AlohaC5

iTrader: (2)

Since winter is setting in and the vette is basically done for the season - its time to think about a possible cam upgrade over the winter in preparation for the 2008 HPDE (Road Racing) season.

I'm currently running a Futral custom cam grind 239/243 .612/.617 113+3 cam with great results - see dyno graph below. However, many consider it a conversative cam for a 383.

I'm thinking about a new Futral custom grind 242/248 .620/.595 111+3 to maximize the horsepower and torque potential of my setup. My concern with a larger cam is losing strong low end torque, which is necessary when coming out of the turns.

I'd like to hear from tuners and those running a LS6 383 with this size cam to learn what your experiences were on the track (good or bad). My goal is to increase my torque numbers across the curve - not peak horsepower.

Should I go larger or leave well enough alone? Are the performance gains worth the potential "driveability" issues since I also drive it around town to work, etc?

hammertime

iTrader: (1)

There is nothing wrong with running a conservative cam. As a matter of fact, I don't see how yours is that conservative. If you are wanting more from the torque curve I doubt going bigger will pay off much.

For your goals, I'd consider a slightly smaller cam with a tighter LSA. What is your static compression ratio and what heads are you running?

AlohaC5

iTrader: (2)

I've been told a tighter LSA (110 or 111) would improve performance on the 383. The compression ratio is 10.9:1. My setup includes: AFR 205 61cc heads with - 5cc Pistons; Ported FAST 90 with P&P LS2 90 TB; YT Ultralite 1.7 Roller Rockers; Comp Cam 921s; Callaway Honker CAI; AR 1 ¾” Headers; and 42# injectors. I agree going bigger is not always better. Was thinking that if I change my cam out for one with a tighter LSA, would going a little larger on the intake and exhaust duration help too.

hammertime

iTrader: (1)

How are you arriving at 10.9:1? I get a much higher 11.8:1 with that chamber & dish combo, plus +.007 deck clearance and .040 thick gaskets. You would have to be below deck or have a much thicker gasket to be that low (or have a larger dish).

Not to refute your claim, but I think your current cam could use the extra compression, if you are at only 10.9. Conversely, if you really are at 11.5 or more, then you may not be able to run less cam without dropping some compression.

AlohaC5

iTrader: (2)

You may be correct. I was told by a tuner that originally installed my AFR heads (not Ed) that my CR was 10.9:1, which seemed a bit low to me, but I wasn't sure how to accurately calculate it after the fact. Are you saying that if my CR is actually 11.5:1 then I should run a larger cam - or stay with what I have? I appreciate your feedback.

Sigforty

I would stick with the cam you have. I am currently running a similar setup with the same Futral cam. I would not see changing the setup as this combo in a 383 works great. I think a bigger cam will produce only marginally bigger numbers and would hurt with low traction. I currently run a 14 turn course at no problem down here and this setup works great getting out the turns. I am not sure of your gearing but I run 3.90s out back.

AlohaC5

iTrader: (2)

I'm running 3.73s with my MN6 transmission. Allan Futral made the recommendation for the larger cam that I mentioned in the first post when I asked him for a "max effort" cam that would still be streetable. I like what I have so I'm still "on the fence" - looking forward to receiving more feedback.

TAF Motorsports

iTrader: (10)

I'd keep it as it is, especially if you drive it around town. IMHO i dont think the gains would warrant the hassle. A tighter LSA on your current setup would have definetly help your torque a little. but you curve looks right where it needs to be. I'd spend the money on chassis and saftey mods if you havent already.

FWIW i'm building a 383 for my AIX camaro 250/254 108 +2 , GM single plane Carb.

AU N EGL

I agree your torque curver is right were you want it. Spend the money on, coolers, ( Oil, and trans), suspension and safety mods.

edcmat-l1

iTrader: (10)

I dont think I would change it either Mike. You've got great driveability, and plenty of power. I know theres always room for more, but I dont know if what you would gain would be substantial enough to warrant the change. Tony may have some insight. Shoot him a PM. May wanna contact Bret too.

