Idle speed too high . . . can't adjust

[tekenaar]

OK, this one was a real stumper until yesterday. I was experiencing some difficulty trying to get my newly built SSD engine to idle below ~1300 RPM. R-Bob suggested changing springs in the distributor advance mechanism, which I did and appeared to help some. Still had "run-on" when the engine was shut off.

Completely went through all of the adjustments and basically reset everything to spec after cam was properly run in with solids. Other than a bit too high idle and the "run-on" problem at shut down, the engine ran extremely strong . . . lots of torque through the gears, no hesitations or bogs.

My son came over with a friend a few days ago and took this GT for a short drive to "prove something to his friend" . . . evidently he'd been bragging on the engine's performance. He returned after a few minutes and said I needed to do something about the brakes, they weren't working too well.

Didn't feel like messing with anything right then, but took the car out for a spin a few days later. Brakes were definitely behaving as if they had no power assist. Thought it might be a kink in the vacuum hose from the intake. On the way back the engine suddenly started running like it was missing on one or two cylinders . . . NOT GOOD!

Got the car home and checked the plugs and ignition system . . . everything checked out OK. Started engine again, still missing. Was going to check valve clearances next, but took a quick look at the brake vacuum hose first. Guess what?! . . . the vacuum check valve housing had split into two along the black/white "assembly" seam!

Result: HUGE vacuum leak directly to #1 and #2 cylinders, as that is where the vacuum fitting screws into to SSD intake manifold. Evidently the valve had separated and was leaking somewhat, but white and black halves were held together by hose pressure so that leak was not obvious visually. Finally came apart enough on my return trip to notice and made symptoms worse.

Definitely a new one for me . . . it's always the unexpected "little things", isn't it!!

[72GT]

If the halves broke clean will you be able to repair it?
I actually thought my checkvalve had a metal body, I will go take a look. Might not be stock though.

[tekenaar]

Originally Posted by 72GT If the halves broke clean will you be able to repair it? I actually thought my checkvalve had a metal body, I will go take a look. Might not be stock though.

Yep, if it's black/white, it's plastic housing. Scraped it out along the edge and used a good thick model glue to re-assemble. Put a C-clamp on it overnight to hold it in place while glue dried and everything's hunky-dory again.

[Killer Texas GT]

Otto,
Just come by the house and grab one I have about 9 of the critters, while your here maybe you can figure out why my brake fluid is diappearing with no leaks in the system but the engine has a terrible miss on all cylinders almost like a backfire but not. Maybe I have one of those bad vacuum leaks.
rk

[tekenaar]

Originally Posted by Killer Texas GT Otto, Just come by the house and grab one I have about 9 of the critters, while your here maybe you can figure out why my brake fluid is diappearing with no leaks in the system but the engine has a terrible miss on all cylinders almost like a backfire but not. Maybe I have one of those bad vacuum leaks. rk

If your brake fluid is disappearing with no visible leaks anywhere, there's only one cause and it explains the miss too. You probably have a leak at the rear seal of the MC and it's being sucked out of the power brake booster into your intake manifold. Brake fluid being sucked into the intake would explain your miss. I'd look there first.

[Killer Texas GT]

I will start there, also will start odering the jets ect. for the tune up, 75 distribuitor is on the work bench ready to go, maybe get back on it next weekend.