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Old 03-24-2013, 06:19 AM
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781 heads porting , 207/172 or 219/188

Ive ported(mildly) my 781 heads,bowl clean-up and gasket match and was wondering if the larger valves are actually necessary if you don't plan on revving more than 5500 RPM. The ports seem to be large enough where larger valves at that low RPM really wouldn't help the ports flow much more than they already can with the very unshrouded 207 intake valve in place. I wonder if anyone ever bothered to make a flow chart comparing the same head with the different size valves in placeI'm willing to bet the flow chart would not show that much difference till over .500 lift. My experiance with valve unshrouding benefits indicates porting flow benefits,ports being equal and matching the original Stock (cleaned up bowl work done) dimensions are almost as much affected by the unshrouding as an increase in valve size where the larger size valve cannot be sufficiently unshrouded without losing large amounts of compression or increasing the chance of head cracking. It seems if the short turn radius is reduced enough in the mild porting the big valve advantage would be limited. Any advice here or considered theories would be helpful.

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Old 03-24-2013, 07:49 AM
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If you are building a "torque" engine with a mild cam do not worry about it.

if you want horsepower put the big valves in the heads and finish the port job.
The big valves make more power.
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Old 03-24-2013, 10:26 AM
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maybe this will help. go to big block chevy heads.
Stan Weiss' - Cylinder Head Flow Data at 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software

Whatever you decide on. Don't use the stock worn valves. Go for some aftermkt stuff. Flow better and haven't had a million cycles on them.. Also make sure the valve guides are tight, not worn. A dropped/broken valve can ruin your day.

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Old 03-25-2013, 04:43 AM
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Originally Posted by BOBCRMAN@aol.com View Post
maybe this will help. go to big block chevy heads.
Stan Weiss' - Cylinder Head Flow Data at 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software

Whatever you decide on. Don't use the stock worn valves. Go for some aftermkt stuff. Flow better and haven't had a million cycles on them.. Also make sure the valve guides are tight, not worn. A dropped/broken valve can ruin your day.
Good advice and the website with all the flow results is a goldmine,too bad the results for the oval port head and the 049(oval also) head were ltd to 600 lift as the lower numbers might have given me more insight to my dilema, but hey, great stock of information. My goals are modest but I would like to see 450-475 horses with this engine. my cam is a middle of the road 228degree ,540 lift ,112 LSA and I'm working on pistons to get somewhere in the CR9.5-10 range. The car is reasonably light 2nd gen camaro and I don't want to rev more than 5500 to make this power. If you hone the small end of the rod for a free floating wrist pin(steel on steel) will one/8th inch hole (chamfered) on top of the rod be enough for the floating pin lubrication?
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Old 03-25-2013, 05:39 AM
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Bigger valves will increase the flow at lower lift also.

But you would need to grind the chamber wall at the valve out to the gasket to unshroud the valve. Flow would be less if you don't wall the chamber wall back.

I can't remember where I saw the flow numbers but do remember that is why I put in 2.19/1.88's in my 781's. I think I saw the flow numbers in some big block build-up article 10 years ago or so.

The heads only need to flow 235 cfm to make 470hp. So, you can make your hp target number with what you have now but it could always be better. Just need to make the call when is enough.
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Old 03-25-2013, 07:55 AM
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"If you hone the small end of the rod for a free floating wrist pin(steel on steel) will one/8th inch hole (chamfered) on top of the rod be enough for the floating pin lubrication?"

Yes, for a street strip engine. I like pressed pins for engines that are primarily street. Makes for a more stable piston/cyl wall as the miles add up.
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Old 03-26-2013, 03:33 AM
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Bigger valves will increase the flow at lower lift also.

But you would need to grind the chamber wall at the valve out to the gasket to unshroud the valve. Flow would be less if you don't wall the chamber wall back.

I can't remember where I saw the flow numbers but do remember that is why I put in 2.19/1.88's in my 781's. I think I saw the flow numbers in some big block build-up article 10 years ago or so.

The heads only need to flow 235 cfm to make 470hp. So, you can make your hp target number with what you have now but it could always be better. Just need to make the call when is enough.
Thanx for the info,a big help. My main concern is of course a crack developing either from over zealous porting (water jacket strike ) or in the case of machining for the larger valves,cracks developing between the valve seats or where I must open up the comb. chamber to unshroud the valves. I've seen too many engines with these sort of problems after professional work was done,not immediately but down the road a ways. This is not a race car and its gotta last a couple of year after I drop all this money into the build. Plus it must make all its power below 5500,also with a mind towards longevity.Here its hard to find standard castings at all,even if you've got the money to pay for them when you find a set, and,if they are in rebuildable condition without having to rob a bank to pay for it.
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Old 03-26-2013, 07:23 AM
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For the engine you are building what is critical is the valve job and the bowl contour under the valve job.
add a 30deg back cut to the valves too.

Nice street cam Lunati 402A2LUN Use a Performer RPM manifold and a 750-850 DP
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Old 03-26-2013, 08:08 AM
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Originally Posted by F-BIRD'88 View Post
For the engine you are building what is critical is the valve job and the bowl contour under the valve job.
add a 30deg back cut to the valves too.

