least not at this moment. I want to clean it, rebuild it, put a fuel filter in line and go from there.
Yes, I had the similar issue with a Jeep of mine, I replaced the plug wires with some expensive Moroso wires and almost immediately one melted and was arcing out on the exhaust manifold. The difference that time was that the misfiring was over the whole RPM range. This issue is only above idle, which seems to suggest to me it's an advance issue but I will check dwell, wires etc.
Dwell was at 30, checked the timing, it had moved down to 4 degrees so I set it back to 14 degrees advance but still have the misfiring and backfiring. While I had my timing light I noticed that if I brought the engine speed up, the timing light sometimes didn't light for a second or three at a time, so I can assume I'm not getting spark consistently.
Man am I getting discouraged. I have a timing issue, a fuel issue, and a cooling issue, all 3 of which I have been trying to solve since I got the car in April. I know I need to open that carb and clean it and possibly rebuild it, but since I know I'm only getting intermittent spark, I am just feeling like I need to sort that out first as I don't see it would do me much good to spend time on the carb until I know I am getting spark.
So now what? How do I isolate the problem from here? Just get a new distributor?
August 21st, 2016, 02:39 PM
