Don Terrill’s Speed-Talk

F-BIRD'88 wrote: ↑Fri Oct 06, 2017 12:45 pm For what is the best carb spacer height I cannot tell you exactly. You are going to have to try a few and see.

I suggest 1" minimum up to 2 1/2" or so. A stack up of 3/4" spacers is easier to carve out by hand with a die grinder. The typical cast alumunim Qjet carb adapter spacer that you see is 3/4" thick.

If you have access to a mill or at least a big drill press it makes carving the holes a lot faster.

You can make up low cost carb spacers out of wood (good plywood) to test with without braking the bank
or spending more money that nessessary. You are going to need to do some drive testing with the spacers
to find the best combo of spacer(s) height and type(s). Be prepared to rejet the QJet carb too.
Even a simple low cost narrow band O2 sensor on the exhaust can really help you dial in the carb.

Qjets are great carbs when properly jetted for the specific engine and bad carbs when not properly jetted.
That is why GM had so many different setups for the Qjet.
I wish I had kept my old 1968 396 325HP 4MV Qjet carb. it was a good one on many of my BBC and SBC motors, way back.

Here is the thing...You have the RPM intake on hand to test against as a bench mark to compare.
I think with that, you can make the factory hi rise cast iron intake with this mod and spacers
do the job very well.
if I was going to do large valves at all I would not go up to a 2.19". I would go 2.12" 2.14" at max.

Calculate the road speed and the resulting engine running rpm at that speed and keep that in mind
* the rpm will be lower than you think) so you don't get all crazy on camshaft duration.

On the heads avoid the thought of hogging out the bowls too much removing that funnel venturi under the
valves. on a mild cam the valve stays close to the seat (relative) and that funnel venturi shape helps the air go around the valve ( at low and mid lift) and go into the chamber. This venturi shape just under the valve matters. When you port the valve bowls think velocity and air flow quality around the valve and pressure recovery at low and mid lifts...( because that is where the valves spend most of the time with a mild cam VS a larger duration/overlap high lift racing cam for a higher rpm race motor.

On a (Mild low rpm) motor where the valves stay relatively close to the seat most of the time there is more to it than just getting more raw flow. And the motor spends most of the towing trip time running at part throttle, not WOT. I believe the BBC vortec L-29 heads are good for this.

One of the smart guys here that does BBC's will tell you which valves ( part numbers) {2.12" to 2.14") to get .
* GOFAST or Joe Sherman or.... VortecPro or

LaVelle wrote: ↑Wed Oct 04, 2017 5:55 pm

ProPower engines wrote: ↑Wed Oct 04, 2017 1:10 pm I would use the 2-0 intake. They are much better then the iron intake.
I just finished a 454 oval port build with 781 heads and the stock aluminum snow flake intake which looks the same as the Edelbrock performer was about 70 hp better then the tall iron intake with a Q-jet carb. Took a bit to tune but was worth the time and effort.

I just finished one like that, 781', a Performer, 230 @.050/ .550 lift cam.
Does 11.38 - 12.43 in my 3700 lbs. Pontiac

LaVelle wrote: ↑Sat Oct 07, 2017 11:33 am F-BIRD'88

What do you think of this for a camshaft?

Lunati High Efficiency hft #06205

210/215 @ .050 ( 260/265 adv.) .500/.513

pdq67 wrote: ↑Sat Oct 07, 2017 3:56 pm I am also going to mention the L-29 heads!

They are true large oval, although smallish, Like 230 or so cc's vs the larger like 255 to 260 cc regular large oval heads, PP's are down around 200 cc's or so if not mistaken.

L-29's also have a 100 cc, fast burn heart-shaped chamber that will probably need the, "beak", trimmed some to keep piston interf. to a min. Good heads imho for a mild build.

pdq67