Ok, I have a 350 chevy with an Edelbrock Performer RPM Air Gap manifold that has both front and rear water outlets. I used a 1/2 NPT to -8AN straight fitting in the front to a fast flow 90 degree fitting with stainless steel braided hose. The rear water outlet has a 3/8 NPT to-8AN straight fitting to a fast flow fitting and they are connected with the above mentioned stainless hose. Now my problem lies with the MSD street pro billet distributor because it has vacuum advance. I know that the vacuum advance canister is supposed to be on the passenger side of the engine, with the canister facing towards the corner of the right front fender. However, with the distributor in that position, the canister is hitting the rear water outlet fitting, and is not allowing the distributor to fully seat in the manifold. How do I get around this without losing the 4 corner cooling? It will be a street driven car, and for mileage purposes, the vacuum advance would be nice to have and I don't really want to lose that either. I want to drop the motor in the car tomorrow, but now I cant cause of this and unfortunately, I have a time constraint. Can anyone please help , I beg of you. Any suggestions/opinions will be seriously considered. Thanks, Paul Moore

 

I was going to reply to this on TGO but apparently they're down for the night, so here ya go:

The position of the vacuum advance canister isn't set in stone. You can adjust the distributor and the position of the rotor to put it anywhere you want, if you go about it the right way. First, take the dizzy back out. Rotate the engine so that the #1 cylinder is on TDC of the compression stroke (both valves closed.) Decide which way you want the can to point, taking clearance issues into consideration (don't forget the firewall,) and make sure you have some room to adjust the dizzy either way when you go to set the timing. Put the cap on the dizzy base (off the car) and make a mark on the rim of the base directly below the #1 plug wire terminal. Turn the shaft so the rotor is about 20-30* before the mark, and stab the dizzy. If the rotor isn't pointing at the mark with the dizzy fully seated and the can where you want it, pull the dizzy, move the rotor a little, and re-stab it. The rotor needs to be pointing at the mark. Check again to make sure you have plenty of room to adjust the timing, and you're done. Put the cap on and wire it up.

 

Ok, so let's say that I were to take the distributor out and have the can on the driver's side of the engine. With the engine on TDC on #1 compression stroke I just take the distributor cap off and make sure that the rotor is facing toward the # 1 cylinder and then put the cap back on right? And then I can run my plug wires in their according firing order, correct?

 

Yes.

Or, if the cap has the #1 terminal labeled, you can stab is so that the rotor points toward that terminal (wherever it happens to be.) This is how I personally like to do it, so that the label is accurate and I don't have to try to out-think myself sometime in the future. Just as long as the rotor points to the terminal with the #1 wire on it, you'll be fine.

 

Why are you using the rear water access? I also have a rpm air gap manifold but I am only using the front outlet and then the access on top of the water pump for circulation. I would put a pipe plug in the rear, it will not make any difference that you'll be able to measure...

 

I am using it because it makes more HP and TQ, it's a fact! One of the guys that I work with was a hot rodder in the 60's all the way up to a couple of yers ago. He started out with small blocks and then went to Big block when he got his 70 Chevelle SS. Anyway, back then the manifolds didn't come with the rear water outlets so they used to drill a hole in the manifold and then tap it. He told me one time that they put an engine on the dyno without the water crossover, and with it on, the engine made an extra 8 HP and 12TQ! After a few more engine were built and tuned using this method, they found out that the average gain was in the range of 5-8HP and 9-14TQ, not bad for some fittings and braided hose. The coolant flow to the rear heads allows the rear 4 cylinders to remain cooler, prevent hot spots, and more efficiently control carb metering/air fuel mixture. Depending on what carb you have, it can help in the tuning process as well.

 

You're correct in what you say, but with the air gap manifold you do have less heat going thru the runners because of it's design keeping the fuel charge about 20 degrees cooler from some research I did communicating with Edelbrock. I have no experience on what each individual cyl temperature should be when averaging all 8 cylinders but I would suspect it's pretty negligable when using the air gap manifold. Since you already have water crossover distributed from the front to the rear I don't know how much temp difference you'll see but it would be a interesting point to find out from someone who has actually done some measurements between cylinders. Anyway, any hp you can get for a few bucks is worth the hassle......I'll do some asking around at our Powertrain division about temp diff between cylinders and see what anyone knows....John