different size cam lobes (flat)
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
different size cam lobes (flat)
Not much to do yesterday,got cuorious about the supposedly flat cam lobe in my 350. ( its been pulled and torn down,sitting on the garage floor). Using my calipers to measure total lobe size,I was a bit surprised. Exhaust lobes were from 1.525 and most were around the number except two lobes..one was 1.475 and one was 1.479 That doesnt sound like much but the flat lobes were lifting the valves .050 less than the others. The intakes were all around 1.515,= or - a few thousandths. .050 is almost twice as thick as your finger nail. Taint much is it? I guess I expected more of a differance.
Racer
Joined: Dec 2005
Posts: 368
Likes: 4
From: . New Zealand
Sorry to hear this, your cam is toast. This translates to .075" loss of valve lift, which significantly reduces cylinder filling ability, therefore less compressible mixture, therefore less power.
I hope you were not going to refit it, you will need to replace it otherwise it would damage your engine internals by degrading further and putting filings into the oil.
This is unfortunately a very common problem now with flat tappet cams, I advise my clients that it is now wise to change to roller cams, even for relatively stock engines.
I hope you were not going to refit it, you will need to replace it otherwise it would damage your engine internals by degrading further and putting filings into the oil.
This is unfortunately a very common problem now with flat tappet cams, I advise my clients that it is now wise to change to roller cams, even for relatively stock engines.
Pro
Joined: Dec 2006
Posts: 665
Likes: 0
From: wilmington nc
I"d be very interested in hearing more about this cam.
hyd. or solid
how much lift
did you use cam lube and oil addtive
did you do 2500 rpm for 30 mins on break-in
did you use rotella t oil for break-in and did you continue to use rotella t
how many miles on engine
sorry to hear your misfortuine on wiping some cam lobes
hyd. or solid
how much lift
did you use cam lube and oil addtive
did you do 2500 rpm for 30 mins on break-in
did you use rotella t oil for break-in and did you continue to use rotella t
how many miles on engine
sorry to hear your misfortuine on wiping some cam lobes
Le Mans Master
Joined: Jan 2006
Posts: 6,505
Likes: 139
From: Butler Pa
http://www.bradpennracing.com/Products/BIO30.html
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
First, this engine was pulled because of a miss that couldnt be found. I bought the used engine for $120, one cause it has 1965 double hump heads and second cause I want a "builder" 350. This is an excellent canidate
The cam in question is an "Erson". 472 lift on both intake and exhaust. (hyd)
The figures that get my attention are the duration numbers. 296* avertised BUT 228* at .060 lift.
With a loss of around .0750 wear factor on two lobes, I can see why this engine was missing. Futhermore, the lift specs are indentical on both ex. and in. with my measurements showing different, average measurements on the in/ex lobes. This cam is plum wore out.
The guy I bought it from (at work) isnt much of a wrench head, he just wanted a "hot" motor for his truck.
The engine also came with a Tourquer 2 manifold. Lots of good stuff there for a vette but cant see this engine in a (auto)pick up truck...no bottom end. Cam power band is rated 2750 to 5750 RPM.
This is a classic case wrong application,IMO. But then,hot rod trucks are cool too.
Thanks for the input
The cam in question is an "Erson". 472 lift on both intake and exhaust. (hyd)
The figures that get my attention are the duration numbers. 296* avertised BUT 228* at .060 lift.
With a loss of around .0750 wear factor on two lobes, I can see why this engine was missing. Futhermore, the lift specs are indentical on both ex. and in. with my measurements showing different, average measurements on the in/ex lobes. This cam is plum wore out.
The guy I bought it from (at work) isnt much of a wrench head, he just wanted a "hot" motor for his truck.
The engine also came with a Tourquer 2 manifold. Lots of good stuff there for a vette but cant see this engine in a (auto)pick up truck...no bottom end. Cam power band is rated 2750 to 5750 RPM.
This is a classic case wrong application,IMO. But then,hot rod trucks are cool too.
Thanks for the input
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Not much to do yesterday,got cuorious about the supposedly flat cam lobe in my 350. ( its been pulled and torn down,sitting on the garage floor). Using my calipers to measure total lobe size,I was a bit surprised. Exhaust lobes were from 1.525 and most were around the number except two lobes..one was 1.475 and one was 1.479 That doesnt sound like much but the flat lobes were lifting the valves .050 less than the others. The intakes were all around 1.515,= or - a few thousandths. .050 is almost twice as thick as your finger nail. Taint much is it? I guess I expected more of a differance.
