cam for 455 Pontiac

[Thumpin455]

I know most of you guys arent savvy to the Pontiacs, but I figured I would ask anyway. Consider it an exercise in building cylinder pressure, and really it would work for about any engine.

Lets say octane is not a problem but you want to build as much midrange and bottom end torque as possible and still have a relatively smooth idle with a high compression 455, say over 12:1. #48 heads with stock ports, stock intake, headers, in a 2nd gen TA with highway gears. Not a pump gas engine, but not a race engine either.

Would it be similar to a cam you would put in a 8:1 455 or would something different work better?
HR, SR, S, or H work better? Im leaning HR.

I was thinking of a 230/234 @ 50 with .500ish lift and a 108.

Yeah I know it would rattle itself to death on 93, but its not going to run that. Dont worry about the fuel, just making cylinder pressure in an efficient manner.

[oldsman71]

Re: cam for 455 Pontiac

installed strait up or advanced? running "special feul" it would have alot of bottom end.
I have crap fuel here :-\

[Thumpin455]

Re: cam for 455 Pontiac

Installed wherever, advanced, retarded, can play with that a bit. Idle to 5500 rpm is the power range, the idea is max efficiency by making the most torque possible so the engine doesnt have to work very hard to move the car. Less throttle angle, less fuel used.

[oldsman71]

Re: cam for 455 Pontiac

it should work, im not a real high compression expert, Im not
anykind of expert lol. most the 13 to 1 and higher stuff I delt with
were on alky in circle burners, them cams bleed alot of compression!
they send alot of raw fuel out the exhaust. so if you can get away with it,
it would get way more energy out of your fuel.

[ghustler]

Re: cam for 455 Pontiac

I know most of you guys arent savvy to the Pontiacs, but I figured I would ask anyway. Consider it an exercise in building cylinder pressure, and really it would work for about any engine.

Lets say octane is not a problem but you want to build as much midrange and bottom end torque as possible and still have a relatively smooth idle with a high compression 455, say over 12:1. #48 heads with stock ports, stock intake, headers, in a 2nd gen TA with highway gears. Not a pump gas engine, but not a race engine either.

Would it be similar to a cam you would put in a 8:1 455 or would something different work better?
HR, SR, S, or H work better? Im leaning HR.

I was thinking of a 230/234 @ 50 with .500ish lift and a 108.

Yeah I know it would rattle itself to death on 93, but its not going to run that. Dont worry about the fuel, just making cylinder pressure in an efficient manner.

Well this tear this apart somewhat.

Lets say octane is not a problem but you want to build as much midrange and bottom end torque as possible and still have a relatively smooth idle

If you dont mind running 100 octane you might as well build a nasty engine and compensate low end with a low set of gears and a stall speed or 6 speed.

12:1. #48 heads with stock ports, stock intake

why?

in a 2nd gen TA with highway gears

12 to 1s again why?

Not a pump gas engine, but not a race engine either.

There really is no fine line between the two, its either a race engine or a street engine.
Because a little driving discomfort comes from too much of something, and opposite not fast enough comes from not enough.
Build a 455 .030= 461, ramair IV cam with 1.6 rockers 3;42 gears and a 3000 stall, RPM intake, and a tuned Holley and smooth out your ports in the heads and enjoy a street engine.

[Ron Ward]

Re: cam for 455 Pontiac

If you are looking for efficiency, I would direct my attention elswhere. The cylinder heads on a Pontiac (stock heads, anyway) are the limiting factor. A 400 inch engine would be more efficient with those heads than a 455. Putting a bigger cam in an engine with those heads is not the direction I would take. I would spend the money on a better set of heads that can take advantage of a bigger cam. If you switch to an aluminum head, you will also have the advantage of handling higher compression ratios with less chance of detonation.


Ron

[Thumpin455]

Re: cam for 455 Pontiac

The fuel is well over 105 octane, very cheap too because I make it. I have race engines but I dont need a race engine. I want to find out just what I can do with an engine more suited to my cattail vodka. Like I said, dont worry about the fuel, I just want lots of cylinder pressure. What is wrong with having very high compression in a street engine other than not being able to run camel whiz in it?

The RAIV cam wont work, its too choppy and it wont get a good signal to the carb, and that means it burns more fuel at idle and low rpms, like where this thing will cruise on the interstate. I dont want to port the heads for two reasons, one I need the velocity and dont need as much air flow since the fuel is oxygenated, second I dont want to spend the time or money to port them. The heads are only limited for max horsepower, not for torque production, 500ftlbs is super easy with stock heads and low compression.

As for the 400 vs 455, I have gotten better mileage from a 455 than from a 400 because with the 4.21 arm vs the 3.75 stroke makes it much easier to lug it right around 1200-1500 rpm while cruising 70-75 mph on the interstate. It goes up hills with very little extra throttle because it has diesel like torque. Got an average of 21 in the 70 GTO with a 2004R and 2.93 gears over a 1500 mile trip, worst it did was one leg at 19 best was 25, usually ran 22mpg on gas. Also the GTO isnt nearly as aero as the TA is, and it already has the 2.41 gears in it.

Now a 403 Olds can pull the highway gear well enough with those huge pistons but with the wimpy 3.3 stroke and the huge chambers in the heads its tough to get the squeeze up without a dome, and domes hurt flame travel. Nobody makes a stroker kit for the 403 and the best we can do is mill a set of 69 350 heads and offset grind the crank a bit, and that is way too much time and effort to put in a 403, but the ports would work nice because they are rather small.

