End of rope... Carb upgrade gone wrong -updated with Vacuum test

[JasonB]

I decided that since the tired 2bbl on my 302 Ford was in need of a rebuild, seemed like a good time to install a 4bbl. I installed a Weiand al intake, 2x 1" spacers, and a Weber 500cfm 4bbl that was previously tested on a 302. The engine will start (finicky), but if you let it fall below 1200 rpm, it dies. I have pulled it all back apart and replaced all gaskets as it sounded like a vacuum leak, but it didn't help. Have also installed new fuel filter/ Checked carba nd floats are correct as well as the needles seem free.<br /><br />I've verified that ignition is ok. Thought i had it up to snuff this morning, so carried it to the water. idled ok for a bit, but would dive when going in gear unless you let it fall in gear.<br /><br />Anyone have any ideas?

 

[rodbolt]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

sounds like ya got an intake vacum leak. some of the 302's had funny head passages and sometimes the intake gaskets would not line up properly. test the intake vacum. if its less than 18" or so start hunting for a leak at the spacers or maybe a vacum port left unplugged.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

Thanks Rodbolt. Just pulled the intake back off and replaced gaskkets, checked all ports, etc. Have to get a vac gauge.

 

[LubeDude]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

It may be in the spacers, why the spacers anyway? Were they new or old ones. They can be warpped and cause a vacume leak from Hell. Raising the carb that much can cause a lean condition. Spacers make the engine think it has a bigger carb and can necesitate rejetting.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

I need at least one spacer to get the throttle cable to clear. Problem persists when I go bact to one spacer. Both spacers are new out of teh box. One is a solid aluminum, tapped for teh lead to teh PCV valve. Teh other is a phenolic i hoped would ceep the carb cooler.<br /><br />On a related note, I have while I had the intake off this afternoon, I checked it carefullly for any sighs of warp or cracks and found zilch.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

As a note on the spacers, they are both 4 hole, so they don't add a ton of volume.

 

[rodbolt]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

I still think you have a vacum leak. would not be the first time I have seen the gasket slip or not line up on the heads and leak. ford had some funny port designs and there were some intake issues years ago.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

I'm going to pick up a vacuum gauge this afternoon and see what it tells me. I'm sure the gasket didn't slip. I know the ones I pulled off last night were in perfect alignment, but the odd thing I saw is that the beads around two of the ports weren't fully crushed to my liking even though the head and intake ceck out as straight and clean....<br /><br />Depending on what the gauge shows, I'm on the verge of putting the stock 2bbl intake and carb back on so we can see if it runs properly and get some use from the boat.

 

[bomar76]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

I bet vacuum leak.<br />Bad gasket seal on intake to heads OR a massive leak in one of those spacer gaskets (I run a 2" open spacer myself...adds plenum volume).

 

[Boomyal]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

Where'd you get the intake Jason? I'll bet the vacuum guage shows a leak. If some one were to have shaved that manifold to account for signifigant head surface cut, that could result in a problem. I don't like the sound that the sealant didn't crush on a couple of ports.<br /><br />...and as is so often usual, something so straightforward ends up a pile of dung.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

Boom, that's what I'm wondering. I've been told that two gaskets can sometimes be used without Ill affects, but I'm skiddish of stacking gaskets that way. Sounds like a good way to get a really ugly leak later be it water or vacuum/intake.<br /><br />The intake was purchased used. That was likely my first mistake....<br /><br />I picked up a vacuum gauge earlier and will try to get a reading later this afternoon and report back.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

Oops. Double post.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

Can I scream now? <br /><br />I took a good look at the gaskets I pulled off last night and what I saw in the daylight would almost make you cry. Keep in mind I have been fighting this problem for well over 3 months on/off, in addition to shelving a Holley that I had carefully rebuilt as I thought the carb was the problem... Lesson learned there...<br /><br />The gasket off the port side had all embossed rings crushed evenly.<br /><br />The intake gasket from the stbd side was a different story. It wasn't 1-2 ports that didn't seal, I think it was all. The gasket was crushed properly at the top. You couldn't hange a fingernail on the embossed rings from either side of the gasket. The embossment at the bottem didn't look touched. Impossible not to hang a fingernail in. I don't believe I could have put the manifold on wrong.... Engine has the same problems with the fresh gaskets put on last night.<br /><br />No evidence of water leaks at either end, en the valley, or in the oil thank goodness.<br /><br />For grins, I went ahead and put the Vacuum gauge on:<br /><br />Here are the results of my Vacuum gauge adventures. Measurements taken with engine warm (hard to keep it running long enough for that....) and Vacuum gauge plugged into the PCV hose coming out of the back of the carb spacer.<br /><br />With the intake torqued at the stock spec of 25lbs, Vacuum at idle -shaky 8-10"<br /><br />Knowing the gasket problem from above, and teh fact that the intake is likely junk anyway, I decided to experiment.<br /><br />Increased bolt torque to 30lbs after intake at operating temp: slightly shaky 14" (swings between 13/15")<br /><br />Anyone else agree with junk intake? I didn't have any known sealing/vacuum issues with teh cast 2bbl manifold that came off. Never pulled a vacuum reading with that set-up, but had no idle or performance issues.

 

[cslaufer]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

I had the same problem years ago with a 307, it ended up being a manifold problem aswell.

 

[Buttanic]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

Fel Pro makes a double thickness intake gasket for small block Chevys that I used when I had the heads angle milled on a race motor I built. They may make one for Fords also.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

^<br />Just bumping this up to see if there are any more opinions. I'm pulling the 4bbl back off for now and shelving the project until after boating seasn, but would love to figure out the maifold problem anyway...

 

[LubeDude]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

There is nothing wrong with using just a slight bead of silcone on the intake gaskets, not too much as it will squeeze out on the inside of the runners. I have done it a lot. Let it set overnight before trying it. Sounds like there isnt a large void.

 

[rodbolt]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

DO NOT USE SILLY CONE ON THE INTAKE PORTS<br /> silly cone is not a suitable sealant were fuel is involved. it will leak<br /> small vacum leaks tend to burn small parts off the exhaaust valves.<br /> memory from my hotrodding days tells me the heads on the windsor design fords had diffent port configurations for the 2 and 4 bbl intakes. there were some aftermarket 4bbl intaakes that were designed to fit the 2bbl heads. if you have the intake for the 4bbl heads and your using 2bbl heads it just wont work properly. years ago we used to put the 351 heads on the 302 and 302 heads on 351's and all kinds of combos. was tricky insureing the intake sealed. most times when running double gaskets the water ports leaked. but silicone will fail if used anywhere near gasoline. its will fail when used with most oils. it tends to get soft, add a vacum source and it pulls through creating leaks. carefully measure the ports, port location and intake runner angles on both intakes. I will suspect you will find they are slightly different. it does not take much. its part of why I quit hotrodding. got to be to many configurations to keep track of. that and 2 kids was getting to expensive. but at the shop I worked at in cleburne TX thats what we specialized in.

 

[JasonB]

Re: End of rope... Carb upgrade gone wrong -updated with Vacuum test

No dis-respect to your advice lubedude, but putting sealer of any form there feels like a band-aid of sorts that will likely come off at the worst moment. My 2bbl may be larger than I thought anyway, so a 4bbl may not be that helpful (whick would stink since I have two good 4bbls that I may not use...) I'm trying to figure out the measurement of my Rochester 2GC to decide how many CFM it is. It looks like 350-380? Anyone know what the stock carb on the Rochester equipped 888's was? I think the Holley that the early ones had is 300.