Okay guys, this is a new 383 with TFS aluminum 64cc heads. I'm going to use an edelbrock pro-flo TPI setup on it, and am torn between two cams. Let me know what y'all think:

1)TFS-31402000-- 270 intake/276 exhaust
Duration at .050 in. Lift (Degrees): 214 intake/220 exhaust
Camshaft Lift: .301 in. intake/.310 in. exhaust
Valve Lift with 1.5 Rocker Arms: .452 in. intake/.465 in. exhaust
Lobe Seperation (Degrees): 110
2)TFS-31402001-- 292 intake/296 exhaust
Duration at .050 in. Lift (Degrees): 230 intake/234 exhaust
Camshaft Lift: .352 in. intake/.359 in. exhaust
Valve Lift with 1.5 Rocker Arms: .528 in. intake/.539 in. exhaust
Lobe Seperation (Degrees): 110

I will be using 1.6 rockers, especially if I go with the smaller cam, BTW. I don't mind a little lumpy idle, and don't want to under-cam the motor. I don't have a lot of experience with roller cams, I tend to think the smaller one might be too small, and the larger one might be too large. It is not a daily driver, but will be driven frequently. Can anyone provide insight/opinions on this combination? Thanks.

 

First, based on how you will use the car select an 80 percent torque bandwidth that best suits your needs, then buy an engine simulation program and build engines using various proposed cams and other components until you get your target torque curve.

The fifty to a hundred bucks you spend for a simulation program and time you spend working with it will pay for itself many times over, by allowing you to "system engineer" the engine rather that just bolting a bunch of components together and hoping it turns out what you want it to be.

Duke

 

Compared to the differences in duration, you have a major difference in lifts. Is the first cam really a roller? Unless your intake ports will support more lift, my vote is for no. 2, with 1.5:1 rockers. I am basing my opinion on your stated usage. I doubt that 230-234 duration (@.050) on 110* lobe centers will pass a smog test. It ought to run really strongly, though. That's MY $0.02. Good luck.

 

SWCDuke,

Can you please explain: "80 percent torque bandwidth". It sounds good, but what, exactly, do you mean? Thanks.

 

thanks for the replies, I have run some DD2K sims on them, quite a bit of difference in hp on the top end between the two. It sounds like either the smaller one with 1.6 rockers, or the larger with 1.5 rockers. I am somewhat concerned about idle quality with the larger cam, anyone have experience with a similar spec cam that can give feedback on idle quality? Thanks again, looking for good info just like what y'all are providing....almost forgot, don't care about emissions, but looking for a good compromise in streetable setup between performance and driveability.


[Modified by frodo84, 12:05 PM 7/4/2002]

 

ttt

 

Not being a cam guru I can share my experience. I run CC 218-224 HR in 355. Very nice and smooth. W/383 next bigger cam would be appropriate I think. 1.6s will help lift and add 2 degrees of duration. A TFS head hits valve saturation at about .550. Any lift past that is wasted. As long as you a rebuilding engine go for roller you won't be sorry. The RRs run much smoother and more importantly COOLER! The best advice I have heard is "Pick what you think is the perfect cam, and go one step smaller. Also call the tech people who have done this many times before. They are not emotionally involved. Is this an auto trans or manual? Keep in mind the total package. You will have to upgrade cooling also.

 

Guys usually talk about peak horsepower, or say: "I want X amount of horsepower." There's a fixation on this, but it's not represenative of overall engine performance. If you have a four-speed transmission you only achieve peak horsepower at four vehicle speeds, assuming you can reach the power peak in top gear, which is probably not very often, if at all. Unless it's a dedicated racing engine you are probably going to spend 99.999999 percent of the time in some other part of the rev range.

A street engine must be flexible - have useable torque throughout the operatiing range, reasonable idle quality, and good response at part throttle. Peak power addresses none of these issues.

The eighty percent torque band width is the rev range that the engine will produce 80 percent of its peak WOT torque. You can compare it to the frequency response of an audio amp - the broader the 3dB points - the better the amp. Likewise - the broader the 80 percent torque bandwidth of the engine - the better it will feel. Below the lower limit of the eighty percent torque bandwidth, the engine will feel soggy, and the top end of the 80 percent torque bandwidth is usually beyond the power peak and the point where the power curve begins to fall off fast, which would represent the upper useable limit of operation, assuming the engine has the mechanical strength to handle this level of revs.

