Thread: Kind of a Drag

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Originally Posted by Good Wrench

That stupid ghost problem is back. It acts just like if you had a cracked cap. Kicks through the intake and exhaust under load.

How many miles are on this motor?
Have you performed a compression test?, what is the compression on each cylinder?
Is the timing steady at idle or bouncing?
What is your vacuum at idle?, and is it steady?
What is the fuel pressure at idle?, and under load?
Does the motor after run?
When you adjusted the valve lash, did you note all valves opening and closing equally?
Why are you running straight 50 weight oil?

Originally Posted by Good Wrench

Ignition was changed a couple years ago with a fresh MSD distributor and a MSD Street fire ignition box. Recently I changed plugs, new Taylor 8mm wires, cap, rotor, coil, no resistance center electrode.

changed gaskets for the base and nitrous plate,

fuel filter which is now a little billet canister with one of those old style q-jet bronze filters in it.

MSD usually doesn't like solid conductor wires (no resistance).

Are you using nitrous?

Have you checked fuel filter for clog/pressure loss?

Originally Posted by 36 sedan

Curious is the trip up hill one direction?

That's what I was beginning to think, but no....
Gardner elevation 1060'
Overland Park elevation 1086'
I think I'm going with the demonic explanation.

.

LOL!
Kinda curios for the answer to the questions I asked. Especially the ignition wires, MSD Street Fire systems do not work with solid core (zero resistance) wires and it can damage the box causing gremlins leading up to failure.
Although, there could be other problems not knowing the age and condition of the motor. He could have burned valves or a bad timing chain. I guess it's time to test.

Hiyall,

Distributor is a street fire with the module taken out so I can use the Street fire box. I just shimmed the endplay yesterday and unplugged the vacuum advance. Cap and rotor is MSD just a week old. The electrode is a low resistance one that I bought separately because the MSD ones didn't hardly protrude out of the cap.

Timing chain is a true roller with 2 degrees slop in it. Crank pully indexed in the stock position. Not sure of the crank timing my timing light quit working. timing was steady when my light worked.

Compression is 160- 165. Pistons are 4 valve relief flat tops I think the compression is between 9-10 to 1.

Vacuum runs nominally at 19-20. With the edelbrock 1406 600 cfm it idles at 950 rpm and 12 on vacuum. With a quck fuel (Aka Holly) 750 cfm it idles 950 rpm at 19 vacuum. Almost 20.

Fuel filter is a little billet casing with a bronze chevy filter. They won't let you use the glass filters at the track now. I don't like bronze filters.

With the Edelbrock the fuel pressure is 5 With the quick fuel it's 6. I have a pressure regulator and a gauge. The gauge is in line after the fuel filter. The choke is electric and operates just fine. The Edelbrock is tuned a stage and a half richer on power and cruise ran good for a while. I rebuilt the carb at the last gremlin showing. Air filter is a K&N with the filter top also. I just cheaned it too.

Wires are Taylor 8 mm silicone that I replaced when this gremlin first showed up. I added heat shield wrapping on 4 that hung close to the headers. The wires are also loomed. Plugs are Bosch racing shorties to clear the headers.
Gas is 91 octane.

Heads are fresh World heads 2.02-150 750 cc chambers I THINK. I had to change the rocker studs to accomodate roller rockers 1.5.

Cam is a Lunati barebones The middle offering. Flat hydraulic lifters.

Oil is 50w cause I need oil with the zinc in it and 50w was the only oil the speed shop had.

The car does have a bottle in the trunk but I haven't used it since this gremlin first showed up.

I also checked for vacuum leaks and changed the carb gaskets and checked bolts on headers and intake, checked hoses ect.

All ground wires are connected to a bronze clamp at the battery with gold connectors. So is the positives too. I have two ground straps at the rear of the motor and a wire from the frame to the alternator bolt then from there to the battery side post I checked the connections too.

