85 running lean

[patrickj]

Hi all i just finished a complete re-build basically stock except for a mild cam and procomp aluminum heads 2.02/1.60 64 cc.Upon inital start the exhaust got red hot and melted vacuum hoses and anything else plastic that was within a foot or so. stock throttle body injectors and ecm.Runs and throttles up nice and does not over heat.has 40 psi fuel pressure and timing is at 8 degs.have not driven it as i do not want to do any damge.Any and all help is greatly appreciated. also no codes no engine light confused:confused

 

[ex-x-fire]

Was that when you were breaking in the cam? I've had that happen too, seems like w/ different heads/cam & a ecm thats just been powered up they run funny. You might want to get a adj. fuel press. regulator.
Start it today & see how hot they get.

 

[vetteboy86]

I've seen this personally too. You also might want to get a dial timing light so you can verify timing that the computer is advancing. Just to make sure everything is in line.

 

[killer408]

You are running lean because of 2 things. You installed a performance cam and added alum heads. Which require more fuel for proper air/fuel mix. The cam needs the fuel and the heads are much more efficent at the burning process so they need more fuel. As stated before, check timing and install a AFPR. For now, unplug vac line from requlator for increased fuel pressure at idle and cap the open line. You will need to get a chip burned, also do the calcs for your injector sizing.

 

[patrickj]

flow or pressure

Was that when you were breaking in the cam? I've had that happen too, seems like w/ different heads/cam & a ecm thats just been powered up they run funny. You might want to get a adj. fuel press. regulator.
Start it today & see how hot they get.

Hi thanks for your input yes it is during cam break in or should i say attempted break in shut it down after it melted a majority of my vacuum lines and split loom.Did not notice the exhaust until it was too late.What do i need to improve on if it does not settle in fuel pressure or flow?Really do not want to tear into it to replace injectors if i can avoid it.Also had the injectors re-built and bench tested before i put them back in.Also do you happen to know where the center vacuum port on the right side of the throttle body might go?Been awhile since i started this project does not show on the vacuum diagram. the ones i found online they are trying to say that it goes to the purge control solenoid but there is nothing there to attach to and i did not remove any of that stuff hope you can help thanks Patrick

 

[boomdriver]

Hi thanks for your input yes it is during cam break in or should i say attempted break in shut it down after it melted a majority of my vacuum lines and split loom.Did not notice the exhaust until it was too late.What do i need to improve on if it does not settle in fuel pressure or flow?Really do not want to tear into it to replace injectors if i can avoid it.Also had the injectors re-built and bench tested before i put them back in.Also do you happen to know where the center vacuum port on the right side of the throttle body might go?Been awhile since i started this project does not show on the vacuum diagram. the ones i found online they are trying to say that it goes to the purge control solenoid but there is nothing there to attach to and i did not remove any of that stuff hope you can help thanks Patrick

1st, You might check but I THINK the 85 (85 or 86 was 24lb) might have come with 24lb/hr injectors. if so, all you require is pressure. 22 lbs was stock for several yrs L-98 TPI.
Make sure the spark plugs are white on the insulator before writting it off as lean.....extra fuel will also make the headers glow...plug color is the way to confirm what the fuel mix is. the whiter the plug the leaner its burning. perfect is a Lt Tan to dull white. You might also need a hotter plug, hotter the plug the colder the exhaust will be usually. Theres lots of fine tuning in engine design.

Now the vac....
the port under the TB does indeed go to the purge. it runs down, splits to the egr solenoid, then a long hard line runs behind the alt to the frame where the harness is, and connects to the purge system. It might have a T down in the nose where the vac tank gets charged also.

Passenger side of TB has 3 nipples.....top is PCV, middle is purge tank, and bottom is TB water exit to heater core (back to system). If you have a water bypass in the TB, make sure those water ports are plugged and the bottom gasket is sealed so thats not pulling in air unmetered air. When there is water flowing in its fine, but when its dry the gasket can dry out and leak air directly into the idle circuit or one of the vac ports.
Rear of plenum has the hole underneath for the MAT, rear corner for brake boost and 2 small on rear side, one for a/c (interior) and the other to Fuel reg and air system control.