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Old 01-22-2001, 07:30 AM   #1
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Camshaft intake centerline

I e-mailed Comp Cams, but maybe I can get help by you guys.I have a Comp Cam that is
210/220 Duration
.533/.544 lift(1.6 rockers)
114 LSA
The intake centerline on this cam is 110 degrees,but it is ground with 4 degrees advance.That means that the cam has 106 degree centerline when I installed it "stright up"???
My question is,Should I retard the cam 4 degrees to make the centerline 110 degrees?
I would like to get some extra upper RMP HP.
right now I fall flat on my face at 5000RPM
Low end is not a problem with 175 HP nitrous shot.
What would be the best intake centerline for my combo? Retard or Advance or what?
Any thoughts?
Thanks a million,
Don


------------------
1990 Trans Am WS6
305TPI 700R4

ENGINE:
150hp NOS kit
March underdrive pulleys
Edelbrock headers(JetHot)
Mac off-road pipe
Flowmaster exaust
Jacobs ultra coil
K&N filter
Fulley ported base,
runners,& plenum
Crane AFPR
Hypertech airfoil
Crane 1.6 rockers
210/220 .533/.544 Cam
W/P Torquer heads
Edelbrock TPI Base
Edelbrock TI Runners
Edelbrock 52mm T.B.
TRANSMISSION:
Richmond 3.73's
Auburn posi
B&M Mega shifter
B&M Transpak
Vette servo
B&M 2400 converter
TCI Trans Rebuild
Nitto Drag radials
FUTURE MODS:
The 700R4 is DEAD!!
Neeed to rebuild AGAIN!!
BEST RUN:
12.48 @ 109.23 MPH
(with stock heads,cam,intake,and crappy Pep Boy's tires)

[This message has been edited by Nitro Don (edited January 22, 2001).]

[This message has been edited by Nitro Don (edited January 22, 2001).]
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Old 01-22-2001, 10:11 AM   #2
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If the spec card of the cam reads 110' ICL, then that is where the CL of the intake is. IIRC, most OEM SBC cam were ground on a 106-108 CL, so this cam is already advanced 4'. In order to get a 106', just retard it. BTW, if you are unsure of any cam, always ALWAYS degree it to be sure. Click the image to open in full size.

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Old 01-22-2001, 11:48 AM   #3
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Don,

Like Z28 said, if you install it straight up it will already be 4* advanced - that is ground into the cam.

Also, advancing a cam makes it pull out of the hole harder - retarding it makes it pull harder on the big end.

Good luck. Click the image to open in full size.

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Old 01-22-2001, 01:15 PM   #4
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Your description doesn't sound like changing the cam timing is the answer. Cam timing is a tuning aid, not a repair.

What valve springs are you running? Besides the coil, what ignition? You've got a problem someplace that you need to fix before you try time-consuming tuning tweaks.

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Old 01-22-2001, 04:36 PM   #5
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Quote:
Originally posted by RB83L69:
Your description doesn't sound like changing the cam timing is the answer. Cam timing is a tuning aid, not a repair.


RB,

I agree. I did notice the WP Torquer heads......

Those pups flow less on the exhaust side than stocker 441's......on the order of 139 CFM at .500 lift.

That will not cut it as a match for the rest of the intake package, especially with nitrous. Hmmmm, I'm thinking a set of TFS or similiar flowing heads would open up a whole new deal here.

I'll stick my Johnson out and call it an exhaust flow restriction caused by the heads.

Good luck. Click the image to open in full size.

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Old 01-22-2001, 05:05 PM   #6
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There is a bigger restriction with the Edelbrock headers that have 1 1/2" primaries. Those headers and NOS can't be good.
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Old 01-22-2001, 08:09 PM   #7
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Quote:
Originally posted by Nitro Don:
I have a Comp Cam that is
210/220 Duration
.533/.544 lift(1.6 rockers)
114 LSA
The intake centerline on this cam is 110 degrees,but it is ground with 4 degrees advance.That means that the cam has 106 degree centerline when I installed it "stright up"???
My question is,Should I retard the cam 4 degrees to make the centerline 110 degrees?
To answer these questions - It appears you have the 266HR-14 Comp. "-14" indicating (as you did) a 114 LSA (lobe seperation angle). The intake centerline of 110 indicates that the intakes center (highest lift point of the lobe) should be installed 4 degrees advanced in relation to the lobe seperation angle of 114 degrees. If 4 degrees advancement is "ground" in the cam, if you install the timing chain so it (the timing chain) has "0" advancement (or straight up as many say), in your particular example the cam should be "installed" with the intake centerline at 110 degrees.
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Old 01-22-2001, 09:59 PM   #8
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Or in other words:

