v8vette84

Well I finally made it back to the track last weekend and got some current times. I have been fighting power issues as the car traps a lot lower than I have seen people with similar mods trap. I ran a 12.2@113. Hell a cam only (plus bolt ons obviously) cc306 95' Z28 on youtube ran 12.4@114. I'm launching the car fairly hard, revving to like 5k and dropping the clutch really aggressively. I'm not dumping the clutch though. The car takes off quick with no wheel spin. I pulled a 1.8-ish 60' with that run I believe. (The time slip is not right in front of me)

My mods are 232/240 .578/.574 110 LSA LE cam, brand new lunati 723925 K5 double springs, 1.6rr's, Ported heads (the flow specs I got put them in between an LE1 head and LE2), massaged intake, 52mm TB, electric WP, 30lb injectors, Long tube headers w/ duel 2.5" exhaust, 3.73 gears, t-56, SLP "Claw" intake with smooth bellows, plus I have used both Madz28's tune and I currently have been using Solomon to try to straighten the car out. The bottom end has like 12k on it with forged rods and ARP rod bolts; stock pistons, eagle crank (yeah I know, I know).

This is in my 84' Corvette.

I have not confirmed what the heads flow, that's on the docket for this winter, I want to send them in to be flow tested. I also have plans to put the car on the dyno before the end of the year.

The trap speed seems quite low for the mods. Others I have seen online with similar setups area trapping 118mph or so.

Does my trap speed look low?

moehorsepower

iTrader: (3)

That does seem low, just for comparison, Back in the day, my 95 Z, lt4 hot (218/228, 525-525) cam, 3.42 rear gear and an auto with a 3600 stall, was running mid 12's, dont remember the trap speed.

SS RRR

iTrader: (2)

What size tire on 3.73 gears? With that cam I think you should have a 4.10 and even higher if you're running a taller rear tire. What RPM are you crossing the traps? Where is your power peak?

v8vette84

I have 275/40/17 on the back (no wheel spin), I cross the line at 6k. Little over or a little under depending on the run. I'm not sure where my peak is, hence why I need to dyno the car. Seat of the pants the power peaks at 6k-6200.

SS RRR

iTrader: (2)

You need to gear down. You need to be crossing the traps at or just a little past your power peak. You are leaving mph on the table with that gearing. If you can, get the car dynoed so you know exactly where your peak is and then look at a gear/mph calculator. If it were my setup I'd put 4.10's if you're running those tires and probably 4.30's if you were going to go with something like a 27" Hoosier.

bufmatmuslepants

iTrader: (3)

Sounds like you need to be shifting around 6800 if it peaks at 6200, where are you shifting now? Your trap speed is low,could be due to shifting early

v8vette84

I'm not sure where the peak is, also if I shifted at 6800 the car would be slower for sure. I shift at or a little over 6k, anything more and you can feel the power start to fall off. I have fought a high rpm power loss problem for awhile now. I have tried new valve springs, lifters(1/8 turn past 0), tunes based on my datalogs and a new air intake to try to figure the problem out. There doesn't seem to be anything that stands out being a problem but according to the mods the car should trap quite a bit faster. So I'm starting to think my heads don't actually flow the numbers I was given when I bought them...

I really need to get this car on a dyno. Then I'll know how down on power she really is.

SS RRR

iTrader: (2)

Yes. Don't guess where your peak is. You can either go to the track and shift at different RPM to see where your best results are, which can be time consuming as **** if the track is crowded, or get it on a dyno and know exactly where it is, then get the gear that would compensate the best.

Casey96SS

I agree with the other guys. That cam definitely needs to be shifted at a higher RPM. Hopefully your Eagle crank is forged. Any idea what your compression ratio is?

Sounds like something is holding you back if it is falling off after 6,200.

v8vette84

Story of my life lately...

Not sure on compression ratio. Stock style head gaskets, stock B-body pistons, I don't think the heads have been messed with cc-wise but I can't say for sure as they are ported.

moehorsepower

iTrader: (3)

Just remember when testing at the track always go by trap speed and not ET,too many factors that are involved.

v8vette84

That's what I'm focused on. Trap speed shows how powerful your car is the way I understand it. ET is made in the first half of the track and the Trap speed is made in the back half.

myltwon

iTrader: (1)

The way I view it is trap speed is the potential of your vehicle, ET is how efficiently you are using it.

Mystery Bird

iTrader: (7)

What track are you running at?

moehorsepower

iTrader: (3)

Basically Trap Speed indicates Horsepower, ET had too many anomalies that could affect it like bog, tire spin, poor shifting ect. this is why sometimes you can hit say a 12.0 et with a 110 speed or a 12.5 with the same speed, because its the horsepower that is pulling you thru..

v8vette84

Empire Dragway

Puck

iTrader: (17)

My much smaller 227/233(I think?) cam still wanted to cross the lines at ~6500. I shifted at 6300 partially because it was a stock bottom end with high miles, and (the real reason) because I couldn't get an accurate shift point with my 700r4 since it uses the ancient shitty method of springs and weights. I got it to shift at around 6300 and left it at that...but it had not slowed down yet every time I rose the shift point so I know it wanted even more.

Possible valve float issues may be cutting you off before your true power peak. Check the installed height of the springs, if installed incorrectly may not have enough seat pressure.

v8vette84

Installed height I haven't checked since replacing the springs but this spring kit was recommended by Lloyd Elliot as I have been talking to him about this issue as well. He said these springs have more than enough pressure for this cam. With my 26918 springs I took off my installed height was 1.740" as recommended by LE. I only swapped to lunati brand parts (Locators, retainers, locks and springs) I guess there could be a big difference but I didn't think it would be enough to suggest the installed height was that far out of whack.

v8vette84

Stock heads or ported?

TravisMcGill2000

iTrader: (2)

I would look into the heads and compression. If the heads wasn't ported right it could slow you. Flow numbers are like dyno numbers. Also is the compression is low that will affect trap speed also. The cam needs to be spun to atleast 6500 also.