[TransAm 474]

Originally Posted by General Z

Thanks for the information. How crucial is using the Rhodes lifters with the 60919? I was going to use the Crower cam saver lifters. Do I need the Rhodes for vacuum or is it another reason? With my current setup I have 16" of vacuum at idle?

At 9.5 Compression, I would run the Rhoads lifter if using the 60919 camshaft, IF you want to retain as much Idle vacuum as possible, however, it probably still wouldn't produce 16" that you have now. I would estimate maybe around 12-13" if Rhoads are used on the 60919 at your compression. If you had 10-10.5 Compression, you probably wouldn't need the Rhoads lifter at all, to produce roughly the same Idle vacuum as the 60919/Rhoads will at 9.5 Compression. Another thing to keep in mind, is the Standard Rhoads lifter produces a sewing machine tick at Idle, some people doesn't care for that, others it doesn't bother. We have used the Crower CamSaver lifter in the past with success, but I'm not sure if they are a USA lifter, they could be an offshore lifter, which could be a toss up. Now, with all of that said, at 9.5 Compression in a 455, it would be fine to use the Standard USA made HyLift Johnson lifter from Topline Automotive and the 60919 camshaft, it will result in a little more attitude at Idle, and won't produce as much Idle Vacuum, but still should produce enough to run Power Brakes without a problem.

[General Z]

Fantastic. Thanks for the info. You guys are rockstars.

[chiphead]

I run the 2802 in a 69 400 with 62 heads, RPM and headers. Idles at 850 with 13"-14" of vacuum, has a pretty good lope. Powerband is 1500-5400. 16* BTDC, 35* all in. It's too small for a 9.5:1 455 if you're wanting to revv it over 5100 RPM.

The thing that stands out to me is the light spring in the vacuum secondaries. That will let the secondaries come open too fast and result in lazy acceleration. If you floor it and it seems lazy, just slowly lift your foot a bit and see if it picks up. If it does, the secondaries are opening too fast. Since a vacuum secondary doesn't have a secondary shooter, you'll get a lean bog until the secondary airflow velocity starts pulling fuel.

I have a 390cfm vacuum secondary on a chevy 235 six cylinder. When I was tuning it, I tried a light secondary spring. As I rolled into the throttle, I could feel the engine sag at a certain point. Raising my foot magically gave more power. If I kept my foot in it, eventually the engine "caught up" with the throttle opening. I then increased secondary spring tension until that sensation went away. You'll likely need to convert from metering plate to metering block so you can change the secondary jetting. I think that requires the 4160 to 4150 conversion kit.

[AG]

I have an 8.9:1 CR 462 with a RAIV cam and Rhoads lifters in my '72 convertible with RA manifolds, 7K3 heads, an HO intake and Qjet. I think it's a great combination and has very good street manners and has gone 13.4 in the 1/4 with a stock converter.

[Jay S]

Does the performance meter you have show MPH times? That maybe would be the better indicator of what HP the engine is making. Mid 14s on the street could be mid 13s on a prepped track.

A 2802 in a 455 is a small cam, so, if the cam timing was retarded, my guess is the engine would actually like it. So I rather doubt cam timing is your issue.. As is I think the 750VAC that has the metering blocks on the secondaries is your biggest issue for your combo, not the performer intake or the cam. Pretty limited on tuning with that carb. If the timing chain was loose when it was installed, was most certainly retarded some. But the 2802 comes with 5* of advance built into it, it has room for some retarding.

Maybe he will comment, but Dennis Jensen on here dyno’d his 70 455 with small valve heads and 9.8 SCR, all stock, no headers, and I think it made 390HP@4800. Best I recall anyway, I think it runs in the 13s in his stock A body. I think he later swapped over to stock round ports with the same short block and it made around 420 HP @5200. The current 112 LSA 60919 with that same set up peaks a few hundred rpm higher, if you are looking for big gains, I think you would be disappointed. I have ran in the high 12s with a completely stock Oldsmobile 455 and headers with the smaller 2801. No question there are better cams for a 455, but it seems like there is something going on more than just the small cam.

