I should have asked this question some time ago but I didn't and now am second guessing myself and the guy at Comp Cams that made the reccomendation. I think I bought to small a cam graemlins/clonk.gif for my combo.......I would appreciate you guys looking at my combo again and give me an opinion. Since I bought a custom small base circle grind I probably can't return it now :( . Evne though I have posted my combo before here I go again!

400 SB .040 over
5.7 Scat rods
3.75 stock crank
Speed Pro Hyper flat tops with 4 VR's
462 double humps 64cc ported w 2.02/1.60 valves & 1.5 Crane gold rollers
Torker II intake
1 5/8 headers
2 1/2 exhaust w/ Flowmaster

ST-10 4-speed
power brakes & steering
no air
10-bolt w/ 3:90 & Auburn posi

That covers the car and engine combo. I decide to go with one of Comps Xtreme solids, specifcally the XS274. Here are the specs on the cam:

@ .015 lift 274/280 Adv 236/242 @ .050
Gross lift .501/.510
Valve timing @ .015
Int 31 BTDC 63 ABDC
Exh 74 BBDC 26 ATDC
Lobe Sep 110
Install on 106 Int CL will be +4 ADV

I ran Pat Keely's DCR calculator last night(should have done long time ago) and got the following:

SR 11.35:1

DCR 9.21 on 106 Int CL(+4*ADV)
DCR 8.93 on 110 Int CL(0*ADV)
DCR 8.64 on 114 Int CL(-4*RET)

I don't mind for this season running a mix of racing fuel/93 octane to prevent detonation, I only cruise with it on the weekends and don't plan on any real highway time. I have plans on going to some TopLIne 72cc x 200cc runnners to drop my DCR closer to the magical 8.0 number, however I have what I have this year. Any opinions on whether I should run it as is or look for a better suited cam and sell the one I have(anyone interested??). What other problems can I expect with this combo. Sorry for the long post but I can't stop thinking about this :( !

Tom

From a performance standpoint the XS274 ought to run real hard and make tons of TQ. But I think you are right --- premium pump gas won't cut it.

There area lot of cams out there these days with really agressive lobes - short advertised duration and big .050 and .200 duration numbers. That's great IMO for small blocks with lower static compression or even Big Blocks where it is harder to build much static compression with open chamber heads and anything but a piston with a gigantic dome. BUT small blocks are getting really big these days and with small 64cc chambers its almost impossible to get a streetable DCR with a flat top piston in a 383 or 406 without going huge on the cam.

Anyway, sorry for rambling. My point is just that When I put flat top SRP's in my 383 (64cc TFS heads) I found that I needed roughly 290* advertised duration to get by with 11.3:1 static CR on pump gas.

I looked at the agressive cams and realized that the agressive cams with 290* advertised duration had 050 duration numbers that put my power band up way too high - like 7000+ So I went back to the good old reliable Magnum line and dropped in the 294s Magnum. (Specs are 294* advertised, 248* @ 050, .525" lift, 110* LSA). It pulls hard from 3000 up to 6500 in my 383 (I shift at 6200) and still bleeds off enough cylinder pressure to squeek by on pump 93.

Another option would be to pick a cam with a wider LSA if you don't mind sacrificing some midrange grunt. The wider LSA cams will bleed off some cylinder pressure without needing as much advertised duration.

Just my opinion.

Thx Eric!

In your opinion are there any other down sides, other than added fuel costs, to staying with this cam if I go ahead and run a mix of 100/93 or 110/93 fuel. I can get either of these octane ratings at my local station here.

Did you need to run a vaccum canister with the Magnum 294S for power brakes? I guess that it partly why I was avoiding the longer duration cams initially as I was concerned about vaccum. My current 327 with a Crane Energizer 284 pulled about 10-11" at 900rpm and my brakes worked fine. What kind of vaccum are you getting with the 294S?

What ever I do here I really need to stay with the small base circle configuration otherwise I will need to do more grinding on my rods to clear the cam and I really would like to avoid that if I can. If I want to try something with more duration I will have to order another custom ground bumpstick and try to unload the XS274 to someone with a little less compression.

Tom

Eric is right to run pump gas your going to have to probably run somwhere in the upper 290's for advertised duration, in fact you could probably go 300-305 if you want but thats my opinion and i know alot of people will disagree. Isky has a nice little 300 duration solid cam with 254@.050 and .507 lift on a 108 they call a Z50. It would put your DCR right at 8.0 if you install it straight up wich is ideal with iron heads. It would sound wicked and back every decibel up i bet youde love it. Also in my opinion you could use more head than 200cc on a 400 depending on what cam your going with of course but thats just my opinion. Good luck

NovaGuy73,

Would it be a safe bet that the vaccum with the Z50 in an 11.3:1 400 would be too low to run power brakes? I love the idea of a wicked sounding idle but don't want it to be completely unstreetable. Any opinions on the Z35 or Z30 cams that Isky offers?

