DC60 or DC65 cam? 2.8 LS

[lvporschepilot]

I'm on the fence with the client about this one. Spoke with John yesterday about the above two cams and he mentioned DC65 is more of a bigger displacement cam with a more radical ramp I assume putting more stress on the valvetrain. The client is seeing it has >.020 more lift and just a degree or two duration more so naturally he is pushing me to install the DC65 to make the higher numbers believing either cam will operate basically the same in the mid range as they are so similar but with the DC65 making 5-6bhp more up top. Client is looking for a streetable engine but does run at Road Atlanta and VIR and other places >5-6 times a year.

What are the thoughts here with builders? Any experience with DC65? Ports are I 39mm/ E 38mm, twin plug with EFI, headers, 2in/2out RSR muffler. 10.6:1 measured compression, light rods, well balanced.

[KTL]

Those cams will be streetable (it'll run fine at low rpms) but I bet they will be a bit weak on power at the low end of the RPM range. I ran S cams in my single plug, headers + straight pipe race exhaust, mildly ported '78-'79 SC large port heads, Weber 46 carbs, 3.2 SS (with admittedly low compression) and it was a bit sluggish below 4000-4500. Reason I make that comparison is that the DC 60 or DC 65 has somewhat similar duration and lift specs. However the S cam has 4 degrees less lobe separation- 98 vs. 102 for the DC 60 & DC 65. Still a fairly reasonable comparison.

[stownsen914]

Keep in mind that a given cam will behave more mildly in a 3.2 than in a 2.8.

[cmcfaul]

Should be fine. As stated above. A bit less low end power but will breathe better on the top end. Suggest you make the top end as light as possible as that car will likely hit max hp beyond redline.

Chris

[lvporschepilot]

Originally Posted by cmcfaul

Should be fine. As stated above. A bit less low end power but will breathe better on the top end. Suggest you make the top end as light as possible as that car will likely hit max hp beyond redline.

Chris

Chris, so far the only super light components at the top end are titanium retainers and Eibach springs, which themselves are significantly lighter than stock springs. You suggest plunking down the cheddar for titanium valves will make a big difference? Springs are sitting at 88-85lbs on the seat and about 260lbs over the nose.

As far as the rotating long-block assembly is concerned, a solid 250 grams per hole has been removed with light rods and pistons, and the flywheel is an 7.9lbs RSR unit with 9lbs clutch plate. When the entire rotating assembly was balanced the crank had to be lightened a significant amount (not entirely sure re total removed), probably a couple lbs or so in total to account for the lighter other bits. Point being, the bottom end is nimble.

[KTL]

250 grams per cylinder is a LOT of weight removed. Light clutch and flywheel assembly will also contribute a lot to the throttle response. If you go titanium valves then you're into replacing the valve guides for a material that complements the titanium.

What kind of induction system is being served by the EFI?

[lvporschepilot]

Originally Posted by KTL

250 grams per cylinder is a LOT of weight removed. Light clutch and flywheel assembly will also contribute a lot to the throttle response. If you go titanium valves then you're into replacing the valve guides for a material that complements the titanium.

What kind of induction system is being served by the EFI?

I don't think I'll bother with the valves if the guides have to be gone through again. Juice is not worth the squeeze.

Induction is via Jenvey ITBs. Car came from the UK not long ago and I'm just refreshing things. The cams in it before were sort of bizarre to me. Newman cams in the UK make them and the intake and exhaust lobes are identical. Maybe they know something we don't, but I thought exhaust needed to be flowed to around 85% to that of intake...