Just leaving the 1.52 and swapping from the 2802 to the 60919 is not going to be a big improvement. Both those need 1.65 rockers. The 60919’s that had 112LSA’s I have had do not need Rhoads lifters in 455s. Bigger rockers require the intake pushrod to be clearanced, So if your stuck with 1.52s, i would pick a cam that has more lift, like a Lunati voodoo 704. There are some Bullet grinds that are similar to the Lunati also that provide a lot more lift without a rocker change.

[kingbuzzo]

Thanks Chiphead...this helps me a lot...would you recommend a different spring or a cliff type rebuild for a q-jet if the carb is from an unknown origin?

[QUOTE=chiphead;6479047]I run the 2802 in a 69 400 with 62 heads, RPM and headers. Idles at 850 with 13"-14" of vacuum, has a pretty good lope. Powerband is 1500-5400. 16* BTDC, 35* all in. It's too small for a 9.5:1 455 if you're wanting to revv it over 5100 RPM

[Jay S]

We have 96 heads in a 71 T37. The 96 heads often start out close to 98 cc, and some get toward 100cc after a valve job. The compression can be in the lower 9s with some 455s and 96 heads, with that cam and the fuel octane it currently likes, my guess is it may be a little lower on compression than mid 9s. Likely it is several things adding up to not meet expectations.

[TransAm 474]

Originally Posted by Jay S

Does the performance meter you have show MPH times? That maybe would be the better indicator of what HP the engine is making. Mid 14s on the street could be mid 13s on a prepped track.

A 2802 in a 455 is a small cam, so, if the cam timing was retarded, my guess is the engine would actually like it. So I rather doubt cam timing is your issue.. As is I think the 750VAC that has the metering blocks on the secondaries is your biggest issue for your combo, not the performer intake or the cam. Pretty limited on tuning with that carb. If the timing chain was loose when it was install, was most certainly retarded some. But the 2802 comes with 5* of advance built into it, it has room for some retarding.

Maybe he will comment, but Dennis Jensen on here dyno’d his 70 455 with small valve heads and 9.8 SCR, all stock, no headers, and I think it made 390HP@4800. Best I recall anyway, I think it runs in the 13s in his stock A body. I think he later swapped over to stock round ports with the same short block and it made around 420 HP @5200. The current 112 LSA 60919 with that same set up peaks a few hundred rpm higher, if you are looking for big gains, I think you would be disappointed. I have ran in the high 12s with a completely stock Oldsmobile 455 and headers with the smaller 2801. No question there are better cams for a 455, but it seems like there is something going on more than just the small cam.

Just leaving the 1.52 and swapping from the 2802 to the 60919 is not going to be a big improvement. Both those need 1.65 rockers. The 60919’s that had 112LSA’s I have had do not need Rhoads lifters in 455s. Bigger rockers require the intake pushrod to be clearanced, So if your stuck with 1.52s, i would pick a cam that has more lift, like a Lunati voodoo 704. There are some Bullet grinds that are similar to the Lunati also that provide a lot more lift without a rocker change.

I agree with Jay on the Lunati 704 VooDoo camshaft being a good choice for a 455 as well. We used one is a 467 using Butlers stroker rotating assembly in a 1979 W72 400 build. The customer wanted to retain the stock, numbers matching look, so it retained the stone stock 6X-4 heads, other than adding the 68404 springs and Ferrea Stainless Valves. It came out with 9.3 Compression, and we used the Crower CamSaver lifter in it. It was a 4-Speed car with 3.23 gears and 275/40/17 tires, and it absolutley screamed for having NO porting on the heads, not even port matched. It also retained the stock W72 Iron Intake. We installed that camshaft at 104° Intake Centerline. At a 20mph roll, in 1st gear, it would absolutley start screaming the tires off, without a clutch dump, and pulled really hard at the same time. We were really impressed for having stock heads on it. It idled realtivly mild, just a tiny hint of attitude, and if memory serves, it produced 14" of Idle Vacuum at 800 RPM. The customer was extremely pleased. This is a 100% street car, so no track times....

[chiphead]

[QUOTE=kingbuzzo;6479053]Thanks Chiphead...this helps me a lot...would you recommend a different spring or a cliff type rebuild for a q-jet if the carb is from an unknown origin?

