jt1 Posted April 23, 2002 Share Posted April 23, 2002 I went to a HPDE at Carolina Motorsports Park this past weekend, and there was a guy there with a chassis dyno. $50 bucks for two pulls. OK, lets give it a try. Strapped her down and let it rip. Here are the results: rpm torque hp 3400 335 220 3600 340 235 3800 348 250 4000 352 268 4200 340 272 4400 330 280 4600 328 288 4800 317 292 5000 309 295 5200 302 300 5400 297 305 5600 289 308 5800 271 300 6000 262 300 6200 250 295 These results are the averages of the two pulls, interpolated from the graphs, so there not perfect. There are a few wiggles, but the graphs are usually within 5 units of each other. Using the 20% loss rule, this indicated 385 hp and 440 ft-lbs. at the flywheel. Ambient temp was 92 deg., but the humidity wasn't bad. Overall I was pretty pleased considering the car's mild manners. Here's the combo: 4 bolt block, 30 over cola 4340 crank Manley H beam 5.7 rods J&E flattops, 0.020 down, giving 10.1 to 1 comp Pump premium gas Trick Flow twisted wedge heads, stock Ebrock air gap intake Holley 750 DP, not certain of jets, a little rich GM HEI ignition, stock Comp solid roller 268AR 224/224 @ 050, 525/525 lift Hooker block hugger headers into single 3" exhaust with 3" flowmaster Future plans are a MSD, cutting the choke tower off the holley(with a drop base air cleaner, the tower is close to the cover and probably a restriction) and playing with jetting a little, maybe with an O2 sensor. Does anyone have any thoughts, comments, or oberservations? I mainly use the car for some street use and the HPDE/road racing thing, and am mainly interested in a wide flat torque curve more than peak hp. I also met hybridz member bubafett, who is a super nice guy. We talked cars until I had to go out for my next run. All in all it was a great weekend, if a little hot. Quote Link to comment Share on other sites More sharing options...
Mike C Posted April 23, 2002 Share Posted April 23, 2002 Excellent. Those are some swell numbers. What does your car weigh and run? I've always wanted to dyno my 355. I have the Comp solid roller 280AR 236@.050 and .540 lift. My motor is basically a '71 Lt-1. It is a '72 high nickel 4 bolt truck block .030 over with TRW single trough pistons (9.8:1) and Pink rods with ARP bolts. Bottom is studded and has a std/std GM nitrided steel crank. Ported 492 straight plug castings with Manley pro-flo valves, CC titanium 10 deg superlocks and Crand TR series rockers. Victor Jr. and BG 4779S3 (1040cfm), MSD 8561 and 6A. My 3500# car runs 12.7's at 110. I figured about 370 hp at the wheels and 425 at the crank, which seems pretty reasonable looking at your numbers. I shift at 6400 in first and about 6200 after that, what's the powerband like with your cam? I'm going to put the 280 cam in a new motor for the Camaro and go with a hydraulic roller for the existing 355 and drop it in my 'vette, but Comp said to expect a 50hp loss with no other changes. I'm not sure I can stomach that...For what it's worth, my car ran no faster with the BG carb which is completely polished and has the choke horn removed than it did with the 700dp with choke removed but horn attached. It did idle a LOT better (4 corner circuit) and started up cold like it had a choke on it. GM Cowl induction air cleaner (I have the ducted hood) and underdrive crank pulley were REALLY good mods, however. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted April 25, 2002 Share Posted April 25, 2002 John it was nice to meet you too. I hope to see you again soon. Working on my motor now. Quote Link to comment Share on other sites More sharing options...
jt1 Posted April 29, 2002 Author Share Posted April 29, 2002 ** Been gone a few days** Mike, my car weighs 2560 without driver. It's only been to a drag strip once for a T&T night. Best was 7.70 @ 93 mph in the 1/8. No quarters anywhere close around here. I've been pleased with how the car runs, but after looking at grumpy's dyno summary page, a lot of combo's similar to mine are up in the 425 - 450 range. Am I missing something? I might be a jet size or two rich, but nothing major. Any thoughts, any body? Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted April 29, 2002 Share Posted April 29, 2002 Heh, you sure the secondaries are opening? My car dyno'ed pretty close to yours and I've pretty much confirmed that the secondaries are NOT opening. My combo is supposed to be good for 450 at th ecrank and made just 300 at the wheels. No jetting has been done etc. - EFI i smy end plan. Quote Link to comment Share on other sites More sharing options...
Mike C Posted April 30, 2002 Share Posted April 30, 2002 Thanks for the info. The 268 street roller you have is tiny. Figure 268 advertised mechanical is only about the size of a 260 hydraulic when you figure lash into the picture. I think the numbers are excellent. I really like my 280 and it makes a TON of low end torque to the extent I have a massive traction problem. The next size up cam from mine is a 286 if I remember correctly and would easilly put you in the 450hp range at about 6800 rpm. I like the comps without split patterns. Quote Link to comment Share on other sites More sharing options...
dsommer Posted April 30, 2002 Share Posted April 30, 2002 JT1, Sounds like we’re running the same combo (very close any way) I’ve got the exact same cam, Edelbrock Performer RPM intake, 750 Edelbrock carb, Hyperutectic coated skirt pistons.030 over, Eagle rods, Trick Flow 23 deg. Heads. I’m in the process of gutting the interior and getting things under way right now for the build. The questions I have for you are the Trick Flows you’re running an angle plug or straight? What tranny are you running (I’ll be running a T-5) Can I see some up close pics of the header and steering clearance? Thanks a bunch!!! David Quote Link to comment Share on other sites More sharing options...
z ya Posted May 1, 2002 Share Posted May 1, 2002 Man, I wonder if the secondays on mine are not opening up as well. I mean the car is fast but it just seems like it should be faster. All I hear is how everyone is having big time traction problems and mine just squats and goes? I am running drag radials but it just seems like I should be smoking the tires a little????? I just changed the secon- dary spring to the lightest so I will se if that does anything. Quote Link to comment Share on other sites More sharing options...
jt1 Posted May 1, 2002 Author Share Posted May 1, 2002 Well, after reading BLKMGK and zya's posts, I thought these guys are talking about vacumn secondaries. I'm running a double pumper, so it HAS to be opening up all the way. Doesn't it???? Huh???? I got a friend to stomp it wide open while I peered down the carb. Heck, the secondary plates were only going to about 10 o'clock, not anywhere near vertical. I needed another 1/2" travel on the throttle cable to get WOT. Boy am I mega pissed. My throttle cable bracket, which bolts with only one bolt to the rear of the carb, had rotated enough to lose that 1/2" travel. I readjusted it and tightened the daylights out of it. I may need to think about a different bracket. I thought the car was a little weak on the track, but blamed it on the hot weather. Thanks for the help, guys. Now I wonder how much that affected the dyno pulls? dsommer, the twisted wedge heads are angle plug, but not nearly as much as the 292/492 chevy heads. I estimate them to be angled about 15 deg, while the 292's are probably about 30 deg. I'm using the hooker block hugger's and the JTR mounts, and the steering column clears the header by about 1/4", no dimple's required. I tried the block huggers on the 292 heads and the front and rear plugs dead center the tubes, not even close to fitting. I posted some photo's at http://www.picturetrail.com/gallery/view?p=999&gid=798227&uid=545559 Check them out. John Quote Link to comment Share on other sites More sharing options...
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