this may be kind of a dumb question but I am finally finishing up my 406 swap and needed a little help. I am using chevy bowtie heads 034 castings with tall chevy cast valve covers and the edelbrock air gap intake with a 650 holley dp carb and wanted to know can the vaccum on the intake be used for the brakes or does it have to be the one on the back of the carb. also is a one and a quarter drop base air cleaner low enough to clear the stock hood on an 87 iroc? also wanted to know which wiring harness the 4 pin plug for the transmission is on(700r4) is it on the engine wiring harness? looked on mine and couldn't find it but I remember unplugging it when I yanked the motor out a while back. at least I think lol anyway thanks in advance for the help.

 

If there's a vacuum port on an intake runner it can be used for the brake booster.

 

there is one on the runner but no room with carb mounted unless a spacer is used and it really looks like it may cause clearence problems. was wondering about that. would the one on the carb be sufficient? it is holley list no 4777

 

The port on the back of the carb is fine too. If you want to use the port on the intake, Edelbrock has a low profile 90 degree fitting for it.

 

I don't think low pro would cover it it would have to be around 1/32 " to clear there is no room so I kinda figured I would have to use the one on the carb but wanted to be sure it would pull enough vaccum or if had to be the one on the intake with a spacer. any ideas on the other two questions? I wanted to use the lock up kit you described in an earlier post with the gm sensors. I have the sensors. and replaced the 2 terminal 4th gear switch with the single switch and the two wires that originally went there are hooked together but need the 4 barrel tranny plug to finish that. looking on the internet there is many variations to that with good results. thanks already for the help

 

The TCC plug should be on a branch of the engine harness.

 

The one on the side is too small for the brake booster. I couldn't get a fitting to fit on the runner even with a 1/2" spacer so I had to T the line off the back of the carb . One to the brakes and the other to the PCV.

 

I'll save you some time. The "low profile" fitting won't work. At least it didn't on mine. I still ended up using a 1/2" carb spacer. It's a plain stupid location for a vacuum port. The rear fuel bowl sits right on top of it.

I use the intake port with the low profile fitting for brakes, and the port on the rear of the carb for the PCV. I had to use a 2" drop base air cleaner to clear the stock hood. I tried later to switch to a 3" element, and the hood wouldn't shut.

Can't help on the tranny wiring, I have a 5 speed.

Hope that helps!! Good luck, and you'll love the torque that 406 will put out!!

 

when you say 2" air cleaner are you talking the drop on the air cleaner assembly or the height of the air cleaner itself? also why do you actually need a pcv filter? I was just going to run the brakes from the rear of the carb to the brakes and put a breather in the valve cover to relieve pressure. also wanted to see too did you use the port in the intake for the coolant temp sensor or the one in the head? I installed the sensor in the intake because it was too large for the one in the head. not really sure why. anyways thanks for the info

 

You may want to re-think the breather idea. You should have at least one PCV valve. You'll want to pull a vacuum in the crankcase on a street car.

 

what would be the big deal using a breather instead of a pcv valve? they are both used to relieve crancase pressure. the pcv valve only works one way which to relieve pressure and breather would do the same I would think.

 

Using a PCV valve in one cover and a breather in the other pulls fresh air through the crankcase to keep it nice and clean. With just breathers the crankcase will be full of stagnant vapors that will condense out and form acids and sludge in the oil.

 

that's something I didn't know. so the spacer idea os better to use the rear vaccum port on the intake and the rear of the carb to pcv valve?

 

also would it hurt to use the breather for now? strapped on cash because of waiting on workmans comp claim so I haven't had a paycheck since sept 12th.

 

There's no PCV port on the front of the carb?

 

err I meant on the passenger side of the carb.

 

I meant 2" thick (or tall) air cleaner element. I got the lowest drop base I could find. It's a Jegs chrome cheapie - like 30 bucks.

You should run a PCV valve for the reasons above. At least do it the old school way, and use a beather on one side, and hook up to the air cleaner fitting on the other. Better than nothing.

I used the stock sender in the head. It could work somewhere else though. You are using the stock type sender for the stock gage right? You are talking about the temp gage right? You don't need a coolant temp sensor unless you still have the CCC hooked up....

 

coolant temp sender is for your temperature gauge. I would rather have it in the head to be accurate but need a smaller sensor for that.

 

wondering if anyone here may have any of this stuff for sale?

 

also my temp sender for the guage is in the intake will this be ok or should I plug that one off and use the spot in the driver side head? Thanks

 

FYI:
I used a Holly 108-12 Flange gasket ($ 15) with the stock manifold vacuum adapter. The gasket is 1/4" thick. It barely clears if the adapter is positioned correctly. I have a holly 650 DP HP 4150.
I've included the pics of the parts but they are in the car and I can't get a camera in there now. I had to use a mirror and a flashlight to check the clearance with it tightened down. It literally fits by a hair.

 

And the fitting:


It fits right into a nook in the carburator, I used extra tape to keep the seal good at the correct position.

 

I just found out some info on the crankcase ventilation, vacuum system and the brake booster. Anyways, it might be of some help.

https://www.thirdgen.org/techbb2/sho...45#post2627545