Comp Cams Publication #145 - Cam Installation and Timing

(Adobe required)

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Old 01-23-2001, 06:52 AM   #9
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Guys,
I have the S/R Torquer tech sheet that came with the heads.The only problem is that the valve sizes it lists are 2.020"x1.600"
Manley valves.I know that I have the 58cc heads with 1.94"x1.5" valves.That means that the flow numbers it gives on this sheet would not be my flow numbers.That sucks!
But here they are:
.500 lift:Intake:221cmf / Exhaust:166cmf
.400 lift:Intake:205cmf / Exhaust:156cmf
The numbers are at 28" H2O unmodified
Im using the valve springs that came with the heads (according to spec sheet)and they are:
1.250" single spring / Max lift: .560"
Installed height: 1.820"
Pressure: 100lbs closed / 280lbs open
My next question is,can these heads be fully ported to make usable power with my engine combo?Should these heads be junked?
Do you think that the spring are to weak for the amount of lift that I have?
To answer RB's other question,I have the Jacobs ultra coil.Other than that,my ignition is stock.
As far as I know,the Edelbrock TPI headers are 1 5/8" not 1 1/2" as someone said.
What would be my next step?
When I opened this thread I thought I had a cam phasing problem.Now I have a exhaust flow problem?
Thanx for your help,
Don

[This message has been edited by Nitro Don (edited January 23, 2001).]
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Old 01-23-2001, 08:57 PM   #10
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Old 01-23-2001, 10:32 PM   #11
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Who installed the cam,,, and did they degree it in? If they didn't, does the timing gear have multiple marks, for "straight up", advanced, or retarded? And if so,, which symbol did they line it up on?

It's possible with 4 degrees already in the cam,,, and if they set the marks on the gears to "advance",,, you could have 8 degrees advancement,, which is way more than I'd ever run,,, ESPECIALLY with the size cam you're running,, the power would drop off even more rapidly than it's "supposed to" with the TPI. I've got years of experience with carbed cars,, but very little expereince with EFI. Maybe some of the EFI/TPI gurus can enlighten you more,, but I would think with your set up, cam size, and the LTRunners,, that you're engine/car would perform better with the intake center line installed at 112 (2 degrees advancement), or at 114 degrees (straight up).

Make sure what you have is "right" before you start spending a lot of money chasing your tail.
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Old 01-24-2001, 06:08 AM   #12
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BadSS,
I installed the cam myself.I didnt degree it in,but I might have to do it now.
I used a Edelbrock timing set.I installed the cam stright up.I did not advance or retard the timing gears.
The way I see it,If I installed the cam stright up,It is at 110*intake centerline,
but sense the cam is ALREADY ADVANCED 4*
the cam should be at 106* intake centerline.
This is the way I see it. I might be wrong.
I think Im going to have to buy a degreeing kit and check.This doesnt make sense.
Maybe I'll retard the cam 4* and see what happens !
Thanks for your help,
Don

One more thing I forgot to write: When I ran 150hp shot or 175hp shot of nitrous my times were a DEAD EVEN. I dont know if this means anything,but I should be a "little" faster with another 25 HP.
Something just is not right.

I just thought of something else.My valve springs are good up to .560 lift,but I dont think they are strong enough for the cam.
I think I'll replace them.
Also,when I installed the rockers.I tightened them by hand until I felt drag from the pushrod(zero lash),then I tightened them 2 complete turns.To much?
My head is spinning with ideas Click the image to open in full size.

Don
[This message has been edited by Nitro Don (edited January 24, 2001).]

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Old 01-24-2001, 10:19 AM   #13
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Whoa!! 2 turns past zero lash is WAAAAYYYY too much. It should be something more like ½ turn.

