here's the deal,
after seeing the results of changing form 1.5 to 1.6 ratio rocker arms I'm wondering if advancing the cam might improve things further.

I started by putting 1.6's on the intake side only, this seemed to give a pretty good gain (based on the fact I had to add fuel in the tune).

I then added 1.6's on the exhaust side. this didn't help any and may have hurt power a tiny bit.

(dragstrip times seem to back both those up)

the cam is installed straight up (0) and even though I crank it up to 6300+rpm (solid roller) I'm begining to think advancing the cam would be a worthwhile thing to do.
Agree? disagree?

engine is a 406ci miniram with compitition AFR210 heads and TPIS 242dur cam.
RJ

 

Interesting. Generally the bigger ratio rockers go on the exhausts, first, to help crutch their weaker flow.

Advancing the cam rotates the torque curve, pivoting at the peak, to the lower rpm side. That boosts the torque below peak at the sacrifice of torque above the peak. Do you need more bottom end? Can the top end stand the sacrifice?

It is difficult to determine if advancing the cam would be a, "worthwhile thing" long distance, or without driving the car.

RACE ON!!!

 

I was supprised too that the exhaust side didn't help.
generally thats what they want you to try first.
the reason I tried the intakes first was because there was a few more CFM of flow available in the heads with the added lift (going from .572" to .602").
the idle did get slightly rougher but nothing else seemed to be affected down low. the gains with the 1.6's was in the 5400rpm and up range.
the dyno run (couple of yrs ago) showed the HP kinda flattening out from 5800 on up, torque was broad and kinda flat as well. I think bigger heads (say 230's) would help the HP at least. but it would take some $$ for heads that flow more than the CNC'd AFR210's (maybe later).
I do have a two piece timing chain cover, so advancing the cam wouldn't be too hard to do. of course it would be a bummer if it lost power and I had to change it back. maybe another dyno run to see what the curves look like now.

 

flip a coin

 

I don’t know anything about a TPIS 242 cam. Is it 242 intake and exhaust? Do you have a cam card with the .050 valve event numbers? I could run some DD2000 simulations. As I understand it. The CNC AFR’s have something like 300/220 cfm @.600 which should support 600 hp in your 406.

I have a nearly similar cams in a 383 and a 427 SBC. Both of my cams are installed 4 degrees retarded.

I was also wondering why your running so low of rpm. 242+ degrees intake should be able to make good power out to the mid 7000’s with a mini ram.

 

I would agree with the miniram I think it would hurt you to advance the cam. I'm also installing mine 4* retarded.

 

I agree those heads would support 600HP, I too am unfamiliar with the cam, could be the weak link ?

 

beats me.
I started out with AFR195's (race ready) and it made 380RWTQ, 350RWHP (might have got more HP with better tune).
switched to the cnc'd AFR210's (no other changes other than porting intake to match and tune) and got 410RWTQ, 416RWHP.

now I change the rockers to 1.6 and the intake side makes more difference than the exhaust side does.

its like the heads are the limiting factor.

the cam is a TPIS #700-701, 242 duration @ .050" (both sides) .572 lift (1.5's at valve) and a 112 lobe seperation. installed at 107 ATDC.

the motor makes power above 6000rpm, it just doesn't make any more power (runs the same times on the strip shifting @ 6000rpm as it does shifting @ 6500+rpm) so I set the rev limiter to 6600 and just shift at 6000 at the dragstrip (I will take it to 6600rpm on road course's if it keeps me from shifting on a straight).

the thing that has me thinking is:
if 1.6's give a more "effective" duration, then the exhaust side isn't going to gain by advancing or retarding the cam (since the 1.6's didn't help any).
on the other hand the intake did gain with 1.6's. so advancing or retarding the cam might help that side.

so if the heads are capable of more HP but its acting like the heads are at the limit then cam timing could be the cause (heck its a pretty big cam and should be able to do a good job).
so there are two possibilitys:
its too advanced, OR its too retarded, for this combo anyway.

guess I'd better play with some simulations before tearing into the motor.

 

The increase in duration from the 1.6 rocker arms is minimal, to non exsistant, depending on whose train of thought you care to follow. The difference is in the lift. If you retard the cam you will swing the torque curve, pivoting around the peak, to raise the torque in the rpm range past the peak. Since HP~Tq x rpm, the power may be increased in the upper rpms, enough, to make the 6000-6500 range more productive. Is there sufficient lower speed torque, now?

RACE ON!!!

PS. What induction do you have on this engine? Could THAT be the limiting factor?

 

When Monty had his mini ram induction I think it had twin 70 mm's

 

If those are the 100% CNC'd ( fully ported ) heads they should flow over 300CFM @ .700 lift. I think AFR eggagerates their flow numbers on their website but only slightly. I would not think the heads are limiting you, look elsewhere, my opinion.

What I would really like to see is the actual flow numbers from your heads if you ever take them off, it would only cost about $50 to get them flowed and show us some unbiased numbers.

