[72LuxuryLeMansLa.]

What is the best way to determine the duration and LSA needed for a desired RPM range?

I have a 1972 Luxury LeMans with A/C. The car is a daily driver. I would like to keep it looking as stock as possible. This means that the stock tires and rims will remain on the car. I will convert the peg leg 2.73:1 rear end to a posi unit with gears that will keep the mileage and manners consistent with a highway cruiser. I will probably never race the car. I am wavering back and forth on using a 200-4r overdrive tranny or a th400(economy being the concern). Now that you know how I will use the car I will move on to my engine plans.

I am going to stroke a 400, probably .030" over, using PPR's 428 stroker kit (3" main, 4" stroke crank, 6.625" forged rods and 5.5cc valve relief flat top forged pistons). I will square and zero deck the block also. I am now leaning towards 85cc KRE D-Ports over SD prepped iron heads. I calculate the SCR to be 9.86:1 using the 85cc KRE's. The exhaust I am planning on is the Rare 2.5" headers with my existing 2.5" H-Pipe and magnaflow system.

Now on to the cam. I DO NOT want a rough idle. I would like a broad flat power curve and peak HP is irrelevant! I also want to use a roller cam. How do I choose what intake duration to use and also what lobe separation is appropriate? Making a w.a.g. I have chosen the:

PPR Tomahawk Hydraulic Roller Cam 270/278

Dur@.050 222/230 Lift@1.5 560/560 LC 112

#TC-01-HR Overlap 50

Any help on how to choose an appropriate cam for my goals will be appreciated.

[David Jones]

Seems like you'll be spending a LOT of money only to limit the potential outcome. You could accomplish your same broad flat power curve with an iron headed 400 and save a TON of money.

[rohrt]

I had the exact same build in mind for myself. So i'm pulling up a chair for the front row on this.

I always thought the rule of thumb was the more durration the higher on the RPM band that you make power. The advent of the roller cam allows power to made at lower RPMs due to the higher lift. The lift looks pretty decent for making good power. I would guess that the cam would make a tone of power right off idle but would run out of steam by 5k rpm. The big power in the lower RPMs should put your cruising RPM closer to where the cam makes peak power, Am I right???

[HWYSTR455]

Originally Posted by David Jones

Seems like you'll be spending a LOT of money only to limit the potential outcome. You could accomplish your same broad flat power curve with an iron headed 400 and save a TON of money.

That's my thinking too. Also, you may want to consider adding long rods (6.80), reduces side loads, and dare I say, makes it more efficient! Heh-heh!

Factory iron heads are great for this type of desired combo, good port velocity at low speeds, and the iron retains the heat in the combustion chamber for a more full burn at lower CRs. Plus they're readily available, and cost effective.

As for cams, if you were to use factory heads, selecting something close to a factory profile makes sense. They did their' homework, and using a cam 'based' off those original profiles with newer lobes would benefit even more. There are 'mileage' and 'towing' profiles offered by most of the popular aftermarket manufacturers, and would be a good place to start. Most will suggest you call and speak to tech in choosing a mileage cam, so they can target your goals better. Just like choosing a larger cam, going the other way has a trick to it too. As an example, some are designed to increase cyl (dynamic) pressure, so low static CRs maybe be required.

Looking at the Tomahawk Hyd Rollers, if you're shooting for mileage and cruising, I'd probably go smaller that the TC-01 on a 400. That would probably be a good choice for the 428 plan, but again, I would probably go one step smaller. On a 400, the TC-10 (210/218)would probably be my choice, if not the TC-09 (204/210), considering the gears your talking about. The TC-10 or TC-11 (217/225) would be my choice on the 428. The TC-09 is close to factory grind, with a little less LSA, give you an idea.

.

[65WJ]

Originally Posted by rohrt

I had the exact same build in mind for myself. So i'm pulling up a chair for the front row on this.I always thought the rule of thumb was the more durration the higher on the RPM band that you make power. The advent of the roller cam allows power to made at lower RPMs due to the higher lift. The lift looks pretty decent for making good power. I would guess that the cam would make a tone of power right off idle but would run out of steam by 5k rpm. The big power in the lower RPMs should put your cruising RPM closer to where the cam makes peak power, Am I right???

I plan on using #62s (heads) for mine.
Can you have more cam than heads can handle?

patrick

[HWYSTR455]

Originally Posted by 65WJ

I plan on using #62s (heads) for mine.
Can you have more cam than heads can handle?

patrick

Yes. If you choose a cam with more lift that the head can use, like for example, in general, factory iron d-ports kind of max out on flow at about .469 . You can go a little higher than that, which allows it to be over .469 for a longer period of time, but 'technically', it doesn't flow expodentially more above that.

You can also choose duration that favors RPMs over 5500, but the heads won't flow much above that RPM. They kind of hit a 'wall' at around 5250. You can doctor them and get more, but then you wouldn't be doing a 'mileage/cruiser' build. Most factory cams slope off above 4800.

