Buick runs terrible with Performer intake

[Austrian455]

Yesterday I installed the Edelbrock Performer intake on my 72 Centurion.
Today I fired it up the first time and it runs terible :eek:

I runs rough and fires out of the carb.
I didn´t change the carb adjustment.
I thought of a vacuum leak. So I pluged all vacuum ports on the carb and on the intake. But it doesn´t change anything. :Dou:

HELP !!

[WDR]

The manifold gasket may be sucking air from the valley. Did you use any silicone around the ports?

[73 Centurion]

Is it possible the distributor is one tooth off?

John

[Robroy]

Have you tried spraying start gas (the kind you spray in to the air cleaner as a aid to get the engine to start) around the intake to see if it suck in air somewhere?
You should hear the rpm change if there is a leak that way...

[Austrian455]

Per, thats a good idea. i´ll try this.
I hope that there is no leak at the manifold gasket. I used that black RTV sealer that fel-pro supplies with their products.
The distributor shouldn´t be the problem because I didn´t change anything since the car war running the last time. I also checked the firing order because of the new plug wires.

[Austrian455]

I installed the manifold like the guys of "carcraft" did.
http://www.carcraft.com/techarticles/116_9906_buick_455_engine_rebuild/index.html
The used a 72-up manifold gasket to plug the smog holes.

[centurion 455 ragtop]

Quick check on a vacuum is to have the engine running without the airfilter on. Then cup your hand and cover the carb. If it starts to choke out you don't have a leak. If the idle smooths out and even increases you have a vacuum leak.Also re-check the firing order.

Question: Did you remove the distributor? Or adjust the timing. If you didn't and also you didn't adjust the carb, then it should run fine. I would say vacuum leak.

I had one on my Centurion a while back and it was the rear rail of the block where it meets the intake. I found it by running my hand back there covering spots at a time and the the idle smooths out. So instead of removing the intake and knowing where the leak was, I ran some fresh high heat silicone over the area, let it dry over night and it worked.

[Sweepspear]

Are ALL of the threaded holes in the manifold closed off?

After I rebuilt the 455 in my Riv, using that same intake, I had a huge vacuum leak that for the life of me could not figure out.
Then, I took a thin screwdriver and started poking it into all of the unused holes used for mounting brackets etc.
I found 1 or 2 (can't remember) on the passenger side that weren't blind holes, but open all the way into the runners. :rooleyes2:

Which was lovely, because I had just had the engine running at 2500 rpm for nearly 30 minutes to break in the cam. :mad:

I still to this day have no idea what they are for, as the stock intake does not have these.

Which reminds me. Why didn't Edelbrock put that one heater hose outlet in the same place as Buick did?

[centurion 455 ragtop]

just thought of this one. re-check all those small vacuum lines going to the carb. One may have cracked or you may have two switched by mistake. Also check your PCV

[Austrian455]

Dale, thanks for your reply. You were right. My intake also has this hole that looks like it´s designed to hold any kind of a bracket. Thats the reason why I didn´t plug it.
I don´t know what this is for. It´s the same diameter like the hole for the power brakes.
OK, now I´m going to put it all together and get her out for a ride.
I´ll keep you posted how it performs. Maybe I can get a camera for a short video.

Thank you all for the help. Good to know that there are other Buick Guys you can count on when you need advice.

[Austrian455]

Forgot to say: Rick, I saw your GS on the homepage of Gessler Head Porting. Really impressiv. Do you also have the heads of your Centurion ported by Greg ?
I saw some pics and the ET´s of the cars he did the heads. Amazing what´s possible with the cast iron heads.

[Austrian455]

OK, everything runs fine. I put all vacuum lines on and assembled it.
It looks good and runs good.
The strange noise of the f..... air pump´s gone. The throttle response is better than it ever was and it performs very good. I think the dual exhaust will give it the performance.

Thanks for your help again.

Here are some photos of the job done.
With and without air cleaner assembl.