Hot Rod Forum banner
1 - 20 of 80 Posts

· Registered
Joined
·
54 Posts
Discussion Starter · #1 ·
1984 Monte Carlo Base Converted SS Body

305 LG4 Motor with 305 H.O. Heads
Edelbrock Performer EPS Intake Manifold

Edelbrock 1902 AVS2 Series 500cfm Carburetor (Manual Choke)

De-smogged/Non-Emission/Non-Computer Setup.

I bought this car a year ago, replaced things, and as I was replacing the distributor with the distributor removed, I overturned the engine...have had idle and acceleration problems ever since.

Car History: I was told at the time of purchase that this was an SS Monte Carlo...I was also told that the motor was a rebuilt 350 with 46,000 miles on it...I didn't know much about the SS Monte Carlo, it just looked like one to me.

Since this was to be my daily driver, I wanted to buy new parts and replace the old parts and jumped into Monte Carlo SS Facebook groups and online forums to learn how to replace everything.

First thing I learned is that this wasn't an SS Monte Carlo by looking up the VIN # and other visual things like black trim instead of chrome trim...the original V6 motor, computer, and emissions were ripped out and replaced with this "Rebuilt 350 with 46,000 miles on it".

After looking up the engine block and head casting #'s, I learned that this motor is actually an 1983-1984 305 with 305 H.O. heads...

It had an Edelbrock Victor Jr. Single Plane Intake and an Edelbrock Performance Series 650cfm electric choke carburetor...I was told both were too big for my 305 motor, and to swap them with a smaller rpm range and cfm rating. I swapped with what I have now (listed in the beginning) and things where better but my timing seemed incorrect and after spending months of playing with it, I decided to replace and inspect the timing chain set. I could never achieve 600 rpm to correctly set factory timing settings.

First thing i found was the Tach was set for a 4 cylinder engine, instead of an 8 cylinder engine, I set it for 8 cylinder. I replaced the timing chain set with a Cloys double roller and installed it correctly. While I was that far into the motor, I wanted to pull the camshaft so I knew exactly what it was I was working with, but nobody could seem to guide me so I slapped the timing chain and cover on without checking it out. I have no idea what the camshaft specs are.

Second thing I found wrong was the timing tab on the timing cover. With the prior 2 o'clock TDC position timing tab fully exposed, I used a spark plug stop tool/TDC finder to find the motors true TDC...seeing how everything else was wrong...the timing marked showed TDC was actually 12 o'clock, not 2 o'clock...so I swapped it with the correct timing tab.

The 3rd thing was the harmonic balancer was the 8" instead of the factory 6.75", so I swapped it for a 6.75".

The carburetor distributor vacuum advance was also plugged up as an emissions setup, so I plugged it up as non-emissions due to my de-smogged/non-emissions setup.

The engine seemed to run and idle a lot better.

Next was my fuel pressure...I was running an electric fuel pump but after it failed I swapped it out for a mechanical fuel pump. The new mechanical fuel pump was pushing 9psi of fuel pressure, so I installed a fuel pressure regulator and the current pressure is at 6, but can be adjusted to 4psi.
 

· Registered
Joined
·
54 Posts
Discussion Starter · #3 ·
My problem I'm having now is I'm too advanced, 24° initial @ 800-900 rpm and 52° total timing @2500-2800 rpm, checking with my adjustable timing light.

However if initial timing isn't 20-24°, my throttle response at take off is late and the engine "skips" as if it wants to stall if I put the gas pedal to the floor. With the engine first warmed up, in Drive the rpm is 600-700, it fluctuates. Once I'm accelerating from 1st to 2nd gear, it seems a bit rough, then smoothes out from 2 gear and on. Shifts about 1700-2000.

As I'm letting off the gas and braking, the downshifting seems late, and at a complete stop, the rpm's in Drive have raised to 700, and if in Park the rpm's are 1000-1300 rpm's and if I shut the engine off, it diesels.

Adjusting the carburetor idle mixture screws really have no effect if little until I take one completely out, then the engine stumbles wanting to stall.

I'm told I'm too lean and to check for vacuum leaks. I retorqued the intake manifold and carburator to factory specs and sequences. However, because my idle fluctuates, spraying the areas down with starting fluid and listening for rpm to rise is ineffective.

I have tried the smoke vacuum leak check. I bought a cigar and blew into the PCV hose attached to the carburetor, and if I had a vacuum leak the smoke would leak out of wherever was leaking...the only place smoke came from was the top of the carburetor, nowhere else...can't be a vacuum leak..
 

