Thanks Bryan, I’ll give the free rev a try. I think it is a vacuum secondary. I have decided to change the carb and intake on the restoration car but I already have a rebuild kit with a new diaphragm that I could use. How do you test a vacuum secondary?

davebdave wrote:How do you test a vacuum secondary?

A very good question. You can do a preliminary test by opening up the throttle the whole way (with the engine off) and then the plunger to the diaphragm for the secondary should easily move by pressing it upwards with your finger. However, since the secondary only opens when the engine is developing sufficient vacuum at high revs, this isn't a complete test.

On mine, I can tell that the secondary is opening because there is a lurch and a sudden increase in power when I stomp on the gas at 3000 rpm or so. The vacuum-operated secondary design doesn't have a smooth transition so the lurch is one clue.

In my younger and more foolish days, here's how I verified absolutely that it was working. Take the hood and the air cleaner housing off the car. Go for a drive with an able-bodied and gullible yet fearless assistant in the passenger seat. Stomp on the gas, and have the assistant (while hanging on for dear life) visually verify that the secondary plunger moves upward. Sometimes this required standing up in the car and peering over the windshield frame into the engine compartment. You can see why I don't have many friends anymore...

I'm sure there is a better and safer way, so if anyone has a suggestion, I'd love to hear it. Perhaps a vacuum gauge that you can see while driving, connected to the intake manifold, and look for the sudden drop in vacuum as the secondary opens?

-Bryan

18Fiatsandcounting wrote:
You can see why I don't have many friends anymore...

Lol, I might volunteer to lean over the windshield if you disconnected the brake boost. The pedal is really touchy from what I’ve found. I have a few old cell phones laying around. I can probably zip tie one underneath the hood and go fro a drive to watch the carb.

However, with Covid I couldn’t get an appointment to register the car until several weeks from now so it will be awhile before I can give it a test drive.

Yes, the cell phone video is a good idea and should work. I didn't mention this because I have only one phone, and since these things cost a small fortune these days, I was reluctant to strap it under the hood while I went for a drive.

Which reminds me: To check that your trunk light goes out when you close the lid, put the cell phone in the trunk on video, close the trunk, open back up, and review the video that the light did indeed go out. Just in case this was keeping you up at night.

-Bryan

this seems like a dashcam opportunity...…
and you might be able to see the results in real time..
thus distracting you while driving and leading to an incident requiring purchasing more and newer parts.....

dinghyguy

Not one smoking gun but three smoking guns! The cams are timed perfectly but the idle ignition was set at 46deg BTDC! I set the points to open at zero on the crank pulley per my Haynes Manual and now idle timing is 5 BTDC at 600rpm. There was a fuel leak that with the engine running was flowing not dripping. I replaced the filter and hose. The primary throttle venturi is covered in condensation but not the secondary so I still don't know if the secondary is operational but I certainly have water in the fuel. I put a bottle of gas dryer in the tank and when I burn it down to 1/4 I'll drain the tank completely and maybe treat it to some airplane gas. After a short drive there is at least one water drop in the new filter.

Speaking of driving, WOW! What a difference! I didn't want to admit it to myself before but I didn't like the way the car drove when I drove it home. In the back of my mind I was thinking "what am I doing with two of these?" Now it revs like crazy, makes an awesome sound and is pretty darn fast. What a kick. I was laughing out loud the whole time!

Thanks for the advise, I still have a few things to check including the vacuum secondary but it's a whole different animal now.

HotStuff by Dave W, on Flickr

water by Dave W, on Flickr

fuelLeak by Dave W, on Flickr

filter by Dave W, on Flickr

Vacuum Secondary works. I strapped down an old phone underneath the hood. Unfortunately I didn't have a lot of phone memory so the car didn't get a proper warm-up. Second gear was complaining on the shifts. The video is edited, I never got past 2nd gear due to 35mph speed limit. If you want to watch the video you may need to open the last photo in a new tab.

