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camshaft specs

 
tonyleah97 tonyleah97
New User | Posts: 6 | Joined: 12/13
Posted: 01/17/14
06:16 PM

the camshaft i have in my engine is one that came from h-o racing enterprises.
i installed it in the 80's. it was actually made by  norris cams.
i do have the specs on the cam, but there measured at .005".
i'm just interested in the valve timing events @ +050".
at .005" the Intake Valve Opens      40* BTDC    Closes  88* ATDC
            Exhaust Valve Opens     93* BTDC    Closes  47* ATDC
would anyone know what the cam timing events are at +.050"?
it's just something that i want to know. when i talk to people about this cam,
and let them know these figures, they compare it to the figures they have that
are measured at +.050".
any help would be appreciated.  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 446 | Joined: 11/13
Posted: 01/17/14
07:36 PM

what is the advertised duration and duration at .050"?

Does this thing happen to have a massive lope at idle and no power until around 3500 rpm?

i've never seen an intake valve close at 88 deg abdc unless it might be on john forces funny car. maybe it's 66 instead?  

your advertised duration might need to be around 320, that's nuts.

insufficient timing at idle will also contribute to high idle temps.  

tonyleah97 tonyleah97
New User | Posts: 6 | Joined: 12/13
Posted: 01/18/14
04:27 AM

the duration @ +.050" is 231* intake & 242* exhaust.
it has a very nice lope at idle. it's in a 455 and runs like nobody's business.
it has power from when the tci 11" converter flashes, around 2800 rpm, right to 5500 rpm. i have the cam card with the usual lift, duration @ +.050" & intake centerline from h-o racing. and the timing card from norris cams with the valve timing specs measured @ .005".
your reaction is typical to the guys i speak with at the track and car shows.
this is why i wanted to know if anyone had the timing events specs on this cam @ +.050". looks like i may have to degree wheel it myself with the engine in the car.  

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/18/14
04:31 AM

You did not provide the duration at .005". No one can do the math if you don't give us all the info requested.

How much lift?

How much if any advance is ground in?  

tonyleah97 tonyleah97
New User | Posts: 6 | Joined: 12/13
Posted: 01/18/14
06:14 AM

intake duration listed as 308* and exhaust at 320*.
lobe lift is .313". LSA at 113.5*. overlap @ 87*.
obviously centerline are 107* & 120*  

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/18/14
06:37 AM

ok thanks i just calculated the duration. came out the same. that's a slow ramp cam and most likely a hydraulic. looks like that cam likely has 0 degrees of advance ground in but i'm not sure i'm dizzy right now, lol.

it looks like it might have 6 - 8 total degrees of advance installed.

Did you advance it for installation?

that's almost identical to the orig pontiac 041 cam.  

tonyleah97 tonyleah97
New User | Posts: 6 | Joined: 12/13
Posted: 01/18/14
12:03 PM

i did not advance the cam upon installation as per h-o racing.
installed straight up.
i was told it was based on the old ram air 041 cam, but there were changes to the valve timing. and that's what i'm trying to find out, if someone has the specs.
i just figured that some guys might of had the same cam in there engine from this time period, the 1980's, and maybe knew these specs. i believe nunzi romano had a similar cam he was selling around the same time frame.
i love the cam. i'm not changing it. the car runs great with it.
if theres a formula to figure the specifications out, that's great.
otherwise, i will put a degree wheel & dial indicator on it and figure it out that way. i appreciate all your help though.  

shyrgfuh70 shyrgfuh70
User | Posts: 93 | Joined: 12/13
Posted: 01/18/14
09:24 PM

sure, no prob. i had a program/formulae to estimate that with but can't find it yet. i'll keep looking.

tuffnuff might have something.  

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 01/18/14
10:26 PM

Icon Quoteshyrgfuh70:
sure, no prob. i had a program/formulae to estimate that with but can't find it yet. i'll keep looking.

tuffnuff might have something.


OK shy, I'll give him lots to read and hopefully absorb.

When you scratch build an engine, It is very important to understand static vs dynamic compression ratio's when it comes to selecting pistons. It also comes into consideration when choosing a cam and heads.,. Really good combo's do require a lot of planning in advance. Found this info to pass along to all of you. It's long and you got to spend time to learn from it, but if it is of interest to you, it is a good ref for you to use.

