69GMC - Lack of Secondaries/Low High-End Power

[geezer#99]

What intake are you running?

[RhapidFyre]

Originally Posted by geezer#99

Where’s your pressure gauge?
You can’t go by the mark on that cheap totally unreliable reg you got.

What’s normally plugged into the open manifold vac port on the front of the carb?

Don't have a pressure gauge, was trying to save 50 bucks but it's probably worth it at this point. The port on viewers right trucks left is for the air cleaner. There's a small house coming off the housing.

Originally Posted by Grumpy old man

that engine has seen some hard miles , How many miles are on it ? Have you done a compression test ?

Last guy I got it from said they built the engine on it, put about 56k. Odometer only goes to 99,999 so can't tell if it's turned over or not.

We have not compression tested yet.

[Grumpy old man]

Have you pulled the sparkplugs to see what they look like and check to see they are gapped 0.45 with the HEI ?

[RhapidFyre]

Originally Posted by Grumpy old man

Have you pulled the sparkplugs to see what they look like and check to see they are gapped 0.45 with the HEI ?

Brand new, did them myself as soon as I got the truck.

[RhapidFyre]

My uncle came up today, big Chevy guy. Said we need to compression test it (which you guys recommended), flush the tank and replace the fuel line. With that being said, I'm going to consider the original problem solved since the fuel supply is bad and the carburetor is too big. If I have any other issues I'll make a new thread.

Thank you all for the help!

[geezer#99]

Before you run away could you tell us what intake you have and what carb was on it before the eddy carb?

[Dwyert4]

What transmission? I didn't notice if you mentioned it. If it's a 700r you need the correct linkage adapter for the eddy. Mine did the same and I got lucky it didn't burn the transmission.

[RhapidFyre]

Originally Posted by Dwyert4

What transmission? I didn't notice if you mentioned it. If it's a 700r you need the correct linkage adapter for the eddy. Mine did the same and I got lucky it didn't burn the transmission.

Not sure, I'll have to check it out after work. Previous owner said it was the original.

Originally Posted by geezer#99

Before you run away could you tell us what intake you have and what carb was on it before the eddy carb?

If it's the air intake, it's the standard circle with the arm coming off. Intake manifold, I have no clue. Would have to consult my father in law again. I believe the old carb was the original Holly quadrajet. I'd have to go pull it and find out.

[davepl]

Originally Posted by Grumpy old man

Post a picture of your engine with the air cleaner off so we can see whats going on , A 750 may be too much carb for your truck who picked that ?

Not likely. GM built the 301 Pontiac with a 750cfm carb and you can run a 780 Holley on a 302 just fine. Assuming vacuum secondaries like a Q-Jet or 3310 of course...

Still sounds to me like it's running out of fuel. If this was me I'd stick a fuel pressure gauge on it so I could monitor it from the cab under load and see if it's falling off. Electrical, of course, don't plumb gas to the cab!