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Category: Categories > Engines > Engine Tuning > Tech Tip

Tip #1047360743
Posted: Tue Mar 11, 12:32 AM EST
This tip has been viewed 002513 times

Author's Name: Cliff Prewitt View author's other Tech Tips
Author's Username: p721dmf Ask the Author a Question or View Answers
Tech Tip Rating: Rate This Tech Tip
Number of Reviews: 4 Read All Reviews

Tech Tip

I was asked if I would like to contribute to tech tips by Bill and so this will be my first effort. I am not a scholar or a rocket scientist,just a graduate of the UNIVERSITY of HARD KNOCKS and earn my living with my hands,turning wrenches.I thought for several days about what my article should be about,and decided on something that doesnt cost alot of money or require specialty tools or alot of expertise.*NOTE* THIS WILL ONLY BE EFFECTIVE ON SOLID LIFTERS. I call it a cranking compression valve adjustment.As most of you know, mass produced and even custom made parts have some type of allowable tolerence.This means it isnt going to be perfect right out of the box and may leave room for improvement by the end user, if he/she is willing to spend the time to check it.I have found this to be the case with cams and timing sets and other related valve train components many times.You will need a good compression gauge,feeler gauge set and a remote starter switch helps or someone to turn the engine over for you.Start your engine and let it warm up for several minutes,it doesnt have to get to operating temp,just so you have some heat and lubrication in the engine.Shut it off and disable the ignition-remove the power supply to the ignition.Remove the valve cover that is the easiest to take off and if you are running aluminum heads,make sure the heads are cool enough to remove a spark plug.Pick a cylinder that is easy to remove a plug and get to the rockers.Using the valve lash specs that your cams manuf.suggested,set lash on that cylinder.Install compression gauge and crank engine 5 compression strokes-watch the needle jump.Record your reading.Next make a SMALL change of.002-.003,more or less lash on either the intake or exhaust valve and repeat the compression test,if the compression reading increases,you are on the right track,if it drops,go the other way.You are in effect,changing valve timing,less lash-valve opens sooner,more lash-valve opens later.You are trying to achieve more cylinder pressure/compression which means more HP.Repeat the changes and combination of changes on both intake and exhaust valve on that cylinder until you achieve the highest compression reading.Go to the next cylinder and check it the same way.If it responds to the change,set all of the valves at the lash you used to achieve the best readings.Put it back together and see what the results are at the track.If it works,you havent invested anything but a little time and we all know we never get paid for working on our own cars.Our reward is going faster!!I have seen huge increases using this method,the most dramatic was an increase from 185lbsto225lbs!!Dropped 3tenths off ET and picked up 5MPH.That was an unusual case,but it worked!!Give it a try!!What the hell,unless you broke your valve cover gasket taking it off,it was FREE.Hope you get some benefit from this.Have fun,good luck,go fast and be safe.Cliff Prewitt

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