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Username Post: 454 Troubleshooting
j_ray_actual
Newbie
Posts 3
07-29-21 07:44 AM - Post#2824101    

Hi all, new here.

I have a 74-75 model 454 cast block and heads with aluminum intake on an airboat. Carb is 750 CFM Quadrajet that is only a couple of months old. Just installed the following: New plugs, new plug wires, new distirbutor.

I've had problems with the motor at 3-4k rpm. Motor will start fine and idle fine. I can rev throttle fine 1-2k rpm. If I floor it the motor will fall on its face until I let off the throttle, If i keep pressure on throttle motor dies completely. Running a mechanical pump 6psi 80gph. Motor is stock from what I've been told except bored over some. I've been scratching my head for a while with this.

I'm no mechanic but I can turn a wrench. Had timing set with older distributor by mechanic. Just installed new distributor yesterday. Still falling on its face at 3500 rpm.

When I revved up until it died yesterday I pulled a plug and it was wet, so it seems to be getting fuel. I just dont know what else to do.

Ground? Valve springs?

Any help would be much appreciated!

Thanks!
Shepherd
Frequent Contributor
Posts 2425
07-29-21 07:54 AM - Post#2824102    

Welcome to CT. Is this a marine engine with reverse rotation? HEI ignition? Are you sure the filter in the carb inlet is new and installed in the right direction?
j_ray_actual
Newbie
Posts 3
07-29-21 07:57 AM - Post#2824103    

Filter at carb has been removed. HEI distributor with vacuum advance. Regular block and carb. Not marine.
Shepherd
Frequent Contributor
Posts 2425
07-29-21 10:02 AM - Post#2824109    

Do you mean the element the requires removing the large inlet fitting?
j_ray_actual
Newbie
Posts 3
07-29-21 10:04 AM - Post#2824110    

Yes there is a inlet fitting at the front of the carb that had a filter and spring in it. It has been removed.

Shepherd
Frequent Contributor
Posts 2425
07-29-21 12:14 PM - Post#2824118    

Ok, you have a stock type fuel pump, no electric, your description sounds fuel related, so start at the tank screen if it has one, and move forward, look for any restriction or blockage. Also, rare, but the fuel pump push rod in the block could be worn and shortening the fuel pump stroke, they can look good, but when compared to a new one you can see the difference. Of course this assumes all is good in the carb.

65_Impala
Very Senior Member
Posts 4849
07-29-21 06:12 PM - Post#2824133    

Where did you get a Quadrajet that is only a couple of months old?
bobb
Super Senior Member
Posts 5929
07-31-21 09:05 AM - Post#2824201    

is this a new problem or did you inherit it?
70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.

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