jpc647

Hi Guys.

I have a 72 Cutlass "S", with a 350/th350 combo. Car has HEI, Edelbrock RPM intake and 1405 carb. On the passenger side, every other plug is lean. Plug 1, closest to the front is normal color, but 3 is shown below. 5 looks very similar to 1, and 7 looks like 3. This one was the worst. Seems very very lean. Agree? Threads are a little oily too.

I was going to try and swap the intake this weekend to the stock replacement, because I thought it would be a better fit for my stock engine, but I'm thinking I might have bigger problems. What would cause this? Plugs and wires are from last season. What could the white coating be?

Car used to have a 1406 carb and I had a lot of hesitation problems, etc. 1405 cured that, but car still didn't "come to life", so I thought changing the intake might help too, better match my combination.

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Intake is also getting oil inside of it?

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oldcutlass

It could be a manifold gasket issue on that side. What gasket did you use? Have you checked for vacuum leaks? Can you post a pic of all 8 plugs separated by bank?

jpc647

The gasket on there is a victor. I'm not sure, I can't barely make out Victor on the gasket. I can and will post pictures of the plugs, separated by bank tomorrow. I bought the Felpro valley pan gasket to replace what is there, if and when I do it.

I've checked everything I can for vacuum leaks. I have been unable to find one. Sprayed water and carb cleaner all around the gasket and mating surface and nothing. All hoses are tight(not that there are very many). Timing doesn't jump around to suggest the vacuum advance canister in the distributor is bad.

Just for reference, the right side of the intake picture where the oil is puddling up, is not the same side the car is running lean on.

jpc647

Plugs are back of engine to front from left to right from drivers side:

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Plugs are same order on passenger side.
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The white coating from the first picture was after a WOT throttle run for approximately 5 seconds, I turned the key off, and coasted to a stop, pulled the plugs and looked. So I'm running very lean at WOT!? I'm confused, I put a bigger carb on and I'm still lean?

DoubleV

Just curious as what your total timing is?

oldcutlass

I don't see a real difference between the left and right bank. They all look pretty close. Yes it may be a bit lean, how does it run?

coppercutlass

Lean is mean. Too leans and you'll burn things up. I ran the same 1405 on a mild 350 just a tick over stock and the plugs read on the lean side. that was with headers. headers will lean an engine out. Now that same engine went into my dads car with manifolds and a more restrictive exhaust and it read rich on all 8 plugs. the difference between the 1405 and the 1406 is metering the 1405 is jetted richer for applications with a mild cam and headers etc. You plugs don't look too too lean. I also ran that 1405 on the same intake you have with no issues. A bit on the lean side aswell but nothing to bother me. I think if you are looking for your combination to come to life you will need to let us know what your combo consist's of. I ran that 1405 carb on a 10 to 1 350 with 10 to 1 compression a bit of a roudier build than my previous mild build and it fed the engine well. A little undercarbed for that particular combo but it didn't run very lean and it still packed a punch enough to run 13.3 at 103 mph in the 1/4 . Now don't rule out the carb I bought a new 1405 and it was missing a float and the one that was in there was smashed. just my experience. If you are up fore it pop the top off the carb and make sure the correct jets are in there etc. etc. I had to do it now twice on a new edelbrock.

jpc647

Maybe I'm paranoid. It's hard to capture the real color of the plugs on camera. When I pulled over and took the first picture on the thread, I should have taken more, but I was in a parking lot and didn't want trouble. All the plugs i took out at that time had those little white deposits on them. Again this was after going WOT shutting the car off at WOT and pulling the plugs. Was hoping they'd be black or dark brown, not white. Again maybe I'm paranoid. Car runs decent. No bog or hesitations anymore, but not a whole lot on the low end. 1st gear doesn't seem to wind out as much as it did with the 1406. Weird. I don't know, but to me the driver side plugs look whiter than the passenger side ones.


I can take the top of the carb off. Did it on the 1406 a dozen time. It might have the wrong stuff, it's supposed to come with pink or orange springs, and it had steel ones in it, so it might be wrong. I've decided I'm probably going to swap intake anyway. I did find two "loose" bolts last night on the intake, which could explain the oil inside. Many people are saying with the 18lb vacuum at idle, I'm just not able to pull enough fuel it immediately off idle with the RPM intake. Maybe I'm expecting too much out of a low comp. 72 motor, but I haven't given up on her yet!

oldcutlass

Have someone sit in the car and floor the gas pedal with the engine off. Check to see if the throttle is opening up all the way. I've seen it happen too many times with a carb change.

jpc647

Thanks, I'll go do that.

BTW, I just did a compression test, mostly for SAG, but the results were:
120, 135, 124, 131, 136, 131, 131, 131.

The 120 was the driver side closest to the front(number 2?), and the 124 was the second to last on the driver side from the front(number 6?). All is well. I really doubt this is an original, unrebuilt, motor. The 120 kinda bothers me, but eh...