· Registered
Joined
·
54 Posts
Discussion Starter · #7 ·

· Registered
Joined
·
54 Posts
Discussion Starter · #13 ·
I would guess you have a vacuum leak at the manifold some where.
I agree, but with the smoke test with the engine shut off and warm, I get no smoke leaking from anywhere, except the top of the carburetor because I have no air filter housing...

While installing the manifold, I did use RTV silicone on the water ports. I heard that, if not done correctly, will cause a vacuum leak you will only find by removing the intake from the engine...
 

· Registered
Joined
·
54 Posts
Discussion Starter · #18 ·
Are you setting the timing with the vacuum advance unhooked from the distributor and hose plugged to prevent a vacuum leak.
I was setting it without the vacuum advance connected.


With the feed passages at the bottom of the fuel bowl, Carter AFB/Edelbrock Performer/Edelbrock AVS design carburetors have a tendency to sludge up the main and idle feed passages if fuel isn't well filtered....it sounds like you might have some plugged passages if you can get no change until the idle mix screw is completely removed.
Good fuel filtering is mandatory with that style carb.
Yea I had a filter on it, the Spectre chrome canister type, but it became bad and rattled. Can't say how long I drove it like that, but not 6 months or more...I did use about a quarter tank of ethanol gas in an emergency, I heard ethanol gas ruins these carbs, but was told in an emergency situation would be OK. I removed the carburetor about a week or so ago and sprayed carb cleaner into the idle mixture screw holes, top and bottom of the carburetor but not the carb fuel inlet.
 

· Registered
Joined
·
54 Posts
Discussion Starter · #19 ·
24 degrees initial is an awful lot. Initial is set and tested with the vacuum advance disconnected and the feed from the carb plugged. A base setting of 24 degrees would be something a racing cam would require. A factory cam typically uses something in the range of 6 to 12 degrees. If your reading 24 with the vacuum advance out of the system it would be a strong indicator that you have the distributor a tooth off which is a common problem on the SBC where R&R’ing the distributor caused by how the oil pump drive tang carries a rotation as the distributor gear disengages from the cam’s driving gear.
Today I'm going to set the initial timing (without vacuum advance connected) starting with 6° and work my way up to 14° and test everything in each of those settings with the vacuum advance connected. I will check timing advance once the vacuum advance is connected...I'm using the ported vacuum port on the carburetor for my distributor vacuum advance.

If I'm going to remove the distributor, I'm going to replace the mechanical advance springs to lighter springs while I have the distributor out. But this is this position the rotor was pointing when I dropped the distributor in...#1 plug wire is plugged at this cap post...
Motor vehicle Automotive design Electrical wiring Vehicle Automotive exterior


Another concern in this area, is when I'm rotating the engine to TDC on compression stroke. I'm doing it by myself most of the time and sometimes I turn the balancer TDC mark slightly too far past the timing tab TDC mark...during those situations, is it OK to turn the balancer back to line up the marks or would I need to rotate the engine clockwise twice back on compression stroke lining up the timing marks ? Exactly how straight do these lines need to be lined up ?
 

· Registered
Joined
·
54 Posts
Discussion Starter · #21 · (Edited)
If your reading 24 with the vacuum advance out of the system it would be a strong indicator that you have the distributor a tooth off
OK, one thing I thought that looked odd and could be the issue to my problem is I'm off a tooth....during distributor drop in, my pointer wasn't exactly pointing at the drivers side front intake bolt, it pointed more between cylinder 1 and cylinder 2.

I've literally dropped this distributor flush with the engine all the way clockwise and the only two directions I can get it in as close to where it's supposed to be are these two positions...
Motor vehicle Hood Electrical wiring Automotive exterior Vehicle

Motor vehicle Electrical wiring Computer hardware Auto part Automotive exterior


From what I'm seeing in multiple YouTube videos is the pointer should be pointing at the first intake manifold bolt on the drivers side, all of them used a long screwdriver to rotate the oil pump shaft...neither of these pictures of mine are pointing there and these are the only two settings I can get near it...
Hood Motor vehicle Automotive tire Bumper Automotive exterior


Is my pictures considered "off a tooth or two" ? Should I grab a long screwdriver and rotate the oil pump shaft to achieve the correct position ?

The second picture is what I'm driving with now...
 

