5.7 Tempest 300 HP from 1987
 

Hello all first post here in a long time,

Anyway I built a old 300 HP Tempest 5.7 block pistons rods, crank and cam with the good old qudra jet carb. Ran great on the stand clean idle about 700 and good reves to 5k + and timing to 38 total advance. Installed it and ran great, Here comes the issues.

So it sat in the yard a couple seasons due to many life and health issues. So when I got out to prep for the water this weekend it had a vac hose split at the carb would not idel at all so fix that so it will start and run and hig idle. . But at a high idle like a vacuume leak. So pulled the pvc and installed my vac guage and it is idle at 2600 to 2800 and vacuume guage fluxuates from 8 inches to 12 wich is way low. Like retared timing. It will rev up ok but i know it is not right. I hope there are still some old Carb guys on here as I am 76 and still at but not as good as i used to be at disgnosing.

Oh only ran white and race gas mixed 50 50 so not an ethenal issue. Any help or suggestions would be grealy appricated. Thanks Bill

Starting simple....are the throttle blades all the way closed at idle? Idling at 2500-2800 rpm seems more than a vacuum leak.

I’m pretty sure there where no pcv’s from carb to valve cover, just crankcase vents from flame arrestor to valve covers on those engines. Maybe your issue ? Or part of ?

yes, lots of carb guys around because many boats having carbs. I redid several quadrajets and holleys last year , like many years. Doh.

Thanks guys carb had got water in it some how. Think one of the monsune rains last year. Think it will clean up ok.
Alss it had ran great with the PVC but I am with you I dont think it had one back then.
Base gasket had got wet to so I am pretty sure a big vacuume leak there to.

Thanks for the help.

Question - how does a carburetor get wet from rain ? Boat cover not on ? Not waterproof ? Or, Poor hatch design ? Left open ?

Well I am guessing it happened when the hatch was off for the engine install. It had a full mooring cover on it and the spark arrister was on the carb. But it was a huge monsoone in Norther AZ so some how water poured in on top of the engine, Because there was rust on some of the fresh bear metal parts. It is a mistery to me how some things happen in my life. But I am truely gratful that I can still fix stuff. I had a 5,0 Mercury break a power steering pump pully in the middle of lake Powell. Never hear of that happening to anyone else. I had a ignition points set arm break off out in Bakersfield one time never heard of that either. Found a pice of wire on the road and wired the arm back on and made in to the nearest parts store. I been wrenching for over 60 years and have had the strangest crap happen to my stuff. oh well sorry for carrying on here.
Thank you gents for the replys help and suggestions!!!.

Dang.

'Carrying on' is fine. :)

Do you all know what hose I can use for the vent to the spark arrestor? The one I had going to the PVC that I am removing is too short now. I have the original pn but thinking there is some that cost a little less. it is the floppy flexie soft kind of hose.
Thanks again

Try search terms crankcase vent hose bulk

I forget what the ID is. 1/2" ? I'll try to remember tomorrow when I work on a stock small block carb'd merc boat.
Some NAPA and other parts stores may have a person that knows they carry bulk vent hose. Don't use heater hose.

Edit in: Oh, no need for me to measure. You are working on your's now. :)

I was gonna take a sample to town today when I go in. I am about 25 miles out in the middle of no where. Well Paulden its right by no where. hehe