So, here's exactly what happened Gremlin shows up doing that trip to Gardner. At the same place on the freeway! I'm just cruising along at 65 MPH at 2800 rpm. First the right side exhaust, Pop!
I lightly touch the throttle Pop through the intake. Steady cruise, Pop, bang, pop! intake and exhaust. Cars move away from me. People put their phones down and grip their steering wheels. Pop, Bang Pop Bang, rumble, Pop bang I turn up the radio and grow red with frustration. I get to where i'm going. At idle, occasional pop through the exhaust right pipe. I pop, bang all the way back home. I go to the speed shop. I get talked into a rediculouly large carburetor, Boo! I buy a new MSD cap and rotor and a different low resistance elecrode. I put them on in the parking lot. Start.. The problem is gone! Yay! Celebratory burnout on the street. Next day play with big Holly clone. Paid 20$ for speed shop employee drag racer to get the car to launch. NO gas mileage but man, what a launch! Drove it to Gardner for work. Used up most of the gas BOO!. I went home and put the Edelbrock 1406 back on and reconnected the vacuum advance and retarded the distributor by ear. Ok .Next day go back to Garner, Same place, same speed, same freeway. Exhaust says Pop. Touch throttle Pop throgh the intake, coast, pop through the exhaust right side. It only seems to pop throgh the intake if I give it throttle. but just a couple time and then it catches and accelerates as much as I want. At cruise it seems to pop,pop,pop through the exhaust. I go home, take the distributor all the way out and inspect cap, rotor, hall effects switch and all connections. Nothing wrong. I twisted the rotor shaft back and forth and noticed some slop so I reshimmed the shaft and tightened it uo to about 10 t0 about 15 thousands end play., Cleaned up everything and checked all connectors. Put it back together and drove to Olathe. Still Pop,pop,pop in all the wrong places. Went back home and parked with the engine running. I open the hood and rapped the throttle and the engine races quick and fine no pop. Idles normal, no pop. I shut it down and cry to Mrs Goodwrench. She' says try new 750 with 70 jets in the front, 80 jets in the back and a 6.5 power valve. She's also been encouraging me to put in a higher stall torque converter But I say let's save the money since i'm unemployed. But I digress. So I wrote this first. And there you are!


PS, Yes I know a 750 is TOOO big for the car but it IS vacuum secondaries and the guy at the speed shop says, " Forget the math buddy! What matters is it works at the track, It'll be like night and day" Well I had to step up on the acelerator cam. But well, it is a strong carb. The guy says, Let me step the jets down 2 notches, 30$ please! I havent tried it yet, he still has my carb. I really don't want it. I want a 650 instead but nobody listens to me. I launch the Edelbrock and the tires break but only slightly and the 750 they don't break at all. I forgot to say I bought a Grand National limited slip so both tires grab now. Midrange is much better and the acceleration pins you to the buckets even at 5000 rpm. It just keeps climbing. The Edelbrock kind of flat lines at WOT.
I sure hope sombody can halp me figure it out. It's still our only wheels. And for the first time in decades, i'm stumped!

Originally Posted by Good Wrench

Vacuum runs nominally at 19-20. With the edelbrock 1406 600 cfm it idles at 950 rpm and 12 on vacuum. With a quck fuel (Aka Holly) 750 cfm it idles 950 rpm at 19 vacuum. Almost 20.

The vacuum readings above points to a problem with your Edelbrock carb. And if I remember correctly this is the carb with the whistle. It appears the carb has a vacuum leak, look for a cracked throttle base (not uncommon if over tightened), or an open passage way at the carb base, possibly an incorrect carb to throttle base gasket.

Originally Posted by Good Wrench

I went home and put the Edelbrock 1406 back on and reconnected the vacuum advance and retarded the distributor by ear.

Move your vacuum advance to venturi port and re-set your initial timing correctly.

Hi 36 sedan,

Carb gaskets are about 3 weeks old. After rebuilding there was no more whistle and that carb always had the same vacuum reading even new. Intake is Weiand dual plane with th Quadrajet base but I put a separator plate in to cover the bigger spacing in the back.

I did have the advace to ported vacuum before. The speed shop guy says my recurved weights will handle the timing at 23 degrees played out at 2000 rpm. He says I had too much total timing.
However, I think at this point is has to be carburetor lean as I think I beat the distributor horse to death. I will do all you suggested. Today in fact. Mrs Goodwrench says to switch carbs and see if the problem is still there. I'll recheck my gasket sandwich as well. I will need a new timing light however, some say they don't work with multispark ignitions, If not then what does?

