ive searched and searched. motor is an 8ba, two new 97's and a offy regular dual intake. the intake has a vacume hole under the rear carb and on the stock manifold thats where my pcv is hooked up. is it mandatory to drill a hole and "tee" the pcv line to the front carb? if i should drill a hole , where? thanks.
I would enlarge the thread to 1/4" pipe if it's 1/8", and through this hole drill a 1/4" hole into the plenum below the carb base to allow all 8 cylinders to act on the pcv, if the port is only on one intake plane. No need to tee it to the front carb.
Look carefully at vac location on your intake. If it is located in a runner leading to 1 cylinder, I'd suggest you move it. A PCV system is a controlled air leak. That leak can lean out that cylinder. Most PCV systems connect near the base of the carb. so that the additional air get homogenized on the way to all 8 cylinders. If you add a PCV to an engine already on the street, you'll have to richen the mixture screws to make up for the extra air. The port you are using was probably there for the vacuum wiper which doesn't move nearly the amount of air that a PCV system does. I drilled and tapped my carb adapters under my carbs. so that it would not lean out a particular cylinder. They made vacuum plates that bolted under the carbs and provided a vacuum port. If you can find 2 of them, I'd yoke them together or possibly drill and tap the manifold.
thanks guys. v8bob, the hole on the offy "A" is already big and is big all the way through. are you suggesting that i drill a hole at "B" in the picture? it wouldnt be a straight shot through the hole already there but i could get it from the top i think. tommy, the runner that the vacume hole is at goes to four cylinders i believe. its the same as it was with the stock manifold. the motor ran fine and the plugs all looked great with the pcv hooked up this way. im thinking i should drill at "C" . if i was to just hook up the pcv at "A", couldnt i adjust the carbs to get the plugs to look correct or am i missing something here. yes im still a little confused.
I split mine and tied into each side of the manifold to give all the cylinders some of the pcv gases and also the vacuum was tied to eack side to see both side of the vacuum. Vergil
vergil your setup is nice man!. alright, i had this made up. im going to run it under the front carb to a y then to the pcv. i think it should work fine and for sure will pull from both sides while keeping them seperate. any thoughts? thanks.
Don't mean to hi-jack your thread,but I want to convert my 60 caddy 390 to a PCV system. It has 6 dueces,but only run the 2 center ones. I have 1"spacers under them .NOW,do I have to drill 2 places in the spacers like the one in the photo,or can I just drill one hole into one side of the spacers???
gary t, i dont really know. im sort of just going on what i think is right, waiting for some expert opinions.
Hello..You need to drill two holes or one in the center and then angle drill two smaller holes to each side from the insides of the first hole..This way you get same amount of vacuum lose to each venture and it doesn't off balance the velocity for the siphon.. Hope this helps and you understand.. Duane.. Duane..
I don't see a problem with that setup, the front four cylinders may see a little more oil fumes than the rear but not enough to make a difference. Your adapter plate looks nice. Vergil
A terrible picture but I drilled and tapped my carb adapters. Then yoked them together and on down to the PCV valve in the valley pan. It works fine.
Ha Ha--just came to me---when I was young--many many moons ago everyone had outhouses ---some were one holers and some were 2 holers--If you had a 2 holer one hole was usually smaller for kids! history lesson for all U youngins out there LOL
I think you could loose some of the clutter in the adapter if you were to just drill in the center all the way through the plenum bores, thus opening both using one hose instead of two with the same result.
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