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View Full Version : Where do you pull a vacuum from on a 88 Prostar 190


rjracin240
11-12-2010, 12:01 PM
Looking for some advice on working on my 88 351W in my 88 190 Prostar.

Have a replacement carburettor to install and want to also do some troubleshooting on tuning........where do you guys suggest hooking up a vacuum gauge. I do not see any nipples anywhere on the manifold or the carburettor base or the carburettor itself to hook the tubing up for a vacuum gage.

Thanks ahead of time for the tips on this.

Luv2Ski
11-12-2010, 12:23 PM
That is a mighty pretty looking carb!

I generally put a quick "T" in the line to the PCV valve. If you go this route, it is a good idea to check/replace the PCV as well as it will mess up your reading if it is not operating properly.

You can just hook up to the gauge directly and leave the PCV detached, it does not seam to make a big difference if the PCV is in good shape.

FourFourty
11-12-2010, 01:50 PM
That is a mighty pretty looking carb!

I generally put a quick "T" in the line to the PCV valve. If you go this route, it is a good idea to check/replace the PCV as well as it will mess up your reading if it is not operating properly.

You can just hook up to the gauge directly and leave the PCV detached, it does not seam to make a big difference if the PCV is in good shape.

Do not hook in line with the PCV.....Do not unhook the PCV, it would drastically shorten the life of your engine....

You should be able to find A plugged port in the manifold or base of the carb. You will probably have to do some plumbing work to get hooked up to the existing line, but it shouldnt be a big deal. Do you have the manual for the carb?? You may be able to find carb info on the web. Make sure you use a manifold vac port, and not a Venturi vac port....

FourFourty
11-12-2010, 01:54 PM
Here you go-

http://www.holley.com/data/Products/Technical/199R7948-5rev1.pdf

Scroll to page 5. There is a vac port for PCV, and you will also see a full man vaccum port on the other side of the carb....Perfect location for your vac guage.

Although I dont see the port sticking out for the PCV. (which doesnt matter cause you have one on your spacer.... However there should be a port on the other side, or at least a plug to pull out so you can install one.

Luv2Ski
11-12-2010, 02:11 PM
Do not hook in line with the PCV.....Do not unhook the PCV, it would drastically shorten the life of your engine....

Hooking up a vacuum gauge to a the PCV supply line will not hurt anything. Once attached, the gauge does not open up a vacuum leak (would be pretty hard to tune anything if it did). Plus it would not matter where you hooked it up, a vacuum leak would be bad regardless if attached to the PCV supply or somewhere else.

You should be able to find A plugged port in the manifold or base of the carb.

Nope on this gen Indimar there are no extra ports that can be tapped into (if there is somebody enlighten me).

Although I dont see the port sticking out for the PCV. (which doesnt matter cause you have one on your spacer.... However there should be a port on the other side, or at least a plug to pull out so you can install one.

I don't think so, the marinized version (4160) does not have this port or a PCV port, at least not the old ones.

airdrew99
11-12-2010, 02:33 PM
As Dr. House would say, "Oh, snap!"

FourFourty
11-12-2010, 02:36 PM
Hooking up a vacuum gauge to a the PCV supply line will not hurt anything. Once attached, the gauge does not open up a vacuum leak (would be pretty hard to tune anything if it did). Plus it would not matter where you hooked it up, a vacuum leak would be bad regardless if attached to the PCV supply or somewhere else.



Nope on this gen Indimar there are no extra ports that can be tapped into (if there is somebody enlighten me).



I don't think so, the marinized version (4160) does not have this port or a PCV port, at least not the old ones.

First off, consult ANY professional engine builder/tuner and ask them if it would be good idea to tap a vacuum guage into a vacuum line that is attached to a PCV valve.... Even at idle, a PCV bleeds off some available vacuum which can cause fluctuations in that line. Not to mention it has HUGE fluctuations when the throttle is blipped compared to a port that runs off another manifold primary chamber. That is why any device to measure vacuum is NEVER hooked to that port from the factory....in ANY application! The only things that they will tie into that line are accessories that consume vacuum ie. Brake booster.

Its not a bad idea for him to leave the PCV unhooked and use that port for short term testing or the like. But is a very bad idea to do it repeatedly or for any kind of longer runs (more than a few minutes) especially if the engine will be shut down for long periods after. The gas vapors in the crankcase from the cold startups will rust the cylinder walls etc while the engine sits, unless it is run for a while with the PCV hooked back up.

I am aware this is a Marine version, however, I doubt they cast a completely different housing for it. So, I would be surprised if the port was not there. it probably is but it probably just has a plug in it. If I am wrong about that, I apologize ahead of time.

No need to give me the "i didnt think so" haha type crap. I was just tryin to point out the correct way to do it, and using the PCV hose is not it.... It will be close, sure. But, its not the best way to do it.

rjracin240
11-12-2010, 08:06 PM
Here you go-

http://www.holley.com/data/Products/Technical/199R7948-5rev1.pdf

Scroll to page 5. There is a vac port for PCV, and you will also see a full man vaccum port on the other side of the carb....Perfect location for your vac guage.

Although I dont see the port sticking out for the PCV. (which doesnt matter cause you have one on your spacer.... However there should be a port on the other side, or at least a plug to pull out so you can install one.

Thanks for the advice, could not open the link came out in chinese think it is an issue with my Dell though.

Snapped a picture of the carb and looking at the side where the electric choke is at on the base toward aft (Left side of picture) you can see that there is a black allen plug. Believe this is the one you are referencing as the place to pull the vacuum for my gage.

FourFourty
11-13-2010, 09:37 AM
Yes, that is the one you want. I actually found a pic of a 4160 non-marine to verify that port is a full man vacuum port. The pic shows it as PCV port, however, your spacer plate has that for your PCV, So you can pull the plug out of that port and use it for your guage.







http://img43.imageshack.us/img43/9780/66572747.jpg

rjracin240
11-13-2010, 10:02 AM
Yes, that is the one you want. I actually found a pic of a 4160 non-marine to verify that port is a full man vacuum port. The pic shows it as PCV port, however, your spacer plate has that for your PCV, So you can pull the plug out of that port and use it for your guage.







http://img43.imageshack.us/img43/9780/66572747.jpg


Thanks 440, stuck here at work today. Hoping to get out to the boat tomorrow, change out the valve cover gasket for the left side and exhaust manifold, put new carb back on and then go out for a spin.
The people att he carb rebuilders said to hook up a vauum gage and adjust mixture to pull the best vacuum. Hopefully will be able to get rid of all my driveability issues and then post a good informative thread with plenty of pic's!
Thanks to all others that contributed to the thread.