AZC4Guy

Hey guys, in the course of fixing an oil leak I have all the accessories off of the front of the motor, including the harmonic balancer. Since I already have this much done, I am considering putting in a beefier cam. Here's my drivetrain on my 86 l98: forged 383, dart heads, 1.6 rr's, Pete K beefy tranny, Dana 44 rear end w/ 373's... carbed motor. Here's the current cam:

Brand: COMP Cams
Product Line: COMP Cams Xtreme Energy Camshafts
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,600-5,800 RPM
Intake Duration at 050 inch Lift: 224
Exhaust Duration at 050 inch Lift: 230
Duration at 050 inch Lift: 224 int./230 exh.
Advertised Intake Duration: 268
Advertised Exhaust Duration: 280
Advertised Duration: 268 int./280 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.477 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
Valve Lift with Factory Rocker Arm Ratio: 0.477 int./0.480 exh. lift
Lobe Separation (degrees): 110
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: No
Grind Number: CS XE268H-10

I have been told that this cam is rather mild. Is this true? I'd like a nice lumpy cam but I'm going to drive the car on the street as well as the track. I put less than 2000 miles per year on the car and do NOT have to pass emissions. your opinions are welcome, thanks so much for shairing your expertise.

cv67

Any head work (porting)?

Think solid roller

AZC4Guy

No porting... just dart pro 1's 200's.

conv90

The duration is not mild IMO.
the lift is MILD.
Probably increasing lift will do the the trick.
In addition your heads will be with good flow numbers above .500" lifts.
With the actual mild lift cam you are loosing all the potential of the 200cc. heads.
with hyd. flat tappets I don't know how much you can increase it.
-Beppe-

AGENT 86

Find some more lift. When i was looking for a cam for my flat tappet 86, it seemed big lift and short duration were hard to find with off the shelf stuff.
Maybe a custom ground cam is in your future.

65Z01

With a flat tappet cam your best bet might be to go with 1.7:1 RRs for .54" valve lift.

tequilaboy

I would vote for something bigger, starting with something like 230/236 duration at 0.050.

I've got a comp 503 (224/230 112 lsa hydraulic roller) in a 350 and I think its pretty mild.

I think a 230/236 in a 383 will run similar to a 224/230 in a 350. The increased piston speed of the 383 shifts the power band down something like 400-500 rpm with respect to a 350, so a bigger cam can compensate for this.

With 3.73s you will need something like 5600-6000 rpm to still trap in 3rd depending upon how fast your car really is.

I'm assuming your trap speeds would be somewhere between 112 and 118 mph, so I think your combination requires a bigger cam.

STL94LT1

Here's another choice. A Comp Cams XFI grind, has about the same duration and quite a bit more lift.

Cam grind # 268XFI H13
Duration @ .050 224/231
Lift 520/515 (1.6 rocker ratio)
LSA 113

AZC4Guy

The numbers for the cam are with 1.5 RR's. FWIW

AKS Racing

Are you willing to convert to aftermarket HR or SR? If you are willing to upgrade, then this opens up many more choices.

Yes, that cam is mild. The old flat tappet Comp Cams were rated (in ascending order from mild to HP) 268, 280, 292, 305.

I would be looking for something in the mid/high 230° duration (at 0.050") on the intake for a 383 with lift in the 0.570" range (make sure to check piston/valve clearance and retainer to head guide/seal clearance).

FWIW, my street car has a 248/254° @ 0.050 with 0.670+ lift solid roller and I would not hesitate to drive this across state. It has been on many long trips.

Aaron

AZC4Guy

Aaron, what do you mean by HR or SR? Hydraulic roller, solid roller?

I am willing to convert if it's what I need to get the most potential out of the heads/motor.

Can you take the time to define the differences? Would I need different lifters? I have to make this decision tonight!!!



Thanks, Steve

rodj

By converting to a roller cam you have a much larger choice of hi lift cams.
To convert flat tappet block ,you need a cam button to hold the cam in , new retro fit roller lifters , different pushrods.
Or you can buy the parts from a late roller block (cheap) but requires holes drilled and tapped to mount hardware.
OE roller uses a retainer plate to hold the cam in and a spider in the valley to hold the lifter guides whereas a retro fit lifter has link bars between adjacent lifters to line them up.
Retro fit is drop in conversion but probably more expensive.

AZC4Guy

Sounds like I am stuck w/ the flat tappet options. I have to order a cam tomorrow if I am going to do this. What numbers should I look for in the new cam? Please remember I hve 1.6 rr's.



Thanks,


Steve

cv67

What stall do you have? There are some nice solid flat tappets that will wake the car up..

AKS Racing

Do not forget that an aftermarket roller cam with cam button will typically require a stronger timing chain cover (more expense).

Steve,
Sorry about not getting back to you sooner, as I had to finish work, fix dinner for the kids, and get them into bed.

To identify a cam, you should probably know how much lift you can tolerate. Stock L98 heads with factory retainers and seals typically can not go much above 0.515" lift. I would think aftermarket heads (whether AFR or Dart) should accomodate 0.570" lift. Still try to hit something in the 220-230° duration @ 0.050" and either a 112 or 114 LSA.

Aaron

Pete K

I agree with everone that the am you have is mild for a carbed 383 combo. Flat tappet cams will only tolerate so much lobe lift before it binds the lifter.
I am going to go against the grain and suggest running what you have. I have always been conservative on my cam selection, and got my ***** busted by my buddys. Usually my car ran quicker than their similar (but bigger cam) combos.

cv67

here you go man..Retrofit hyd roller.


This one has your name all over it.


http://forums.corvetteforum.com/show....php?t=1589307

5abivt

I don't mean to be rude, but aren't flat tappet lifters like dinosaur technology ? I thought the whole world would 'wan't to run a hydraulic or a solid roller setup.

AZC4Guy

What is entailed in converting?

Pete K

2 things:
1) Lots of money
2) The need to recheck cam to rod clearances due to the stroker.
Cam lifters, pushrods and cam button are needed. These parts often add up to 1k .
The cam to rod clearances need to be rechecked when swapping a larger cam. Most engine builders give the minimum acceptable clearances (by grinding the rods) to avoid hitting the cam. Bigger cam may involve regrinding. At the very least, rechecking. Jumping to a roller conversion would not be a simple "bolt in" at this point.