Originally Posted by chiphead

I run the 2802 in a 69 400 with 62 heads, RPM and headers. Idles at 850 with 13"-14" of vacuum, has a pretty good lope. Powerband is 1500-5400. 16* BTDC, 35* all in. It's too small for a 9.5:1 455 if you're wanting to revv it over 5100 RPM

Not sure if you're running a vacuum secondary holley or a Qjet? Either way, they're both vacuum secondary carbs. The holley would need a stronger spring in the secondary dashpot to keep it from opening too soon. The Q-jet may need a secondary flap spring/cam/pulloff rebuild. For a Qjet, I think the baseline on the spring was 3/4" turn past where the doors shut. Pulloff release time of 1.5-3 seconds depending on converter and gearing.

The OP should likely re-baseline the tune with a stronger secondary spring. 02 sensor AFR and vacuum gauge really tell you what the carb is doing. Low vacuum and lean AFR dip going to heavy throttle would indicate too-fast secondary opening. The other thing that I wonder about is the converter. Is it flashing to a high RPM, or is it coupled pretty well to the engine? A 455 with a 2802 should pull pretty hard to 4000 RPM or so. If the converter is flashing really high, that may keep the engine from doing its best work. I've seen converters so loose, that the car has to catch up to engine RPM.

[steve25]

Now that where full off the rails with this thread let me try to get the train running again.

Starting with Cliff's post as to why the Cam can make such a difference here's how the Manifold relates to the power band seen.

Here are the flow numbers I took @ 28" on a stock Performer back in 2019.

Runner
2 231 cfm

4 222

6. 225

8. 231

1. 216

3. 247

5. 232

7. 220

Average = 228

The worst flowing runner is capable of making 55hp, and the best can make 63 hp .

This will never happen with this Manifold since number 1 , the plenum is just far to small, and number 2 , the runner area is too small to make 55 hp per cylinder but for running the Intake on 350 cid or less, because there is just too high a level of port velocity.

So running this type of Intake on any iron headed D port motor , and especially if a well done bowl port job was done will limit peak hp to no more then 444 hp at the very best just going by the numbers.

Cliffs findings in his post goes to show full well why you should never overpower any Intake with better flowing heads.

The result will always be less hp being produced then your head air flow numbers would suggest and also the motor will have a far narrower power band then it otherwise would.

All of you folks running 290+ cfm aftermarket heads and a stock tripower have bought yourselves a expensive ticket on this misfit Boat .

[General Z]

Originally Posted by steve25

Now that where full off the rails with this thread let me try to get the train running again.

Starting with Cliff's post as to why the Cam can make such a difference here's how the Manifold relates to the power band seen.

Here are the flow numbers I took @ 28" on a stock Performer back in 2019.

Runner
2 231 cfm

4 222

6. 225

8. 231

1. 216

3. 247

5. 232

7. 220

Average = 228

The worst flowing runner is capable of making 55hp, and the best can make 63 hp .

This will never happen with this Manifold since number 1 , the plenum is just far to small, and number 2 , the runner area is too small to make 55 hp per cylinder but for running the Intake on 350 cid or less, because there is just too high a level of port velocity.

So running this type of Intake on any iron headed D port motor , and especially if a well done bowl port job was done will limit peak hp to no more then 444 hp at the very best just going by the numbers.

Cliffs findings in his post goes to show full well why you should never overpower any Intake with better flowing heads.

The result will always be less hp being produced then your head air flow numbers would suggest and also the motor will have a far narrower power band then it otherwise would.

All of you folks running 290+ cfm aftermarket heads and a stock tripower have bought yourselves a expensive ticket on this misfit Boat .

Given this data, I wonder if ONLY replacing my intake and keeping everything else the way it currently is would wake up the car? I'll probably still change the cam, lifters, springs, chain too, but it's a thought, to just try the intake while the engine is still in the car, before buying all the parts.

[Murf]

Ar some point you’ll probably end up with a different carb & intake manifold either way, I think.
It’s so easy to change intakes on a Pontiac, I’d try that first. It might make enough power for you without going any further. Do the compression test as mentioned above either way. It’s always good to know what you’re working with. I’d also plot out the ignition curve to see if anything weird is going on. I’d also check to make sure the timing marks on your damper are tell you the truth.

