sluggish 289

[myagi]

Well. I'm slowly getting all the gremlins out of my 289 powered B3000 but I'm stumped again by the sluggishness of the engine.

First the specs;

1) rebuilt 289 C code with stock heads (new Comp Springs) mild porting on intake and exhaust
2) Comp Cams DEH275 grind (dual energy) camshaft - longer duration - loping idle
3) stock Autolite 2100 2 barrel carb on stock intake
4) stock exhaust manifolds from 70 F150 (for now)
5) stock EFI fuel pump regulated with Holley bypass style regulator down to 5 psi for carb
6) new GM style HEI distributor with new Accel wires and Autolite plugs (plugs are all light brown after 300 to 400 miles)
7) vacuum shows consistant needle at 15 Hg - low idle
8) Compression 140-150 psi on all cylinders
9) Timing set at about 10 degrees initial. Shows around 20 if I raise rpm to 2500.

The engine fires right up and idles well. I'm getting decent mileage on highway and accelerates normally but if I mash the pedal, it feels very slow to respond. When I get up to 45 mph or so it feels like I'm driving a 4 cylinder. No top end power whatsoever

I'm leaning towards either inadequate fuel supply, poor timing curves, or plugged carb.

Any ideas where to start first

 

[RonD]

Whats the exhaust system like?
Too much back pressure building up can really slow you down.

Can you drop the cat out of the way and take it for a spin?

 

[kimcrwbr1]

are you using the vacuum guage to adjust tir idle air needles. Confirm your timing is correct and adjust the idle air needles out for the highest lean vacuum pressure or engine rpm. set the idle speed and do it again. Turn the needles out one at a time for the highest possible vacuum pressure 17-20 hg do them both a couple times so the vacuum pressure only drops if you turn them in. Then shut it off and count the turns on both. Count the turns in and then back out. They should be within 1/2 turn between the two. Allways adjust the idle air the same way whenever you change the timing. The best way to set the timing on any ford V-8 is by engine ping. Especially if it has been modified It may take some time to dial it in but rule of thumb is advance the timing until you hear engine ping at medium speed when you go WOT slowly back off the timing until you dont hear the ping. Once again allways adjust the idle air any time you change the timing. Dont worry about base timing it will take care of itself for performance you want to set it by all in or total advance. If you have access to a dynamometer you can tune it much better. Trying different jet sizes time using engine ping and adjust the idle air with a vacuum guage will get you real close.

 

[kimcrwbr1]

What size of jets are you running and what is your venturi size. It should run nice with a 1.21 venturi 2100 or 2150 with #48 jets for HP and fuel economy. The venturi size is stamped on the accelerator pump linkage side of the float bowl in the circle.

 

[allnpt0]

Bring your timing to 14 degrees initial and see what happens. I bet that helps you out alot.

Pete

 

[myagi]

The carb stamp shows the venturi is 1.14

Also tried setting the carb for highest idle using the method you described (similar to where I've read elsewhere) but adjusting the screws doesn't really seem to affect idle speed until it gets down to within 1/2 turn from fully closed and then engine stalls.

Can't really see a noticable difference on the vacuum gauge either

Right now I have each idle screw set at 1 1/2 turns

This is why I'm thinking either a vacuum leak that so far had elluded me or the carb is FUBAR'd. Havn't noticed any ping either and that's at a point where I had the base timing set where the starter would barely roll the engine



PS. Getting decent fuel mileage but like I said before, feels like a 4 cylinder on the hills and grades and the cat convertor is temporarily disabled until I get this thing running properly.

 

[ancient]

Could the cam timing be retarded, possibly a tooth?

 

[RonD]

Light up a cigar.............

Smoke test for vacuum leak, the inventive and cheap kind

You need:
A cigar(cigarette smoke doesn't work)
A match(to light the cigar)
A vacuum line, of the correct size and length
Scotch or Bourbon, some say this is optional, they are no longer my friends

With engine off remove a larger vacuum line from manifold
Attach your vacuum line in it's place
Sip drink
light cigar

puff cigar
blow smoke into vacuum line
sip drink
repeat

Watch for smoke where it shouldn't be.

Pro smoke machines for this test run $800+
You can get a good cigar and a damn good bottle of scotch and still be way ahead

And no this will not cause engine cancer........that's an old wives tale.

