[General Z]

Originally Posted by Stan Weiss

Post #68

If the valves are floating @ 5000 RPM find out why and fix it!!

I am not saying a bigger cam will not make more HP than the Summit 2802, but as shown above the Summit 2802 should make enough HP for you to be running in the 12's.

Stan

Stan

Good info, thanks. They were floating somewhere OVER 5000. I dialed in the governor to 5000 and no more valve float.

[Gach]

Originally Posted by General Z

True, but this is a street cruising convertible that sees plenty of highway use. It'll never see a racetrack.

Basically what I’m saying if you over gear first and second you’ll experience exactly what your experiencing. Especially with that cam and the Crower 60919 might not be any better, well maybe initially. So there’s trade offs. All bottom end and no mid range. The motor after the shift now needs to get back up to peak torque. So it’ll feel like a locomotive. T-400 will keep it in power band and peak torque range.

[Gach]

Originally Posted by General Z

Good info, thanks. They were floating somewhere OVER 5000. I dialed in the governor to 5000 and no more valve float.

Oh boy that explains a few things valves floating, sure it felt better once that issue was resolved. But definitely 700R4 gearing isn’t helping.

[blueghoast]

Anyone have the @50 dur and valve lift specs on the 60919 crower cam.
Thanks

GT

[Gach]

For Pontiac 428-455 engines from 1955 through 1981
Basic RPM Range: 2000 to 6000
Valve Lift Intake: .470
Valve Lift Exhaust: .470
Intake Duration: 304
Exhaust Duration: 316
Intake Duration at .050”: 231
Exhaust Duration at .050”: 240
Lobe Separation: 112

On cam card Gets installed @ 108. Those numbers are with 1.5 rocker with 1.65 rocker it’s 520 lift and actually picks up a little more duration not sure on exact duration with 1.65. But thinking around 236 and 246 duration.

[steve25]

A 50 CC pump should not be needed on any Pontiac motor that’s running a duel plane type of intake .
Your just crutching something else that’s wrong with the carb by using it.

[grivera]

I’m sure the Crower cam would do great but the risk of wiping a lobe during break in would be enough for me to correct the obvious issues in this build before throwing in the towel. As already mentioned, degree in the cam with a new timing chain, swap in a Performer RPM and work on the current carb or a 68-72 factory intake and well built Q-jet.

[General Z]

I found a like new Performer RPM locally for $300 and am going to pick it up. Of course the car isn't doing anything until the snow melts. It's on casters up against the garage wall currently for the winter. I'm finding the idea of lowering my shift point via the governor to pick up more speed intriguing as well.

I stumbled upon this in another thread: "My first 455 ran a full .5 quicker at the track when shifted at 4600, compared to 5000. It was still "pulling" at 5000, but a torque motor needs to be where it is making torque to run the best." - Lee

[Stan Weiss]

First the computer can only show you somethings, but you must really test for the best results.

Second while you hear engine torque is so important it is really torque at the rear wheels that accelerates the vehicle.

Lets take the dyno sheet posted in post #68 and extent it to 5800 RPM

Now lets look at torque at the rear wheels in each gear.

Stan

[Dragncar]

Originally Posted by General Z

I found a like new Performer RPM locally for $300 and am going to pick it up. Of course the car isn't doing anything until the snow melts. It's on casters up against the garage wall currently for the winter. I'm finding the idea of lowering my shift point via the governor to pick up more speed intriguing as well.

I stumbled upon this in another thread: "My first 455 ran a full .5 quicker at the track when shifted at 4600, compared to 5000. It was still "pulling" at 5000, but a torque motor needs to be where it is making torque to run the best." - Lee

My pump gas 455 with ported HOs and solid roller always ran its quickest when I got into 3rd gear as soon as possible. I was in 3rd by 100 feet, that is how quick I shifted.

[Lee]

People have ran mid/low 12's with that combo, nothing wrong with it. SHOULD blow the tires away anywhere in first gear, and possibly in 2nd.

Either there is a defective part (worn cam lobe, for instance) or the tune is WAY off. About 1 car in 5 that I work doesn't even have full throttle - start there if you have not verified.

[Lee]

People have ran mid/low 12's with similar combos, nothing wrong with it. SHOULD blow the tires away anywhere in first gear, and possibly in 2nd.

Either there is a defective part (worn cam lobe, for instance) or the tune is WAY off. About 1 car in 5 that I work doesn't even have full throttle - start there if you have not verified.

[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.

[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

[grivera]

OP- I have an RPM in my bird with a 1” drop base and use a 14x3” element, clears hood but not by much. Definitely measure.

[chuckies76ta]

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.

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?

[Stan Weiss]

Originally Posted by General Z

Good morning,

Got a plan:
1. Wait for spring, because the car is put away for the winter.

2) Do a cranking compression test. - Post results here
3) Check valve springs seat and open pressures - Post results here

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.

What I believe needs to be done

Stan

[General Z]

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

Thanks. My car is a 67 Firebird with a 400 hood. Currently running one of those spreadbore to squarebore spacers which is like .85" and the bowtie overdrives plate for the kick down cable. I have a drop base air cleaner and a 3" tall filter. Hood clearance is probably 3/8"+ right now.

[Jay S]

While you change the secondary spring, you really should also richen the secondary jets a few sizes on your 750 Holley. You could start by reading your plugs, but normally on big CID’s on a 750 you want want to go up at least 2 jet sizes. My guess is a 750 on a 455 needs closer to a 2 to 3 jet increase front and back from the base factory setting. The carb is big enough, but it is set up out of the box for smaller cubes. With the engine running very lean all those other performance upgrades just send the performance sideways.

[General Z]

Originally Posted by Stan Weiss

What I believe needs to be done

Stan

Yes, thank you for the reminder. I need to do the compression test.