[General Z]

Originally Posted by chuckies76ta

You still need to take a look at your distributor. Confirm your initial timing, mechanical timing and total timing. You should also confirm TDC matches the mark on your balancer. Very easy to do all of these. you can verify this before driving season comes.

Are you running a vacuum can on the distributor and if so do you have it connected to a vacuum source?

I don't remember my initial but my total is 36-38 per my dial back light. Yes, I'm using vacuum advance, connected to ported vacuum on carb. I did confirm TDC was correct last time the engine was out, 10 years ago.

[b-man]

Originally Posted by SD455DJ

General Z - just remember the RPM intake is 1" taller than the regular Performer and stock 4-bbl intakes, so check to make sure your air cleaner set-up doesn't have an unexpected collision with the hood on your Firebird.

Dennis

According to the Edelbrock catalog it’s actually 1.25” taller so take that into account.

Also when running a Quadrajet be aware that the secondary throttle plates sometimes hit the opening of the plenum so make sure you don’t need to add some clearance before installing the intake.

[General Z]

Originally Posted by b-man

According to the Edelbrock catalog it’s actually 1.25” taller so take that into account.

Also when running a Quadrajet be aware that the secondary throttle plates sometimes hit the opening of the plenum so make sure you don’t need to add some clearance before installing the intake.

Yeah, that's pretty tall. I hope I don't have a problem.

[Maurice Hood]

Z, if your current setup is still in the car then just loosely ball up a piece of aluminum foil and set it on top of your air cleaner and close the hood. Open it back up and measure the thickness of the foil. That will tell you how much clearance you have. If you are not already using one, a drop base air cleaner will allow you a little more clearance.

[General Z]

Originally Posted by Maurice Hood

Z, if your current setup is still in the car then just loosely ball up a piece of aluminum foil and set it on top of your air cleaner and close the hood. Open it back up and measure the thickness of the foil. That will tell you how much clearance you have. If you are not already using one, a drop base air cleaner will allow you a little more clearance.

Thanks. I've previously done this silly putty and I do use a drop base already. The spread bore to squre bore spacer I'm currently using is awfully thick. I'm hoping this rpm fits.

[General Z]

Update:

I measured and the bottom of the carb with the Performer as it sits now, will be almost EXACTLY the same height as it will be on the RPM. So that's a relief.

I also blew compressed air past the venturi for the vacuum secondaries and they didn't budge. I'm thinking maybe they have never worked, or years ago when I was dinking around with springs, I messed something up. The spring quick change adapter hasn't arrive yet. That will have a new diaphragm and cork gasket.

I'm starting to think, maybe with functioning secondaries and the RPM, I might be plenty happy with the car. I also need to keep in mind that this is a family, street cruising convertible, where street manners are of the utmost importance. Seat of the pants feel when mashing the pedal is the bonus.

[ta man]

Did you have a spacer on the performer?

[General Z]

Originally Posted by ta man

Did you have a spacer on the performer?

Yes, the Edelbrock Spreadbore to Squarebore, 2696, which is .850" thick.

[SD455DJ]

General Z – With your current 0.85” tall adapter plus the 3/8”+ clearance, so 0.85” + 0.40” = 1.25” total, that is the same height difference as the stock RPM intake. Certainly that is too close for comfort. If your secondaries weren’t functioning properly, you’ll have 100 hp instantly when they do open, so maybe you won’t need that new RPM after all. I would still check everything else that was mentioned by all the others just to be sure.

Dennis

[General Z]

Originally Posted by SD455DJ

General Z – With your current 0.85” tall adapter plus the 3/8”+ clearance, so 0.85” + 0.40” = 1.25” total, that is the same height difference as the stock RPM intake. Certainly that is too close for comfort. If your secondaries weren’t functioning properly, you’ll have 100 hp instantly when they do open, so maybe you won’t need that new RPM after all. I would still check everything else that was mentioned by all the others just to be sure.

Dennis

I hope you're right about the power. I won't be using a spacer with the RPM. It appears that the thermostat height is the same on both intakes. I used a level from the base of the carb on the current setup and measured vertically from the thermostat flat to the bottom of the level. Then, I measured on the RPM in the same manner. The measurements are nearly identical, so I'm optimistic.