 

[kimcrwbr1]

The best way I have found to locate a vacuum leak is take a chunk of vacuum tubing about two feet long stick one end in your ear and listen around with the other end. Stick the end in the carb to see what your listening for then go around all the gaskets around the carb base, manifold gaskets wherever engine vacuum is present. You should have around 20 hg vacuum pressure above 1500 rpm and 17-20 hg at an idle. Have you checked the wet float level yet you can run the engine with the top off of the carb you want the center of the fuel to be 3/4 of an inch below the top of the float bowl. Also while you have the top off of the carb check the size of the jets in the bottom of the bowl. #48s would probably be good for your motor. allways pull the float and bend the tang never put pressure on the float needle. What is the best vacuum pressure you are getting at an idle 15 is a little low especially on a fresh rebuild did you go through the carb also maybe you can port the power valve nozzles a little larger to increase fuel supply when you put your foot into it. One common missed vacuum leak on a 2100-2150 is the choke preheater fitting. It points back toward the firewall at a 45 degree angle on the choke thermostat housing put a plug in it or cap the fitting with a 3/8 cap from a home air condition system. GL you will figure it out.

 

[kimcrwbr1]

http://www.therangerstation.com/Magazine/Summer2003/VacuumLeaks.htm

 

[kimcrwbr1]

Also did you surface the base of the carb before you put it on. I glue a sheet of 200 grit to a flat piece of plywood square to the edge and carefully sand the base until it all shines the same use a new gasket and just snug it down never overtighten the carb. Just good and snug and check it after a few warm up cycles and I use metal lock nuts to keep it snug. these type nuts never let me down
http://www.ebay.com/itm/50-Keps-Bolts-W-50-Lock-Nuts-5-16-18-x-1-1-2-in-/360285854080?pt=LH_DefaultDomain_0&hash=item53e2b5d980

 

[fangotango306]

did you buy your hei on ebay....if you did, like me. get rid of it. my 302 ran gutless and would not rev over 5000 once in a while... and my timing read out like yours. i temp wired a junk yard duraspark box and distro, and it was night an day. i dont know if this helps or if you wanna rip into your carb or spend hours hunting the vac ghost. i spent $29 at u pull for the dura spark stuff and it fixed mine untill i went jacobs elec.

 

[myagi]

Hmmm. some really interesting stuff there. The vacuum at choke housing ???? I disconnected the automatic choke and converted it to manual but wouldn't have thought there was any vacuum on the fitting running from the choke housing. I was missing half the stuff to make the auto choke work properly. I'll have a look at this next

Also, yes the HEI was an eBay purchase. Tons of spark. Truck starts right up and mechanical advance seems to work properly when checked with timing light.

The one tooth off suggestion was already checked when I removed the timing cover to repair a gasket leak. It's dead nuts

 

[kimcrwbr1]

Ford V-8s run best with the max advance possible at high rpm. If your only getting 10 degrees of a curve that is a big issue. Your total advance or all in should be looked at closer that is why your not getting it to ping. normally the vacuum advance counts for ten degrees and the mechanical advane another 14 degrees. You can map the curve and compare what is recommended for your engine. Start with base timing write down the rpm and degrees then raise the rpms 500 and write down the advance keep stepping it up until the advance stops moving then you can map the curve. I am posative 20 degrees at 2500 rpm is not enough advance. You should get between 14 and 18 degrees mechanical advance add the vacuum and that give you all in or total advance. The correct curve will bring that engine to life. Where the choke bolted to the carb the one mount has a hole right next to it you can probably just stuff a plug in the hole or fill it with silicone and let it set up good before starting it.

 

[myagi]

Well, I did find a small vacuum leak at the automatic choke housing. I've since fixed that but it didn't make a huge difference in the reading on my gauge.

I also reset the carb idle adjustment screws using the vacuum gauge for highest reading and highest rpm as suggested by kimcrwbr1.

Then I checked my timing and adjusted until it started to ping then backed off a few degrees. The engine wouldn't roll over (too much advance) until I backed it off a little more.

I would say that it seems to have a little more oomff than it did before but not what it should be.

I have noticed the unburnt gas smell whenever I start it up and shut it off. It's very noticeable and I would say it's running very rich.

I don't know a whole lot about this carb (it came with the partially disassembled engine) but I'd say that somebody may have been messing around with the jetting before I acquired it. Is this likely ????
I don't know what else to do at this point. I havn't verified the timing curve yet but as the harmonic balancer is 47 years old, I'm thinking some slippage of the outer ring is also possible