Good thread.

Now i've finally got my car running like a trooper i'm going to the dyne in the next couple of months so i'll do a similar thread

 

The 74 L-82 and all the L-82's through 1980 are exactly the same internally except for exhaust, timing, and pollution control. Again, as stated previously and documented with my dyno sheet and video (which will not work with the new photo bucket but witnessed by fellow forum member Karol), my 65,000 L-82 with Mcjack's shorty headers, 2.5 inch duals with Monza turbo mufflers, Holley 650 CFM 4175 vacuum secondary carb, comp cams 1.52 ROLLER TIPPED rockers, not true roller rockers, no pollution control, and 36 degree timing all in 2,500-3,000 RPM did 233 RWHP, with the 3 other pulls at 225-229 RWHP. The other pieces of the puzzle/guess for the OP is that I run a K&N air filter in the stock dual snorkel air cleaner housing and the engine temperature for the dyno run was 160 on a 70 degree day. One last thing, my compression test revealed 160-165 PSI on 7 cylinders with #6 showing 90 PSI (a weak cylinder). If number 6 cylinder had 160-165 PSI like the others, I believe that the dyno pull would probably be around 240 RWHP from an internally stock 78 L-82 that was rated at 220 NET HP in 1978 with my changes. If one assumes that the Mcjacks are good for 8-15 HP and the roller tipped rockers are good for 5-10 HP (if anything), then the OP's L-82 should be around 218-220 RWHP as many have predicted.

Another example of a 78 L-82 4 speed on the same dyno with 100,000 miles on the dyno and compression of 140-145 PSI with 2.5 inch magna flow mufflers, OEM cast iron exhaust manifolds, edelbrock performer intake, OEM Q-jet, and a cam of unknown origin, no pollution control, and an open paper air cleaner resulted in 248 RWHP-Form member Karol.

Hope that helps!

 

Woo Hoo. I got it right at 218!!!

 

+1

If your $hit can't live on a dyno, it damn sure isn't gonna live on the drag strip.. The load is not nearly the same on an inertia dyno compared to real street/track passes... A dyno pull will only last a few seconds... The more power the car makes, the quicker the pull will go.

Eddy current dynos like a Mustang Dyno can/will load the engine a lot hard with the Dyno brake... It's definitely harder on the engine then an inertia dyno...

That being said, I once made 47 pulls in one day on my turbo bike tuning... Just keep the heat down and don't make hot pulls..

I made 10 pulls in one day in my Z06, all of them over 800rwhp and on pump gas/meth... No issues at all.


To the OP, 218rwhp is pretty decent numbers for a stock '74 350.. My stock '71 350 with an L79 cam and headers only made 205rwhp.. That was with no air cleaner and hood open.. Thru a t400.

 

+2 for me getting it right as well!

 

well isn't that funny? a stock L-82 with as much wheel H.P as the factory net rating. just shows the N.H.R.A factor ratings were about right. well done!

 

Me Too! 212 is right between the 206 old carb and the 218 new carb. This is really not right. The same engine might test 200 hp on one dyno and 230 on another. Correction data can be tweeked, calibration can easily be off 10-15%. This is not a perfect science folks.

 

I have got the same numbers from 2 dyno as long as the correction factor is the same. These are very expensive machines and set up correctly should give you approx. the same numbers meaning it will spit out your real RWHP.

That being said they can also be set up to give about any number you want. Ever notice dyno operators almost always ask how much you think your car will make? That could be for setting the peramaters but then it could also be to make the customer happy. Always tell them you have no idea.

My friend has a properly calibrated chasiss dyno, took a few months of phone calls between him and the manufacturer before it finally gave the correct RWHP. He told me he had a Viper day and he said you should have seen all the long faces to point where some of them said the dyno wasn't working properly, they couldn't take the reality of there big bad vipers making way less than they they thought in the bars.

 

Your friends is likely properly calibrated and has the right correction factors imputed and I agree with you they are expensive and should be correct. That said there are many that are setup, maybe right, maybe not and never recalibrated. There are also many operators that have no clue how to set their correction factors and parameters up correctly. 10 to 15% off is not as unusual as you would think.