What valve springs are you using (mfr & part #)? that was what I was suggesting, that the valves may be floating. Of course, adjusting them too tight will float them too...

If you are running a stock ignition module, then you don't have enough juice to reliably fire the cylinders at high RPM in a N/A motor, and nitrous makes it worse. You might want to call Performance Distributors in Memphis (don't remeber the # of the top of my head) and order one of their modules, it should help alot.

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Old 01-24-2001, 12:30 PM   #14
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-----When I installed the rockers.I tightened them by hand until I felt drag from the pushrod(zero lash),then I tightened them 2 complete turns.To much? ------I put this at the top of my response, even though it was the last thing you said. This very well may be your problem. In fact,,, I’d say if it’s not THE problem,, it’ll be most of it. Like RB said,, set hydraulic lifters at half a turn. That usually falls within pre-load specs of most lifters. This should make a big difference. If I were you, I’d adjust the valves before I did anything else,, “get what you got right”,,, then make a change if needed.

----I installed the cam myself.I didnt degree it in,but I might have to do it now.-------I always do, but 95+% of the time the “quality” manufactures stuff will set up accurately using the “marks.

----I used a Edelbrock timing set.I installed the cam straight up.I did not advance or retard the timing gears------That’s OK, it’s better than if you had set the marks to advance it.

-----The way I see it,If I installed the cam straight up,It is at 110*intake centerline, but sense the cam is ALREADY ADVANCED 4* the cam should be at 106* intake centerline. This is the way I see it. I might be wrong.-----The Lobe Separation Angle (LSA) is 114* – that doesn’t change no matter how much you advance or retard the intake lobe center. The amount of intake lobe center change is always based on the LSA number. Since your cam has 4* advancement “built in”, installing the timing chain gears “straight-up” would set the intake lobe center at 110* (LSA still 114* but over all 4* advanced). In order for the intake lobe center to be at 106*, it would have to have an addition 4* advancement at the timing chain for a total of 8* advancement,, LSA would still be 114*.

----I think Im going to have to buy a degreeing kit and check.This doesnt make sense.-----I may get flamed here, even though I always check cam phasing, I don’t know if it’s something an occasional builder needs to buy. If I were you and the valve adjustment didn’t “fix it”, I’d pull the timing chain cover and make double/triple sure the marks are lined up and not off a tooth (no offense meant).

-----Maybe I'll retard the cam 4* and see what happens !-----If the Edelbrock gear set advances/retards 4* at the cam,, if you “retard” the timing gear and it takes 4* degrees from the cam,, your intake center line should be at 114* (matching the LSA),,, making the cam “straight up” (even though the timing gears are retarded). If you do it, don’t expect MAJOR changes,,, I’d guess with the size cam you have,,, you wouldn’t see much decrease in response at low RPM, but you MIGHT pick up 200 more “usable” RPMs up top.

About the 150 and 175 shot running the same. Barring traction problems, if you’re not picking up et,, then you may be running out of fuel pump. That’s a wild guess since I don’t know what pump you’re running. More nitrous has got to have more fuel. More nitrous with out the proper supply of fuel will cause a lean condition and “spark knock”,, which could cause the computer to retard the timing,,, negating any increase in pill size.
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Old 01-24-2001, 01:49 PM   #15
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Don,

You've gotten some good advice in this thread, so I'll try to focus on what I think may help you the most.

-As RB said, you have WAY WAY overtightened your rockers. I suggest 1/4 to 1/2 turn more after the pushrod cannot be spun by hand. Right now, your valves will probably not close all the way, and even if they do, it is not for enough time. THAT is job 1.

-Also, your heads are not junk, but the WP S/R head with small valves does not match the rest of your combination (or, more acurately, your intentions for the combo). You can help flow quite a bit by porting and polishing the heads, paying particular attention to the bowl area (just under the valve seats). The heads you have work okay as an upgrade for a stock 305, but they are the S/R series - and S/R stands for Stock Replacement.

-You cam selection- well, flip thru the Summit,Jegs, or PAW catalogues and look for the Nitrous HP series - those cams are made for nitrous motors. They have 113* LSA's and a whole boatload more exhaust duration than intake. It's exactly what the doc ordered for nitrous motors.