Here's a list of factory cams on Wallace Racing site:

http://www.wallaceracing.com/camcode1.htm

Here's flow info I picked up somewhere way back:

(attached)

.

[HWYSTR455]

More complete head flow numbers at Ron's Pontiac Page:

http://ronspontiacpage.com/reference...flowcharts.htm

.

[rohrt]

What always throws me is this; The LS3 heads flow 300cfm, stock cam specs - intake lift .551 exaust lift .524 with durration at .50 204/210 with a CL or 115 and I think its rated at 430hp and get 25mpg.

what is the key to making more power with less cam? Why can't the same principle that work for the LS work for a pontiac motor? Is it just a matter of fuel injection?

Hope this doesn't come accross as smart a$$ I really want to know.

[HWYSTR455]

More flow at lower lifts. Port velocity.

.

[72LuxuryLeMansLa.]

I said a broad flat power curve, but I didn't say I wanted low power levels! I want high "Average" Power, not a spike at 6000 RPM that I will rarely ever see for more than a micro second! I guess we found the first bit of information that my original post omitted.
I would like to make at a minimum 1 h.p. per cubic inch. If you have factory heads that will do that and not cost as much or more than out of the box KRE's, Packe em' up and I'll pm you with an address to ship them to. A set of 250cfm iron from SD will cost at least $1680.00 while a set of KRE D-ports complete unported that will flow as much and have plenty upside, will cost $2037.01 shipped for a whopping $357 more!
The mileage I am speaking of is not great mileage for a 250hp car; I am looking to be more efficient but still be able to have fun when I have the desire. So decent mileage for a 450 hp car maybe a little different than mileage for a 210 intake duration cammed engine would be.
The main point is this, How to select the proper duration and lsa for a street only car that will provide the desired power levels without dumping fuel through the engine with a fire hose. Is it really just a guessing game and you just pull numbers out of the air and try them? I'm not asking for anyone to give me the cam numbers, but to explain to me and others the process used to determine these things on our own.

Thanks

[bobzdar]

Originally Posted by rohrt

What always throws me is this; The LS3 heads flow 300cfm, stock cam specs - intake lift .551 exaust lift .524 with durration at .50 204/210 with a CL or 115 and I think its rated at 430hp and get 25mpg.

what is the key to making more power with less cam? Why can't the same principle that work for the LS work for a pontiac motor? Is it just a matter of fuel injection?

Hope this doesn't come accross as smart a$$ I really want to know.

It's a matter of aerodynamics. Ls3 won't get the same mileage in an old pontiac as a new 'vette because the drag is too high, plain and simple. If you want a higher mileage pontiac, get a '79-'81 base bird and put a lockup TC in or a manual trans and 2.73 gears. Then put a 744 or 041 cam in a stock 10:1 400 and you should get 20+mpg with 400 horsepower. I did it in a '78 trans am, but only at around 350hp and 20mpg even. Better aero awith the '79 nose and losing all those flares and spoilers with taller gears should be worth 1-2mpg.

If horsepower doesn't matter, the OPs plan is way overkill. Use a '67-'70 4 barrel 400 and throw a decent cam in, lockup converter or manual trans and go. All that extra money for a 428, roller cam etc. won't gain you much, if anything, in terms of economy - though it will make some more power.

All these guys wondering why their pontiacs get such poor mileage need look no further than that massive power sapping th400 with non lockup converter and their distributor and carb tune. I picked up 4mpg swapping a th350 for a 4 speed, no other changes. Th400 would be even worse.

[Evil Stu]

72LL,

This is a good read. It was written to pick HFT cams but the general concepts should apply.

http://www.pontiacstreetperformance....camselect.html

HTH,

Stu

BTW, Car in my sig sees 8~9K miles a year, not many long Hwy drives tho'. Most of Nova Scotia is 2 lane, 50mph type roads.

[72LuxuryLeMansLa.]

Originally Posted by bobzdar

It's a matter of aerodynamics. Ls3 won't get the same mileage in an old pontiac as a new 'vette because the drag is too high, plain and simple. If you want a higher mileage pontiac, get a '79-'81 base bird and put a lockup TC in or a manual trans and 2.73 gears. Then put a 744 or 041 cam in a stock 10:1 400 and you should get 20+mpg with 400 horsepower. I did it in a '78 trans am, but only at around 350hp and 20mpg even. Better aero awith the '79 nose and losing all those flares and spoilers with taller gears should be worth 1-2mpg.

If horsepower doesn't matter, the OPs plan is way overkill. Use a '67-'70 4 barrel 400 and throw a decent cam in, lockup converter or manual trans and go. All that extra money for a 428, roller cam etc. won't gain you much, if anything, in terms of economy - though it will make some more power.

All these guys wondering why their pontiacs get such poor mileage need look no further than that massive power sapping th400 with non lockup converter and their distributor and carb tune. I picked up 4mpg swapping a th350 for a 4 speed, no other changes. Th400 would be even worse.

