Cam change - what to expect
 

Hi,

I'm wondering if I should change my cam.
The car is a 66 GTO with 462cui, E-heads, 10.25:1 CR, 4 speed Muncie, 3:55 gears performer intake with Sniper EFI.

The cam is a hydraulic roller with 224/230/110 degree.
The idea is to use a 236/245/112 (old faithful) and maybe another intake.

I think it's a rather small cam at the moment and I have too much low end torque for street tires.
What could I expect? Is it worth the money and time? :)

Thanks!!
Chris

More then any thing else you need a higher flowing intake !!!
Stuffing in a bigger Cam will buy you nothing but a poorer idle and less fuel mileage.

That performer intake is choking off a good 25 CFM of intake flow per cylinder out of your E heads!

You did not post up what you have bolted on to the Exh side of those heads , but a higher flowing intake could add another 30 to 40 hp to your motor as it sit’s right now!

You need at least a Performer RPM intake to make good use of those heads.

I have some d-port headers which are a PITA to remove/install... If I have to remove the engine again, maybe I would like to change to something else.. not sure if thats a good idea.

Which intake would be best for my Sniper EFI? I don't really have a problem with hood clearance, even if it was a little higher.

The idle quality is great at the moment.. runs at 700rpm and a good amount of vacuum for the brakes...

So you think moving the torque/power up in the rpm range wouldn't make much sense? I read that the old faithful works pretty well with the 462.
Would I also need to change valve springs? Not sure if the E-heads 72cc will take the cam without modification.

The springs that the E heads ship with are said to be good for .580” lift.,but NOTE, they are not a good hydro roller cam spring in my opinion!

They use a flat wire damper and these have been know to have issues as you run more lift over .500”.
They have been known to unravel thru the outer spring with the end result many times of a broken off head of a valve if the failure takes place at a high enough rpm.



In my first reply to you I suggested a Intake .

Below is a dyno chart comparing the Comp XR276HR cam (224/230/110LSA) to a custom ground HR cam close to the Old Faithful specs (289/308, 236/245/114LSA).

For what you are doing I'd move up to this cam:

Comp Billet Roller Cam (HR) 288/294, 236/242, .521/.540, 112 LS

It's a custom grind and available from several of the big Pontiac shops......

Cliff what intake was used for both of these test?

Do Not see many folks complaining about TORQUE !
Pontiacs big advantage has always been Torque In the band you cruise in..
A Pontiac Common " not" problem !

I don't want to complain about torque, but I just cannot use it at low rpm.... if there was more power upwards, I would still have more than enough power down low but additional more power higher in the rpm range.

And sorry... I already have a performer rpm intake, my fault. I upgraded when I bought the Sniper EFI, but some people prefer a single plane... don't know if I should get something else. The performer rpm intake still leaves me some space under the hood... I could add a 0.5" spacer. At the moment I run a thick gasket and a heat shield to prevent the ECU from too much heat.

that looks very nice... didn't think that I could gain that much by another cam!

maybe a cam like you wrote and some better valve springs would be a good choice... I would still use 1.5 rockers since the heads will not work with 1.65 without modification as far as I know.

You might consider dropping down to 3.23 gears to taper off some off the low end torque.

"...in most applications we use the Crane 99893 valve spring, installed at 1.790-1.810", I set the intakes on the tighter side of the tolerance, I test all the springs and always put the ones with the higher pressures on the intake valves, since the intake valves weigh more and also have the momentum of the charge pushing on the back side of the valve while the exhaust valve if anything has pressure pushing or drawing it closed and the valve is lighter. On my digital InterComp spring tester the seat pressures on a new set of springs will range from 147-157lbs typically @ 1.800" and 380-390lbs @ 1.200" open pressure."
Dave Bisschop
SD Performance

That comment by Dave was made in 2015 regarding using his Old Faithful hydraulic roller cam.


Side note- the Crane 99893 was a popular choice by Dave Bisschop and others. But if memory serves me right there could be an issue in availability with that Crane spring.

Another spring that is used is the Comp 26925.
Page 301 here:
https://www.compcams.com/valve-spring-chart

Although much will depend on the actual verified installed height on the cylinder heads in use.
And one should test new springs at that verified installed height with their retainers to check the amount of actual pressure... Never trust catalog numbers !