I agree with everyone else, the cam is too small but it should run better than it sounds like it does now.

Good luck & try to have fun getting to know what you’ve got before going in deep. ��

Murf

[JLMounce]

Originally Posted by General Z

Given this data, I wonder if ONLY replacing my intake and keeping everything else the way it currently is would wake up the car? I'll probably still change the cam, lifters, springs, chain too, but it's a thought, to just try the intake while the engine is still in the car, before buying all the parts.

I had an Edelbrock P4B on my 455 for some time. Not quite the same as a Performer manifold, but close enough for comparison. It hit hard off idle and was done by about 4800 rpm. It fealt kind of "soft" everywhere when you couldn't get the torque converter to help you out off idle. I feel like this is kind of what you're feeling from your combination?

I don't have an apples to apples comparison because I replaced the entire top-end at the same. Went from a set of stock #62's to as cast KRE D-ports, a mild roller cam (232/238/112) and a torker II manifold. This really woke the combination up.

Car went consistent 13.4's at 104mph in 8500 ft air on street tires after the change.

I do think going to a different intake is going to help you out. I would typically say Performer RPM myself, but as I mentioned previously, I think you'll have trouble getting that manifold under the stock hood of your firebird.

[vicgto]

I don't believe the 750 Holley is too small, but like others have said it may require tuning along with other components as it's probably a few things causing the issue. What are your jet sizes? What size exhaust do you have?

[Dragncar]

I ran un ported 96s on a .060 over 1970 455 and got down to 12.07 @109 MPH.
A Holley 3310 style vacuum secondary carb is a fine carburetor. I got down to 12.30 with one and won many races with it on my 455. 12.07 was with a 850 DP. As long as it is a duel feed type and a jet plate in the secondary you are good. A light spring and the right jets and you are fine. They are tunable and come on the sort of rich side but I will not get into leaning one out for power.
A "Performer" should not be on any 455. They are a good intake for a Pontiac 350, that' about it.
RPM is better. Myself, I like single plane intakes for a 455. They have enough grunt you will not miss anything and the boost on top end is worth it, as long as you have a good cam.
I like those cheap Tomahawk intakes designed after a fully ported HSD. I got down to 11 flat with one.
The cam, its too small. The rule of thumb on a street performance Pontiac 455 is 230ish intake duration @ .050. 455s are voracious and can take a lot of cam and carb.
I ran high 12s with a .230 Erson cam, the 12.07 was with a Crower sft in the .250s @.050, 108. Pretty lumpy for the street.
Now you run a decent fuel pump, but have you taken off the sock off the pickup in the tank ? I took mine off and put a short piece of hose on it.

The chain ? If it really does have some slop when new a short chain is in order. Now normally I am all in on the Cloyes, but their short chain was not a IWIS. Rollermaster has gotten a bad rap by some, and deservedly so IMO. BUT..... they now sell a .005 short chain that is IWIS AND has nitrided sprockets AND......................a big AND here is a Torrington bearing for only 165.72 $
Like half the price of a Sims. This is now the best Pontiac roller chain on the market. But some street guys might not like the little roller bearings in there, I get it.
My current engine has billet caps so its been aligned bored. Thing was, a simple, basic Elgin 3/4" wide Morse chain was a little tighter than the .005 short chain so that is what is on it right now. You can get those for like 30-40 $. Cloyes does sell a 32$ version of that chain, I have one but it was on the lose side so its still in the box.
I have a extra RPM intake I can part with if interested, used only one season.
Keep at it, you have a lot more power in your 455. Just go get it.