Tom

Well if power brakes are a concern run a vacum canister. The 292 dosent look bad but im willing to bet that pump gas would still be marginal. If pump gas is the main focus then id get the Z50 or somthing like it and run a vacum canister. It will be completely streetable with your stickshift. Thats the beuaty of a manual tranny, no stall speed to worry about. smile.gif

Ran some numbers on a couple of Isky grinds last night and it looks like the Z35 will be a little better. Same duration @ 050 but a little more lift and a little less overlap. Gives better bottom and top numbers(probably due to my smallish heads). The Z35 installed on a 112*ICA(-4*) gives me a DCR of 8.2. Might need a little octane boost??? The numbers with this cam from Dyno 2000 are:

HP TQ
2000 138 362
2500 183 385
3000 226 396
3500 283 425
4000 343 451
4500 402 469
5000 446 469
5500 474 452
6000 479 419
6500 475 384

With the Z50 cam:
HP TQ
2000 119 312
5500 460 439
6000 468 409

I am guessing the Z35 will still have a pretty good lope to it as well.

The Comp XS 274 is over 400 TQ from 2000 to 6000 with HP 165 @ 2000 and peaks at 477 @ 5500 but the DCR is 9.1/9.2 installed on 106 ICA, if I go to 114ICA the DCR drops to 8.6. Straight racing fuel territory and will probably never hook with street tires and stock suspension having this much torque!

What do you think??

Actually, I finally got around to tuning the idle mix on my Speed Demon and I found that I could only get about 8" vacuum at 1000 RPM in Park :eek: I wound up changing to a 4.5" power valve.

I use a vac can for sure. Brake pedal was very hard without it. Now the brake pedal is "acceptable" and I have power brakes as long as I am not caught in major stop-and-go traffic. The can has a check valve that keeps a vacuum after deceleration when vac levels are higher than idle.

The 294s is on the ragged edge of what I personally consider streetable. More than that I personally would not try on anything less than a full time strip car - too lumpy and idle becomes unstable. The 294s idles between 850-950 RPM in gear and sounds wicked IMO. It is not the rock steady idle speed that I once had with the 282s.

As for your current cam, I think the major limitation besides octane requirements would just be top end. It should pull to 6000 easy enough, but it just might make too much TQ off the line to hook up. You might want to move some of that power up in the RPM band where you can use it. That's the problem I had with my Comp 282s.

Eric,

Do you have the cam specs on the 294S that you could send to me? I'll run that one through Dyno2000 program and see how it compares to the Isky Z35 cam. I think the Z50 cam would be a little too much and like the numbers show, with everything else being equal, my combo likes the Z35 much better. I am wondering since you are running the 294S in a 383 if I would see a little more vaccum with the added air flow in a 400??

Tom

those cylinder heads are prety ineffecient, if you bolted on a pair of Vortec heads the comp ratio would be the same, but the Vortec combustion chamber is light years better than the old dbl hump heads. Dynamic compression ratio is only part of the equasion. you guys are too hung up on the desktop dyno stuff.( IMHO sorry) with the right combo of parts, you can run 11.5 compression on pump gas easy.

keep the cam and get better heads. 8')

Doug

Comp 294S = 294* advertsied, 248* duration @ .050" lift, .525" lift, 110* LSA, 106* ICL.

Dr Flowgood, why do you say we're too hung up on DCR? I think bowtie1Z28 used the DCR calculator apropriately to make a good observation. I used it to get my 11.3:1 mill to run on pump premium. True there is more to the equation than just DCR, but it is a pretty useful tool. I think his intention is to replace the heads eventually anyhow - I got the impression he justs wants help for the interim.

ps. the camel humps are ported which IMO probably makes them better than stock Vortecs if the job was done right.

Can you guys help me out here? What is the DCR calculator and where do You get it? I assume it about dynamic compression ratio. Is it a software item? I'v never heard of it.


I'v work too much overtime lately, I guess. I'm out of the loop!


Larry

The reason you probably made more power with the Z35 cam is your heads...step up to an aftermarket head and your power figures will go up conciderably then the Z50 would probably make more power. The Z35 is probably a good pick but your DCR is still a little high for pump gas. I dont know what i concider my limit of streetability as far as cam goes cause a good friend of mine runs an erson 312 268@.050 .575 lift cam in his 350 and it drives great, i know this first hand, and he puts as many miles on his car as the next guy, but it idles around 1300 and the idle jumps around a little. But thats all in personal taste. Also i agree with DR.Flowgood on the desktop dyno thing. Its fun to tinker with but dont let it be the deciding factor, when i compared the dart pro 1 215cc heads to a brodix Track 1 215cc head the power figures were way in favor of the track 1 and the flow figures are very similar.

