304 performance issues

Let me say upfront I’m enjoying working on this engine even with the multiple problems it has. The main issue is a lack of power.

The first thing I notice was that some vacuum hoses were missing others were cracked, disconnected or plugged so I replaced all the lines, PCV and CTO switch.

The engine was still lacking power and the choke would not open after warm-up so I knew there was a vacuum leak somewhere because it was still running at full choke, turns out the distributor vacuum advance along with the EGR wasn’t working properly.

I plugged up the advance and EGR fixed the choke and it was still running rough so I checked the float and there wasn’t much gas there as the float was out of specs, I adjusted the float but the engine still ran ruff.

I checked the spark at the #1 cyl and got a good blue spark. I then checked the timing and I found it so far advance the timing mark wasn’t even close to the scale. I adjusted the timing to specs, still running rough.

I pulled the carb and coil and replaced it with a known good one with no improvement. I also checked the engine compression, ignition wires, cap, rotor and plugs which all check good and the exhaust for any restrictions and found none. The charging system is reading 14 volts and it has fresh gas in the tank. When I open the throttle under load it shows power so I’m thinking it’s not a bad valve.

Although the #1 cyl had good spark I thought I would check the right bank at #2 pulled the wire without a difference in idle pulled #4 no difference in idle. I didn’t have time to check 6 and 8 because I had plans last night but it could very well be that the right bank isn’t working at all at idle.

My next focus will be the distributor/trigger wheel then the control unit.

Edit: Fuel pressure checked and with-in specs, checked firing order.

 

hmm
firing order of the plug wires correct ?
easy to mix them up
I don't know engine history, unless you've posted elsewhere, have you performed a compression and leakage test ?
you've corrected enough wrongs, one would think there would be some improvement
vac reading ?

 

Just a thought maybe you jumped a tooth on the timing chain might explain the timing being off and also lack of power valves out of time with the crank?

 

Jim, I understand it’s hard to troubleshoot multiple problems like this engine has from the opposite side of the country but I do appreciate your input.

My first post was long with much info so some things could easily have been missed. The very first thing I did was a compression test and checked the firing order. The engine has good compression with all wires going to the proper cyl. I haven’t preformed a leakage test yet nor a vac test (the vac test was next to do until I found no spark at #2 cyl).

You would think with the improvements I have made to the engine so far that it would be running better, but it’s not, I feel like a detective tracking down the bad guy who has tried to cover his trail.

I think the PO tried to mask the problems by over compensating in other areas like advancing the timing, adjusting the carb to run rich (one of the mixture screws was set a 4 ¾ the other at 3 ½) and setting the choke to full rich. With each repair I make I’m getting closer to solving the real issue but I don’t believe its going to run better until I find the root of the problem.

If you’re thinking the mixture screw that was set at 4 ¾ feeds the right bank that has issues, your correct.

As mentioned I plan to trouble shoot the ignition so I checked volts to the coil last night with the key on 12.12V with the engine turning over 4.98. Another clue to chase down.

 

Good thought Brian, I did check the timing, compression and piston at TDC so I believe the timing chain and its position are correct.

 

well, some day I will absorb what I read
how about the year of engine ? or has that been posted already ?

 

Sorry, just in my sig never did post it. 79

 

okay
Motocraft ignition system; you replaced the vac advance, correct ?
the pickup sensor inside the dist
the rivets that hold it to the plate can come loose
this allows the trigger wheel to dig into the sensor
there should be no movement of the sensor on the plate
there is also a measurable "air gap" for the distance bewteen the sensor and trigger wheel; if they have hit or are worn, replacement of the sensor and trigger wheel would be necc.
Where the dist plugs into the engine harness, corrosion can build up on the pins of both halves of the plug, the green nasty kind; cleaning and or replacement of the plugs + dielectric compound cures that.
The same 2 plug connectors at the electronic ignition control box; same corrosion problem; good ground contact to the fender for the box.
Wild card guess: bent push rod and/or worn rocker pivots/bridges, usually excessive valve train clatter accompanies these symptoms.
Vac reading may be next clue as to what's going on...
forgot to add broken valve spring as possibility as well....

 

I haven’t found a good vac advance yet and the flaps only sell the disturber with the vac advance I just plugged the vac line for now for troubleshooting purposes, but I may very well need the whole unit when all said and done. I’m going to Maine tomorrow to meet a guy that may have a good vac advance.

I will check for corrosion in the two places you have mentioned a well as the remaining ignition system. Thanks

 

Does '79 have a catalytic convertor? It would in CA, but I'm not sure about 49 states. A common problem is a plugged cat.

