400 Combination Opinions
 

I have the following combination planned, and I would like opinions from folks that have run a very similiar combination. Goal is to maximize torque/hp below 5200rpms. Car will be street driven, an ocassional run at the strip, hopefully a few sucessful street races against fellow employees tuners, and power brakes are needed. Must run on pump gas and not ping. I ran the compression ratio calcualtor and it shows about 9.8:1 (even though Pontaic rated it at 10.75:1). I ran the DCR calcualtor and it came in around 7.5, which according to what I have read indicates it will be fine on pump gas. I currently have an edelbrock cam (2157) in the engine that nets the same DCR, and I do not experience any pinging, so I feel good about the 2801. The Summit and the Crane cams seem so close, Desk Top Dyno really shows no "significant" difference, so the Summit seems like a much better buy. I modeled a ton of cams and for high compression large valved 400s running 5000 rpms or less, no other cams did better (well except the XE262but I believe the DCR would be too much), comments please?

1968 Firebird
Block: 400
Heads: 1968 #16
Intake Manifold: Edelbrock Performer
Carb: Edelbrock Performer 750 w/ Elec Choke
Camshaft: Summit 2801 or Crane H-272-2
Distributor: MSD ProBillet
Trans: TH400 w/ shift kit
Gears: 3.55
Converter: Stock. Considering 2500
Exhaust: Dougs full length headers, Flowmaster American Thunder tranverse muffler

How does this cam come out in your calculator. Ultradyne ground with 112 LS.
Attachment 123372

That should be a very strong combo but I'd be especially leery of that cam with that compression ratio despite what the calculators say. I had detonation issues with 91/92 octane running a much larger cam at 9.7:1.

400 combo
 

Most Crane cams are single pattern cams, and pontiacs like a dual pattern, also the 16 heads are at 72cc's which makes the CR pretty high depending on the piston (which you didn't mention) If they are flat tops you will get pinging on lower octain fuels whether you hear it or not. Performer manifold is basically a 68 stock as flow numbers go but lighter, still a good manifold, don't get me wrong. 2500 stall will work fine with 3.55's as at 60MPH you will turn around 3200 rpm, and trans kit will be OK. but watch for rear end hop with this combo and rebuild your driveline with new joints ect.

Shell up here is selling 93 octane with our regular Unleaded at 89 now, not 87 and yes I can feel a differance in my low compression rides.

I have a 428 HO engine that I will be changing the heads on just because of the octane problem. I will either run 4x or 6X for the bigger chamber and I'm parking the 62's on the shelf. 62's also have the 72cc chamber.....

good luck

It helps to post the cam specs, rather than just the part number(s), even though I happen to know them, most folks have to do research to find out the specs before helping you out.

Anyhow, the 2801 is taunted as a 068 replacment cam, which it is not. You can get away with more compression with the factory cam, as it has a lot of off seat duration, and wider LSA.

The torque converter stall speed opens up the doors for more camshaft. I would move up to the Crower 60916 cam, or something very close to it, with a 2500rpm to 3000stall converter and 3.55's. The engine will enjoy more power across the rpm range, only giving up some "grunt" below about 2500rpm's, compared to the two smaller camshafts.

Also keep in mind that other things, like deck height, will effect the engines ability to manage any octane at any given compression ratio. 9.8 to 1 is no problem at all. However, we've seen engines much lower than that, with the pistons .030-.050" down in the holes, run so hot, overheat, detonate, that they couldn't be driven on days with the outside temps higher than about 50 degrees!