It,s obvious some of the guys on this site need to understand the difference between static and dynamic compression ratios, and that's understandable as its a difficult concept to grasp at first, but you need to understand it before selecting a combo's components.

The differance between STATIC COMPRESSION RATIO AND DYNAMIC COMPRESSION RATIO is where the piston is in the cylinder when the valves close and the piston can actually start compressing the REMAINING VOLUME IN THE CYLINDER VS the STATIC COMPRESSION THAT ASSUMES THE PISTON STARTS COMPRESSING THE INSTANT IT LEAVES BOTTOM DEAD CENTER AND STARTS UPWARD ON THE COMPRESSION STROKE!

Let me try and explain, the short version is that the PISTON COMPRESSES NOTHING until BOTH VALVES ARE CLOSED.,. that's the only compression ratio that matters, since that is the only compression ratio the engine ever sees.

Static compression is simply the differance between the cylinder volume at BOTTOM DEAD CENTER (BDC) and its compressed volume at TOP DEAD CENTER (TDC), into the combustion chambers.,. dynamic compression takes into account that on the piston's upward compression stroke, the valves have not yet closed and nothing gets compressed by the piston until they do, that of course depends on the cam and rockers, pistons and connecting rods, the cylinder volume, the rod/stroke ratio, ETC.,used, in the combo, and the rpm levels to some extent. BTW, ALUMINUM HEADS can "usually" operate at a higher dynamic compression simply because ALUMINUM releases heat to the coolant much faster than iron, its the lower heat levels that remain in the cylinder that help prevent detonation.,. when you increase the dynamic compression, the heat levels in the head's combustion chamber rise. The difference in the RATE heat leaves the cylinder allows a slightly higher dynamic compression level from aluminum, before the same HEAT levels are REACHED & MAINTAINED in the combustion chambers

Here's a calculator for static cpr, which you need to figure first

http://www.rbracing-rsr.com/compstaticcalc.html

or

http://users.erols.com/srweiss/calccr.htm

Let me point out a few things, first look at this chart

http://www.iskycams.com/ART/techinfo/ncrank1.pdf

Then lets assume your 350 SB engine has a static compression ratio of 11:1 but you've installed this cam

http://www.cranecams.com/?show=browsePar...lvl=2&prt=5

Looking at the cam specs we see that the effective stroke is not the 3.48" that the static compression ratio is measured from ,at BDC, BUT from about 2.6 inches from tdc where the valves close as the piston moves upward, so your true working compression is closer to 8.1:1 NOT 11:1

Here is a longer and more detailed explanation and also access to the software, to figure dynamic cpr with the cam your using in your engine.

http://cochise.uia.net/pkelley2/DynamicCR.html

http://www.diamondracing.net/cocalc.htm

Here are some different calculators

http://www.kb-silvolite.com/calc.php?action=comp2

http://www.wallaceracing.com/dynamic-cr.php

http://www.smokemup.com/auto_math/compression_ratio.php

Keep in mind that you can easilly run a stattic compressio of 11:1 with aluminum heads if you keep the cam timing in a range so that the DYNAMIC COMPRESSION is CLOSE TO 8:1

Take the time to understand the concept, it's VERY IMPORTANT

read this

http://www.diamondracing.net/cocalc.htm

http://victorylibrary.com/mopar/cam-tech.htm

http://victorylibrary.com/mopar/otto-c.htm

http://victorylibrary.com/mopar/cam-tech-c.htm

http://kb-silvolite.com/article.php?act ... 42f4eb4c49

http://victorylibrary.com/mopar/rod-tech-c.htm

http://victorylibrary.com/mopar/piston_position-c.htm

http://www.iskycams.com/techtips.html#2003

http://victorylibrary.com/mopar/rod-tech.htm

http://www.zhome.com/ZCMnL/PICS/detonat ... ation.html

http://www.chevytalk.org/threads/showfl ... Post397334

If cams are a mystery please take the time to read these, it will get you a good start

