Vortec Heads
gaboi68
08-29-2006, 03:09 PM
Will a set of 350 vortec heads off a 1996 chevy p/u work on my 91 9c1 350. If so, what else will i have to change?
silicon212
08-29-2006, 04:07 PM
Will a set of 350 vortec heads off a 1996 chevy p/u work on my 91 9c1 350. If so, what else will i have to change?
They will bolt on fine, but you will also have to use the intake from the '96 (assuming it's TBI) because a standard intake will not fit.
They will bolt on fine, but you will also have to use the intake from the '96 (assuming it's TBI) because a standard intake will not fit.
CD Smalley
08-29-2006, 10:03 PM
There are TBI manifolds for the Vortec heads available from several sources. They are quite expensive though. Expect to pay around $400+ dollars for the manifold alone.
kdrolt
08-30-2006, 09:35 AM
There's a lot more to this than just bolting a new set of heads & intake onto the engine.
Briefly, the cowl overhang will interfere with the installation of the distributor, the 91-93 Bcar distributor won't fit into the L31 intake manifold hole.... so you need a distributor from a TBI truck to mate with the L31 intake..... but you will need to install the intake/distrib together as a unit because the cowl overhang will still prevent the distributor from being installed after the intake. OR you have have the L31 intake machined for a larger & slightly recessed hole, so that the 91-93 Bcar distributor (with the fatter flange) will work with it. Doing that SHOULD allow separate installs of the intake, followed by the distrib. Most people don't want to deal with either of the above.
Then there is the exhaust. The exhaust will have to be somewhat custom because the L31 exh manifolds won't fit nicely... so you pretty much need to use headers and duals thereafter. That's the mechanical stuff, and most of this info is from knowing what Dave Stutzman went through trying to get the L31 heads & intake into his 91 Caprice 9C1. He posted more of the details, along with a posting from the Philly-based mechanic that did much of the work, on the 9C1 board on Yahoo, if you really want the details. That's 1 guy that I know about (and I know him too btw) that's actually tried this --- all the rest of the people that have L31 are using them in 3rdgen Fcars, or in 1990-earlier Bcars, or in C/K trucks. No one else in a 91-93 Bcar.
You'll also need bigger fuel injectors and/or raising the fuel pressure to have the needed fuel delivery you need to cope with the airflow the L31 heads will provide, and above and beyond all that you will need a custom tune of the EPROM in the ECM.
Yes it is all do-able but it is not so easy to do unless you are very well prepared and have done a lot of research beforehand to know about all the pitfalls of the Vortec L31 heads/intake installation into a 91-93 Bcar. There are several threads discussing this on the Impala SS forum, that provide a bit more detail, as well as the info on Yahoogroups. Anyone really serious about the L31 heads/intake swap ought to go looking for those threads before they jump in.
IMO it might be easier to do the modified-for-Gen1-use aluminum LT1 head & LT1 intake swap, instead of the L31, because that one is very well sorted out by the 3rdgen owners (there are many discussions on www.thirdgen.org about it)... including the conventional distributor behind the intake manifold. The intake gets drilled for the distributor placement and the (aluminum LT1) heads get welded for use in a conventionally cooled Gen 1 sbc application.
You could then either run a speed density batch ECM (like the TPI owners do when they swap for the LT1 intake/heads) or run the MAF as used in the 94-96 Bcars. You'll still need tuning (duh) but it might not be that far from stock depending on what type of ECM/PCM you use.
Decent power can be had from the LO3 and LO5 without having to use L31 heads. Several people have proven it... so there is an alternative already in the 91-93 models. Some gains can be had the traditional way (exhaust, cold air intake, cam) along with ECM tune and fuel tweaks (more fuel pressure, bigger fuel pump, larger injectors), but the big gains are had once the heads are ported. That's when I defer to Fast355 and his posts at www.thirdgen.org
HTH.
Briefly, the cowl overhang will interfere with the installation of the distributor, the 91-93 Bcar distributor won't fit into the L31 intake manifold hole.... so you need a distributor from a TBI truck to mate with the L31 intake..... but you will need to install the intake/distrib together as a unit because the cowl overhang will still prevent the distributor from being installed after the intake. OR you have have the L31 intake machined for a larger & slightly recessed hole, so that the 91-93 Bcar distributor (with the fatter flange) will work with it. Doing that SHOULD allow separate installs of the intake, followed by the distrib. Most people don't want to deal with either of the above.
Then there is the exhaust. The exhaust will have to be somewhat custom because the L31 exh manifolds won't fit nicely... so you pretty much need to use headers and duals thereafter. That's the mechanical stuff, and most of this info is from knowing what Dave Stutzman went through trying to get the L31 heads & intake into his 91 Caprice 9C1. He posted more of the details, along with a posting from the Philly-based mechanic that did much of the work, on the 9C1 board on Yahoo, if you really want the details. That's 1 guy that I know about (and I know him too btw) that's actually tried this --- all the rest of the people that have L31 are using them in 3rdgen Fcars, or in 1990-earlier Bcars, or in C/K trucks. No one else in a 91-93 Bcar.
You'll also need bigger fuel injectors and/or raising the fuel pressure to have the needed fuel delivery you need to cope with the airflow the L31 heads will provide, and above and beyond all that you will need a custom tune of the EPROM in the ECM.
Yes it is all do-able but it is not so easy to do unless you are very well prepared and have done a lot of research beforehand to know about all the pitfalls of the Vortec L31 heads/intake installation into a 91-93 Bcar. There are several threads discussing this on the Impala SS forum, that provide a bit more detail, as well as the info on Yahoogroups. Anyone really serious about the L31 heads/intake swap ought to go looking for those threads before they jump in.
IMO it might be easier to do the modified-for-Gen1-use aluminum LT1 head & LT1 intake swap, instead of the L31, because that one is very well sorted out by the 3rdgen owners (there are many discussions on www.thirdgen.org about it)... including the conventional distributor behind the intake manifold. The intake gets drilled for the distributor placement and the (aluminum LT1) heads get welded for use in a conventionally cooled Gen 1 sbc application.
You could then either run a speed density batch ECM (like the TPI owners do when they swap for the LT1 intake/heads) or run the MAF as used in the 94-96 Bcars. You'll still need tuning (duh) but it might not be that far from stock depending on what type of ECM/PCM you use.
Decent power can be had from the LO3 and LO5 without having to use L31 heads. Several people have proven it... so there is an alternative already in the 91-93 models. Some gains can be had the traditional way (exhaust, cold air intake, cam) along with ECM tune and fuel tweaks (more fuel pressure, bigger fuel pump, larger injectors), but the big gains are had once the heads are ported. That's when I defer to Fast355 and his posts at www.thirdgen.org
HTH.
kdrolt
09-01-2006, 08:54 AM
A footntote to the above:
http://www.thirdgen.org/techboard/tech-general-engine/125878-do-g-m-make.html?highlight=Bcar+flange
is a thread that shows the differences between TBI distrbutors, especially w.r.t. the distributor hole, and the corresponding distrib mounting flange. Look for my post near the bottom.
http://www.thirdgen.org/techboard/tech-general-engine/125878-do-g-m-make.html?highlight=Bcar+flange
is a thread that shows the differences between TBI distrbutors, especially w.r.t. the distributor hole, and the corresponding distrib mounting flange. Look for my post near the bottom.
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