A critical parameter in engine flexibility is the bottom end of the eighty percent torque bandwidth. A medium performance engine such as a 327/300 has an eighty percent torque bandwidth that starts at about 1200 to 1500 RPM. Factory SHP engine's eighty percent torque bandwidth starts at about 1800 to 2000, and 2200 is probably a reasonable limit for a high performance street engine. Once it gets to 2500 the engine is not going to be very satisfying in normal street driving.

When system engineering an engine, I select valve timing that yields the target low end of the eighty percent torque bandwidth. Then you build top end power by working on inlet and exhaust flow - heads, manifolds, induction and exhaust system.

Top end power is expensive, because it requires a lot of detailed work. You can make a stock set of heads make as much power as you want with bigger cams, but as you gain top end power, you kill the bottom end of the torque curve and can end up with a stone.

For a maximum performance street engine, select valve timing that gives you an eigthty percent torque bandwidth that starts at no more than 2200, then spend as much money as you can afford on heads, inlet, and exhaust system to get top end power.

Using an eighty percent torque bandwidth criterion on vintage carbureted engines is a good system engineering requirement, but modern engines are much better. For example, the current Z06 LS6 engine has a NINETY percent torque bandwidth that begins at about 1500 and extends beyond the rev limit. That's why the LS6 feels so strong everywhere without being "peaky", while having excellent fuel economy and driveability.

With the availability of inexpensive engine simulation programs it just doens't make any sense spend several thousand dollars on an engine build by guessing what components to use without doing simulations and comparing the results to some realistic and reasonable requirements. Anyone who is contemplating and engine build should buy a simulation program and start working with it in order to gain an understanding of how it works and what it can do. Then start selecting components and running simulations.

In the time it takes you to build one engine, you can test literally hundreds of different combinations, which will go a long way toward ending up with a good engine once you buy all the parts and put it together.

Duke

 

thanks again, all, for the replies. Duke, I understand what you mean now. For this application, it is an auto (700r4 with 2200 stall converter) and I am looking for just what you are talking about, that being good to decent bottom end (hence higher stall), and good heads with free flowing (hooker) exhaust. Using DD2k, the larger cam gives a fifty hp gain @ 5000 rpm, they both peak right around there. Since DD2k doesn't give me manifold vacuum numbers below 2000 rpm, I am concerned about idle and off idle performance. The larger cam spec states "Fair idle, broad midrange power with a 2,800-6,300 rpm powerband", while the smaller one states "Good idle, strong low-end power, with a 2,100-5,600 rpm powerband". That tends to push me away from the larger cam, but the DD2k sim really points toward the larger cam except for the idle/driveability issue. With a 2200 stall, I may still want to go to a 3.54 rear to help if the larger cam is selected. I'm tempted to buy both, although pricey at around $250 each. Does anyone have any experience with a similar grind in a different manufacturer's cam?

 

So where is the bottom of the eighty percent torque bandwidth for these cams. Just compute it from the peak torque value then look at the table or curve and see where it lies.

Especially with an automatic, I would recommend 2200 as an absolute maximum for the beginning of the eightly percent torque band unless you have very short gears, or are willing to put up with sluggish performance in normal driving. Certainly with an automatic, idle quality is more of an issue than with a manual. The automatic isn't going to like and engine that has to idle at 1000 or 1200 and neither will you or your brakes.

Duke

 

IMO - If your not bound by emission testing I would go for the larger cam. I have a some what larger solid roller and it has 13-14 inches of vacuum at it's 850 rpm idle. I can put it in lockup fourth gear below 2000 rpm and go WOT and my little 383 just motors away. At a minimum go with 10.5 C/R. I'm a Crane cams guy:) My motor spends the majority of it's life under 3000 rpm with my 700R4

This Crane H-roller cam might be a good choice also. It's in between your above choices - The write up is referring to a 350 ci motor


3. PowerMax Hydraulic Roller Retrofit Camshafts for Non-Emissions Controlled Vehicles


Application Series & Grind Number
Fair idle, moderate performance usage, good mid-range HP, mild bracket racing, auto trans w/2500+ converter, 3000-3800 cruise RPM, 9.5 to 10.75 compression ratio advised. Basic RPM 2500-6000 PowerMax
Hydraulic
Roller
HR-284-2S-12 IG

Cam Specifications


Degrees Duration @ .050 Int./Exh. Degrees Advertised Duration Int./Exh. Degree Lobe Separation Open/Close @.050" Cam Lift Int./Exh. Lash Hot Int./Exh. Gross Lift Int./Exh.
222/230 @ .050 284/292 advertised
112
4 38
52 (2) .000
.509/.528


[Modified by gkull, 2:48 PM 7/5/2002]


[Modified by gkull, 2:51 PM 7/5/2002]

 

Thanks again, I think that based on Duke's numbers the larger cam is a little large.....Gkull, thanks for that info, I assume those lift numbers are with 1.5 rockers. If so, I think that is a good compromise. I plugged those numbers into DD2k and liked what I saw. If you have decent idle with a somewhat larger cam, I think I will be happy with this. Looks like I need to make a call to Summit at this point, thanks again. Also, Gkull, I am going to a bowtieoverdrives 700r4, with a 2200 stall, what stall are you running?