Thx for all of the opinions!! Eric is pretty much right on the money with my situation here. I do plan on upgrading my heads next year, for now my budget won't allow for a set of Vortecs and the correct intake that I would need to go with them. They way I see it $150 for a cam that will give me something much better than what I had is the more cost effective route right now. If I had $700 or so to blow on a set of Vortecs right now I woudln't, I would wait a little longer and save a little more cash so I could by some better heads such as Pro Toplines or AFR's which should yeild much larger gains than the Vortecs will. As far the the DCR calculator goes it looks to me like it is a good tool but by no means is it going to provide guaranteed real world results. There are way to many variables involved in chosing a cam that I won't ever come close to understanding but the DCR calculator helps make it a little clearer.

Eric & NovaGuy73....I am going to run the Comp 294S tonight in both Dyno2000 and the DCR calulator just for comparision tonight. I want to see how it stacks up to the 3 Isky grinds(Z35, Z50 & Z60) I am considering.

Tom

ldrisner

The DCR calculator can be downloaded Here (http://members.uia.net/pkelley2/DynamicCR.html) It's at the bottom of the page.
George

When you do run them through DD2k watch the overlap. That will be a way to compare how the different cams will idle. The Isky's have a 108 LSA which will create more overlap per degree of duration. Not saying that's a bad thing, just watch out you don't get too huge a cam that won't idle.

BTW The .050 duration will have more to do with the RPM band regardless of advertised duration so I would put the cams in DD2k both ways (advertised duration and 050 duration) and compare.

Good luck.

Eric,

This whole process of choosing a cam is extremely confusing and frustrating :confused: . Don't know if I will ever feel comfortable with any decision but I am confident that the Comp XS274 was not going to be right for my combo. I am pretty sure I have settled on the Isky Z60 grind based on my number grinding and the Isky guys recommendation. The numbers are pretty close to the Comp 294S and I think it leaves a little room for better heads next year. The specs are:

292*dv
259*@ 050
.548 lift
108*Lobe Center(as you indicated Isky's are)
76* Overlap

Might be a litle high on the 050" but since I have a manual trans and will need a vac canister anyway I think I will be fine! Will let you know as soon as I get it back up an running sometime towards the mid/end of May graemlins/hurray.gif .

Tom

For what its worth,

I ran a Comp xe274 hyd cam in my 406 ( with Vortec heads btw) and liked it. standard base circle too.

Since you already have the comp cam , why not give it a try? then you can swap in the bigger cam if you want. that would be a great chance for a "camparison" test. :')

good luck with the motor

Doug

Dr.,

What was your static compression ratio?? I am guessing that you had dished pistons and it was under 10:1. Also another guess is that you used standard 400 rods too, hence the reason you were able to run a standard base circle cam. I think the XS274 would be a great all around daily driver cam for the 400 with the right compression ratio which in my opinion I don't have. Thx for your comments!

Tom

Bowtie,

static compression was about 11.5 it had a 9.000 deck with SRP flat top forged slugs (-5cc reliefs) the rods were eagle 5.7" h beams , I should have mentioned that, sorry I also ran that cam with the stock type 400 rods before that.

I made every effort to smooth any sharp edges on the pistons and the combustion chamber to help curb detonation problems. The engine ran great on Sunoco 94 octane . I played with the timing at the track quite a lot and the car was fastest with 32 degrees total timing. and no pinging. I tried raising the timing with and without race gas added and the car slowed down.

at that time I had a 700r4 trans with a 2500 stall converter and 3.42 gears. I drove it from Michigan to St Louis in 99 for the F body.org national event 3 days after I slapped it together, it was great on the highway, It was a little muddy below 2200 or so , but at 80 mph it would just purr. got ok milage too for a 12 sec car. at the time the super vic for vortecs wasnt out yet , I would have liked to have tried one. carb was a holley 750 vac. ( I was poor) 8-)
I also had a good cooling system. a Griffin rad and a Howard Stewart high flow water pump.

PS, I drilled the steam holes on the Vortecs but I have since swapped over to Dart 230cc pro1 heads and did not drill the steam holes . I believe its more criticle on a cast iron head than aluminum.

well , thats been my experiance with them. Im thinkin about writing up a Vortec head FAQ. to dispell some of the rumors


Doug