Low buck 350

[prairiehotrodder]

I put together a mild 350 for a 1980 chevy malibu that my son is racing in the jr. street program. In my cheapness i made a big mistake and i'm kicking myself. The motor has flat top pistons, a comp XE268 cam, chinese air gap intake, 750 holley Vacuum carb and 1 5/8 headers. The big mistake was using TBI cylinder heads. How much power did i throw away by not using some mild alum heads such as the blueprint head or the edelbrock E-street ? The Tbi heads are the 193 swirl ports which i now understand are about the worst of the worst.
I'm leaning think i threw away nearly 100 hp.
Brian

[lefty o]

with a good head, and better cam you probably threw away 100hp. same cam with a head like you mentioned, 30hp or so imo.

[mag2555]

Your 193 heads could make a maximum of 360 Hp with what they flow with a better build then what you have going on.

A average set of iron heads of the non Vortec line could make 430 hp with what they flow with a proper build.

[mt-engines]

How many of you guys have ACTUAL DYNO DATA on tbi heads?... because like most posts I see on here.. its just regurgitated hearsay at best.

[rustbucket79]

I figured those heads with the small chambers should be better than smoggers, but alas no hard data to back it up. We don’t mess with much factory iron (heads) any more, but I promise for the most part they’re pretty disappointing on the dyno. Oh, and Speedmaster, those were worse than factory.

[68maliblue]

I'm working on a set of 193's for a low budget 307 build and trying to make them better is like polishing a turd. They are not much of a performance head. The only reason I'm using them is 1) they were free and 2) I don't want to invest much in a 307. I don't think you're giving up 100hp with your build however. I would agree with the others with 30-40hp.

[1980RS]

I'm working on a set of 193's for a low budget 307 build and trying to make them better is like polishing a turd. They are not much of a performance head. The only reason I'm using them is 1) they were free and 2) I don't want to invest much in a 307. I don't think you're giving up 100hp with your build however. I would agree with the others with 30-40hp.

Cut out the swirl vane it will make a big difference. Lot's of grinding though, me personally an older set of 882. 993's or 487's would be a better choice and less work.

[F-BIRD'88]

nixna on the 882 heads nor 462624.. Might as well stay with the tbi heads.

Low budget port the hell out of a set of 305 ho heads.
Or the "worthless". L 30 305 vortec head 059..
These flow 220 out of the box.
Don't be afraid to adjust the installed C/l of that xe268 cam for best ET (torque).

[travis]

I’ve never tried to use them in a performance application, as they fall on their face around 4000-4500 rpms with a small cam from what I’ve seen. But…they will give some pretty amazing fuel economy numbers in a heavy vehicle with tall gears.

[mag2555]

Well maybe someone can post up some dyno results from a build of similar cid and Camming to the OPs build instead of lightly insulting us all who are just going by the flow numbers such a head is known to provide?

[prairiehotrodder]

I've never had any dyno experience but I know that Edelbrock used to claim their performer RPM package made 420 hp. So using that as my standard and guessing that my motor is making 275 - 300 hp. And the main difference being the heads. Of course thats just a bunch of guessing. If i feel rich this winter i may swap the heads. I allready advanced this cam to the +4 spot on the timing chain to try to get it to idle better. I also had to put in a bigger squirter to get rid of a huge stumble and i drilled holes in the rear butterflies of the carb to also help the idle. All things that really shouldn't have been necessary on a mild engine like this.
Brian

[F-BIRD'88]

What MPH is the. car running now ¼ mi. ? This tells the
net HP

Help the idle: Moving the cam or drilling holes will not help the idle but re curving the diz will..
Suggest. a short 10 deg mech advance curve
26 + 10 = 36. (Normal sbc heads)

The TBI heads apparently don,t want as much WOT advance,. so
20 + 10 = 30 total. plus minus

Car will idle and run best with a 3500++ converter

[prairiehotrodder]

What MPH is the. car running now ¼ mi. ? This tells the
net HP

no idea, haven't taken it to the track in its current setup.

[rfoll]

Holley carbs have a stop screw for the secondary throttle plates. You can open the plates a little to allow additional idle air without drilling holes.

DSCN1457.JPG

DSCN1456.JPG

If you remove the screw and install it from the top it can ve adjusted without removing the carb.

[F-BIRD'88]

The 750 vac sec holley carb will likely benefit from the
venturi signal copper tube mod so the secondaries
open up all the way.

Your torq converter must be very tight (low stall)