dickgi

Hi, I just got a 2003 Z06 and am looking at some upgrades. I have heard that the valve springs should be upgraded so I was looking at what else I could do to improve performance. I have been looking at the Comp Cams 283THR7 camshaft with 26918-16 springs and 7955-16 pushrods. Has anyone done something like that?

COMP Cams: ***** Thumpr, 283THR7<br>High Performance Street/Strip, Rough Idle

COMP Cams: Beehive Valve Springs: Top 1.075" O.D., .650" I.D.; Bottom 1.310" O.D., .885" I.D.

COMP Cams: Hi-Tech Pushrods: 5/16" Diameter, 7.400" Length

foggy

That lobe sep is pretty tight at 109* .. Would be hard imo to tune it due to very low vacuum signal.
You would also need supporting mods at LT Headers, Etc to really get to it's potential.
I'd look at something with less duration AND wider Lobe Sep Angle- 112-114.

dickgi

I do have LT headers, a K&N intake and a 160 degree thermostat. Comp Cams does have something with less duration but the lsa is the same:

http://www.compperformancegroupstore...GEN3CAMSThumpr

dickgi

May opt for the BTR Stage II system 227-230 duration, 0.614" lift and 113 LSA. They offer 0.660" dual springs so that should work and then add a set of chromoly pushrods.

NSFW

I've been geeking out on cam design stuff lately, so I did some math on those two cams, and a third just for contrast...

The ***** Thump and Thumpr both have 109 degrees lobe separation, but the ***** Thumpr has 16 degrees of overlap @ .050 and the Thumpr has just 8, which is quite a big difference. That will give the MT a chopper idle and worse low-RPM behavior, but more top-end performance.

Intake valve closing angles are 36.5 for the MT and 32.5 for the T, making both of them relatively strong at low RPM, at the expense of high RPM power (as compared to cams with IVC around, say, 45-50 or so).

Compare to, for example, TSP's Torquer V2: 232/234 @ 112, or 9 degrees overlap and IVC of 48. Similar overlap and thus similar idle as the Thumpr, but more power-end power and less low-RPM power. Not that I have any real opinion of that cam in particular - it's just an example of a cam that makes different tradeoffs. It has more lift than the other two, but some of the big cam companies will do custom grids for little or no extra charge so you could get the same basic lobe shape with a different lift if you want.

Which cam is better for you depends on what you want and what you're willing to trade off to get it.

brownrd

For an aggressive DD I like the Ed Curtis designed Street Sweeper HT. 228/232 .612-.600 111 +3 This cam has 8 degrees of overlap and an IVC at 42 degrees. I had mine custom ground by Cam Motion because I like their gentle lobe design. Cam Motion does not charge extra for a custom grind and is easy to deal with. Suggest calling them and talking through what you are trying to achieve - they will provide good advice. Also running BTR .660 dual springs and Manton 11/32 push rods. Manton will custom cut push rods to any length that you want and are great to deal with. This cam does not create any issues with piston to valve clearance and will even allow the heads to be milled by up to .030" to increase compression. As always if you go this route check PVC before running the engine. Overall driveability is good with minimal surging after a good tune. Pulls strong from about 2500 rpm to 7000 rpm.

vettenuts

dickgi

Are 11/32" that much stronger?

Time for a C-5

Seems like Comp stopped upgrading their designs years ago. Check out Brian Tooley Racing, Cam Motion, TSP, EPS, etc. I went through the same a few years ago trying to decide on a cam. So many options. Real low LSAs can be tough to tune. How do you plan to use the car...daily, fun toy, x-cross, drag strip? I have a buddy that works for PAC and his engineer coworker suggested a good single spring for longevity and ease on the valvetrain rather than a double spring for a non max-effort build. Lots of people replace the timing chain and oil pump while they're in there. And lifters and trays if the heads come off. Rocker trunnions and valve seals too. Figure out your endgame to plan the entire package. Good luck!

JHrinsin

Talked to the folks at Comp about their LS cams at the SEMA show and yes they are dated and others have past them by with better designs. Supposedly Comp is coming out shortly with a new series for LS (as well as ones for the LT) with much improved lobs design all with the aim of boosting the torque curve especially in the lower and mid range. Time will tell, but it could be very promising.

93Polo

https://www.corvetteforum.com/forums...stiffness.html

dickgi

I bought the 2003 Z06 for fun in the summer (it is not a daily driver or strip car). It has LT headers and 160 thermostat and a tune with 376 rwhp. My target is 410 rwhp so I went with the BTR Stage II system 227-230 duration, 0.614" lift and 113 LSA cam, BTR 0.660" dual spring kit and BTR 11/32" chromoly push rods. The engine only has 45,000Km (or 28,000 miles) so I am thinking the timing chain and oil pump may still be okay. It sounds like you have to drop the oil pan to change the pump so not sure if it is worth it to get something like the Melling high output oil pump...maybe worth considering?

93Polo

I would change both. The oil pan does not have to come off. Further if you are changing the cam both have to come out.

I would go with a Melling stock volume high pressure pump.

I would buy the SAC City alignment tools for the front cover and a good harmonic balancer install tool. The balancer is a known failure point on the Corvette LS1/6, replace it with a Powerbond or ATI depending on budget and goals.

JHrinsin

The PO put together the warmed over LS6 in my '99 FRC and it made 410 rwhp with this combo;

Callaway Honker CAI
descreened 85mm MAF, ported LS6 78mm throttle body, stock LS6 intake manifold, 36 lbs/hr injectors
stock 243 heads (non Z06) with GM MLS head gasket
forged Diamond -2cc pistons (slightly lower static compression ratio, Cometic 0.040 MLS head gaskets would have helped) forged rods, ARP bolts
Comp custom ground 226/230 0.598"/0.608" 113+2 camshaft
Comp trunion kit, 0.675" lift dual springs and Ti retainers
Manley push rods, LS7 lifters in LS2 trays with LS2 chain and Melling HP oil pump
1-3/4" LG P LT headers with cats and X-pipe (ceramic coated)
stock Z06 Ti exhaust
160 degree thermostat
93 octane tune

dickgi

The Melling 10295 oil pump and GM Performance 12646386 timing chain are not that expensive. I found the Powerbond PB1117N balancer is reasonable but the ATI part looks expensive.

93Polo

Looks like a solid parts selection

Time for a C-5

Low 400s is no problem with a BTR II cam and stock 243 heads. I went with the Melling oil pump ($60 if I recall) and replaced the timing chain with a stronger LS2 chain for $45 and used the same gears. These parts have to come off anyway so no extra time/labor. Consider upgrading the rocker trunnions while you're in there too.

dickgi

The rocker trunions are mostly for high rpm protection? I guess the extra spring pressure comes in to play as well.

93Polo

Rockers are lift, RPM, and pressure. I'd go with a bushing style such as CHE, Straub or Smith Brothers. I have installed the Straub kit and the customer service is great.

Go with an ARP bolt on the harmonic balancer, the factory bolt is torque to yield. Getting the torque is difficult, I would not want the complexity of getting the proper yield. ARP bolts or studs for the heads. Bolts work fine but if you plan on doing heads later, the studs can save some time as you won't have to clean the bolts holes out again. Factory heads bolts are torque to yield as well.

Time for a C-5

Yes to both, and more lift from the cam. Another "while you're in there" that could prevent some valvetrain chaos down the road.