A cam swap, proper lifter adjustment, and some port/polish work on your heads will go a long way toward improving your performance.

Good Luck Click the image to open in full size.

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Old 01-25-2001, 06:35 AM   #16
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BadSS,Box of Rocks,RB,
I want to thank you for all the info and help you've givin me.
As soon as I get the car back from the tranny shop,I will adjust those rockers.
I got the 2 turns method on a web site that claimed I'd get more HP.I'll stick with 1/2
a turn.
I think it will be a good idea to change the springs.The current springs came with the heads and I dont know for sure what they are.
I think its better to remove them.
do you think that 1.265" diameter springs will fit the S/R heads that have 1.250" springs on them now?
The springs that Im looking at are
K-Motion 1.265" springs is good to .610 lift.
What do you think?
As for the Ignition I will put that second on my list.I know that it needs a aftermarket one.
With the Nitrous,I have a knock sensor cut-off switch that I have been using.So engine knock is not an issue.
I might pull the heads and have them sent out to be ported.
With the cam and nitrous,would comp cam
with 230/244 duration .530/.570 lift (1.6) and 112 LSA be a good nitrous cam? It does have alot of exhaust duration.
I now understand the cam centerline.
Thanks,
Don (late for work,co-worker beeping horn) Click the image to open in full size.
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Old 01-25-2001, 10:15 AM   #17
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I know of no 1.25" springs on the planet that will survive at over .500" lift, period. I've seen the K-motion springs advertised, and I've seen the horror stories from people who pshed the envelope, just like the GMPP springs. I don't think they're a good idea.

Call Comp and see what they have to say about springs, since you're using their cam. They'll give you better info than I can. If there is any one place that the suddem failure of a cheap part can cause instant total catastrophic engine destruction, valve springs are it. For the cam you are talking about, you're way into large-diameter spring land; in Comp's product line, that requires the second step in 1.45" springs, bare minimum. Even the lift you have now would require the first step in their 1.45" selection. If you pull the heads I would recommend getting the larger spring pockets cut, it's not that much money. In fact, Crane (maybe Comp too) sells the tool to cut the seats yourself.

That looks like it would be an excellent nitrous cam for a 4-barrel setup. It might be too much for the computer to deal with though. The one you have now should be OK, as long as you are keeping the TPI. You can't get the stock computer to work very well past 220° intake duration in a 350, and 230° is pushing it even for a custom chip, because the idle vacuum will be so low and unsteady. In fact I have been helping a friend for whom we built a 433, which being a 4" stroke tends to tame the excessive duration problem. We used a 230°/236° roller; even with a Haltech computer, getting it to idle right was difficult.

I have no experience with those heads in an application like yours, I can't offer any insight into what their flow or other characteristics are. About the only motors I have run into where people had used them were some mildly warmed-up street motors, for which they seemed to work really well. I've never seen anybody try to get all-out racing level performance from them though.

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Old 01-25-2001, 04:28 PM   #18
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RB,I really cant say what springs I have.I can only go by the S/R spec sheet that says
"Maximum Lift .560". I remember even calling W/P tech line,and was told that with a hyd.
roller I could go up to .600 lift.I now think,"that is a bunch of crap!"
The spring that Comp recomends is a
1.437 dual spring,seat load 120 @ 1.800/
open load 290 @ 1.250
The S/R springs are 1.250 single spring
100 lbs. closed and 280 open, installed height of 1.820
The K-Motion springs are 1.265 single spring with .610 lift 130 @ 1.700" closed and
380 @ 1.150
I would like to stay with the single spring
so I wouldn't have to pull the heads,if I can.
The 230/244 .530/.570(1.6) 112LSA is a TPI computer compatable cam,from Comp Cams.
I think this cam would have a really radical idle stuffed in a 305 Click the image to open in full size.
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Old 01-26-2001, 06:39 AM   #19
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As it turns out,my S/R heads are already machined for 1.440"springs.I just have to use a spring locator that W/P sells.Then I can use the double spring that Comp recomends for my cam.
Don
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Old 01-26-2001, 06:39 AM
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