I said "peak HP is irrelevant" I never said HP "doesn't matter" ! The fact is I really can't have a standard transmission. I have had two Operations on my lower back and have serious pain problems.... Auto is most certainly required

[HWYSTR455]

Originally Posted by 72LuxuryLeMansLa.

The main point is this, How to select the proper duration and lsa for a street only car that will provide the desired power levels without dumping fuel through the engine with a fire hose. Is it really just a guessing game and you just pull numbers out of the air and try them? I'm not asking for anyone to give me the cam numbers, but to explain to me and others the process used to determine these things on our own.

Thanks

Well, for me, it's been experience, no science at all to it. I'm a hobbyist, not an automotive engineer. I know what a factory 350 2bbl 68-72 LeMans runs like, and about every flavor of 400, 428, 455 in those years too, and use the way they were cammed from the factory as a reference. I've also used about every off the shelf aftermarket cam known to man in the search for one that worked for me, was like an entire summer I changed cams almost every weekend, no kidding. All my stuff was for a car I not only would horse around with on the street, but used as transportation too, so it had to idle, etc. With that in mind, I've found that LSAs less than 110 tend to 'dump fuel' as you call it, at lower RPMs. They also had more choppy idle. I use durations in the range of 225-235 on 400s, with LSAs in the 112 - 114 range, and was always able to drive them anywhere. With more cubes, you can add 10 degrees. You can also review popular builds, and you will get expected results. The 400 you speak of has been done many times in many ways, doesn't have to be redesigned.

On the heads, I thought you already have heads, no? What's on the car now? Or does it not have an engine? All d-port heads flow (or can flow) roughly about the same. The ones that have press in studs and small valves need a little more work to make 'right', but it's no big deal. You can buy core d-port heads from any of the popular vendors, pick one close to you so shipping is less. Or pick a set up locally, and have a local machine shop go through them. All they need is good valves, guides, a valve job, and setup with the springs for your cam. Nothing special. They will flow well enough to meet your 450hp goal. You don't need hardened seats, it's a waste installing them.

If you need a primer on cam dynamics, selection, etc, do the homework. I'm not sure where to go for that, I'm guessing it needs considerable theory first of all, then what's applicable to Pontiac in specific. I doubt there is a simple answer there, sorry to say. It's not going to be a simple formula to choose what you want. Maybe use something like Desktop Dyno and model the configs you intend, see what to expect. All the head and cam files are available, as well as the program, from Ron's site I posted above. Then you can swap cams and see the impact, where power starts, peaks, etc, all in a matter of mins.

Sorry I didn't catch what you were after in the first place, hope you didn't become too frustrated here. Now that you've asked, think I may do some homework on the subject too, since it sparked an interest in me!

.

[HWYSTR455]

Oh, and just to say, my current driver, the 71 LeMans, has a 400-based 461 e-head stroker, with a 4L80E, and 373 gears. It was based off a 550hp build, and probably makes 575+, has A/C, and I can drive it anywhere. It can sit in traffic or idle in the driveway for days, in 100+ weather, and I knock back 21-23 mpg in it. I had to check it multiple times, so know it's accurate. I have other board members that can verify that too by the way, it's not BS.

.

[bobzdar]

Originally Posted by 72LuxuryLeMansLa.

I said "peak HP is irrelevant" I never said HP "doesn't matter" ! The fact is I really can't have a standard transmission. I have had two Operations on my lower back and have serious pain problems.... Auto is most certainly required

Then get a lockup torque converter. You don't even need an overdrive trans with those rear gears to get good highway mileage, though it will help get off the line. The 200r4 will sap less power and give you an even lower highway cruise rpm than the th400, but it may not hold up to your engine. I think with the 200r4 it's easy to wire up the tc to lock up - I know my buddy installed a switch in his GN to allow him to manually control it for long trips so it wouldn't unlock when he passed somebody. He would get 25mpg on the highway in his car cruising at 75mph.

[amcmike]

To be honest, I thought your original hyd roller cam choice for that combination engine size and gearing for your goals was spot on.

Plus, with that SCR, you should be able to run on 87 Octane intead of requiring premium which will save you money at the pump.

[rohrt]

Originally Posted by bobzdar

It's a matter of aerodynamics. Ls3 won't get the same mileage in an old pontiac .

There a larg number of posts on the other sites where F-body guys are getting anywhere from low 20s to high 20s with different LS swaps.

I'm more interested in why people would not like the cam choice of the poster.

[bobzdar]

Originally Posted by rohrt

There a larg number of posts on the other sites where F-body guys are getting anywhere from low 20s to high 20s with different LS swaps.

I'm more interested in why people would not like the cam choice of the poster.

F-body guys in a 2nd gen? Please link to the combo, I haven't seen that. I can see 24-25mpg as being about the limit without getting crazy. A stock 4th gen only does 27mpg.

[rohrt]

The posts are scattered all over on the pro-touring site and on the ls1 site, but here is one that was decent.

http://www.ls1tech.com/forums/conver...o-ls1-mpg.html

I would sure like to see what that (Dur@.050 222/230 Lift@1.5 560/560 LC 112) roller cam woud do in the 428