.

Chris, I just completed a chassis dyno test on a MUCH milder (stock iron heads, 8.3 compression, small HFT cam) 455, but with a FAST throttle body EFI system. So many people speculate on whether such systems need a single plane or dual plane, I wanted to see for myself.

I tested a Performer and an old P4B square bore against a Holley Street Dominator, a Tomahawk, and a Torker II intake. All totally stock, except for removing the water crossover.

On my motor, the dual planes made more power below 4350rpm. Above that, the single-plane intakes made more power and extended the power band. All 3 single planes performed VERY closely, but the Street Dominator was marginally the best of the 3.

I suspect that a single plane intake would perform similarly on your motor.

The OF cam has great bottom end power , you won't be losing any torque. Good tires will help huge on the street for traction..I run 2 sets of rears..275/60 BFG tires..which I call cartoon car tires..instant smoke..good for cruising and showing off...for real traction. I also have a set of M/T et's..which are far safer for full throttle hits on the street.

I have a set of Crane 99893 with retainers and keepers that were used on my heads when they were setup for the OF cam still in perfect shape.

Dyno of the OPs cam, ported d-port heads and a Torker 2 intake = 492 HP

https://www.motortrend.com/how-to/hp...e-stuska-dyno/

Tom S made 432 HP with the same cam and stock d-ports.

Regulations over here don't allow such tires on the street, so I'm using 255 60 15 BFGs. They look good... thats it :)

I have following options on the Butler website:

1. 236/242, .521/.540, 112 LS

2. 236/242, .521/.540, 114 LS

I guess I'd go with the larger LS for a better idle. My old cam has 224/230, .503/.510, 110 LS. Butler sent me these valve springs: https://www.summitracing.com/parts/lun-73100-16
Could I keep them or should I change them? (I guess change since 333 lbs./in. seems too low)

Maybe I could also install a torqer 2 intake and match it to the heads.. not sure if there is a lot to gain over the performer rpm...
I also think my 2.5" dual exhaust with FlowFx mufflers (like the Magnaflows) may be not be perfect, but changing to 3" will not make too much of a difference to justify an investment of another 1500 $.

Depends on the long term goal you want.

463 @ 5300 RPM target with 1.65 rockers.
https://i.imgur.com/2fwfzD0.png

You’re exhaust system is good enough, it wouldn’t be a very good investment to change it at this point.

Same thing if you have the RPM intake, they’re tough to beat on a street engine. Find a used TII to save some $ if you want to experiment. There are tons of them out there. Having run both on the same 455 I honestly couldn’t really feel much difference at all between the 2 on the street in power or driveability though.

The 236 duration HR cams seem to be the sweet spot for a 455 street engine. A properly chosen one could make more power everywhere compared to what you have now and may make traction even worse.

Before swapping a bunch of parts maybe try a taller wider 275/60/15 tire if you have room? They’ll cut down overall gearing and should give a little more bite.

On the bright side having more power than you can use and trying to harness it is a much better problem than not having enough!

I bought a car years ago w/ that HR in it. I cannot remember the lsa. (224/230)

Was a station wagon cam in a 455. Would have been really good for towing. Just a mellow cam.

Yes - change cams to the cam with spec's near the Ole faithful cam. I cannot really say much about EFI. But for a carb'ed engine - the RPM is a great intake.

The dyno chart I put up is a DIRECT comparison between two cams with NO OTHER CHANGES and it was done on the same dyno, same engine builder, same dyno operator.

I don't think we will ever get a better comparison between the XR276HR cam and the larger OF clone because there was only one change.

I'd also add here that the XR276HR cam made enough cylinder pressure that the 9.3 to 1 455 with professionally ported #96 heads pinged so hard it required rod bearing replacement before the dyno testing could continue. I only got involved because EVERYONE at the dyno facility including the guy who takes out the trash was blaming the Q-jet for ALL the issues.

Folks need to keep in mind here that a 455 is a huge engine and putting a relatively small cam in it not only leaves a lot of power on the table it can make them octane sensitive even with a relatively "low" static compression ratio.......FWIW....