Alright so i built a 302 for my truck and ive got it running and what not but whenever i rev the engine and let off it seems to hold the rpm for a second after i let off. for example if i rev 3k it will hold it for a second and slowly go down. Anybody got any ideas why it does this? I think the carb is getting way to much fuel. It dumps fuel into the secondaries even when they're not open up. This is a brand new holley 600cfm carb also.

 

First, just because it's new doesn't mean "bolt on ready". You still need to look it over, and make some adjustments. Is your ignition timing set right? No vacuum leaks anywhere? Plug wires on right? Firing order right? This may sound stupid, but they are the first things to check. Most times on a Holley 600, you can back out the adjusting screws 1 1/2 turns from bottom for a good starting point. Make sure at WOT, you still have 0.015 in of travel in the accelerator pump pivot. Make sure that it is closing all the way. If you have the throttle open too much, uncovering the slots inside the butterfly area, you will bleed off fuel. Those are enrichment ports. After you have double checked all these, post back. Good luck.

 

Honestly there's no way i can read my timing tab because my lower radiator hose is in the way. I know my plug wires are on correctly and my firing order is right. The truck runs great under driving conditions. i just think its weird how when i rev it up it stays up there for a second. Im starting to think that it may be my vacuum advance or mechanical advance in my distributor.

 

I also dont have a rough idle. and it does not hesitate under hard accerlation. so its got to be my timing situation somewhere right?.

 

no ideas huh?

 

You do need to do what you have to do to set the timing at specs.

Are you sure that carb doesn't have a vacuum dashpot or an electrical solenoid to slow down the throttle closing?

 

I thought I replied last night, but I guess something happened. Before you go after a possible carb problem, you need to make sure your base timing is set correctly. You say you rebuilt a 302, but the lower hose is in the way of the timing marks.....The only way that would happen on a 302 is that you are using a 289 water pump where the lower hose exits on the pass side of the engine. Are you sure about the engine? Where does the lower hose exit? How many holes on the balancer for the pulley?

 

I'm positive the engine is a 302. Being that i ran the codes on the block through many programs at my college(i'm in their auto technologies class) i also bought the gasket kit for a 302 and if it wasnt for a 302 the gaskets would not have worked. And the timing cover is the right one also. This whole motor came out of a 69 mustang. Even when i ordered the water pump for it on NAPA pro-link it was in its own sub category for that year of 302.

 

Ok, a little "schooling" first. The only difference between a 289 and a 302 are the 289 is internally balanced, and has a 0.130" shorter stroke than the 302. All gaskets will match. The early model 289 had the water pump exit on the pass side of the engine. Later 302 had it exit on the drivers side. If your water pump is in the way, then you either have the wrong water pump, or wrong timing marks installed on the engine. Trust me on this. I have probably disassembled and/or rebuilt about 80 289/302 engines in the last 20 plus years. I am not insulting your intelligence, just making sure that you have the basics covered first! Oh yeah, if the vacuum advance is installed on the wrong port of the carb, you may have similar problems. The vac adv goes on the port on the pass side of the metering block of a Holley carb.