Ya see when you run ethanol in a low compression engine you lose lots of efficiency and thus mileage, so I want to make use of the properties of ethanol to see how far I can push the mileage on it. It will stand high cylinder pressures, run much cooler than gas, and it has a more efficient burn than gas due to vaporization as opposed to atomization when it hits the hot intake tract. So cranking up the compression is more for efficiency than it is for ultimate power, even though the idea is to make plenty of torque in the cruise rpm, and maximize the distance traveled for each revolution of the engine.

One way to do that and still have a car that isnt a pig is to use a large engine but only tap its full output when needed. A tiny engine like a 2.0L would get good mileage but it is so low on torque that you cant lug it do to low rpms and the reciprocating mass attached to the crank such as a clutch needs to be sized so it wont be a detriment to acceleration, but it needs to be bigger because of the added stresses put on it by having increased torque in the engine, so that means custom stuff.

I know, it dont make sense if you think in terms of gasoline. If you dont know how ethanol works and what it does or is capable of, then it sounds like a grenade. Doesnt it?

[TheSilverBuick]

Re: cam for 455 Pontiac

I'd just find the equivelant to an RV cam, something in the .450 lift range meant for low static compression engines.

[Thumpin455]

Re: cam for 455 Pontiac

I have lots of ideas and probably 7 or 8 cams sitting around here that fit the RV size, just wonderin if anyone has ever stuffed in a cam and it pinged like crazy despite having 8:1 compression...

Summits 2802 works good, but with the wide LSA it doesnt build the cylinder pressure like I want. It is a great cam for a mild 400 or 455 though, quite similar to the 068. Its the cam going in the 65 I am doing..

[jays67]

Re: cam for 455 Pontiac

the 500 ish cam with 230/234 duration cam runs good in smaller pontiac {350} we are planing a stroked 400 as we have a set of ram air IV heads but thats another story

in the lil motor that cam sound huge and lumpy

as for fuel I see were you are coming from as we run alky in our race car and you need to keep the compression high [were at 14:1] I am interested to see were this goes as I would like to do the same thing

[joe_rocket45]

Re: cam for 455 Pontiac

if mileage and efficiency are the goals.. the wide LSA and no overlap is key.
then decrease the duration until you get an early intake valve closing point that brings your DCR as high as you can run on your 105 octane (depending on heads, combustion chamber, load)

[Ron Ward]

Re: cam for 455 Pontiac

As I am unlearned in the ways of alcohol (as a fuel, anyway) let me throw this out there....

I know alky runs cooler and is much less prone to detonation and you can get by with lots of compression because of it....

What about a centrifugal supercharger? Wouldn't this get your cylinder pressure up where you want it?


Ron

[ponchoman]

Re: cam for 455 Pontiac

Lets say octane is not a problem but you want to build as much midrange and bottom end torque as possible and still have a relatively smooth idle with a high compression 455, say over 12:1. #48 heads with stock ports, stock intake, headers, in a 2nd gen TA with highway gears. Not a pump gas engine, but not a race engine either.
Would it be similar to a cam you would put in a 8:1 455 or would something different work better?
HR, SR, S, or H work better? Im leaning HR.
I was thinking of a 230/234 @ 50 with .500ish lift and a 108.
Yeah I know it would rattle itself to death on 93, but its not going to run that. Dont worry about the fuel, just making cylinder pressure in an efficient manner.

I don't understand why this combo. You've got the disadvantage of the large journal 455 making high compression through #48 stock heads because you want to stick with 4.21 rods and build low end torque - but you're then forced to go to a questionable cam in terms of performance.

[ponchoman]

Re: cam for 455 Pontiac

BTW, I know you know your way around Pontiac motors - which is why I'm confused with this post. Still trying to figure out where you're trying to go with it. Unported #48 heads with that high compression are going to be REALLY hot. If you're also going to be lugging the motor around, that's likely going to generate more heat. I'd be real curious what the projected tq curve would like like on a build with that high compression, and that small of a cam and such a low flowing head. If you're just "hogging out" the heads when you port them, then sure you'll lose velocity. But if you have a quality port, you'll retain the port velocity but simply do a better job of moving air - and redirect the location of where that velocity is. Like maybe the highest velocity won't be right at the pushrod bulges....

Would you also be running a sump and an electric bypass fuel system? I'm guessing if not, you'd really be at risk of some fuel delivery issues resulting from building up heat in those heads.

You asked why not build a high compression street motor if fuel was not a problem. One word - ESPECIALLY in pontiacs. Heat.

[TheSilverBuick]

Re: cam for 455 Pontiac

I'm "thinking" Thumpin455 already has the parts (if not together) to get the Pontiac mill up in the 12-14:1 compression range to run on pure Ethanol. And is looking to use that compression to make up for the 30% loss in BTU power from standard gasoline. Now he is looking to see exactly how far he can take that comression. The Ethanol should burn cooler so that is why he's not so worried about heat. What he is looking for is loafing the engine along at low rpm for mpg (Yeah, 455 and mpg, I got the same affliction, lol!). So since he wants to loaf th engine below 2,000 he can't have much overlap/duration that would kill the low speed air flow. At the same time he's looking to keep the low rpm dynamic compression high for efficiency as he doesn't fear detonation with the pure Ethanol.

He doesn't need high flowing heads for the low cruising rpm he's going for.