Can't rev past 3000 rpm

[boulky12]

Hey guys, So I've always had this issue with my truck but never got around to it cause it always drove fine.

It wasn't until I raced one of my buddies in his truck that I figured out how much of a slug this thing is and that I should at least attempt to improve it a little.

According to GM, a stock 305, in 86 made 160 hp @ 4000 rpm.

I can't even get past 3000. Highest I've went is 2700 maybe 2800. And this is with the slack taken out of the throttle cable.

I know my carb isn't 100 percent. I'm not even sure if my secondaries are kickin in, but i still would think that you'd be able to get to the 4000 rpm on the 2 barrels.

I was thinking this was a timing issue, so I decided to mess with the timing today.

My timing tab and balancer don't have the numbers like what I see on Youtube. This is what I have, and from my understanding the middle of the wide notch is 0, the point of the next notch is 4, and the next one is 8, and so on.



Before I started turning the distributor, this is what it was set at



I started advancing to 0, then 4, then 8, and went for a test drive everytime, and noticed no difference at all? I did have the vacuum advance plugged everytime I changed it.

I still can't even get past 3000 rpm.

Are these adjustments too little, or could there be a bad component, or am I just doing this wrong?

Sorry for the long post. I would really appreciate some help. Thanks.

[fitz]

Clogged catalytic converter?

[boulky12]

Clogged catalytic converter?

I chopped that off and replaced it with a straight pipe when I first got the truck.

I did leave the old looking flowmaster on it tho. Do those get clogged?

[boulky12]

Could it be possible that the distributor was dropped in incorrectly or jumped teeth over time?

[1967KaiserM715]

Hei or ordinary dizzy with points?


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[boulky12]

Hei or ordinary dizzy with points?


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Hei

[1967KaiserM715]

Take your timing light and rev the engine, do the timing marks move? It almost sounds like it isn't advancing, although you should be able to see some difference between degrees, biggest ones are how hard/easy it is to start the engine.

While it is possible to be a tooth off, you would notice it at idle, either it would die with ought your foot on the gas, or it will pre ignite and run really rough(if you could even start it.)

Have you checked for arcing spark cables(wait for dark, then use no lights nearby).


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[boulky12]

Take your timing light and rev the engine, do the timing marks move? It almost sounds like it isn't advancing, although you should be able to see some difference between degrees, biggest ones are how hard/easy it is to start the engine.

While it is possible to be a tooth off, you would notice it at idle, either it would die with ought your foot on the gas, or it will pre ignite and run really rough(if you could even start it.)

Have you checked for arcing spark cables(wait for dark, then use no lights nearby).


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Yes the timing mark does move. It moves to the left (toward the 4,8,12) when I rev it so i think it is advancing. I did turn the engine on and off after I would make an adjustment and I could hardly tell a difference. I believe it was getting harder to start when I advanced it towards the 8 and 12 mark.

Engine idles good and dosen't run rough so I guess it's not too far off, but still could be.

I have not checked for Arcing spark cables, never have. What exactly would I be looking for?

Thanks for your input

[1967KaiserM715]

Sounds about right it would get slightly harder to start the more you advanced, I don't recall the exact value, but stock idle timing should be close to 4degrees.

For the spark plug cables, you don't want to see any flashes of light. The cause is normally a worn casing, either a crack, worn through, even a slice. That's why you want to look at the engine in the dark, makes it easier to spot an spark of light. Short of it is an arcing cable reduces voltage to the plug, which results in low power.


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[boulky12]

Sounds about right it would get slightly harder to start the more you advanced, I don't recall the exact value, but stock idle timing should be close to 4degrees.

For the spark plug cables, you don't want to see any flashes of light. The cause is normally a worn casing, either a crack, worn through, even a slice. That's why you want to look at the engine in the dark, makes it easier to spot an spark of light. Short of it is an arcing cable reduces voltage to the plug, which results in low power.


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Alright. I know the cables are pretty old so I wouldn't be surprised if they are arcing. I'm bout to go out there and check

[boulky12]

Alright so I definitley saw some serious arcing on about 5 different wires.

I'm gonna get new plug wires ASAP

Thanks Kaiser

[bd]

While you're at it, do a complete tune-up.

[boulky12]

Alright so I installed the new plug wires and I still can't get past 2700 rpm.

I tried messing with the timing a little more to see if it would help with the new wires. I noticed that when I advance it, my rpms go lower at WOT. When I had it at 0 I could only up to 2400 rpm. But when I retard it and put it back to where it was I can reach 2700 rpm.

I thought you were supposed to go faster when you advance?

I set the timing to where it was before, for now. Like this:



What do yall think I should try setting it at?

When I advance it - gas mileage is horrible and lower rpms @ WOT

When I retard it - I get higher rpms @ WOT but if I retard it too much the rpms in park drop really low and the truck dies when put in gear.

I notice when I rev it to 2500 in park, it sounds dang close to redline. Is this engine really this much of a slug or is there something I can do to reach higher rpms?

Thanks guys

[boulky12]

While you're at it, do a complete tune-up.

I've changed spark plugs, wires, Used but good Distributor cap,  air filter, fuel filter, 2 oil changes, seafomed her, and cleaned the inside of the carb as best as I could. All within the last 6000 miles.

I think the only thing I haven't changed that consists of a tune up is the rotor. Would that affect the engine this much?

[Rattler12]

What type of tach do you have ? Factory or after market?  If it is an after market universal for use on 4, 6 or 8 cyl engines do you have it on the proper setting ? If the engine sounds like it's redlining it probably is.......your tach may be your problem