GJLS

Well i got a good deal on a new set of Performer rpm's 2.02/1.60 so i called cam motion to order a sd friendly roller cam and Terry Williams recomended this cam

dur@050
220 In
228 Ex
Lift
542 in
524 ex
114 lobe sep.
110 In centerline

I sure hope i dont have piston to valve clearance problems what do you think ?

Jerry

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Black 94 #555
Team Powerdyne


mailto:gjls@home.comgjls@home.com</A>

eatingdodgesforlunch!

You definately need to check piston to valve clearance. I'm probably wrong, but .542 lift sounds really big for SD friendly. Are you planning on porting the heads and intake?

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Nothing strikes faster than Lightning!

FMOS Racing

Those numbers are basically identical to the cam I had in my truck (and that Joe C. now has in his). The difference is that Terry tailors the opening and closing events to keep the vacuum higher on the speed density cams.

Because of the timing of the valve events, there's not much danger of piston-to-valve problems. Matter of fact, the cam I'm currently running is a .574 lift on a 228/234 lobe and it didn't have any problems on a stock Lightning short block.

With the Cam Motion blower cams the exhaust valve is closed before the piston reaches TDC and the intake valve opens very shortly before the piston hits TDC. The .05 overlap angles are actually NEGATIVE. What this means is that even though they're decent duration and good lift, there isn't any signigicant valve opening while the piston is at the top of its travel.

BTW, I lost a little bit on the motor with that cam, but I picked up 5 tenths and 3 mph under boost. Of course your results may be different and its always good to do a piston-to-valve check rather than take other people's word for it.

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Later!
Jeff S.
Lightning #74 in '95 - 11.92@115.2-lotsa mods
Lightning #582 in '00 - 13.36@101.75- Swanson chip
1993 Probe GT - daily driver
1973 Datsun 240Z - project car
Drive 'em like ya stole 'em!


[This message has been edited by FMOS Racing (edited 08-28-2001).]

GJLS

Thanks Jeff i will check the clearance just to be sure.
How did your truck idle with that cam ?


Jerry

GJLS

eatingdodgesforlunch! I'm going to have a friend of mine clean up the ports and match them

Jerry

sstock

Geez, I hate to sound like a negatron here but I really can't see how in the world that cam can work right with speed density. even with the lobe centers spread to 114 and the cam appears to be advanced 4 degrees, what kind of vacuum can this deliver at idle? Jeff can you chime in on the vacuum?
Then again what is the minimum vacuum required for the speed density system to work corectly and reliably? That is a ton of lift and that is nice.
Should work well with those heads, but I'm skeptical that you will be able to live with the cam on a day to day basis. Hate to have you put it together to surge you to death!
Hey Jerry another thing to consider is the fact that your blower has limitations that far exceed the scope of this cam and heads. In other words this combo of heads and cam would be better suited on a blower with more airflow capabilities, like Jeff had with his Vortech. It is all about combinations and the perfect marriage of all the components.
I don't mean to contradict the guys at cam motion, because I'm sure they have way more experience in this arena than I do but, I have a gut feeling it is too much cam, thats all. Maybe Cam motion is not up to date on our smaller blowers
Many of us have benched race these cam, head, blower combinations to death and the fact is that with superchargers especially small ones you dont need alot of intake duration or even a large intake valve to make good power. Remember Crowder's speed density "L" that was running high 11's with 206 degrees of intake duration and under 500 lift as well, with worked over GT 40 heads.
Ken Woodward has just put his AFR 185's in and kept the stock cam although he has 1.7 rockers on them. He will be filling us in on this and I am guesing he will be in low to mid 12's with his Kenne Bell.

Later
Steve

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94 Crimson #2826
Born May 6, 1994
NLOC member #343
Team Powerdyne,
13.49@ 102mph
Wanting 12's

'GREASED'

FMOS Racing

Steve, several people, including Chuck P and Harold N, are already running versions of this cam in speed density blower trucks.

Even though my cam had similar numbers, it used a slightly different lobe profile and it wasn't speed density friendly. It pulled ~13" of vaccuum and you need at least 16" to keep the SD happy.

There's more to a cam being able to pull the vacuum than just the raw cam event numbers. Cam Motion is masterful in the way it grinds the lobe profiles.

And BTW, I had that cam ground when I was running aluminum GT40 heads and a Powerdyne.

Later!
Jeff

lightngsvt

Yep I do have a similar cam in my 93. Still stock shortblock and with 1.9 / 1.6 valve in my Performers there was PLENTY of P to V clearance. Mine was setup for NA/nitrous not an S/C though. Even with a very minimal amount of tuning (thanks Raymond B!) my truck is perfectly acceptable on the street. So dont worry about it, trust Cam Motion and be happy when its all together and running!