 

at the moment I'd say the low speed torque is OK, idle is a little rough (so I put it at 1000rpm). dyno graph shows peak torque pretty much the same (410rwtq) from 4000rpm to 4800rpm, with about 370rwtq at 2500rpm.

induction is: MAF, twin 58mm TB, miniram, ported/reshaped filter housing, K&N.
Exhaust is: 1-3/4" headers, no cat, mandrel bent 3".

RJ

 

the heads were 100% cnc'd by AFR. at the time I bought them AFR's web site showed them flowing something like 283+cfm @ .600"

If I ever take them off I'll get them flowed, but barring a problem that should be awhile.

 

I went out to the AFR site and your right. They say something like 288 at .600

So they might be limiting you somewhat on the upper end, but AFR claims that the 210 fully ported support 600 crank shaft hp

 

RJ, If you have it installed with a 107icl, then it's already advanced 5 degress. i'm running a similar combo. 406/same cam/super victor FI intake and brodix 215 heads. I've got mine installed at 105 icl or 7 degrees advanced. I'm of the belief that Torque is king on a heavy street car, which is why i advanced the cam so much. I originally had a SR on the car, but that turned out to be too much torque for the rear end. So i switched to the SP, but it slowed the car down. Anyway with the cam at 105, i've gone 11.24 at 120 with the SR and 11.30 at 118 with the SP. I'm a little disappointed at the lack of top end outa the SP, but i'm also running thru a stock LT1 exhaust. Conclusion, if you already have the cam at 107, leave it alone, its not worth the work for 2 degrees. If it's staight up at 112, you'd find some low end torque by advancing it and IMO, that would be a good thing.

 

so your saying that a intake center line of 112 ATDC is straight up? not 107ATDC..... (your talking about the TPIS #700-701 solid roller right?)
well that could explain a few things!!!!!!!!

I originally wanted to go with a straight up setting since I'm running a richmond 6spd. the gear ratios are very close together and at WOT the RPMs only drop a "maximum" of 2100rpm (from 1st to 2nd) even less in higher gears. so if I shift at 6000rpm in 1st gear it goes to about 3900rpm into 2nd gear (not too bad). from 3rd gear to 4th gear it only drops 1300 rpm so a shift at 6000rpm puts it at 4700rpm into 4th (all that torque below 4700rpm is not helping me at WOT going thru the upper gears).

hmmm, if your right about the intake center line then I'd be willing to try retarding the cam 2 or 3 degrees just to see how it does.
RJ

 

The term, "straight up" is interchangeable with the term, "split overlap". That means that the intake and exhaust centerline numbers are the same. And because one is measured in cam degrees and the other in crank degrees, the lobe centerline numbers and the lobe separation angle are equal, at "split overlap", hence the term. If your cam card specs a 107* intake centerline and the corresponding opening and closing points, the 5* advance is "ground into" the cam, by the indexing of the cam sprocket location. In short, Yes! Ralph is correct and this is an explanation as to how it works/why.

Your original post states that the cam was installed "straight up". I get the feeling, now that is not the case.

Since you seem to have sufficient bottom end, I would try retarding the cam, to or closer to "straight up". It may help the 6000-6500 rpm range. That MiniRam ought to be good for it.

As an additional point of concern... How are the valve springs? I have seen instances, recentl, of "good" springs holding back the rest of a great package.

RACE ON!!!

 

CFI-EFI,
my cam card states: degree intake lobe to 107 ATDC.
I was taking that to be "0" or straight up so thats what I degreed the cam to.

the valve springs are AFR supplied, don't remember the rating's but they were pretty high, I installed them with a minimum of shims since I didn't plan to go above 7000rpm (I'd have to look it up to tell you just what pressure there at).
what kind of problem have you seen lately? too much pressure or valve float/bounce?

 

OK, you installed the cam "to spec", but that is advanced 5* and not "straight up". The cam grinders know a lot more about this stuff than all of us combined. The way you have it installed SHOULD be about the best. In your case, I would NOT advance it. I think *I'D* query the cam grinder to see if they can shed any light, otherwise, I'd try retarding it 4-5*.

The spring specs won't help me, help you, but again, I'd run them by the cam grinder, to see if they're up to snuff. The amount of shims affect the installed height, and both, seat, and over the nose pressures. Do you know those pressures? Again, I'd run them by the cam manufacturer.

The problem I've seen lately with springs, are those that were too weak. The problems weren't evident. The engine didn't exhibit classic valve float problems. It didn't "break up" at higher rpms, or "shut off" as valve float usually produces. It just sort "laid down" and didn't produce the performance at revs, it should. It would keep revving, just not productively. There must have been some undetected valve bounce. I hope this helps, a little.

RACE ON!!!

 

just rechecked the advertised spring rates.
looks good, TPIS's reccomended spring is about 180lbs @ seat, 440lbs open.
I've got these set at 180lbs @ seat, 460lbs open. they are a little bit stronger spring rate than the TPIS springs.
shouldn't be a problem, but I'm not going to rule anything out totally.
I'll bounce some questions off TPIS and see whats going on.
really its just a matter of time and a few gaskets to change the cam timing. so it might be worth a try.
RJ