grumpyvette Posted June 17, 2009 Share Posted June 17, 2009 have you taken a exhaust back pressure reading at full throttle? did you degree the cam in or only install it per the dot-to-dot marks? what was your total ignition advance at 3000rpm? what was the true F/A ratio? what was the vacuum reading on the intake at full throttle? go any pictures of the spark plugs? 1 Quote Link to comment Share on other sites More sharing options...
rucus01 Posted June 17, 2009 Share Posted June 17, 2009 My exhaust is different than what year one uses for dyno testing, they used long tube headers I have Sanderson cast iron block hugger "headers" manifolds. The intake manifold temps were just over 100 (I am in Phoenix and our daytime temps are running in the high 90's). Water temp in the engine runs about 160 degrees. I can't quite figure that out either since I run a stock Z car radiator, no thermostat only a restrictor plate because of the electric water pump. I admit my exhaust after the manifolds sucks cause the shop didn't listen to what I want and gave me what they wanted. Going to the track this Friday to see what numbers it runs then will probably run a lager straight pipe with no mufflers next time to compare. Still waiting for Year one to respond... If you do the SAE correction for those conditions it shows you should of made 371 at the crank. Poor exahust and a tune that is a bit off, and I can see you dropping to 300 fairly easy, which is about what you made. Do the things we mentioned and tighten up your tune and you should be able to hit 270-280 at the wheels under the same conditions. I would check the things that you did on the motor for problems (exahuast leak,plugs,plugwires,are the secondaries on the carb opening?) Quote Link to comment Share on other sites More sharing options...
fastzcars Posted June 19, 2009 Share Posted June 19, 2009 I second Rucuso1, and double check to make sure the throttle blades are opening all the way. I gained 20 hp on the dyno on that one! : Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted June 20, 2009 Share Posted June 20, 2009 (edited) Year One crate engine advertised as a 400+ hp engine. Dyno results I end up with 236 at the wheels. Seems I lost 100HP in shipping. You all missed it. It's called density air boys. Hot dry phoenix air sucks, bet your at 5000ft +++ loosing 20% of your advertised HP to start with so your at about 320HP max right out of the box at the flywheel. Throw in the drivetrain losses of another 20% and your at about 260HP at the wheels if it's all properly tuned. Nope, your spot on there dude, get it tuned drive it to sez/dni and see what happens It takes alot of motor to run at altitude. Edited June 20, 2009 by dr_hunt Quote Link to comment Share on other sites More sharing options...
JIM73240Z Posted June 20, 2009 Share Posted June 20, 2009 that would be true if we were at altitude be we sit a 1500-1800'. not exactly high like flagstaff or santa fe. it has been in the mid 90's for a few weeks now. jimbo Quote Link to comment Share on other sites More sharing options...
Savage42 Posted June 20, 2009 Share Posted June 20, 2009 Well, you should come to Oregon in the winter, when it's in the 50s and almost no altitude. This will help your numbers!! There is no doubt that hot, thin air will zap a ton of HP. Is it always that hot early in the morning? I'd dyno it then!! Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted June 20, 2009 Share Posted June 20, 2009 Well, you should come to Oregon in the winter, when it's in the 50s and almost no altitude. This will help your numbers!! There is no doubt that hot, thin air will zap a ton of HP. Is it always that hot early in the morning? I'd dyno it then!! This time of year it's always hot in Phoenix and areas around there. Midnight would be a better option. Quote Link to comment Share on other sites More sharing options...
280Zone Posted June 21, 2009 Author Share Posted June 21, 2009 I have heard back from YearOne, they are suggesting to swap to a carb arount 700 to 750 CFM. Well you got the temps about right, temps during the Dyno were aroud 90, and our elevation is about 1100 feet. have you taken a exhaust back pressure reading at full throttle? I have no idea how to do this. did you degree the cam in or only install it per the dot-to-dot marks? The cam is degreed by who ever builds engines for YearOne. what was your total ignition advance at 3000rpm? 15 degrees what was the true F/A ratio? Dyno graph shows about 12 (percent?) at lower RPM's moving hitting about 13 at 5500 RPM what was the vacuum reading on the intake at full throttle? vacuum guage reads 8.5 In-Hg not connected, connected and at idle vacuum reads 20 In-Hg, full throttle vacuum reads 29.5 In-Hg go any pictures of the spark plugs? I'll be pulling them on Sunday. throttle blades are opening all the way? I'll check this on Sunday as well. Quote Link to comment Share on other sites More sharing options...
Savage42 Posted June 21, 2009 Share Posted June 21, 2009 Well, that ignition advance is about half of what it should be. Being that retarded will certainly cut down the power!! You want around 36 degrees at 3500 rpm. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted June 21, 2009 Share Posted June 21, 2009 http://forum.grumpysperformance.com/viewtopic.php?f=56&t=495 you check back pressure with a simple test, explained in this thread Quote Link to comment Share on other sites More sharing options...
