scyzoryk

Engine info:
-Rebuild 355 (brand new Hypereutectic Flat Top pistons, forged chevy rods, Brand new Eagle cast crank)
-Drive train: T56 from 1995 z28 + 3.55 gears

Heads (2.02 + 1.6 valves, with .550 max lift spring with 1.5 RR)
Flow numbers:
Intake Exhaust
lift 100 87 87
lift 200 147 139
lift 300 191 172
lift 400 235 192
lift 500 270 198
lift 550 272 201

Compression ratio with above setup will be 9.5:1
The car is 1981 Corvette, with will be 100% street car (rarely sees anything above 5000rpm).

I am looking for 400RWHP with good street manners. and I need good cam/intake/carb combo recommendations.
S.

Atilla the Fun

yeah, uh, good luck with that.

scyzoryk

???

z28freak84

XE282 would work great

Doom86

If you want to make this work you are going to have to change some things. You'll need to be more realistic to get proper advice IMO. That power in a 350 doesn't come anywhere near the RPM you want NA. 9.5cr is also probably not going to work either.

What were you planning for induction?

scyzoryk

I am more concerned about proper street manners, driveability and RWTQ than getting that 400RWHP.
Anything between 350-400RWH will be plenty.
I would like to get a cam with lots torque @ 1500-5500 rpm
S.
ps. The engine will be NA with carburetor. I need advice on proper intake/carb.

NAASBC355

I like the 8-412-8, or at the biggest with those gears, and low comp. ratio 08-422-8 hyd. roller cams. You need to change the springs on those heads to actually match the cam you want to run. Id say 670 street avenger Holley, and a good performer air gap or RPM air gap would do just fine. I don't see anything wrong with that combination dunno if it will do 400 wheel hp tho. I don't have my dyno software up on this computer yet so I cant run a sim. I can see 350-375hp range. Plenty of torque tho.

~Couch

Atilla the Fun

If you go TPI or stroker, then you can have 400 HP at 5000 rpm. But if the 400 HP isn't critical, then THIS cam would be BEST: COMP 08-000-8, 3011/3033-110

NAASBC355

I'd have to disagree every experiance I've had with TPI wheather I did it or someone else usually there is a rather large loss in hp over a Carb. I guess it depends on which TPI you use. Not to mention the vast expense in computerized fuel injection over a carb. I just ran a sim on it and introducing a TPI set up over a 4 barrel lost over 100 hp. As far as that cam I assume it's some personal custom grind you have cooked up like a 206@ .050/ 212 @ .050 which is cool and exactly like 12-408-8 except the lift is much higher, huh interesting a smaller cam than the ones I had suggested, but it would have real high valve lift creating less vacuum, a higher operating rpm band, and those cam profiles are for fuel injection if I'm not mistaken, and if it's "your cam" how is he supposed to get the specs to know if it will work. Not to mention XFI lobes have valve velocities, and lift rates for fuel injection and yet you want to put it on a 110 LCA which a computer cant run so are you suggesting he run 110 LCA fuel injected, or fuel injection lobe designs in a carb. motor. I'm confused. I'd suggest he sticks with conventional stuff. If he wants more lift all he has to do is buy a set of rocker arms instead a custom ground cam. .521/.512 lift is kind of backwards for a carb don't you think. Those specs look more like a turbo cam with a really narrow LCA than anything else IMO. "Best" is relative there is no such thing as "best". Ever changing variables make it impossible to have or make a "best". We haven't even discussed the elevation at which the car will be operating at and already we have decided what would be "best". No one alive can lay down the law without developing, and testing an idea which is "best". Whats "best" for him may not be what would be "best" for any other person that walks up asking the same question. Who's to say what is "best" all we can do is make professional educated guesses.

~Couch

NAASBC355

Comps crappy sim software says with the setup I suggested, and those flow numbers that motor should produce 407 hp @ 5500 leaving the intake runner length needing to be: 24 inches long, from the top of the barrel of the carb down to the valve. So with this power band a good duel plane is required leaving the choices at rpm air gap or performer air gap, now I can't account for rotating assembly weights, and port designs (flow isn't everything), but usually that sim gets within 25-30 hp in either direction of correct. It allows me to see trends that are set by the cam and power curve 400 hp would be an expensive stretch with short block parts getting light enough, but 375 hp isn't out of the question, and using all conventional stuff to get there has it's merrits.

