The need for speed/Question for Gear Heads.

[Guest zfan]

Well I went to the track Friday night and left thinking I should be faster and what to do to go faster? First is this motor running at max potential? Anyway here is my specs on the car:

 

1971 240Z weight is 2820 with me in it.

 

385 sbc

 

Forged 4340 crank

forged 4340 6" H beam rods

Forged JE ultra light pistons 11.0 to 1 compression

Comp cams camshaft 236/242 duration-520/540 lift, 4 degrees advanced, with 110 lobe seperation. Cam card is XR288HR-10

1.60/1.50 roller rockers bring lift up to 553/540.

Canfield 200cc heads with cnc chambers/bowls blended and full radius valve job 1000 miles ago.

Victor jr. intake/port matched.

Holley/Proform 750 dp carb- jets are 75 primary and 81 secondary.

Hooker super comp long tubes

2.5" dual exhaust with H pipe.

 

Transmission

 

Built 1989 Corvette 700r4 with a 9.5" Edge racing converter 3500rpm stall.

1987 300ZXT 3.70 LSD rear end

B.F. Godrich drag radials 235/60-15's

 

My times are all pretty close so it seems like I am out of power with this set up.

 

I ran:

 

1.78 60ft.

330 4.834

1/8 7.390

mph 97.00

1000 9.621

1/4 11.49

mph 120.40

 

I ran 4 times and had one that I just broke the tires lose and ran a 12.0 but the car seems to hit a wall at 11.30/121.97 as that is my best time. I am wondering if a cam change is next or better breathing heads. Any guesses?

 

Mike

[Turbo Meister]

I am wondering if a cam change is next or better breathing heads. Any guesses?Mike

 

Mike,

Before I went Twin Turbo my engine was quite similar to yours, except I had a TH400 trans and Ford 9" rear with 4.11 gears. My best time was 11.15 at 123 mph using the trans-brake to increase launch rpm. If your rear suspension can handle it a t-brake works. Your carb setting seems on the rich side. My best runs were with 69 primary and 79 secondary jets.

If you are street driving the Z I would not make any changes except to lower the compression ratio and then Turbo, Supercharge, or Nitrous the engine.

Hanns

[Scottie-GNZ]

Before you make any upgrades, how much HP did it make on the dyno or how much were you expecting if it was not dynoed? 11.30 @ 121.97 is 390rwhp by my calculator.

[Guest zfan]

Scottie,

 

I have not dynoed this motor as of yet. I really do not trust them for much except for tuning/air fuel ratios.

 

Mike

[Guest zfan]

Hanns,

 

I know this may sound funny but I have always resisted the nitrous thing. I am not going to lie and say I have not thought about it a time or two, but I guess my lack of knowledge in that area has me scared.

 

So many people I have met trash motors on the giggle gas. That said I know Rick B. aka Ricer Rick and a few others swear by it.

 

Super chargers are expensive at this point.

 

If I could go back I would build a low compression single turbo but hind site is 20/20! DAMN!

 

Mike

[Guest white280z]

Mike,

 

You are definately under-cammed. Those heads will breath well with valve lifts well into the mid .700s. But for reliability, I'd stick with the following: 250/260 (@.050) Duration, .600/ .630 lift. - Your car should respond with mid to high 10s!! - providing you have the traction. (your engine is finished making horsepower by 5000 to 5500 rpm Max with your current camshaft. - It will pull beyond this, but very slowly due to your rapidly plummenting torque curve)

 

 

I have a drag racing 75' 280Z (Car featured in the Spring 1996 Zcar Magazine - Awsome V8 Issue) that has had three iterations of engines:

1) 350 CID - in 1988 ran a (best ET) 12.20 at the Enis Motorplex. Equipped with iron 64CC Bowtie heads,Crower mechanical flat tappet .240/246 .545/.555 camshaft, TRW 10.5:1 forged flat top pistons, Hooker 1 5/8 headers, 350TH transmission W/2500 stall converter, 84' Corvette positrac IRS W/3.90 gears. M/T 8" slicks.

2) 391 CID - in 1990 ran a (best ET) of 10.05 at Enis Motorplex . Equipped with iron 64CC Bowtie Heads, Crower Mechanical Flat Tappet 250/260 .600/.630 camshaft, 12:1 Ross Pistons, 1/5/8 headers, 4 link /narrowed (36") Ford 9"/ 4.57 R&P/ M/T 14X32.5 slicks/willwood rear disc brakes, 8 point roll cage.

3) 434 CID in 1993 ran a (best ET) of 9.05 at Enis Motorplex. Equipped with 220 CC AFR Aluminum Heads, Isky 280/286 .730/.760 Solid Roller Cam, Ross 13:1 pistons Crower Roller Rocker Arms, Crower 6" Billet Rods, Crower Billet Crank, Edelbrock Victor Intake, 1030 CFM Barry Grant Carburetor, Powerglide/ transbrake, and TCI 5000 RPM Stall Converter, 1 3/4 Headers (Needed larger, but all that I could find) splayed steel 4 bolt main caps, and on and on and on----.

 

Currently, I still have the 75' 280Z, (described above) an 88' 300ZXT with a TPI 357 (.040 O/S 350 4 bolt main block/ 2.02 FI Heads), and a 1977 280Z powered by a 502 Big Block Chevy.

 

Regards,

Steve

[Guest zfan]

Steve,

 

Do you know of a Company with good techs that I could talk to regarding cam changes. I have talked to Comp and they were ok but not real helpful. I have heard that Crane has good techs.

 

My heads are currently set up for 600 lift max but that could change, that said I still want some driveability too. Its a Hydraulic roller so I know I am limited unless I make a change to Solid roller.

 

 

Mike

[Guest white280z]

Mike,

 

You might want to talk to Ultradyne, or Isky. Erson used to be an excellent source of information, but I do not know if that is true any more. I've learned quit a bit by reading, talking to various camshaft grinders/manufacturers and good old fashioned trial and error. The camgrinders will give you recommendations, but they are just that. There are far to many variables in the equation for any exactness on their part.

 

I, and many others that I know of, have used engine building software. This software utilizes complex algorithyms to calculate HP, Torque, RPM capability, etc. The calculations are based on data such as: engine bore and stroke, (for displacement) camshaft information from a timing card- or manufacturer, compression ratio, carburation, intake manifold type, etc, etc. Some of these programs even have the top manufacturer's cylinder heads available in a drop down menu. All you have to do is choose one of interest, and all of the flowrates/specifications are automatically loaded into the program.

 

I've read several articles from Hotrod magazine, and a few others where they have compared the computed/calculated results, with the actual dyno figures and they are within a few percent of each other. The advantage here is clear, you can build almost any kind of virtual engine, for any kind of application, without the expensive trial and error that plagues almost any engine builder.

 

Regarding lift, high lift cams generate good flow rates with minimum penalty to your torque curve, but they are valve spring killers!! (dropping a valve will instantly transform your engine into a boat anchor) Try and keep maximum lift around .600" to .630". Increasing duration, with a resultant increase in overlap, will allow your engine to breath better, but at the expense of low end torque. You'll quickly find out that all things are a compromise.

GM has done significant research on wide LDAs around 122 on their LS6 engines, and have found good drivability (idle and low end torque) and decent power, and extended upper rpm capability. - So you might want to increase your LDA from 110 to around 112.

 

Sorry to be so long winded, but this is a very complex subject!!

 

Regards,

Steve