Nice street cam Lunati 402A2LUN Use a Performer RPM manifold and a 750-850 DP
The bowls have been blended back into the throat concentrating on reducing the short turn radiuses slightly to get a straighter shot to the valve pocket from the intake. Same deal on the exhaust reducing the short turn radius near the seat a bit,not too much removed, more of a blending also. The lunati cam looks good on paper but I've heard the steep ramp for quick opening times is murder on the guides and lifters as well as making it necessary for more spring pressure than is normally needed for a similar dimension cam without the "voodoo" quick lift characteristics, not to say the voodoo design isn't a clever and powerful cam but I got to think of longevity of all the valvetrain components, giving everything the most chance for as long a life as possible. That said , I've also heard the lunati grinds can make a lot of extra power for the size grind that they are. it was a good suggestion I'll keep in mind if the crane doesn't give me enough midrange.
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Old 03-26-2013, 09:34 AM
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That is not a voodoo cam. Just use the recoemded valvetrain or equal stuff.
Leave the cam design to the experts That cam was designed by a true expert to run fine on the street.
It is a Ultradyne cam grind, but made by Lunati . Everything you have heard is BS. Promoted by people that have no clue what they are talking about.

When you set the lash on this cam set it cold .004" tighter than the hot lash spec.
( the lash opens up slightly when the motor warms up.
Shut the hood and drive it.
The advertized duration of a Lunati cam and a crane cam are measured at different specs. .006" VS .004" Hyd cams
You cannot compare the durations. between the two different specs.

This is a street mechanical cam. The "ramps" are designed for street use. And are not overly aggressive.
In fact if you bother to set the lash as I recomended you will be hard pressed to even tell it is in fact a solid lifter cam, when the motor is running.
(the slightly tighter "cold lash method" lash becomes the recomeded hot lash spec once warmed up)

Crane also sells a very very similar street mechanical also designed for the street along very very similar lines.
Look it up. ref: crane # 133841 and 131101 On a 108LSA. ( If you want a snotty agreesive midrange pull use this one.)

all these are street cams easy on the valvetrain just like the Lunati/Ultadyne design is.

Again the lift check spec of the adv durations are not the same. These cams are more alike than different when actually measured with the same spec.

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Old 03-26-2013, 10:08 AM
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Crane also sells a very very similar street mechanical also designed for the street along very very similar lines.
Look it up. ref: crane # 133841 and 131101 On a 108LSA. ( If you want a snotty agreesive midrange pull use this one.)

all these are street cams easy on the valvetrain just like the Lunati/Ultadyne design is.

Again the lift check spec of the adv durations are not the same. These cams are more alike than different when actually measured with the same spec. The lunati is @.020" . The 2 cranes are the same "F-278-2" cams lobe pairs but shown at different "advertized duration" specs of .0135" and .014" Same cam different specs.

Both/all these cams including the Voodoo cams are all designed for street use and will not tear up the valve train.
You read too much BS.

If you were to actually measure the Lunati cam using the Crane .0135" "advertised duration" spec it will be +/-2 to 3 deg difference at max.
They are both designed to do the same job.

I use and recomend this stuff in your oil to help esure a successfull cam break in.
GM EOS or Crane "superlube" and a can of Moly Slip E

Use Crane or Isky or Moly Slip Moly Paste on the cam lobes only.

Then I use a 1/2 can of the Moly Slip E in the oil on each oil change.
www.molyslip.com

Last edited by F-BIRD'88; 03-26-2013 at 10:29 AM.
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Old 03-26-2013, 10:35 AM
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Using the larger valves allows you to grind in a nice new "up high" oriented valve job.
Flows a lot better. Critical on getting these heads right and worth the bother.
Grinding in a new 2.07" valve job will require a deeper valve seat orientation, which flows a bit less.
In these heads a higher oriented 3 angle high perf valve job is better and the larger valves are better too.

You only risk busting thru when you go for the 2.25"+ valves in these heads.
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Old 03-26-2013, 12:16 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
That is not a voodoo cam. Just use the recoemded valvetrain or equal stuff.
Leave the cam design to the experts That cam was designed by a true expert to run fine on the street.
It is a Ultradyne cam grind, but made by Lunati . Everything you have heard is BS. Promoted by people that have no clue what they are talking about.

When you set the lash on this cam set it cold .004" tighter than the hot lash spec.
( the lash opens up slightly when the motor warms up.
Shut the hood and drive it.
The advertized duration of a Lunati cam and a crane cam are measured at different specs. .006" VS .004" Hyd cams
You cannot compare the durations. between the two different specs.

This is a street mechanical cam. The "ramps" are designed for street use. And are not overly aggressive.
In fact if you bother to set the lash as I recomended you will be hard pressed to even tell it is in fact a solid lifter cam, when the motor is running.
(the slightly tighter "cold lash method" lash becomes the recomeded hot lash spec once warmed up)

Crane also sells a very very similar street mechanical also designed for the street along very very similar lines.
Look it up. ref: crane # 133841 and 131101 On a 108LSA. ( If you want a snotty agreesive midrange pull use this one.)

all these are street cams easy on the valvetrain just like the Lunati/Ultadyne design is.

Again the lift check spec of the adv durations are not the same. These cams are more alike than different when actually measured with the same spec.
Thanx for the info, sorry about the mix up on your cam suggestion,I thought you were referring to a 60202 voodoo cam,my mistake(I don't have these numbers memorized yet) which takes a much heavier spring than the crane cam I'm using ,its the heavier springs that wear everything out quicker,although its nice to have that extra protection I don't need it with my planned 5500 redline(even if the motor pulls to 6000 or beyond) You probably haven't read my other entries here but I don't plan on racing this motor so a solid cam is certainly not in the planning (I don't like having to adjust valves anymore than I have to) and although your suggested cam is a powerhouse for sure its a bit beyond my horsepower needs. Once you go beyond that magical 500 HP you open up a whole other can of worms like new tranny's,driveshafts ,rear ends,frame connectors,bigger brakes,four link rear suspension set ups,tubbing for traction,I don't want to go crazy,just have some laughs with the car(although I'd go crazy if I could afford to) but thanks for the technical on the valve seat placement,certainly something to think about while I'm busy with it.
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