 

Yes, all 79s came with a cat, but I have true dual exhaust without cat although I did check for blockage and found none.

 

With the vacuum advance disconnected or not working, you'll notice a major power loss. To give you an idea, I was getting 9mpg and felt like I had half the power with the vacuum advance disconnected. After I got it working, mileage went up to 20 (hwy) and now I can peel the tires thru 1st, 2nd and 3rd easily. Just trying to give an example. If I were you, I'd start there and fix that...then check the timing. After that, I'd check the fuel system. Hope that helps.

 

any more info on bank 2? do you have fire on the bank? or just not on 2 and 4? how old are the wires? could just be bad wires or plugs. is the timing very stable? could be the dizzy gear is worn and/or missing teeth. doutful thou.

 

Pete, Mike thanks for your input. The timing, fuel and wires were checked in the first post, I haven’t had a chance to revisit the right bank for spark. Will do, and let you know.

Update, I didn’t have must time to troubleshoot the ignition system this weekend but I did find a complete distributor with vac advance.

What I did do was recheck the coil doing a bench check and found that the primary is reading low at .25, acceptable resistance is (1.13-1.23 ohms at 75 F). The secondary is reading within range at 8500. The reason for the recheck was a yellow spark from the coil.

Next I want to check the trigger wheel and sensor so I unscrew the two screws holding on the rotor, and what do I see? Points!! Points in my 79:?

At that point, I thought it would be best for me to step away to think about what I found.

1)The PO swapped in an older 304 with point system.
2)The PO may have had a bad ECM and to save money switched to a point system bypassing the original malfunctioning ignition system.

I will check the EMC unit and if it’s good then maybe the PO swapped in an older engine.

I found no tag on the right valve cover and I haven’t checked the block yet to see if it’s even a 304 or 360.

Thoughts?

 

Could be either 1 or 2, but I'm leaning more towards 2. Previous owner of my Jeep did the same thing, but only switched the distributor. Everything else from the electronic ignition was still under the hood, so at first glance, you'd have thought it was electronic. If you have the money, I'd check out the hei distributors...specifically the one made by DUI. One advantage is it's powered by one wire, but if you have power steering, it'll be a tight fit.

Oh..I forgot. You mentioned that you had a yellow spark. Might want to check those points and make sure they're clean. Any resistance there and could lead to a weak/intermittant spark.

 

since somebody swaped in a points dist. and the coil is bad, i would drop in a hei dist. and see what happens. there are alot of opinions here. many manufactures make a retro fitted hei for the amc v8s. jmho.

 

Update, I checked the block and it’s a 304 and also checked the ignition module and found it to be bad which leads me to believe it was just a disturber swap not an engine swap.

I used a jumper wire from the battery + to coil + with no change in spark so I will pull the distributor next and check it out thoroughly.

Knowing the ignition module is bad and possibly the distributor the HEI may be the best way to go, but I want to find the problem first before moving onto an upgrade.

I have a part number for the ignition module 322 0451 can the module be used for both 6cyl and 8? I’m thinking not, but thought I would ask having only found one part number for both engines (not saying their isn't two part # for 6 & 8 rather that I only found one).

 

Just my opinion, but I'd pull that Points Dist. take it to the store and use it as a core swap for a '79 and up V8 Electronic Dist. Grab you an '80 Camaro w/350 4 Pin HEI Module, and some 8mm or bigger Spark Plug wires. and a Ford TFI Coil. NOT the CANISTER Coil!

Go home, remove any Resitance Wire or Ballast Resitor in the ignition. and Wire the HEI up like this to your system:


Mount the HEI Module to a computer Heat sink or something that can pull heat from the Module efficiently. this gives you the best of both worlds from the TFI and the HEI. In my opinion, the best ignition for the $$'s.

 

mbalbritton, thanks for the reply, your post and a little research lead me to the answer I was looking for concerning whether a ford ignition module could be used if it came from 6 or 8 cyl. I found this “All DuraSpark modules will interchange”.

If this is true I have a few extra DuraSark modules, a good 79 distributor, and a TFI cap so all I would need to buy is the TFI coil, adaptor and wires. The fact I have a few DuraSpark modules I believe the best choice for me would be the TFI upgrade opposed to the GM HEI module.

I will be able to spend some time troubleshooting the distributor tomorrow and will let everyone know the outcome.

 

If you're going to run the Duraspark Module, leave the Resistive Wire or Ballast Resistor in the circuit. DO NOT remove it. The DS Module can't handle 12V all the time. And there are different DS modules. there's a Duraspark I and a Duraspark II. II being the later and the one you want.