i am currently helping my dad with his project car. it's a 427 powered '67 camaro ss/rs. the car is meant to be a driver of course, but will only see weekend use.

first question is regarding carb size. currently the intake is the old style edelbrock torker with a 750 cfm edelbrock carb. that combo is going by the wayside for a torker2, holley combo. i'd like some input as to what size and variety of holley would work best. here is a list of known engine components- 12.5-1 pistons, 2" headers, iron hi-po oval port heads (no porting, stock valve size), comp cams xe284h cam and lifters, crane roller-rockers (stock ratio), lunati springs, 160 t-stat, holley hi-volume mech. fuel pump, mallory electronic ignition system. the drivetrain particulars are 4.11 gears, th350 with a manual shift valve-body, aprox 3000 rpm stall 'verter.

due to the gears and the tc, the engine will be opperating in the 3000-6300 rpm range. my dad is thinking about the 870 street avenger carb, but i'm thinking a 750 double pumper might be better for this application. opinions?

secondly, what is the best way to optimize ignition timing for this setup?

thanks in advance for your considerations.

 

From my experience on this type of combination, an 830-850cfm carb will give you the best performance. I have a friend with a 454 in his '68 with about the same set-up as yours (he is using a Team G intake) and we tried(borrowed) several carbs on it before settling on a Barry Grant 825 cfm street/strip carb. It's still streetable and will run low 11's in the heat, all day long, bracket racing.

On the timing issue. You will have to run race fuel with a compression that high (or at least a 50/50 mix with premium). Big blocks like alot of timing, especially with dome pistons, so I would start out around 36 degrees total and work your way up from there. As far as the curve goes with the stall your running and assuming the car is less than stock weight, you should be totally advanced by 2500 rpm.

My .02 pesos

 

Keep the Torqer. It's a better manifold than the Torquer II ever dreamed of being, IMHO.

750CFM at least. Vac Sec will work fine if it's mostly street driven. For max-effort stip performance I'd go double pumper. Even on the street I'd go double pumper if you can keep you foot out of it!

Agreed with Whit on the timing curve. That'll get you pretty close for starters. Play with it from there and see what works best on your combo.

 

I'm no engine pro, but I'd say the Holley Street Avenger isn't your best selection for that engine setup.

I'm pertty certain the Street Avenger series is only 2 corner idle and primary power valve only?

Aside from that, you don't need the choke and tower to restrict air flow.

I'm having trouble tuning a 700 Mech Holley with a CC292H...grabbing 5" of vacuum - the idle is killing me. If I open the throttle blades too much, I'm edging into the transfer slots and fouling my plugs.

I would recommed looking at a four corner idle and twin power valves. Lose the choke as well, you wont be needing that I'm sure.

 

69- if you have to open the throttle so far to hold idle that you're too far into the transition slots, a time-honored solution is to drill a couple small holes into the primary throttle plates. That allows more airflow without having to be too far into the idle transition slots. Start small and work up as you can always drill them bigger but UN-drilling them is a bit tougher. 3/32" is a good starting point.

Note that even on a very mild engine there will be a small amount of the transition slot showing below the throttle plate. THis is by design.

 

Thanks for the tip Damon.

I have been talking to a good friend of mine who suggests tweaking the secondary throttle blades to open slightly allowing more air to enter...which will allow me to back off the primary idle screw.

It sounds good in theory, but I wont be able to attempt this test until next season when the car somes out of storage.

If I recall correctly from my video, Holley presets the primary throttle blades to enter 0.040" into the transfer slots. I know I'm over that measurement, but it was the only way to keep the engine idling (at least I thought).

If that doesn't work, I'll try drilling holes in the blades. I can always epoxy them shut if things go wrong, or replace the blades.

 

I'm running basically the the same combo in my 69 camaro.
I'm using a 750cfm Mighty Demon. Makesure w/ your compression your @ least using 100 octane. That big boy will thank you.

 

thanks for all of the input. just an update-

when we went to replace the old cam with the cc xe284h, the first thing my dad and i noticed were that the intake ports on the iron oval port heads were HUGE and the intake manifold ports had been enlarged to match the heads. and, layed side by side, the new comp cam was dwarfed by the old one! the old cam, the size of the head ports and the 12.5-1 compression ratio leads me to believe that someone wanted a 7,000 rpm 427 and, hopefully, put the motor together with a forged rotating assy.

any thoughts about the old double head/intake gasket trick to drop the compression a bit?

 

If you're lucky, you might drop half a point...but I would never double gasket.

You'll be raising the head from the deck and degrading quench.

Slap in the required pistons and keep the motor happy. That's what I would suggest.