~Couch

scyzoryk

Like somebody said my vette (3200 pounds) will be be my toy with 100% street use, used 1-2 days a week.
I am from NYC, so low elevation and 93 octane fuel avalible ,but since my vortecs are cast iron the cr has to stay around 9.5:1 (correct me if I am wrong). I would love to push it to 10/10.5:1 but I am affraid about detonation.

As for the gears. I still didn't decide what I want 3.55/3.73/4.11

I prefer to go aftermarket non custom grind cam. I was thinking about puting one of those extreeme 4x4 cams (big torque from the idle, and low cam lifts to fit my .550 springs). But if you guys know cams making lots tq and in addition produce good hp # let me know.
S.

Doom86

Messing around with DD2k and that head flow data you posted it looks like that cam that couch suggested is good for what you want. It's peaking at 5500 RPM and staying flat to 6000 RPM. Loads of torque under the curve too.

NAASBC355

I wish my copy of DD2K was compatable with win. 7 or I would have better information thanx for the post!

~Couch

scyzoryk

I emailed Comp cams and they suggested:
COMP Cams 12-423-8
What do you guys think.
S.

NAASBC355

It's all a ballancing act but we have had 11:1 work fine on the street with iron heads. In the summer you have to use NOS octane booster, but we live in Houston. Thats the place down here in Texas one block north of hell. Up there you will have no problems with 10:1. As far as gears don't get into the 4... area. You don't have enough valve train to run out the gear just get a nice 3.73 posi set up and you'd be set. The 4x4 cams are actually for higher rpm power then low end torque it seems. I guess for stomping on the floor and watching mud fly all over. Ive got to stick with the cams I said before

~Couch

NAASBC355

I have that cam in my hand right now. I think thats one step bigger in the series then what I already told you to get, and I think it's a little more than what you really need. If you want torque I still stand by 08-412-8, or 08-422-8 which has the highest hp and torque for your combination. If you think that you want more later you can put higher ratio rockers on the 08-422-8, and effectivly make it the 08-423-8 or close enough that you wouldn't be able to tell the difference, but once you plug in a big cam you can't go back. It's far more common to over cam something than it is to under cam something. The heads determine potential the cam just tells the heads what to do with that flow. As usual I'd say less is more in this case. Who did you talk to at Comp?

~Couch

scyzoryk

Quote:

Originally Posted by NAASBC355

I have that cam in my hand right now. I think thats one step bigger in the series then what I already told you to get, and I think it's a little more than what you really need. If you want torque I still stand by 08-412-8, or 08-422-8 which has the highest hp and torque for your combination. If you think that you want more later you can put higher ratio rockers on the 08-422-8, and effectivly make it the 08-423-8 or close enough that you wouldn't be able to tell the difference, but once you plug in a big cam you can't go back. It's far more common to over cam something than it is to under cam something. The heads determine potential the cam just tells the heads what to do with that flow. As usual I'd say less is more in this case. Who did you talk to at Comp?

~Couch

I emailed them. They send me those :

12-422-8



12-423-8


and also suggested 750cfm carb with performer rpm air gap intake. They said that with by 4bolt engine I shouldn't limit my self to 5000rpm and can easily run it up to 5500/6000rpm.

From the charts it seems that 12-423-8 produces the same tq with more hp in that rpm range (1500-5500) than 12-422-8.

And as far as compression ratio, I called my friend (he is building that engine for me), and we decided to push it to 10:1 (we will use the embossed shim gasket)

S.



.

Orr89RocZ

iTrader: (20)

YOu can get up near 480-500 hp on motor with a 350 but it wont be that streetable. One more racey combo I seen was stock port vortecs with 2.02 valves, 246 duration solid flat tappet cam with .480 lift, single plane intake. makes power, but wouldnt really be that streetable.

My friend had a 350 vortec motor with LT1 factory hyd roller cam and rpm air gap intake/750 carb. Ran mid 13's at 99 mph in a 83 chevy shortbed pickup with 12 bolt rear. Not exactly lightweight. estimate it at 350-360hp because he ran neck and neck with my bolt on L98 which was around 300-310 hp on crank.

NAASBC355

10:1 means I am now on board with the 276 I think that would be a great combination. My only concern now is that you spray those gaskets with copper coat spray on gasket stuff. Those make for good gaskets, but make sure that you have atleast .030-.040" between the piston, and the head, and you should be just fine. The compressed thickness is .010-.011" so as long as you haven't 0 decked it you should have enough clearance.

