Hey guys, I am getting started on "minor-mods" on my '86 K5 Blazer 4x4 tomorrow. This truck is my daily-driver, sand/mud toy, and is also be used to tow a race trailer.

I have seen the gains of using a TBI spacer with later model trucks, would a 1" spacer help sitting under my Q-Jet lightly modded 350?

Remember, this 350 is going to be used in a 5700lbs truck that will rarely see 4500-5000 max RPM.

The Blazer currently has:
-Stock 8.5:1 CR 160HP 350
-3" single exhaust w/CarSound High-Flow CAT and Dynomax Race Magnum UltraFlow muffler
-Beefed up 700R-4 tranny w/new "towing" converter and Trans-go shift kit
-Beefed up NP280C transfer case
-4.11 gears/posi front and rear
-4" lift, 33" Dunlop A/T tires, and 15x10" M/T Classic II rims.

Here are the mods on the 350:
-#3706 Performer EGR intake
-Stock computer controlled Q-jet w/a "G" secondary hanger and secondary "CC" rods changed
-Crane HI-6 Ignition Box
-Accel Super-Coil
-Full length "coated" headers (SMOG legal)

The dist is also computer controlled and will remain stock for the time being. I might add a 'timing chip'.


Any help is thanked and welcomed.

Only way to know for sure is to try it. I picked up .2 in the 1/4 when I REMOVED the 1" 4-hole spacer from my Holley 300-36 dual plane intake. My guess on your set up is that a spacer wouldn't be any advantage.

If you try one definately use the 4 hole. I had good luck with one on my old tow vehicle.

Thanks guys.


Another question, right now the Q-jet carb is only set to flow 600cfm total because the butterfly's can't open fully from the factory.

With some minor mods to the linkage the Q-jet can flow up to 750cfm like the '70's non-computer controlled versions.

I wondered if the 750cfm would be helpful?

My '87 Camaro had pretty much the same motor. Same CC-Q-jet with the same "G" hanger and "CC" rods. It would run out of air at 4500-5000 RPM. I always figured it was the heads, but maybe it was the carb too.

What do you guys think?

TTT

Bump.

Sorry, I don't have much to offer on whether a spacer will add anything to your truck. I have throughts that it won't, but no real evidence.

On you question about opening up the secondaries. Additional cfm will only add more rpm to your truck right now, and the heads may very well be more limiting than the carb.

If the truck will currently turn to 4500rpm before tucker'n out ... then more carb will not gain you much below that point.

A good way to tell, is to stick a vacuum gage on your intake. Anything more than 1-2" at full load / full throttle, and you are restricting the intake (need more cfm) ... if not, changing the carb won't do anything but cause headaches.

Thanks, Neal

From everything I have read, spacers are not a good thing for torque. They can reduce your vacuum signal which will have a negative effect on flow at lower RPMS. Unless you are running above 5000 RPM, they are not considered a good mod. A heat isolator, on the other hand , might be a good thing. What I have seen is 4-hole and no more than 1/2" tall.