[SD455DJ]

Well, I may have exaggerated a bit, but it'll feel like it when all 4 bbls open when they're supposed to. Here is an actual dyno comparison of a 2-bbl (2GC) and 4-bbl (Q-jet), both on stock cast iron factory intake manifolds on the same 455 on the same day. This 455 has the 2802 cam and 9.94 static compression with small valve #15 heads.

You can see that the average torque and hp through the pulls (3000 to 5000 rpm) are way in the favor the Q-jet (412 lbft/309 hp vs. 478 lbft/360 hp)

Dennis

[General Z]

Originally Posted by SD455DJ

Well, I may have exaggerated a bit, but it'll feel like it when all 4 bbls open when they're supposed to. Here is an actual dyno comparison of a 2-bbl (2GC) and 4-bbl (Q-jet), both on stock cast iron factory intake manifolds on the same 455 on the same day. This 455 has the 2802 cam and 9.94 static compression with small valve #15 heads.

You can see that the average torque and hp through the pulls (3000 to 5000 rpm) are way in the favor the Q-jet (412 lbft/309 hp vs. 478 lbft/360 hp)

Dennis

Wow, that’s some exciting data. Thank you for sharing it! Much appreciated.

[Schurkey]

Keep in mind that the primary side of a Q-Jet is substantially smaller than any of the 2GCs, particularly the larger ones that would have been installed on a 400+ CID engine.

The difference between a Q-Jet without, and with the secondaries functioning would be even more dramatic.

[Stan Weiss]

Originally Posted by Schurkey

Keep in mind that the primary side of a Q-Jet is substantially smaller than any of the 2GCs, particularly the larger ones that would have been installed on a 400+ CID engine.

The difference between a Q-Jet without, and with the secondaries functioning would be even more dramatic.

General Z is running a Holley 750.

Stan

[SD455DJ]

Originally Posted by Stan Weiss

General Z is running a Holley 750.

Stan

Which would be half the cfm at 375 (assuming square bore), similar to the Rochester 2GC (from a '71 455 - which this one was for the dyno test).

Dennis

[indymanjoe]

Originally Posted by General Z

Good morning,

Got a plan:
1. Wait for spring, because the car is put away for the winter.
2. Drive it with my G-Tech and note the data.
3. Confirm if secondaries are opening.
4. Install the vacuum secondary spring quick change kit I ordered.
5. Swap to the RPM intake.
6. Drive with G-Tech and note the data.
7. Assuming secondaries were, or are now opening, try springs.
8. Determine if the above made enough difference to make me more satisfied with the car, while keeping in mind that it's a family, street cruiser.
9. Pull the engine to address the oil leak and also get into internals, depending on the above data.
10. Tinker with transmission governor, to possible lower the shift point.

I dont live far from you at all. may have seen your car at bakers or the dustoff if ya been there, i just massaged my governor last summer and boy what a difference it made. also if you want to go to a track we like Onadega milan and lapeer and would love to have ya join us. It is addicting though LOL Definitely helped me to dial in my combo. Hence the cam swap im doing now LOL

[General Z]

Originally Posted by indymanjoe

I dont live far from you at all. may have seen your car at bakers or the dustoff if ya been there, i just massaged my governor last summer and boy what a difference it made. also if you want to go to a track we like Onadega milan and lapeer and would love to have ya join us. It is addicting though LOL Definitely helped me to dial in my combo. Hence the cam swap im doing now LOL

I go to Bakers one in awhile. I was at the Pontiac show there last year with my Firebird and my Solstice. My Firebird is a matte black convertible. I had a Camaro out to Milan and Lapeer in the past. No drag stuff for this old convertible though.

Did you lower your shift points with your governor?

[indymanjoe]

yes,made a big difference. th-400 though.

[indymanjoe]

the drag strip is a good place to test is what I meant.

[General Z]

Update: I changed to the Performer RPM intake. I replaced the diaphragm, cork gasket and went to the next to lightest spring on the vacuum secondary. I finally took it for a ride, and there's a noticeable difference. The guys that said the intake was choking it seem to be right. I didn't end up doing step by step testing, just did it all at once. I haven't driven it yet with the G-tech meter set up to see any quarter mile improvement. The difference is big enough that I'm doubting I'll change cams when I pull the engine to do the rear main seal. This 2802 is broken in and doing fine.

I'll still probably lower my shift point from 5000, per the suggestions above and try that.

Thanks everyone for all the support and suggestions.