im finally going to be buying my heads and manifold for my 350 build and i am still way uncertain on what to get. i was set on vortec heads with gmpp tbi manifold and external egr to pass emisions. but i talked to someone today that said he has seen drivability problems with this set up even with tuning because without exhaust crossover the manifold doesnt get hot enough to boil the fuel and it will run real rough and even foul plugs. he said the exhaust wont get fed into the intake to heat it up until the egr opens which takes a while. is this right? why would gm make the manifold and hardware to plum the egr if it doesnt run? also where is this crossover on standard heads? is it actual exhaust gasses going into some chamber below the floor of the manifold? doesnt the water flowing through the manifold cause it to get hot? i want to use this set up but if there is to many driveability probs i guess i could use world torquer II and the edelbrock tbi manifold. this is supposed to be a direct replacement and does have the crossover right? i guess there is so many opinions on this that i am a little confused. any help is appreciated. thanks

 

You heard wrong. You can tune around EGR. A properly tuned vortec 305 TBI pulls clean to 6300 with even so much as a mild LT1 cam. It idles smooth with just the right amount of lope.

 

so do you think the vortec heads are a better choice than the world torquers for good low end torque and driveability?

 

I'm running vortec heads (steam holes added) on my 406 with a 350 TB (soon to be 454 ). I like em. I've got a slight RV cam cuz I built it for torque. No problems from day 1. Good luck!

Mike

 

what kind of power are you making with the 406?? sounds like a good build but how did you have the 400 block work with the sensors? is it in a truck or car?

 

I never dyno'd the sucker. It's in my 71 Chevy Pickup right now, but it's been in a couple things starting with my 88 chevy van. Therefore, I'm running a 7747 truck ecm. The sensors were simple...O2 sensor in the exhaust manifold, map sensor hooks up to the TB, Knock sensor in one of the plugs in the side of the block, temp sensor in the intake, used the 350 TBI distributor, brackets, & accessories. Right now, the 350 TB is acting like a restrictor plate at 95 MPH, so I'm switching to the 454 TB and DIY-PROM'n it. I don't know the power or torque #'s but I can tell you this, it was awesome for towing when it was in my van. I had 3.40 gears in the rear and you still couldn't stop it off the line. I actually ended up breaking both motor mounts one night when I embarraced my buddy's S10 4.3L blazer in a race. Anyway, I highly recommend the set up and even though it's not in an F-Body right now, it has a lot in common with them. I used the vortec heads initially so I could stick with the stock intake which will now need to be bored out for the 454 TB. Anyway, I don't wanna hijack the post, so I'll stop now.

Mike

 

A friend of mine has this in his Caprice and has no issues. The GMPP manifold has extra water passeges to heat the manifold instead of using the EGR I am told. He did have to tune the ECM however, but it did run prior to the tune.