Need Help ASAP...!!!
 

Hello,

I have a 1987 (original Date) 454. In roughly 1990 - 1995 it was upgraded to an HP-500 by High-Tek Marine.

To the end of last season, the thing ran like a sewing machine.

This season, I have done all the usual PM items... Plugs, wires, cap, rotor, etc...

in addition, I replaced the fuel pump, and eliminated the circulating water pump with a cross over.

Fired the Boat this past week on the hose, and for the first 20 minutes all the thing would do is turn over, pop, and it hick-up'd (popped) once pretty hard through the carb (Holley 850).

Once I realized that I had the cap on wrong :eek: one half turn clockwise off, I adjusted it, re-traced my wires, and gave it another try...

************** The Problem***************

The Engine fires up, and some may say that its fine...

Like most of you though, I know this thing like I know my own Ass...

-It has a small vibration, like something is out of balance...?

-It idles very poorly. If I drop into neutral, it stalls out most of the time. If it does stay running, it is very sluggish...?

-If you NUT it, it either POP's or HESITATES then all seems ok..?

-There is a loud sucking sound from the carb. When you close the hatch, there is an audible whistle / vaccum sound with or without the flame arrestor in place...?

??? What did I screw up, and or break ???


Please Help... Like to run this weekend


Thank You In Advance,

sounds like the timing is still out a lil bit.

set it around 8*-12* initial and get a total timing between 30-34*

double check the firing order 18436572, if all is ok timing wise maybe some varnish built up in the carb, take it off soak it and put new gaskets, needles and seats, mine got gummed up and did the same thing

I would guess fireing order also.

Carb cleaner, new plugs

Blew the power valve out of the carb when it backfired.

Also have you been putting ethanol treatment in the tank

Just a thought, maybe the engine builder changed cams and used a #4-#7 swap cam. I used them in my rebuilds??? What gph fuel pump did you use? Pretty sure if you used a 130gph pump, you'll need a regulator.

X2 - very common on Holley carbs with a bad backfire thru the carb - relatively easy to change out - pop the primary float bowl and metering block off the carb and replace with another 6.5 PV.

Thank You !!!!!!!!!!!!!!!!!!
 

Thank you to all, for the help...

I am getting on all of your suggestions this morning.

-Carb re-build
-Replace plugs
-Re-check firing order
-Set timing

**** Anybody know any GOOD Carb Guy's****

Toledo Ohio, and or Metro Detroit area

Jim,

We have worked with various carb tuners over the years. About 4 years ago we began a carb program with Patrick James @ Pro Systems and have been using them exclusively since for our new carb and rebuilds. We supply Patrick with numerous mechanical parameters of the engine, including head flow, camshaft data, mechanical compression ratio etc to determine the fuel curve. He then builds the carb to spec, flow tests and dynos the carburetor prior to delivery. To date we have in excess of 50 carbs in the field (many on OSO) with a 100% satisfaction ratio. Highly recommended.

Bob

Did you check to see if you have a vacuum leak ? Carb is bolted down tight ? :confused:

You may want to make sure you don't have a valve hung up over winter?