1977 Ford E350 460cid vacuum diagram?

[DOC]

I did a tune-up and it failed the emissions test due to hi HC at idle. I'm thinking its vacuum leak because the idle is rough and it surges at a stop.
If you can help I would would be saved. I have to pass emissions ASAP.
Its on the RV I bought off here and its turning out well except the BS government hoops I have to jump through.

[Ah Pook]

Did you change air filter, oil, oil filter and fresh gas before the test?

[DOC]

Did you change air filter, oil, oil filter and fresh gas before the test?

Yup, total tune-up. Plugs, wires, cap and rotor, air filter, oil and filter, gas treatment. And a fresh tank of gas. Adjusted the air fuel mixture screws down from 5 turns to 1.5 turns. Ran it for about 50 miles or so. Still failed the tailpipe test. I think its the vacuum lines that were screwed up.

[zteknik]

Wish I could help.The oldest manuals we have back at the shop are late 80's

[Great-Kazoo]

1977 460 vacumm diagram

https://images.search.yahoo.com/search/images;_ylt=A0SO8z31K4BTRAEA6w9XNyoA;_ylu=X3oDMTB0 bTh1YXVpBHNlYwNzYwRjb2xvA2dxMQR2dGlkA1ZJUDA0OF8x?_ adv_prop=image&fr=yfp-t-901&va=1977+460+vacuum+diagram

Did you change the PCV valve, air canister filter, and spray clean the egr valve? Is the EGR valve working? If you think it's a vacuum leak, whats the (IIRC 21") gauge telling you at idle? If it's a vacuum leak replace the vacuum lines. From the looks of it the ford has a sealed canister unlike a GM. So i'd splice the lines together by passing the canister.

[DOC]

That is something I havent tried yet.

[GunsRBadMMMMKay]

Sometimes you can find where the leak is by spraying starting fluid or carb cleaner around suspected areas and listening for changes in idle. Something that old, if the vacuum lines felt dried out/brittle and I had the time and money, I would just buy a roll of new line and some assorted connectors/t's and set aside some time to go section by section and replace it all - but that might not even be your problem.

[Great-Kazoo]

Sometimes you can find where the leak is by spraying starting fluid or carb cleaner around suspected areas and listening for changes in idle. Something that old, if the vacuum lines felt dried out/brittle and I had the time and money, I would just buy a roll of new line and some assorted connectors/t's and set aside some time to go section by section and replace it all - but that might not even be your problem.

use something other than starting fluid. it's too light and has a tendency to be picked up by the intake and evaporates too fast. . As much as i despise WD40, it or something similar (oil based) works better since it doesn't burn off quick .

[cofi]

Surging at idle is almost definitely a vacuum leak.....on something that old I would use that diagram kazoo posted and just replace all the hoses vs trying to find the leak....vacuum hose is cheap

[Colorado Osprey]

Anybody ever try a mixture of E-85 and gas at a 1:2 or 33% ratio to get these older (pre-80's) non-fuel injection engines to pass.
It used to be a fairly common practice to add high test alcohol to get vehicles to pass.