Vesa

If choosing one or the other what do you think will be the true difference? Idle quality, vacuum, exhaust sound, low end grunt, TOP HP, torgue curve, HP curve, peak rpm for TQ and HP etc...

Number 1: mechanical flat tappet cam (specs when assembles at 114 intake centerline)
Part nr 216-40450
Grind nr CB294-1/294-1 S-14
Intake open 0.050 14 BTDC
Intake closing 0.050 62 ABDC
Exhaust open 62 BBDC
Exhaust closing 14 ATDC
114 LSA
114 Centerline
Valve lift .340 intake .340 exhaust
Valve adjustment .028 intake .030 exhaust (0.7mm ja 0.76mm)
Duration at 0.050 256/256
635hp at 5800rpm and 634ftlbs at 4000rpm.

Number 2. mechanical street roller:
XTREME ENERGY 11-772-8. INTAKE MASTER 4875, EXHAUST MASTER 4876B, ENGINE CB XR286 R-10, GRIND NUMBER CB XR286 R-10
DUR @.050 int 248 exh 254
LOBE LIFT int .3850 exh .3890
VALVE ADJUSTMENT .016 .018
ROCKER RATIO 1.7 1.7
MAX GROSS VALVE LIFT int .653 exh .660
DUR @ .015 TAPPET LIFT int 286 exh 292
LOBE SEPARATI 110, ADVANCE 4
VALVE TIMING
VALVE SPRINGS 953-16 .015
INT open 37 close 69
EXH open 80 close 32
THESE SPECS ARE FOR CAM INSTALLED 106 INTAKE CENTERLINE

Setup where used:
Car is 3460lb including driver. TH400, 3500stall converter and 3.08 rear end. Merlin all aluminum. 10.1:1 compression ratio. Intake Merlin single plane. AED Holley 870 double pumper. Hookers Super Competition headers 2 1/8" / 30" primaries and 3 1/2" / 10" collectors and dual 3" exhaust system with H-pipe.
Merlin III aluminum 350cc Heads, 2.300/1.880" valves, 1.8 ratio Scorpion Aluminum roller rocker arms:
0.2 144 105
0.3 210 138
0.4 266 165
0.5 310 189
0.6 345 207
0.7 360 218
0.8 360 223

427Hotrod

How many cubes??

JIM

krz-fasc3

Specs say it's a 540. Looks like it hooks well. Both cams look small for a engine that size. Solid roller the way to go. Whats the goal?

TheFinn

10 sec club?

427Hotrod

I see Merlin all aluminum? Does that mean 540? That could mean 632 or more to me??

Comparing a flat tappet to a roller here....so huge differences. You can do well with a flat tappet...but I can tell you THAT one is definitely less than impressive...especially if it's a 540 with Merlin heads on it. Those heads and 3.08 gears are going to be interesting.

More details???


JIM

Vesa

Yes it is 540cid and the block is Merlin X.

Goal is to get to 10.X ET, now I have 11.14, but the track was not in good condition. And I do not want to loose the current street manners (well I do have also a even smaller cam for street usage, but still whatever I choose it should not be any less streetable that the solid flat tappet described above).

That roller has a bit less degrees, but clearly more lift which I think is the worst disadvantage for the flat tappet.

How does the extra lift change the engine? Of course maybe 40-70hp more top end due to lift and roller profile, but how abbout peak torgue and peak hp rpms?

And having 3500stall and 3.08 rear gear what will the change in LSA 114->110 mean?

Or should I order a custom street roller with pretty much the same specs as the above roller, but with 114LSA?

427Hotrod

Take a read through Part II of the articles I wrote covering the 555" motor we just built for Doug *Snowman*'s C-3 named Bruiser. We tested a hyd roller, a hyd roller with solid roller lifters, a solid flat tappet and a solid roller. I detailed a lot of *how* I select cams for these nasty street motors as well as roughly how they compare. Next month the dyno results will be published in part III...but I can try to sneak you some rough ideas before then if you're interested.


http://editions.amospublishing.com/K...1&pagenum=1&f=


JIM

63mako

Here is a similar build. 548 with iron heads. Heads were well ported. If you get ahold of 427hotrod this cam was removed and replaced. Has only dyno time on it. Might be available. Dyno sheet are posted and the cam specs are on post #2. You need a bigger cam to pull the HP your looking for. The 308 gear is probably hurting your times.
http://forums.corvetteforum.com/c3-p...777-hp-na.html

Vesa

I´ll go and read immediately

Vesa

One more stupid question: I understand that degrees determine pretty much the rpm range where the power is produced (maybe together with LSA and lobe profile etc), but does the amount of lift play some role in rpms as well or is it just so that you better give as much lift as your heads, intake etc flow maximum and then you reach max power for each rpm level. And if you choose a bit less lift, the power numbers are cut a bit down in each rpm level?

gkull

HP potential is a function of CFM per intake cycle. head flow, duration and flow numbers at a given valve lift.

The more cfm the heads flow and the more lift decrease the need for big duration and it's negative manners.

With big flow heads like yours I would use a custom roller like the RT series from Comp Cams with around .700 lift and keep the duration near 250 with only 2-4 degrees between I-E because of the 2 1/4 primary size.

Vesa

So street roller 256/258, 114-112 LSA and .700 lift should do the work. Will I get durability problems on street with that high lift and valve pressures?
And if comparing to flat tappet 256/256, 114 LSA, 0.57lift where would the tq and hp peaks move roughly to? From 4000/5800.

gkull

You have 540 ci. You can't base anything on what the manufacturer says about the cam for a 396-454 BBC.

You can't really compare S-flat to S-roller. Street rollers have milder ramps than the racing grinds. The customs lobes from CC with 40XX numbers are pretty easy on the valve train.

What is your max RPM?

GDaina

take a look at comp cams 308AR solid roller, around .650 lift, decent street manners

427Hotrod

Vesa...you have mail.


JIM

Vesa

will print that out and learn it out today !!! Thanks!

Vesa

Now the peak tq is at 4000 and peak hp at 5800 and redline I keep at 6500.