[Modified by frodo84, 5:14 PM 7/5/2002]

 

Frodo84, I had Bakers here in town build two 700R4s for me and I'm not dissappointed yet. I dogged the hell out of one for over two years and its still ticking. The total was $1250 for drop, rebuild, beef up and reinstall. I'm sure the guys at bowties are good, but sometimes a long distance job can be a pain. Good luck on the cam, I've had some lumpy ones installed and now I'm going back to smaller versions using rollers. The high duration high lifts suck for the frequent street driver. Also you need to pay attention to the rear gear. That 700R4 will put your cruising down in the lower RPMs. Since you are planning on a high stall then you need to get the cruising RPMs up past this stall or you will be heating up the tranny and getting some **** poor hiway performance. I'm running a 3.75 gear with a 700R4 and the 70 MPH cruise is around 2400, in an 85 vet.
Another thing to look at is the different lifts, if you are running the DD2, try running several lift patterns and you'll see that the .5 is usually more than enough for the street, not much improvement after that. I'm not fond of the 1.6s as the system seems to work better with the 1.5s, if you need more lift, buy the cam that has it, if you want more duration, buy the cam that has it.
Good Luck on the build.

 

That cam with the 112 lc should provide a nice idle. With 1.6 rockers it would be .544/.563 lift. my somewhat larger cam is 240/248

I ask for a 9.5 inch 3000 stall what I got is more like 3500. with my 700 I've tried everything from a 3800 to a custom 1400 rpm stall. The 1400 was also with a full manual valve body when I was really into auto-X & open road racing.

I have a manual toggle switch for OD and it's fourth gear only. I also have no kickdown in any gear. It won't down shift till your crawling up to a stop light. With no down shifts there are never any suprizes when you go to WOT in the middle of a high G turn. Out every combo I've tried it's the best

When you have a lockup converter having high stall is not a penalty. When I'm going down a level freeway I can blip the throttle to 3500 rpm. But it's an efficient converter because at a steady state cruise of 70 mph it might only go down 300-400 rpm when I hit the switch.

When you buy a TC get the smallest diameter you can. It's the same idea as a light weight flywheel for more instant rpm. I'm not sure why your buying a 2200


[Modified by gkull, 4:45 PM 7/5/2002]

 

Duke,

I just looked at my D2000 simulation for the motor I'm getting for my '66. I'm at 80% from below 2000 to above 6000 rpm. Does this mean I'm being too conservative? ;-)

I hope to have it soon, do you happen to have an engine hoist I can borrow? How about an extra pair of hands...

 

Dryseals,

Thanks for the info, I've already got one from bowtie in a crate in my shop. I agree that I might have to go to a taller rear gear, Pyle brothers in Baytown or maybe Parsons in Beaumont for that. I think you sent me your phone # one time, I'll find it and give you a call.

Gkull,

I bought a 2200 from bowtie because I think it will really stall higher than that, and didn't want it too high for heat reasons. The guy at bowtie made me a deal, if I want a higher one, he'll give me credit for this one as long as I don't run it too long. With the pro-flo, I'll use a '7747 ecm to control lockup, or that's what I'm saying now anyway. I can burn chips for it. I just called summit, $300 for the cam, I can trade them for the 1.6 rockers for the 1.5s.....I really like that the crane falls right in between the two TFS (Crane, I was told) cams. I'm going to use a two-piece timing cover, just in case.....Thanks again to both of y'all.

 

I'd say if you've got 80 percent torque bandwidth from below 2000 to 6000 you've got a great street high performance engine.

No I don't have a hoist. E-mail me with where you live in RB. Like most people, I wasn't born with an extra pair of hands - just the normal one pair. ;)

Duke

 

Parsons is good, I've had him do two differents rears, one in the Vet and another in a truck. No complaints.

 

Yes, he recently worked on my truck, a little over $600....what does he charge for a dana 36? I was quoted $840 with new gears and all bearings, total out the door by Pyle brothers....

 

I paid 11 something for mine. This was a 3.75 gear in a Dana 36 with all new bearings and u-joints, I figured while he was under there I would let him take care of anything he could get to.