· Registered
Joined
·
54 Posts
Discussion Starter · #26 · (Edited)
Last picture in your this post has the vacuum advance can in the correct position but tge rotor pointing at cylinder at cylinder number 8 terminal. This is OK if your put the number 1 plug wire into this terminal and then proceed with the firing order from there.
There is absolutely zero requirement for the rotor to point at the "front cylinder intake bolt"....that's a bunch of hogwash from idiot mechanics
OK then, no need to R&R the distributor...that isn't causing my issues then...

I'm pretty sure my issue is either timing or vacuum leak...but I'm thinking more of timing...

I think my timing tab and balancer are mismatched, causing me not being able to set the timing right...

I started another thread yesterday discussing the 3 different timing tab and harmonic balancer matchups in GM production history from 1969-1995...just my luck too, in 1984 they transitioned from 2:00 timing tab to the 12:00 timing tab...everything from 1985-1995 was 12:00 and everything prior to that was 2:00 timing tab...and depending where your OEM balancer timing groove was before the keyway, 10° or 40°, depended which timing tab it came with.

Monte Carlos factory came with 6.75" balancers and there are two different Dorman 6.75" balancers that have 3 GM interchange OEM part numbers:

#1. 594-009 Dorman Harmonic Balancer - OEM interchange part numbers "C312304, 66509" - Model and years - 79,81-88 Monte Carlo Base and 83-88 Monte Carlo SS.

# 2. 594-010 Dorman Harmonic Balancer - OEM interchange part number "C312302" - Model and years - 70-74 Monte Carlo Base.

Looks like mine should be the 594-009 Dorman or GM C312304, 66509 Harmonic Balancer - 79,81-88 Monte Carlo Base and 83-88 Monte Carlo SS.
 

· Registered
Joined
·
54 Posts
Discussion Starter · #28 ·
Looks like mine should be the 594-009 Dorman or GM C312304, 66509 Harmonic Balancer - 79,81-88 Monte Carlo Base and 83-88 Monte Carlo SS.
What I have is not Dorman branded. It's an "ATP Automotive Graywerks 102069" and here is a picture of it and the distance between the timing groove and keyway outlined in blue. Is this 10° or 40° of distance from the timing groove to the keyway ?
Tire Wheel Automotive tire Light Camera accessory
 

· Registered
Joined
·
54 Posts
Discussion Starter · #30 ·
What I have is not Dorman branded. It's an "ATP Automotive Graywerks 102069" and here is a picture of it and the distance between the timing groove and keyway outlined in blue. Is this 10° or 40° of distance from the timing groove to the keyway ? View attachment 624466
Here is the 1970 Chevrolet Monte Carlo 6.75" harmonic balancer by the same brand, ATP Automotive Graywerks 102075 Engine Harmonic Balancer
Vehicle brake Font Disc brake Automotive tire Automotive wheel system


This one looks to be 10° before the keyway, so the one I has a 40° distance before the keyway, meaning I should have a 2:00 timing tab, not the 12:00 timing tab I have...

But with the piston stop tool, the mark showed 12:00...🤔...however, from what I'm learning, what matters is the timing tab matching the balancer...which in my case, would be the 2:00 timing tab ?

Hopefully someone is following me here lol
 

· Registered
Joined
·
54 Posts
Discussion Starter · #33 ·
This sounds like an accelerator pump causing a lean condition, not necessarily a vacuum leak. A weak pump shot could be to blame.
Are you still having this particular problem when you accelerate fully?
Just at take off and through 1st gear, 2nd-3rd gear are good I believe. Downshifting seems slow or late, I could be wrong.

If I floor it from a dead stop, it skips, backfires, and stalls if I leave the gas pedal floored, I have to ease way out of a complete stop to take off.
 

· Registered
Joined
·
54 Posts
Discussion Starter · #35 ·
Grumpy says.
If your balancer is 40 degrees, and after the year 1984, it looks like you need the 12:00 tab.
I have a 12:00 timing tab now, so we know there isn't a mixmatch.
Tynan, you found top dead center withe tdc tool. Did you mark that on your balancer and then set timeing off that mark?
With the new 6.75" balancer and using the TDC tool, the groove already on the balancer lines up to 12:00, which is what would be directly between the two lines I made using the TDC tool.

I already had taken off the 8" balancer and replaced it when I bought the TDC tool and discovered the 12:00 thing.
 
1 - 20 of 80 Posts
Top