As skunk said ... multiply by rocker arm ratio. If you have stock rockers then multiply the "difference" by 1.5 ... result will tell you how close you are to .472". BTW ... expect a 0.002"-0.003" variance due simply to normal "caliper-in-hand" measurement error.
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Burning Brakes
Joined: May 2007
Posts: 945
Likes: 0
From: Ventura California
Use a different method w/ your caliper. First measure around the smallest diameter of lobe to determine base circle, then measure the largest diameter. Subtract first from second; that is what lobe lift is. There's often a difference in base circles not due to wear. Measure both 1'st & 2'nd & find difference for each lobe. If you see alotta variance between "differences" then you have flat cam.
As skunk said ... multiply by rocker arm ratio. If you have stock rockers then multiply the "difference" by 1.5 ... result will tell you how close you are to .472". BTW ... expect a 0.002"-0.003" variance due simply to normal "caliper-in-hand" measurement error.
As skunk said ... multiply by rocker arm ratio. If you have stock rockers then multiply the "difference" by 1.5 ... result will tell you how close you are to .472". BTW ... expect a 0.002"-0.003" variance due simply to normal "caliper-in-hand" measurement error.
Pro
Joined: Dec 2006
Posts: 665
Likes: 0
From: wilmington nc
Well i had to try it on my old cam. allways wondered what it was , looks like it was around a .474 .487 solid lifter cam. I called a lota places with the number off the end of that cam no one knew without sending it to them, which i allmost did. thanks jackson
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
The specs I used were off the Erson web site for that cam model number. Thanks for the advice on cam lobe measurements..I will certianly try that way tomorrow. This could be very interesting.
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
well, that was interesting as well as informative. Thanks for the heads up.I am in your debt. This old dog always like to learn a new trick.
Funny thing I found..I got different measurements on different sides of each lobe.I suspect this is due to "side loading"? Seems towards the edge of each lobe,nearest the front of the engine,measured less.Thats also where the "oil burn" marks were the greatest.
All the base circle lobes were between 1.210 and 1.214.
Lobe peak measured from a paltry 1.472 up to 1.523.
worst difference was .262
best was .312
supposed to be .472 when new.
over all loss from new specs would be (worst lobe) .262. Thats almost half the lift.
Thats a far cry from advertised .472. Taking into consideration my meger measureing skills, adding a few thousandths still leaves much to be desired. This cam is trashed.
Thanks to all that posted. Hope this helps someone thats wonders what a flat lobe on a cam is and why it causes a miss.(or backfire )
Funny thing I found..I got different measurements on different sides of each lobe.I suspect this is due to "side loading"? Seems towards the edge of each lobe,nearest the front of the engine,measured less.Thats also where the "oil burn" marks were the greatest.
All the base circle lobes were between 1.210 and 1.214.
Lobe peak measured from a paltry 1.472 up to 1.523.
worst difference was .262
best was .312
supposed to be .472 when new.
over all loss from new specs would be (worst lobe) .262. Thats almost half the lift.
Thats a far cry from advertised .472. Taking into consideration my meger measureing skills, adding a few thousandths still leaves much to be desired. This cam is trashed.
Thanks to all that posted. Hope this helps someone thats wonders what a flat lobe on a cam is and why it causes a miss.(or backfire )
Le Mans Master
Joined: Jan 2006
Posts: 6,505
Likes: 139
From: Butler Pa
This is so the lifter will spin in its bore. If it didn't spin, the lobe would be gone in no time.
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
Pro
Joined: Nov 2004
Posts: 529
Likes: 113
From: Atlanta area
Remember Ghoast, you have to multiply the lobe dimensions by 1.5 to get valve lift, so .312 * 1.5 = .468 lift @ valve (not bad for caliper-measured vs. the .472 spec lift). And your lowest difference, .262 * 1.5 = .393 lift. That's your problem .472 - .393 = .079 lost lift at the valve.
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
Remember Ghoast, you have to multiply the lobe dimensions by 1.5 to get valve lift, so .312 * 1.5 = .468 lift @ valve (not bad for caliper-measured vs. the .472 spec lift). And your lowest difference, .262 * 1.5 = .393 lift. That's your problem .472 - .393 = .079 lost lift at the valve.
Thanks guys..you all have really helped me thru this.
