lt1 swap, headlight/vacuum
Thread Starter
Pro
Joined: Jun 2002
Posts: 662
Likes: 2
From: chatam nj
lt1 swap, headlight/vacuum
just swapped in the c4 lt1. motors runs and all, now working on odds/ends.
I connected the headlight vacuum line to the right side intake (below the vacuum port for the fuel pressure). the headlights worked with the original carb motor. I pulled the headlight vacuum line and the port seemed to have low/weak vacuum. the lt1 has the lt4 hotcam, the cam the issue or is should I use a different port on the intake (eg should I use the vacuum off the throttle body)? any thougths.....
I connected the headlight vacuum line to the right side intake (below the vacuum port for the fuel pressure). the headlights worked with the original carb motor. I pulled the headlight vacuum line and the port seemed to have low/weak vacuum. the lt1 has the lt4 hotcam, the cam the issue or is should I use a different port on the intake (eg should I use the vacuum off the throttle body)? any thougths.....
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
just swapped in the c4 lt1. motors runs and all, now working on odds/ends.
I connected the headlight vacuum line to the right side intake (below the vacuum port for the fuel pressure). the headlights worked with the original carb motor. I pulled the headlight vacuum line and the port seemed to have low/weak vacuum. the lt1 has the lt4 hotcam, the cam the issue or is should I use a different port on the intake (eg should I use the vacuum off the throttle body)? any thougths.....
I connected the headlight vacuum line to the right side intake (below the vacuum port for the fuel pressure). the headlights worked with the original carb motor. I pulled the headlight vacuum line and the port seemed to have low/weak vacuum. the lt1 has the lt4 hotcam, the cam the issue or is should I use a different port on the intake (eg should I use the vacuum off the throttle body)? any thougths.....
Drifting
Joined: Jun 2012
Posts: 1,990
Likes: 183
From: Port St. Lucie Fl
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
Use a vacuum gauge to see what the levels are. I don't think the LT4 cam is that much radical at all. The headlights will need a constant source, there are lots of them on the intake, just don't "T" into the PCV or power brake booster! To be safe don't use the one from the EGR, it might be timed.
Use the check valve and filter too
Use the check valve and filter too
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
I believe from the factory the FPR actually connected to the bottom port and the top port was for the HVAC in a C4. Regardless, those ports should work fine for the headlights.
The LT4 hotcam isn't the greatest cam for producing idle vacuum but it should easily produce enough vacuum to operate the headlights. It will operate the HVAC and the brakes fine so the headlights should be no different. Double check that you don't have a vacuum leak on the engine.
Did you do any other work to the car that could have upset the headlight system?
A vacuum gauge makes troubleshooting quite simple. Here is a link to lots of good info about the headlights with the vacuum diagrams and some suggested checks.
https://www.corvetteforum.com/forums...tem-works.html
The LT4 hotcam isn't the greatest cam for producing idle vacuum but it should easily produce enough vacuum to operate the headlights. It will operate the HVAC and the brakes fine so the headlights should be no different. Double check that you don't have a vacuum leak on the engine.
Did you do any other work to the car that could have upset the headlight system?
A vacuum gauge makes troubleshooting quite simple. Here is a link to lots of good info about the headlights with the vacuum diagrams and some suggested checks.
https://www.corvetteforum.com/forums...tem-works.html
Thread Starter
Pro
Joined: Jun 2002
Posts: 662
Likes: 2
From: chatam nj
lionelhutz, Thank you so much for the details. I'll double check the linest. I removed all of the cruise control, charcoal can and all hoses. all of the headlight components are new and worked before the old motor came out. really odd.