Something I forgot to mention, In the distributor cap the burn marks are right at the front of the tabs, and clean afterwards. Is that normal?
Anyway, I'll look at the fuel and vacuum parts. Thanks!

Dyno says the best timing is 11 BTDC. I had it st at 10.

Well, I went out and got the wd 40 ans started spraying all over that carb, base and intake manifold seams. Checked all hoses. Nothing. It popped twice through the exhaust. Otherwise ran like a striped ape. It's just got to be a vacuum leak somewhere.

When you check and adjust timing make sure your idle speed is below 800rpm or you risk your mechanic advance interfering and giving an incorrect reading. Here's a link to the light I use, it works with multi spark MSD and all other ignitions, some rental stores rent this light.

If you have adjusted the 600 Edelbrock correctly something is wrong with it, it should be the same or slightly greater vacuum than the 750 Holley, a drop from 19" to 12" is wrong. The gasket I referred to is not the base to manifold gasket, but rather the carb body to throttle plate gasket, make sure it is correct size and not allow vacuum to escape. I always check the gaskets in a kit to be sure they are correct, you'd be amazed how many are not or have multiple gaskets to satisfy other carbs as well.

The popping through the exhaust and intake both is concerning to me, especially the loud pops you describe. A manifold/carb vacuum leak can cause intake pops because of the lean mix (concerning in itself), but along with exhaust pops of magnitude sounds like something else. I've experienced this before with a bad EGR valve and smog pump system, but I'm guessing you no longer have that installed. Thus the burned valves or timing chain thought. However, the Holley 750 running good kinda rules this cenario out.

So back to the Edelbrock, a 7' vacuum drop is significant enough to really muck things up, but this usually causes a lean condition (intake pop yes), the exhaust pop is usually a late fire issue or an exhaust manifold leak pulling in enough air to ignite any left over fuel in the exhaust (usually rich mixture contributes to this). But it does seem to be carb specific, possibly if the vacuum leak is effecting the metering circuit, which with that much of vacuum drop it most certainly is, and you are alternating between lean to rich as the metering circuit reacts. I believe we just found your culprit.

If money is an issue, that Quick Fuel carb can be re-jetted and adjusted to do a pretty good job at a very reasonable cost. And a 750cfm vacuum secondary is not too much for the motor, if tuned correctly. Heck I'm running twice that on a 327 (dual quads) lol...

So, I change carbs and see what's up. The Edelbrock does run rich I stepped it up just because I got some more umph out of it. The exhaust is Flowtech headers, 3" to 2and a half collectors, a T crossover pipe and knockoff Flowmaster mufflers. It amost seems to pop in the right muffler too. These pops intake and exhaust always show up at the same time. Other times the engine runs great. I did check header bolts and collector bolts but didn't find anything obvious.

Ok, so i'll put the super glut Holley back on and see what's up. I'll bet at this point you're right.

The speed shop fellow took the front jets from 72 to 70 and the backs from 82 to 80. I had accelerator pump cam two notches up from their stock and it erased the flat spot I had.

When I had it first the af mixture seemed to be fine. In fact it seemed like nothing but water was pouring out of those pipes. A lot leaner than the Edelbrock which spews out hydrocarbons. I don't know what it will do now.

That carb seemed to be almost adjusted great right out of the box. I was impressed. But it did glut gas. But I remember now all Holleys do anyway.
OK , It gets a carb change tonight. I'm so excited I won't be able to eat dinner i'm sure.

If at a steady cruise speed, the motor lurges/stammers slightly (runs un-even, feels like the motor wants to rock back and forth) the primary main jets are too lean. If wide open throttle feels lacking power, secondary main jets are too lean. And, on vacuum secondary carbs, if at wide open throttle it feels like a slight delay then ramps up throttle, the secondaries are opening too soon, install heavier secondary vacuum springs until this condition goes away.

Good luck!

THANKS! The secondary spring on this carb is adjustable with a screw so hopefully it will be in range.
Question, should I use the vacuum advance still? It is adjustable so perhaps I can dink with it some. I know, first things first.