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Chuck P
1993#3951 (24k miles, mod'ed and lots of custom parts)
NLOC#138
MiLOC#10

00 Focus ZX3
99 GT conv
91 GT (race/show car- in hibernation)

sstock

Hi all, negatron here again.
I guess I'm a little knuckleheaded here and can't understand how lobe shapes, ie symetrical or asymetrical can change the vacuum pulled on an engine. The .050 duration times are the accepted method of comparing timing from one brand of cam to another. From the .050 duration #'s, the overlap period of a cam can be determined. Now if my understanding is correct on this, the overlap period is the time that both intake and exhaust valve is open at the same time. This is what determines the drivability aspect of the engine, which engine vacuum is a directly related to.
Further, the .050 duration figure is the accepted # that engine builders feel measureable valve flow happens. What happens after the .050 is directly related to the lobe shape in relation to "area under the curve" and opening rates. But IMHO, I cant understand how brand A cam manufacture cam can delver more vacuum than brand B with equal .050 duration and overlap periods. Now after that .050 time all the way up to full lift it is a different story and thats where a quick opening lobe can make more power than a say off the shelfer.
I'm not in total disagreement with what you are saying, but your explaination is not complete enough for me to change my opinion.
I still think the cam is too big.
Lets keep this thread going and bench race this one alittle.
Jump in!
Later
Steve
Later
Steve

------------------
94 Crimson #2826
Born May 6, 1994
NLOC member #343
Team Powerdyne,
13.49@ 102mph
Wanting 12's

'GREASED'

FMOS Racing

Steve, what you're not seeing here is the overlap period. The .050 durations don't give the overlap, they only tell the amount of duration per individual lobe. If you don't know either the starting or ending point of the valve event, just knowing the .050 duration doesn't really tell you much.

On my cam (if I remember right, I'll try to verify this when I get home tonight), the exhaust valve passed .050 closing 5 degrees before top dead center and the intake valve crossed .050 opening 4 degrees later. That cam was actually considered having a NEGATIVE overlap even with those fairly stout lift and duration numbers. Cam Motion achieves that by using rapid intake opening and exhaust closing rates.

Rather than overlapping at TDC of the end of the exhaust/beginning of the intake stroke, the blower cam has more duration before the bottom of the power stroke and after the end of the intake stroke. This gives extra time for the exhaust gases to exit without impinging on the amount of time the intake charge needs to get in. And because the intake is coming in under pressure, there's less need for scavenging and a desire to avoid blowing fuel and oxygen out of the exhaust valve.

That kind of capability is what the custom grinders bring to the table. It's what that extra $130-odd over the cost of an off-the-shelf cam gets for you.

Compare the above cam to an E-cam and you'll think "Oh crap! There's no way that will work!" since with only 220 degrees of duration and .498" lift, the E-cam does have concerns of piston-to-valve problems and the idle is outside of what speed density can accomodate without significant tuning. BUT, it's because of the difference in the individual valve events that its a problem for the E-cam and typically not one for the custom grind.

According to Terry, he has ground similar profile cams to .590 lift on 302s with heads that flowed to that lift without P-to-V problems. And he said the 351 could handle even more because of the way the piston accelerates in the cylinder.

GJLS

Wow so much info Thanks guys for all your Input.
Steve i talked with Terry at cam motion before i ordered a cam and he assured me that this cam will work with a sd system it sounded to me like he know's what these trucks need to make power.

And i also have an EEC Tuner installed so a i can make some adjustments if needed.

Jerry

Thundrn_Lightning

Good discussion.

One of these days, my "nitrous" Cam Motion setup will come to life. I did not specify SD, though, I will be mass air by that time. Interestingly, the numbers on mine look pretty close to the other guys...

Later,

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- Kevin
Black '94 #907

sstock

[QUOTE]Originally posted by FMOS Racing:
[B]Steve, what you're not seeing here is the overlap period. The .050 durations don't give the overlap, they only tell the amount of duration per individual lobe. If you don't know either the starting or ending point of the valve event, just knowing the .050 duration doesn't really tell you much.

Jeff, I understand what you are saying about the start and finish points on the respective intake and exhaust lobes. The overlap period is a direct result of both intake and exhaust durations with the respective lobe separation angles.
And this is my point: if cam motion grinds a cam say at an intake and exhaust duration of 220 degrees on a lobe separation angle of 114 degrees, and the intake lobe centerline of 110 degrees.
The intake valve will open at top dead center and close at 40 degrees abd. the exhaust valve will open at 48 degrees bbdc and close at 8 degrees btdc. Doesnt matter who grinds the cam if those specs are the same the cams opening and closing points as well as the overlap period are going to be the same. So I guess my question is, what does cam motion do to bring said 351 more vacuum than say comp cams with the same cam specs?

Steve

Lightning Struck

You need to know that profile of the lobe to make those calculations/assumptions. Without knowing a few more things about the cam you really can't use the mathematics as a comparison. Try comparing a roller cam to a flat tappet..The ramps are steeper the top of the lobe is much flatter..Profile is what the cam manufacturer can change..Especially if its a roller cam..

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Curt
'93 Red Lightning #4232
http://www.geocities.com/lightning_struck93/index.html

sstock

Curt, I dont see either how profile comes into play, those duration figures are given at the industry standard of .050 lift. Doesnt matter what the lobe is shaped like cause I'm sure they are a little different from manufacturer to manufacturer. So calculations are not assumptions, they are all figured from the 360 degree circle.
Later
Steve

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94 Crimson #2826
Born May 6, 1994
NLOC member #343
Team Powerdyne,
13.49@ 102mph
Wanting 12's

'GREASED'