John Scott Posted June 21, 2009 Share Posted June 21, 2009 You all missed it. It's called density air boys. Hot dry phoenix air sucks, bet your at 5000ft +++ loosing 20% of your advertised HP to start with so your at about 320HP max right out of the box at the flywheel. Throw in the drivetrain losses of another 20% and your at about 260HP at the wheels if it's all properly tuned. Nope, your spot on there dude, get it tuned drive it to sez/dni and see what happens It takes alot of motor to run at altitude. DA is a bugger considering thin air. Here, day starts at 7000, fast times for all...then will reach over 9000 by late afternoon. Often sees over 10K. Gotta figure it into the equation or you can get real bummed with hp figures. Quote Link to comment Share on other sites More sharing options...
280Zone Posted June 24, 2009 Author Share Posted June 24, 2009 FastZcars was on the money! The back throttle plate were NOT opening! Afer finding that I still bumped the timing up and checked the plugs. Plugs looked good not soaked or white. Converted the carb to manual secondaries and threw the slicks on getting ready for next Friday! So for a large two barrel carb I guess 238 to the wheels isn't all that bad. The air cleaner has proven to be restrictive so I'll run without it to see where I am at now. Current forcast for Friday is rain and 108 degree daytime temp Quote Link to comment Share on other sites More sharing options...
rucus01 Posted June 24, 2009 Share Posted June 24, 2009 FastZcars was on the money! The back throttle plate were NOT opening! Afer finding that I still bumped the timing up and checked the plugs. Plugs looked good not soaked or white. Converted the carb to manual secondaries and threw the slicks on getting ready for next Friday! So for a large two barrel carb I guess 238 to the wheels isn't all that bad. The air cleaner has proven to be restrictive so I'll run without it to see where I am at now. Current forcast for Friday is rain and 108 degree daytime temp Check your timing with a dialback gun at 3000. You want to be in the 32-39 degrees range. With those heads it will prob run best around 34-35. If you get it on the money I would bet you do over 300 at the wheel. Quote Link to comment Share on other sites More sharing options...
fastzcars Posted June 24, 2009 Share Posted June 24, 2009 Glad you found it! But at thoughs high temps, I would agree with Dr Hunt, power will be down no matter what! Good luck on friday! Quote Link to comment Share on other sites More sharing options...
Zfan1 Posted June 25, 2009 Share Posted June 25, 2009 RWHP can be misleading to say the least. I have dyno'd my 2840 lb Z, with me in it and I have a best of 373 rwhp and 400 rwtq. Not great for a 385 sbc with 11 to 1 compression, AFR 210 heads and large hydraulic roller cam. That said it runs 10.80's at 125 in the 1/4. If you do the calculations it comes out to more like 445 rwhp. Dyno guys said torque convertors can screw the numbers up. Like the others said, weather, altitude, tuning, all play a big part in the mix. Good luck at the track and let us know how it went! Quote Link to comment Share on other sites More sharing options...
280Zone Posted June 29, 2009 Author Share Posted June 29, 2009 As luck would have it, the daytime temps reached well over 100 on race night. Still getting no bite off the line all 60 foot times are over 2 seconds, best 1/4 mile run was a 14.0 I guess I'll keep adjusting variables and see where it gets me. Is anyone running close to a 12.0 without LSD? Quote Link to comment Share on other sites More sharing options...
Savage42 Posted June 29, 2009 Share Posted June 29, 2009 I'd think you'd be hard pressed to run a 12 flat w/o an LSD. Hard to push a car with such a limited contact patch. Quote Link to comment Share on other sites More sharing options...
John Scott Posted June 29, 2009 Share Posted June 29, 2009 Is anyone running close to a 12.0 without LSD? Countless slips with 1.9s and 2s with low 12s, with best 12.2 open diff. Best 60's were mid 1.8s. DA 7821' for the 12.2 This was running AZ Zcar springs, front sway bar 225 50 16 555 nittos. With the OBX lsd, added rear sway, car and I gained 30 lbs, 1.701 60' same skinny tires, 12.061 DA 8042'. Guess uncorrected rwhp is 320 Quote Link to comment Share on other sites More sharing options...
HICKL Posted June 30, 2009 Share Posted June 30, 2009 As luck would have it, the daytime temps reached well over 100 on race night. Still getting no bite off the line all 60 foot times are over 2 seconds, best 1/4 mile run was a 14.0 I guess I'll keep adjusting variables and see where it gets me. Is anyone running close to a 12.0 without LSD? I am running 11.50 with best of 1.592 60' with stock dif. Street slicks of course. Quote Link to comment Share on other sites More sharing options...
280Zone Posted July 1, 2009 Author Share Posted July 1, 2009 Are you running an Automatic trans and what stall speed converter? Do you have any burnout secrets you can share so I can hook up better? Quote Link to comment Share on other sites More sharing options...
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