Still with 18lb vacuum at idle, it can't be a radical rebuild. I guess I'm swapping intakes tomorrow night.

Back to putting the car back together...

TripDeuces

Drivers side are odd, 1 3 5 7.
Considering the engine looks like it was cold before your WOT because of the fuel puddling in the intake you may not be getting a correct reading on those plugs. The plugs don't look that lean. You can't go by the ground strap. I can see a tan line on the porcelain about even with the top threads, that is correct and overall there is a tan coloring. You are not that far off if at all. Something else is going on here.
Like Oldcutlass said, check the carb opening. Not knowing the TH350 very well is it dependent on that other cable for line pressure?

captjim

Couple of thoughts. First, plug reading is an inexact science, ET runs are a better test. Second, many refer to the RPM intake as the best all-round choice for a SBO. Just for grins, several years ago, I swapped my RPM for a Performer. The car was noticeably quicker at part throttle, was quicker in the 1/4 (not by much, like .08) but this was on the first run and I had really dialed in the other combo. It also revved quicker, I hit my shift points sooner. This was on a fresh 9 to 1 355, port work and good valve job, headers, 3.42s and a $700 converter. Carb was a 670 Street Avenger. And the Performer was better. Unfortunately the thread disappeared with the latest ROP crash. My point is that on a stock or very mild application the stock intake or Performer is a better choice. IMHO. Also, if you do go to stock, sell the RPM and E-brock carb and get a dialed in Q-jet and don't look back. For what you are doing it is the best choice. Again, IMHO.

1970-W30

No offence JPC647, but the statement "Still with 18lb vacuum at idle" is not right. Vacuum is measured in inches not pounds. 18lb would be pressure, 18 inches is vacuum. No big deal, I've seen it posted wrong that way many times, odd that nobody ever mentions this common terminology error.......

Octania

Since we're picking nits, it's inches OF MERCURY.

You could use water or Gatorade or liquid oxygen but Hg was handy because it's heavy as hell yet liquid, so instead of a 30 ft column of water, you need only at most a 30" or so column of mercury.

Abbreviation "in. Hg" will do nicely.

But, yeah, at least "inches" of something for a vacuum reading.

jpc647

Sorry missed this. Base timing is like 17/18, all in I'm around 36(guess). I just bought a new timing light as my old one wasn't a dial back one, so I'll be rechecking it. I don't understand the whole re curve thing with the weights, or if it would be to my advantage to do it.


You think that's fuel in the intake? I thought it was oil. I let the car run in the driveway for 10 minutes or so before I went up the street, took it around the block a couple of times and then did the WOT run. That picture was taken a couple of days before, when I swapped the carb, but each time I've had the carb off, I've noticed a small puddle in there. I will check the carb opening and report back. The girl friend got tired of being in the garage last night with the compression test, so I didn't want to push it. There is a metal line running from the front of the intake to the transmission. Is there a way to check proper operation(vacuum pressure or something)

CaptianJIM!! Someone mentioned a thread about you doing the test on ROP on another thread and I couldn't find it. Very Interesting! I'll be swapping the intake this weekend. I figured I would go to the Performer, try it with the 1405 e-brock I have. If I'm still not happy I'll have the Q-Jet glass beaded and redone. I took it off a parts car with the stock intake, I just don't know what pieces are missing,(like springs etc), so It's going to be tough hunting them down. Also I know nothing about the Q-jet's except for you really have to take them all apart to calibrate them. Without knowing my motor specs, it's hard to dial in the Q-jet.


Thanks for the clarification! No offence taken! It'd rather be corrected and learn,


Learning as I go. Thanks.

coppercutlass

Do you already have a performer in take or are buyin one ? Because I have one if you want to trade for the rpm just thought I would mention it.

jpc647

Damn, I wish I had known that. I already bought one a couple of months ago. :/

jpc647

Well I swapped intakes today, what a day.

Car seems different, not sure if thats in a good way though. I'm at about 20* base timing, the vacuum advance is rotated all the way into the firewall, (which to be fair is only a tiny bit further than before). The car will start to stumble and stall if i bring it down to 13/14 base.

What can I do to give it more timing? The vacuum advance doesn't seem to be able to rotate on the metal plate of the distributor, so what can I do, purposely make the distributor 'jump a tooth'? Why would a rocket 350 need 25*(ish) base timing!? The engine has definately been rebuilt. When I took the intake off there wasn't so much as a piece of sludge, or dirt, or anything. It looked really clean. Beginning to think someone advice before about the cam being 'retarded' might make sense.

Also, with the performer intake, the idle on the carb doesn't seem to adjust evenly. Like, the drivers side adjusts okay, but when I screw the passenger side in, and it starts to stumble, i turn it out about a turn, any more and it starts to stumble again. The drivers side I can turn out 5x and it won't stumble....