engine and drivetrain Failure of a guibo, or other diagnosis? (fixed!)

[Stacey]

Mr. KF, a couple thoughts..

I have an extra guilbo or two lying around the garage if you get impatient. You're just going to destroy it again anyway the next time you launch. ; )

Based upon your diagnosis, I'm still thinking you have issues with your main jet circuit. DCOEs will idle and rev just fine without a load on them, just by fuel from the idle circuits. I know you checked the venturis. No sign of air filter carnage from your backfiring episodes that might have lodged in there killing your vacume? Also, I'm sure you've already checked this too, but just in case, did you pull the plugs and make sure you don't have one fouled from an overly rich condition? Same symptoms.

Evenings this week are fairly open if you need some wrenching assistance.

[POP3Y3]

man, K! that looks sweet! are they hard to sync up or do you use a syncromiterizermabob?

[KFunk]

Mr. KF, a couple thoughts..

I have an extra guilbo or two lying around the garage if you get impatient. You're just going to destroy it again anyway the next time you launch. ; )

Based upon your diagnosis, I'm still thinking you have issues with your main jet circuit. DCOEs will idle and rev just fine without a load on them, just by fuel from the idle circuits. I know you checked the venturis. No sign of air filter carnage from your backfiring episodes that might have lodged in there killing your vacume? Also, I'm sure you've already checked this too, but just in case, did you pull the plugs and make sure you don't have one fouled from an overly rich condition? Same symptoms.

Evenings this week are fairly open if you need some wrenching assistance.

Yeah... I'm thinking I may have to launch a tad gentler next time. At first I spun the tires on purpose, just so I'd know the limits of where they spin. Then I kept being more and more gentle on launches, and it still spun more than I'd like.

I can't really bet on having any time in the evening this week to work on the car. Perhaps I can just unbolt the carbs tonight and take them to my apt. in Athens and fiddle with them at night when I have time.

I did pull the main jets while sitting at the Speedway in Carrol. They were still there of course, and no real sign of debris. Perhaps something could be lodged up inside of there, but I dunno.

I'll have to atleast shine a flashlight up inside the venturis and check them out tonight. I didn't get too great of a look while in Carroll.

Brian, all I've got to work on them is a screwdriver so far. My friend may have a wide-band sensor I can shove up the tailpipe soon, but that'll be a while before I get to that.

[KFunk]

OK, finally got to parents' house to work on it again. Compression test is a bit... odd.

So, before this, I did a comp. test on Saturday. All 4 cylinders were between 125 and 132. A bit low, but uniform. No surprise, its had some wear.

Today, I warm it up and let it idle some, then do it. I get roughly 135-120-120-150. WTF?

Well, the pistons are in there. The 120s are a bit worrisome, but maybe its not warmed up enough, and in any case the car should still run.

But what the heck happened in #4? Could a valve be stuck or something and give it more compression? I guess I'll wait a little while till it cools off and pull the valve cover again. This time I'll check the valve lash on everything, and look closely for busted stuff on #4.

I can't do any load testing without the guibo, will get here Friday.

I may have to drive some other car on Sunday. Perhaps my friend's Plymouth Acclaim will be up to the task. [/i]

[KFunk]

The extra compression might be explained by a little extra oil in the #4 cylinder (an idea from rsafier).

Makes sense, since that plug has looked a little wet, even before the autocross on Sunday, but not on Saturday when I did the first comp. test.

Oh well, no major deal.

I blasted carb cleaner around everything while engine was running, no definite signs of any vacuum leaks.

I took off the back carb last night and took apart and examined as much as I could. Don't know what I'm looking at really, but no major signs of bad stuff. There was a bit of gunk around the 'pump exhaust valve', or whatever it is that sits at the bottom of the float bowl.

The fuel strainer in the top had a bunch of gunk sitting around it, but didn't appear to be clogging the element. Some clogging there might explain the symptoms.

I wrote down all my jet sizes, etc., and they're pretty darn close to the specs Stacey sent me. I'm not sure about my venturi size, not sure how to get to that right now.

Friday or Saturday I'll put the guibo in, and the back carb back on, clean strainer in front carb, and go for a drive. If still having problems, I'll take off the front carb and check everything over.

I'll also probably switch to my velocity stacks, and zip tie some window screens over them to make filters.

[Marty]

If you have gunk around the pump jet try removing the jet well (its the square little projection on the bottom of the carb that's held in with 4 screws its the lowest point in the float bowl and if you have crap in the bowl it might well have settled into the well and at high revs gets picked up and pulled into the main jet.

[KFunk]

OK, its fixed! One stinkin tiny little screw!

Of all things, the tiny little screw that holds the condenser on the distributor. It wasn't making a solid ground, thus wiggling and killing my motor under load. I had checked the wire on the back of the dizzy before, and it seemed tight, but I didn't mess with the screw.

Yes, I know I should switch to electronic ignition by now, but I'm too lazy/cheap to do it.

Of course, I also replaced the guibo. It was broken into 6 separate chunks, without any bolts connecting the driveshaft to tranny. Two chunks/bolts were deposited on the highway. It was propelling itself by the nut/bolt heads pressing against the outside of the flange. Yes, both flanges are a bit worse for the wear, but doesn't justify any further work for right now.

I'm also much happier with using the OEM bolts/locknuts sent to me by Bill Williams, aka maximillian. I had nylock nuts on it before, which are probably not good enough. The OEM nuts are all metal, which cuts in there somehow, not sure what they're called. But I covered the bolts in red loc-tite and tightened the crap out of them.

My tranny mount was also ripped into pieces, which explains the reason I had trouble grabbing 2nd gear. I've ummm... got something in place for that, which should hold it for a while.

It's on now for Sunday! The trailed racecar Datsun 510 is pre-registered, so I'm a gonna go for 'em, iff'n I have to break every bolt in the car doin it. He's got coil-overs and adj. camber plates, which I do not have at all. But he's only gotten me by a couple seconds when I had crap for traction and only the 32/36.

C'mon up tomorrow Brian! I may actually have a working speedometer/odometer tomorrow as well.