http://www.newcovenant.com/speedcrafter ... haft/1.htm
(read LESSONS 1-8)


http://www.wighat.com/fcr3/confusion.htm

http://www.chevyhiperformance.com/techarticles/95298/

http://www.idavette.net/hib/camcon.htm

http://www.centuryperformance.com/valveadjustment.htm

http://www.totalengineairflow.com/tech/valvelashing.htm

http://www.chevytalk.com/tech/engine/Cam_Selection.html

http://www.chevytalk.com/tech/101/Cam_Theory.html

http://www.babcox.com/editorial/ar/ar119736.htm

http://www.symuli.com/vw/camp1.html

http://www.symuli.com/vw/camp2.html

http://home.wxs.nl/~meine119/tech/camqa.html

http://www.chevytalk.org/threads/showfl ... Post200511

http://www.crower.com/misc/valve_timing_chart.html

http://www.speedomotive.com/Building%20Tips.htm

http://chevyhiperformance.com/techarticles/94138/

http://www.aera.org/Members/EngineTech/engine.htm

http://www.zhome.com/ZCMnL/PICS/detonat ... ation.html

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Pontiacman8 Pontiacman8
Moderator | Posts: 5775 | Joined: 02/08
Posted: 01/19/14
08:02 AM

Here's what I came up with using a old formula to figure those specs.

the Intake Valve Opens      1.5* BTDC    Closes  49.5* ATDC
           Exhaust Valve Opens     54* BTDC    Closes  8* ATDC
This may not be 100% accurate but should be close.

This formula does not work for all camshaft specs.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

tonyleah97 tonyleah97
New User | Posts: 6 | Joined: 12/13
Posted: 01/19/14
05:23 PM

thanks. this is exactly what i've been looking for, whether it's exact or not.
i couldn't find a formula to figure this out. can i ask what formula you used?  

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 01/19/14
06:45 PM

Icon Quotetonyleah97:
thanks. this is exactly what i've been looking for, whether it's exact or not.
i couldn't find a formula to figure this out. can i ask what formula you used?


I use Wallace calculator and it's quite accurate, for my needs.
Some dynamic compression ratio calculators (like KBs) ask for an additional 15 degrees of duration be added to the IVC @ 0.050" lift point figure. This works OK on older, slower ramp cam lobes, but the faster lobe profiles may need to have 25 degrees or more added.,. to be accurate.
If the intake valve closing (IVC) point isn't known, it can be calculated.
Divide the intake duration by 2
Add the results to the lobe separation angle (LSA)
Subtract any ground-in advance
Subtract 180
The result does not need to have any amount added to the IVC point, like the KB calculator calls for.

http://www.wallaceracing.com/dynamic-cr.php

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

tonyleah97 tonyleah97
New User | Posts: 6 | Joined: 12/13
Posted: 01/20/14
05:38 AM

thanks again tuffnuff. i don't know why i've never run across that website before. it has just about every imaginable formula you can use on a car. even formulas for figuring out your mortgage.
now when i talk to someone about cam lobe positions, it will make more sense referencing the open and closing points at .050".                                                 when measuring at .005", it does make the cam look wilder than it really is.
thanks again for your help.  

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 01/20/14
07:06 AM

Yep, but looks can be deceiving "if" cam dynamics are not fully understood.,. the 45 degrees on each side of the lobe (acceleration/decelleration ramps) added together, make 90 degrees and this adds earlier lift figures, as well as total advertised duration.
The .050" lift figure, is the cam industry's "accepted" norm.
Here is a pic where it points out the flow window/flow curtain.
Flowcurtainarea

And you welcome

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

mwhite004 mwhite004
New User | Posts: 2 | Joined: 01/14
Posted: 02/05/14
11:30 AM

bruce from canada, this has nothing to do with your static and dynamic compression ratios.i am trying to find someone who has a set of original pistons for my pontiac 400 c.u. i scrapped one piston,i can by another one or a set but they seem to have 8 valve reliefs instead of 4.which would change compression ratios and also the differance in piston weights,i would have to have the crank balanced again. i do not want to do this.i would rather replace the stock piston.if you any info please contact me at.     mwhite004@sympatico.ca    thanks bruce.  

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