[General Z]

Originally Posted by Dragncar

I ran un ported 96s on a .060 over 1970 455 and got down to 12.07 @109 MPH.
A Holley 3310 style vacuum secondary carb is a fine carburetor. I got down to 12.30 with one and won many races with it on my 455. 12.07 was with a 850 DP. As long as it is a duel feed type and a jet plate in the secondary you are good. A light spring and the right jets and you are fine. They are tunable and come on the sort of rich side but I will not get into leaning one out for power.
A "Performer" should not be on any 455. They are a good intake for a Pontiac 350, that' about it.
RPM is better. Myself, I like single plane intakes for a 455. They have enough grunt you will not miss anything and the boost on top end is worth it, as long as you have a good cam.
I like those cheap Tomahawk intakes designed after a fully ported HSD. I got down to 11 flat with one.
The cam, its too small. The rule of thumb on a street performance Pontiac 455 is 230ish intake duration @ .050. 455s are voracious and can take a lot of cam and carb.
I ran high 12s with a .230 Erson cam, the 12.07 was with a Crower sft in the .250s @.050, 108. Pretty lumpy for the street.
Now you run a decent fuel pump, but have you taken off the sock off the pickup in the tank ? I took mine off and put a short piece of hose on it.

The chain ? If it really does have some slop when new a short chain is in order. Now normally I am all in on the Cloyes, but their short chain was not a IWIS. Rollermaster has gotten a bad rap by some, and deservedly so IMO. BUT..... they now sell a .005 short chain that is IWIS AND has nitrided sprockets AND......................a big AND here is a Torrington bearing for only 165.72 $
Like half the price of a Sims. This is now the best Pontiac roller chain on the market. But some street guys might not like the little roller bearings in there, I get it.
My current engine has billet caps so its been aligned bored. Thing was, a simple, basic Elgin 3/4" wide Morse chain was a little tighter than the .005 short chain so that is what is on it right now. You can get those for like 30-40 $. Cloyes does sell a 32$ version of that chain, I have one but it was on the lose side so its still in the box.
I have a extra RPM intake I can part with if interested, used only one season.
Keep at it, you have a lot more power in your 455. Just go get it.

This is fantastic information. Thank you very much. Love your E.T. as well. Yes, I'd be interested in that RPM. I'll message you.

[Gach]

Originally Posted by blueghoast

Yes, I've got the same combo other then mine is only .030 over @ 9:50:1
Runs super strong and I run a 3:73 gear with a 350-turbo trans 700r4
coming later. I run a 750 vac sedary holley but with the rear metering
block so I can jet the rear of the carb too. I run 72 front and 78 rear jets.
I run the RPM intake also but the torkerII will work as well. The RPM will
fit under the hood of the 67-firebird at least it did on my friends firebird.
Hope this helps and thanks to Gach for his info. I run 38-40 degree timing too.

GT

Originally Posted by General Z

Given this data, I wonder if ONLY replacing my intake and keeping everything else the way it currently is would wake up the car? I'll probably still change the cam, lifters, springs, chain too, but it's a thought, to just try the intake while the engine is still in the car, before buying all the parts.

Yes you could do that, but also even with cam change read what blueghoast did to his vacuum secondaries Holly crab. So this is kind of how it works. Evidently with cam your running now, it need more fuel on the secondaries going to a better cam and intake and not changing the crab like blueghoast did is going to compound the issue you’ll be disappointed. So definitely make the modifications to that vac secondary carburetor. Trust me thats a issue with those carb’s.

[blueghoast]

You Know after listing to all of this I'm wondering if his secondaieres is
opening at all, It kind of sounds that way. I wonder if the diaframis blown.
I would check to see if it is working and also change the spring in it too.
I always run the lite spring or you could go with the next one down?

GT

[Gach]

Originally Posted by blueghoast

You Know after listing to all of this I'm wondering if his secondaieres is
opening at all, It kind of sounds that way. I wonder if the diaframis blown.
I would check to see if it is working and also change the spring in it too.
I always run the lite spring or you could go with the next one down?

GT

They definitely a tricky carburetor to tune, but once you get it right they work good. So who knows.

[Dragncar]

OMG, there is no issue with 3310, 750 vacuum secondary carbs. They are easy to work on, I mean way easier than a Q Jet.
You jet them like a double pumper and you can put .120 needles and seats front and back in them.
A 750 DP will not run any faster on the vast majority of engines.
They make a adjustable vacuum advance kit.
Easy as can be.https://www.amazon.com/Quick-Fuel-Te...s%2C693&sr=8-5