L-72 tune up

[Alss]

[ QUOTE ]
Al, what is the LSA (lobe seperation angle) on the cam? Also, recheck the duration, and if the card lists both, post both the advertised and @ .050" or .010" or whatever numbers. That roller has a lot more duration than the factory 143...I'm gonna guess it has a tight LSA, which is gonna hurt anything down around where you're wanting to put the idle...

And a word of advice, don't go swapping carbs/distributor just yet...I've heard *rumors* of folks getting those factory parts to work "ok"...

[/ QUOTE ]

OK Rob, I have the cam card in front of me here are teh specs:

Lift at valve .575 intake .597 exhaust
lash .024 intake .026 exhaust
duration at .050 256 intake 264 exhaust
advertised duration 296 intake 300 exhaust
exhaust closes 18 Deg ATDC
exhaust opens 66 Deg BBDC
intake opens 18 Deg BTDC
intake closes 58 Deg ABDC
Lobe separation 112
Center line of 110 Deg will make the cam 2 Deg advanced

And no worries about the "stock" parts leaving anytime soon..I WILL make them work. I can build the car just have not alot of experience with tuning them..a new learning curve for me. Thanks for the help.

Albert

[YENKO DEUCE REGISTRY]

I have to agree with Rob on the LSA thing - I too tried a 'better' cam when I built my engine, and kept all else stock. I could not get that thing to idle at less than 1300+/- RPM because of the tight cam.

I then took it out, put in the stock cam that I bought from my local dealership, and was able to get the engine tuned through conventional means - with the help of others

Now, it's a solid 14.2 @ 99MPH runner, looking to get another tenth out of it at SCR9

[Mr70]

With that ET,what RPM does it idle at now Marlin?

[YENKO DEUCE REGISTRY]

[ QUOTE ]
With that ET,what RPM does it idle at now Marlin?

[/ QUOTE ]

The car idles around 900 - special thanks to K.Marple for that.

At SCR7 I was launching just off idle around 1200rpm, but last year at SCR8 I got my spring clamps installed - 2 per side, and continually raised my launch rpm until the final round where I think I was hitting the tires at around 2000 rpm. There was still a slight bog, without tire squeal, so that tells me that I could have raised it higher. I was a bit timid however, because my car has it's 'born-with' original drivetrain - and I do this for fun, not to get my best ET by breaking something.

Not sure who I'll banter with this year without Frankie

[Alss]

Cam was selected as it was suppoed to be close to the stock L-72 cam but be a roller..machinist is very knowledgable and has done alot of motors for me. Going to try the dialback method when I get some time to play. I have had bigger cams work with stock components..this one will just require some time..and I'm learning as I go Thaks for all your inputs

ALbert

[Alss]

OK, had some time to play with the motor a bit..here are the results..set timing by ear and test drove..ran good but.....timing mark(flash) is at 12 o'clock instead of on the tabat 2 o'clock!!!!, almost 50 degress out of place!!..any ideas of what I have skrewed up!! Runs great otherwise..HELP!!!!!!

ALbert

[HS PROFESSOR]

possibly wrong balancer or timing pointer??? if it runs well,doesnt ping, and turns over when hot........crank it up some more!!!! you'll know your close/gone too far when it doesnt crank very fast when hot. good luck....


bob

[TDW]

If it is the original balancer, chances are the rubber has slipped some. Did you check where the timing marks are at TDC? That is where I would start checking things.

[YENKO DEUCE REGISTRY]

Mine was the same way, the balancer was fine, it was just me over compensating for other items that were out of tune! The real test was a shot down the 1320, what felt fine on the street was like a dog on the strip

[Alss]

well, checked the marks at TDC and the balancer mark is dead center of the tab..I rember this from assemble but double checked anyway..balancer mark is in direct line with the keyway (correct?)..gonna check the dwell next then pull out my hair ..have some time tomorrow PM and will go at it again. Thanks everyone.

ALbert