~Couch

scyzoryk

I checked everything again and with my setup and gm performance .020 composite gasket I should be at 9.8-9.9:1 compression ratio.
So that 276 cam is a go
thanks for help guys and I will post some dyno sheets once I put it in.
S.

NAASBC355

Sounds good one last thing is I would still change the springs on those heads to actually match the cams needs. Just because they can take that kind of lift doesn't mean they will match the setup. That cam recomends 986-16 or 26986-16. They are cheap insurance. While the springs are off check retainer to guide seal clearance. Dial the cam in at no later than 106, but for street use probably better between 102-106. I would hate to see you come this far just to float valves, bend pushrods, or pull studs.

~Couch

Doom86

While I like the XR276HR personally I don't think it's what you want. It's trading your low end power for high end power which IMO is fine since you are going t56, but again it's not what you wanted originally.

Attached is a copy of what DD2003 predicts with the XR264 and XR276 overlay(dotted line). I'm assuming shorty headers and performer RPM intake. Also used 9.8cr and the head flow data you provided.

NAASBC355

try advancing the 276 to a 102 center (+4 over where comp has it) and see what happens I'm curious. I agree that the comp ratio is still a little low, and the smaller cam should have more torque, but Comp has real dyno evedence, and DD2K can't cover all the dynamics involved.

~Couch

scyzoryk

Springs: COMP Cams 981-16 (comp cam recommendation for vortec heads and this cam)

Exhaust: long tube headers with true dual 2.5” chambered exhaust.
Intake: Air gap performer RPM
Carb: …still can’t decide between Street Avenger 670 or 770 (I a leaning towards 670cfm)
S.

scyzoryk

As for dialing the cam...I have no idea how to do it ...
Any good websites for that?
S.
ps. I can ask my friend to help me, but I want to understand whats what...

Orr89RocZ

iTrader: (20)

Article for insight? compressions too high but the ported vortecs and decent duration cam made good power.

http://forums.corvetteforum.com/c4-t...fold-test.html

NAASBC355

I was adressing the guy with Desktop Dyno 2000. You can do it on that sim program he's got. I wish I had a version Win 7 compatable and I would do it, but I don't. As far as actually doing it you just degree the cam see what where the intake centerline is in relation to TDC, and adjust with bushings or chain keyways. Comp uses 106 CL, and I think it would be better served at 102 in your case advanced 4 degrees. If you want to know more about how to do that just go to comps website "how to degree a cam"

~Couch

scyzoryk

What did you meant by "Dial the cam in at no later than 106, but for street use probably better between 102-106. I would hate to see you come this far just to float valves, bend pushrods, or pull studs.
"

scyzoryk

never mind...
I got it
S.
Thanks again!!!

NAASBC355

670 has higher velocity for lower rpm use, 770's the oppisite. I'd say 670. As far as those springs go you need to get a hold of Eric, or Brian or anyone else at comp that can do math. The 981's are meant for an opperating range of 1.700-1.250, and your max cam lift is .510. See any problems here? It will overshoot that springs valve open limit by .060 which amounts to imediate engine failure. I can tell you from experiance you can't install 981's at 1.750 and keep the valve on the seat there's just not enough pressure.

~Couch

NAASBC355

Sorry i mixed up two separate thoughts. The springs, and retainer clearances can cause mechanical failures, the cam timing is just changing the rpm band where the cam will opperate best. Sorry two completely unrelated issues.

~Couch

Orr89RocZ

iTrader: (20)

981's are weak springs. Stock replacements. If you want to run an XE grind with 224 duration, i'd go with 120-130 lbs on the seat minimum. Your expecting to turn 6000-6200 rpm and by then you could have valve float. Comp cams would recommend 986 or 987 springs for something like that 276 cam.

scyzoryk

The one I got are very similar to 987...
S.
ps. 981 was a typo...

Orr89RocZ

iTrader: (20)

981 did you mean 918's? beehives are decent springs for that cam. But anyting in the same class as 987's will work good.

NAASBC355

there are no 918's there are 26918's which are very good springs but a little much i think. They reccomend 986 or 26986. He sent me his spec's he's got what basically amounts to 941 comp springs. Like that crane spring that was so popular when they were still kick'n

~Couch

Tobias05

go with some 4.11's for that T-56. What kind of clutch do you have?

NAASBC355

Hey there Devil gotta disagree. If he used 4.11's he'd basically have no first gear at all. This motor won't rpm all that high 7,000 is wishfull thinking, but it will have boat loads of torque. The cam wants a lower limit of 3.73 to utilize it well. Id say 3.73 or higher.

~Couch