With a zero deck height, 9.8 SCR will be fine with the right cam choice........Cliff

BAB

There wasn't enough information on the Ultradyne cam you attached, I need specific timing events. I went to the UD web page and Ultradyne does not supply them. I did find an Ultradyne 276 with the following specs @ .050
221/230, .467/.467, IVO 2.5, IVC 38.5, EVO 51, EVC -1.0, 112 LS, 108 IC

The UD cam performs almost identical to my exisitng Edelbrock 2157 (you can just about trace the curves on top of each other) with the following adv. specs (this cam is 204/214 @ .050)
278/288, .420/.440, IVO 34, IVC 64, EVO 79, EVC 29, 112 LS, 105 IC

For comparisons here is the results of a Summit 2801 and Ultradyne 276 (using head flows in Jim Hands book and my engine description)

RPM 2801 HP 276 HP 2801 TQ 276 TQ
2000 158 149 416 392
2500 205 194 431 408
3000 254 240 444 420
3500 308 295 462 443
4000 359 349 471 458
4500 402 398 469 464
5000 434 433 456 455
5500 440 449 420 429
6000 427 446 373 390

In my book the 2801 is the better cam because I do not plan on running the engine above 5000 RPMs. The 2801 has better torque in the area I want. The HP doesn't show that much difference down low because HP is a mathmatical calculation highly dependant upon engine RPM. At low RPMs the increased torque will not be fully represented in HP, yes once you get above 6K RPMs and carry some torque with you the HP number will go up dramatically. If I maximize my TQ for any given RPM the HP will follow suit, (again keep in mind 5000 RPMs)

The popular Crower 60242 does almost identical to the UD, the Summit 2801 makes more low end torque, and the Crower only beats it above 5000 RPMs. I have not tried the Crower 60916, but I don't believe the my program will show a difference, since the durations are nearly identical. I do know from reading posts that there is a difference, and I was under the impression the 60916 requires a lot of compression.

The goal is a 500 RPM car that has torque and great throttle response, BUT can run on pump gas. Maybe the best I can do is my existing Edelbrock, it appears to work as well as most of the popular cams, a little less down low torque, and runs up to 6K.

I would go to the 2801, IF it can run on pump gas WITH the high compression heads.

if your only gonna turn 5000 rpm, why modify your mill at all?..cam it to turn 7200 and wow your pals..

Hahahahahaha....7200 RPMs....cool but the engine is stock.
I would prefer to go to 5500-6000, but from what i read on this forum, the stock pontiac rod bolts will not live there very long , is this correct?

I figured any of the cams I was looking at could run up to 5500, for top end speed.

I went out to the shop and checked the cranking pressure with the edelbrock cam, the Doug headers are on the shelf and not installed, cast manifolds are in place. Warmed engine to 130 degrees (pretty cold today in NY), choke fully opened, pulled dist wire, and cranked it for a few seconds.

185 PSI
Only checked 1 cylinder.
I haven't "heard" any pinging.

OK, so this should answer some questions.
Will the Summit 2801 work with this pressue?
Will the Crower 60242 be better?

I ran the Crane H-272-2 in my 1969 .030 400. TRW pistons. #48 heads. A 3.55 posi and a stock converter. It was a great cam and did a 13.6 qtr on a set of 225/70-14's driven by me on my 1st trip down a dragstrip.

Dave....sounds great.
My last car was a 69 camaro (actually had a few of them) with a .030 454, mild built and it ran 12.8 at the strip, with a good set of tires. Was an fun car on the street, torque was awesome. Had to be careful slap shifting to second, the rear would ocassionally show up in the passenger window :-)

I consider the Crane h-272-2 and the Summit 2801 to be about the same, so thanks for the advice it is encouraging. I may actually get the Crane over the Summit, since the price of the Summit Cam w/o lifters and a better set of lifters ends up being about the same as the 272.

1funride,

Below is the cam I am refering to. I'll find it hard to believe the 2801 will out perform this cam however I'm open minded. Also the cam is now made by Bullet Cams.

Attachment 123394

BAB
Entered in the information you supplied. It makes less torque down low and more HP on the top end. Keep in mind this is just a simulation, but i believe it offers good engine characterisitcs and a convient way to compare cams. I'll call this cam an UD 280.

RPM 2801HP 280HP 2801TQ 280TQ (below numbers carry left to right as seen here)
2000 158 146 416 382
2500 205 190 431 399
3000 254 235 444 411
3500 308 291 462 437
4000 359 344 471 452
4500 402 395 469 461
5000 434 433 456 454
5500 440 451 420 431
6000 427 451 373 335

I am just working off these simulations, and haven't used these cams myself.
I entered the information you gave me and all the numbers lined up with the CAM Card.

