Hey guys,, I'm tying to get this 86 150 lariat started. Has the 351w 1850 Holley carb. I've been looking at this vacuum diagram to long I think cause nothing makes sense now. A buddy thought he would help and started messing with the vacuum hoses and I didn't know where they were to begin with so I took them all off think g would just put them Back on. but looking at the diagram looks like there are all these chk valves and things that I don't have .. Is there something basic that will help me understand this ? Is there any info you need to know from what I'm looking at or is this pretty standard system for all other trucks??
Thanks a lot

 

Yours is the 351HO which, fortunately, has the DS-II ignition system and no computer. However, it compensates with a myriad of vacuum lines. Here's a reference for what all of those acronyms mean. But, the first question to be asked is whether or not you need to put everything back as it was? If you have emissions inspections then answer is probably yes. If not, then you could go simple:

• Vacuum advance from carb to distributor
• Vacuum to the plastic manifold on the firewall for HVAC and transmission
• Vacuum for brakes
• Vacuum for cruise - if you have it.

So let us know which way you need or want to go and we can help with that.

 

Thanks a lot Gary,, was just reading some other threads that came up under vacuum. Was just reading some of your advise ..
No emissions here. It's loud already. When I picked it up from a buddy the whole heat riser contraption was the first thing I looked into he said it was gone.
No cruise hooked up on it and the a/c is not hooked up. That explains a lot of the open ended connectors loose stuff just hanging there, but it's confusing me.
If I could just get it running again I'd be thrilled, and my wife would love her parking spot back . Funny how all my stuff that runs sits outside and the stuff that doesn't run is in garage,.. She just doesn't understand

 

Tranny hose ?. Is that the single metal hose sticking straight up the middle under firewall??
Thanks

 

Assuming you have an automatic tranny it would be a C6, and there will be a little steel line by the tranny dipstick on the back of the engine, passenger's side. A rubber line goes from it to a plastic manifold on the firewall pretty much directly above the steel tube. Another vacuum line goes from that manifold to the "tree" screwed into the back of the intake manifold.

And from the plastic manifold you will have a hose going to a check valve and then a tee. One side of the tee goes to either the "coffee can" or the sphere, both of which are used as vacuum reservoirs and are mounted on the passenger's side inner fender. And from the other side of the tee a line goes toward the corner where the fender meets the firewall, and into a grommet where it feeds through into the cab to power the HVAC system.

Another line normally goes from the tree to the cruise diaphragm, which is on the driver's side fender near the firewall. And a big hose goes from the tree to the power brake booster.

Surely you have the PCV line connected, from the front of the carb I think, but maybe the rear, to the PCV valve in the rear of the passenger's side valve cover.

And the last line you need, I think, is the line to the vacuum advance on the distributor. It will be from what is called a "ported" connection on the carb, meaning that it doesn't have vacuum at idle.

 

If he does have a aftermarket 1850 Holley, it has a PCV connection on the pass side rear of the carb, pointing toward the pass side inner fender. But if he is still using the factory aluminum spacer under the carb, a lot of them also had a large hose barb coming straight out pointing toward the firewall, and that can be used for the PCV also, or it can be used for the brake booster if you use the PCV connection on the carb.

Your dist will hook to the little port on the front pass side of the carb, pointing to the pass side inner fender. When you get it running right, this port will have no vacuum on it at idle when you pull the hose off.

This carb usually has one more small port down low underneath the bowl on the front. I usually plug this off, I usually don't need it, but it's a manifold vacuum port if you do need it.

 

Thanks, Dave. As you know I shy away from Holley's so am not familiar with the connections and model #'s. In fact, I'd missed that the 1850 is an aftermarket. Good catch.

 

I'm not sure what emissions controls you have but in general here are some possibilities. Also not familiar with that carburetor, so bear with me.

Vacuum line to: (M) - Manifold Vacuum, (P) - Ported Vacuum (S) - Ported Vacuum Switch

Brake Booster (M)
Transmission (?)
Heater Controls (M)
PCV Valve (may also go from PCV valve to EVAP) (M)
EVAP Purge (S)
Distributor (P)
Air Cleaner Thermal Valve (M)
EGR Valve (S)

Other lines that look like vacuum lines are choke fresh air lines and bowl vent lines.

Pics / diagram would be helpful and we could help interpret it for you

You could do a smoke test to find any disconnected lines or leaks.

(Cigar works well, although I have a smoke machine.. )

 

The 1850 is a non-emissions carb. It doesn't have all the ports to hook all that other stuff up, it's really not made for it. It's more of a 60's style carb, with just the things you need to get the engine running. I have 2 of them on different vehicles, I really like them, they run good on the little 302's and 351w's. They come setup for a manual choke.

I am working on a 1975 logging truck(f750) with a 361 big truck engine, and someone has added the same carb on it. The only thing I am afraid of with the big truck, is when they swapped the carb out, they got rid of the governor that was on the original carb, so the guy will have to be careful or he can over-rev this engine and damage it.