AlohaC5

iTrader: (2)

That's what I've been thinking. I thought I would see what the tuners (like yourself!) and other experienced road course drivers (like you Tom) thought based on their experiences, etc. I really like my setup, which has proved to be a very fast combo on the road courses. It seemed like many were running larger cams in the mid 240 range in their 383s. Thanks Ed. Looking forward to getting you in the car at the track next season!

edcmat-l1

iTrader: (10)

Looking forward to that too.
I kinda hate to mess with a good combo, and yours is def a good combo. That being said, if theres a grind out there that will work BETTER without sacrificing something (driveability) then I'm all for it. Tony Mamo would probably be the best source for a recommendation.
And BTW I cant see your compression being that low. Should be at least 11.5:1, depending on the valve reliefs, and the piston out of the hole.
Just got done with a 383. almost 12:1 with a DCR of 8.8. Should run pretty good.

edcmat-l1

iTrader: (10)

Bump for ya Mike!!

AlohaC5

iTrader: (2)

Good info. So much for thinking a 242/248 .620/.595 111+3 would kill my low end torque if you're going to run a larger 250/254 108+2 in your 383 for AIX. I'm definitely interested in seeing your dyno graph once completed. I'm assuming you're running high compression, race fuel, etc. What gears are you running - 3.73s?

TAF Motorsports

iTrader: (10)

Pray

iTrader: (7)

I just switched from a 239/244 .651/.612 112+2 LSK/XER to a 244/248 .612/.615 114+4 XER grind in my 383. I lost three tenths of a point in DCR with the new cam. According to the dyno I lost as much as 50lbtq under 4,000 from there the tq stays the same but the hp goes up 20rw. The car went from trapping 127 to 130 so it can't be that bad. It also feels much better on the street. The throttle response is instant and viscious. Jut leaning into the gas on the street at any thing under 50mph and the tires go up. I will have to get it back on the exact same dyno it was on before but I think the numbers are pretty accurate.

I also agree on your compression ratio. With my 205's at 59cc with a .040 gasket with -7cc Diamond pistions I was at 11.8 SCR and 8.79 DCR with the first cam I was running.

AlohaC5

iTrader: (2)

I'm wondering if the larger cam would be more ideal for 1/4 mile tracks vs. road course applications - but the cam for the Camaro AIX setup is interesting. I'm not sure I'm willing to trade the lose of 50 rwtq at 4K for a gain of 20 rwhp up top. Sounds like your trap speed increased by 3 mph, which could be within a margin of error (multiple runs). What made you decide to go to a wider LSA - 112 to a 114 - since I hear the 383 likes a tighter LSA? If you had to do it all over again - what would you do based on the before and after comparison? Thanks.

TAF Motorsports

iTrader: (10)

Yup, you defintly need to keep your DCR up, regardless of displacement.
12.5:1 8.9DCR

Pray

iTrader: (7)

Well I have to admit that this isn't an apples to apples comparison. I don't have the 205's on the car any more. I am running some PRC LS6 2.5's. But looking at the graph I am down 10-15rwhp and 30rwtq at 3,000 and 3,500. By 4,400 bot are cought up and pulling away. By 5,500 I am up 10rwhp/rwtq and at 6,500 I am up 20rwhp and 10rwtq. I went with the 114+4 because I was having alot of off throttle surging with 112 cams. All the 114 cams I have installed have ran great. Plus, at some point I am going with a 402 or larger engine. I think I may swap back to the other cam since this new cam isn't doing any better in the off throttle area. Like I said, I need to get back on the same dyno and get some real comparison numbers. I am willing to be the 205's would have made more tq and more hp across the board. So I don't think it is all in the cam. The weather between the runs was almost identical. The average mph's are about 3mph gain with the new combo. If I had to do it all over again I would go with the smaller cam on a 112+? with less intake lift. I would use XER lobes on the intake and exhaust.

Brett

AlohaC5

iTrader: (2)

I think I'll keep my current cam with my setup as it is for now next season. I may move up to the larger cam recommended by Futral should I decide to remove the heads and have them decked from .61 to .59 to increase compression (already at 11.5:1), and/or move up from the AFR 205s to the AFR small bore 225 heads. Sometimes its just better to leave it alone especially with the results I was able to achieve with my 383. The need to "mod" and search for that extra bit of HP or TQ is a real sickness for which there is no cure... I appreciate everyone's feedback and recommendations.