1 funride,

That's pretty interesting. Just for information purposes the 280/288 cam resulted in 13.30's with 2.0 60fts in my car (70 GTO, exhaust manifolds, 412 CI, 4spd, 3:55 gears, wide oval tires, 14.5" of vacuum @ 900RPM). I enjoy the post since I keep hearing alot about the 2801 and 2802 cams being a good bang for your buck.

1funride,

What happens if the higher HP engine uses a slightly higher numerical gear, so that at the same MPH, the higher HP engine runs at roughly a 500 higher RPM? That means the higher HP engine makes more HP at every MPH, correct? Does that mean you need to run the engine at 5000+ to realize the advantage of the higher HP??

Just trying to understand your logic, as you are only looking at flywheel numbers, not the torque at the wheels at MPH, using different gears on each.

Compare the HP numbers when the higher HP engine is running roughly 500 RPM higher.

Motor-Daddy

Interesting question. I had to lean back for a second on that one.
I "believe" what you are stating may be pretty beneficial in a race car running high RPMs, since you can launch at a high RPM and do not need to pass through lower RPM loads. I believe for the street, where your engine must run loaded through low RPMs to reach the higher ones, maximum torque up to 5000 is still better. If you maximize the torque in every RPM up to 5000 you are making the maximum HP at each of those RPMs at the engine crank. That being said, the higher gear would net more torque at a given MPH, but you could do the same (add gear) with any cam, and if that cam has more torque at that RPM it would still be making more HP. So my reasoning is, run maximum torque up to your RPM goal, of course you need to match the whole system together with the car, gears, torque converter etc.
That is where my question comes in for my engine and car combination and what apears to be a darn good summit 2801 cam. My engine has 185psi is this too much for this cam type, or do I need to add more duration to lower the dynamic pressure to elimiante pinging? Current no pinging at 185psi (that I can hear).

This was with the H272-2. More power was in it, but not much tuning had been done at the time of this dyno run. I had them stop at 5200 rpm. As you can tell it seemed to be about done.

Not only beneficial in a race car, but also a street car.

Example:

You are cruising down the road in second gear at 30 MPH in two different scenarios with two different rear gears, with the higher numerical gear geared to run at 500 RPM higher at 30 MPH. According to your power numbers you previously listed, which one will accelerate at a greater rate from a 30 MPH roll? Which one at a 15 MPH roll? How about a 60 MPH roll? What about a 1 MPH roll in first gear?

And your statement about adding more gear to every cam. Sure, you could add more gear on any cam, but regardless of which gear you select for the 2801, I can pick a higher numerical gear and out run you at every MPH, because the higher HP at every MPH will make a greater rear wheel torque at EVERY MPH.

GTO-David
That is great information, thanks.
Do you know what pressure you were making with the 272 cam?
Did you have any pinging?
That cam seems about same as 2801.

Motor-Daddy
I couldn't follow your reasoning. A street driven car is pretty limited for the most part on how extreme the gear selection can be. For any given rear gear, there will be a fixed engine RPM (many factors to consider, but true for the gears input to the engine RPM), the camshaft selection is a resultant of the desired engine RPM and is not a primary contributing factor to RPM. So with any gear selected the engine with the most torque will result with more "power" to the wheels "at that RPM". Bump up the RPMs again for both cams and the same rule applies. My cut off was around 5200 RPMs, so my range is strictly limited to off idle to 5200, anthing above that is a don't care for me.

I'm sorry you don't understand. I'll leave it at that, as people are tired of hearing the truth, and when I try to tell them, they stick to their guns (as is the case here), which causes problems between the truth and their beliefs. That ultimately leads nowhere, because even though they asked a question, they already had their mind made up, and don't want the actual truth, they are only looking for reassurance of their beliefs. If the response doesn't reassure their belief, they don't want to hear it.

Sorry I couldn't help.

May I suggest the 066? It makes more low RPM torque.

Never any pinging on 93 octane and I couldn't begin to tell you about pressures.