12 replies to this topic

[lefty86]

anyone have any good suggestions on where to set the cam timing with a stage 2 colt cam in an ew4. this car will never see a dyno but i'm sure somebody has already done this. any help would be great.

[Doodson]

I dont know on a street car but on a race car with that cam I put the dist. all the way to the back towards the firewall. So on a street car (maybe about 3/4 of the way back) Do you have an adjustable timing gun?

[lefty86]

i really after the valve timing but this is also very helpful. i don't have a timing light that i can turn back but my car is a race only vehicle. its also totally stripped so there should be far less load. you said yours is all the way toward the firewall, mine is about half way however my head was milled a bit too. do you know what your total advance is and at what rpm do reach full advance. also have you ever messed with the advance curve.

Edited by lefty86, 26 July 2005 - 04:59 PM.

[Doodson]

i really after the valve timing but this is also very helpful. i don't have a timing light that i can turn back but my car is a race only vehicle. its also totally stripped so there should be far less load. you said yours is all the way toward the firewall, mine is about half way however my head was milled a bit too. do you know what your total advance is and at what rpm do reach full advance. also have you ever messed with the advance curve.

<{POST_SNAPBACK}>

Im sorry I dont have that cam rite now , I have the stage3 triflow. I dont remember what it was at when it was in the car , I did have about 210lbs of cranking compression with dome top acura pistons.

[lefty86]

wow 210 is a lot. i just checked mine i only got about 120. thanka anyway

[Doodson]

wow 210 is a lot. i just checked mine i only got about 120. thanka anyway

<{POST_SNAPBACK}>

120 cranking compression ? that cant be rite ? I dont think the car would run with that low.
I think stock is around 160-170

[Gasoline Fumes]

wow 210 is a lot. i just checked mine i only got about 120. thanka anyway

<{POST_SNAPBACK}>

Throttle open or closed?

[gtpilot]

When you install the cam, generally you should be installint it at split overlap @ TDC...varying the cam timing relative to that position is done dependent on CR, intake and exhaust flow numbers and where you want peak torque to come in.

Kirk

[Greg Gauper]

wow 210 is a lot. i just checked mine i only got about 120. thanka anyway

<{POST_SNAPBACK}>

120 cranking compression ? that cant be rite ? I dont think the car would run with that low.
I think stock is around 160-170

<{POST_SNAPBACK}>

It depends on how much valve overlap you have due to your cam.

When Jay and I compared cranking compression numbers at the Runoffs last year, I had 205-210 with a bone stock cam, but Jay's numbers were in the 120-130 range due to having a racing cam with more overlap. Both our engines were 10:1 CR which is the maximum per our rules.

Kirk,

I assume by 'split overlap' you are referring to the technique where you set the crank at TDC, but at the point where the exhaust is just closing and the intake is just opening, and carefully measure the spring heights and adjust the cam gear for equal amount of opening i.e. if the exhaust is open more than the intake, then advance the cam gear, but if the intake is open more than the exhaust the retard the cam gear. Is this what you mean? I assume you use this to get the cam timing in the ball park, and then fine tune the timing on the dyno to get the power band where you want it?

[gtpilot]

Kirk,

I assume by 'split overlap' you are referring to the technique where you set the crank at TDC, but at the point where the exhaust is just closing and the intake is just opening,  and carefully measure the spring heights and adjust the cam gear for equal amount of opening i.e. if the exhaust is open more than the intake, then advance the cam gear, but if the intake is open more than the exhaust the retard the cam gear.  Is this what you mean?  I assume you use this to get the cam timing in the ball park, and then fine tune the timing on the dyno to get the power band where you want it?

<{POST_SNAPBACK}>

Greg,

You got it right!

Kirk

[Buford]

Greg,
Building a street perf EW4 engine now. Want to go .040 over and 10:1 comp.
Which pistons are you guys using? I'm considering the OPM +.040 dished ones.
GUDE will be doing my head and he wants to shave .040 off. Need some guidance here. What is your combination to get 10:1??? How many cc's are your combustion chambers??

Thanks

[Greg Gauper]

Answer.....

I don't know........I basically dropped off a block & head at King Motorsports, wrote a big check, and now have a really good engine that's 8 seconds a lap faster than my previous motor

The pistons are a custom design that Scott & Jim at King came up with. I have no idea what they look like cuz I haven't had the head off since I got the motor, which has run flawlessly in over 12 races. The head is limited prep rules per the GCR i.e. stock valves, no porting or polishing, just port matching. It is 10:1 CR. The pistons have been relieved for valve clearence to run with more duration. We are limited to 0.370" maximum valve lift which is pretty close to stock. The rods are stock but have been race prepped (lightened and polished, with ARP bolts). I run the stock flywheel that has been lightened considerably (by King). I'm running a Walt Puckett 4-1 header from OPM.

I can say that Scott at King Motorsports (and possibly Kirk, he will chime in if I'm wrong) strongly believe in taking as little off the head as possible and getting to your CR with the piston design. My head had very little taken off, just barely enough to insure a flat, clean surface for the head gasket.

I just installed the cam that I got from fellow racer Jay, but haven't had much time to determine what it needs, plus I'm still running a bone stock ECU.

Unfortunately, my season got cut short do to a start-line crash at the June Sprints and my next time out will be next weekend at Gateway in St. Louis.

[gtpilot]

Don,

I am not in favor of decking the head any more than the absolute minimum to get it flat. That said, we use pistons that follow the contour of the combustion chamber very well (pop up with the appropriate valve pockets) to get our compression - and we run zero deck height on the piston to the block.

Getting your head done by Gude...support a RPR dude! What are they billing you for the work? Drop me an e-mail @ [email protected]...

Kirk