CarbCam by Dave W, on Flickr

Pooch by Dave W, on Flickr

Secondary by Dave W, on Flickr

That's a really cool video of the secondary linkage opening; thanks for that!

Yes, at 46 oBTDC, I'm surprised your engine even ran. Sounds like it is in much better shape now, and since your secondary is working, sounds like a good cleanout of the old gas and some minor fiddling is all you'll need. One thing I noticed: It appeared like your fast idle linkage (the one on the far left in the video) pulled upward a few times. The good news is that it works. The puzzling news is that fast idle system is only supposed to work when the transmission is in 3rd or 4th gear, and you mentioned not going past 2nd. So, a low priority, but perhaps something else to look into.

But, this reminds me of the Sammy Hagar song, "I can't drive... 55!" with the line, "I can't get my car out of 2nd gear." But I digress.

-Bryan

PS: I have a similar picture of our dog in my car, but he's a black lab.

Thanks Bryan,
I wondered what that arm was for. I should have said that I didn't get past second gear in anger. Probably I shifted to third at some point in the uploaded video. The full video was 8 minutes long and I went to third a few times. Sammy Hagar was a Trans Am Fan and so he's alright in my book. His TA had the license plate IEATZ28. But I'm getting off topic.

Labs are the best!

davebdave wrote:I wondered what that arm was for.

Yes, it's an early emissions control device. The basic idea is that when the car is in 3rd or 4th gear and the clutch is engaged (pedal all the way up), the carb is not allowed to fully return to idle when you let your foot off the gas. Of course, it doesn't return to idle anyway since you're in gear and moving merrily down the road, but the thinking was that it didn't allow the carb to go way lean under those conditions, which leads to higher temperatures and NOx formation. Why the system doesn't also operate in 1st, 2nd or 5th gear has always been a mystery to me.

So, there is a vacuum hose from the intake manifold (facing the master cylinder, but downward slightly), and that hose goes to a black electrically operated valve on the sidewall. The other end of that valve goes to the fast idle connection on the carb. There is also a push-button switch near that valve, and when the car is idling in neutral and you press that switch, the idle speed should increase to 1500 or so. If all is working as it should.

Yes, our dog is awesome! Totally food motivated, more so than any other dog I've seen. Poor guy, seems like all he can think about is eating....

-Bryan

18Fiatsandcounting wrote:

davebdave wrote:I wondered what that arm was for.

Yes, our dog is awesome! Totally food motivated, more so than any other dog I've seen. Poor guy, seems like all he can think about is eating....

-Bryan

Oh yeah, eating and chewing (eating practice)


stick by Dave W, on Flickr

Yep, chewing and eating! Our prior lab, Spencer the Wonder Dog, chewed on rose bushes for fun. Thorns didn't seem to bother him. I never did understand that one...

-Bryan

Hi All, progress has been pretty much nil lately buy I'm tinkering with the spider again. I'm putting the accessories on the engine and I'm not sure what this threaded hole on the exhaust side of the block is for. Can anyone fill me in?

Thanks,
Dave

WhatsThis by Dave W, on Flickr

Wow, it has been a while Dave, and to answer your question, that threaded hole in the side of the block is the drain for the coolant galleys in the block. Early models had a spigot of sorts, while later models just sealed it with a plug. Remove it when draining coolant from the block, but don't forget to close it back up.

-Bryan

Thanks Bryan, I hope all is well with you. I was thinking maybe it was for a chassis ground. Which brings the question; where do you ground the block? The project has been sitting neglected awhile but I primed the oil pump and oiled the motor before installing the timing belt last week so I figure I have a limited amount of time to get it running before the prime goes away.

As far as asking these “where does this go” questions, this is why we bought the running sister 1971. That plan backfired because we just drove that car (instead of working on the original) and we now keep it 2 hours away at our second home.

Oh and on a whim I picked up a barely running 1965 Austin Healey Sprite which sucked up any remaining time.

Hey, why am typing, I need to get to work on the spider.

Dave