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cam selection
#1
Looking for some camshaft suggestions for my 351 C4v.
Engine is a factory rebuild of some sort, compression = 155-160 across the board and leakdown is in the 10 % range
4v heads with dot (assuming open chamber ) by 2E25 date code , but not 100% sure.
750 Holley vac.secondary's and unknown headers but in very good shape.
Has Holley street dominator manifold (single plane ) and Mallory unilite distributor.
I measured the cam's lobe lift at the pushrod and came up with .248''
that would equate to stock 2V lift specs, and who knows , may also have retarded cam timing.
18'' of engine vacuum at 16 degrees of initial would substantiate my 2V cam conclusion.
been looking at Sealed power CS650 and some kind of substitute for the D1ZZ-6250BX.
Found Lunati-10321001 at Summit racing but I am not sure if that is a direct replacement.
anyone care to make any suggestions based on my limited specs. ?
Boilermaster
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#2
4v heads with a 4* don't necessarily mean an open chamber head. The only way to know for sure is to either pull the intake and use a mirror to check the casting number or pull the heads. I suppose a 3rd way would be to CC the cylinder at BDC and TDC but that's getting a little elaborate. D1AE-GA heads are 4v closed chamber with the dot.

The compression numbers you're reporting are fairly high for an open chamber/stock piston setup. I am thinking it's more likely you have close chamber heads.

As far as cam grind goes, you really want to know what you have for heads (compression) and then read this article paying particular attention to dynamic compression: http://pantera.infopop.cc/eve/forums/a/t.../319104265

There's a chart which lists the static CR vs the dynamic CR vs Intake valve timing (valve closing). Select this aspect of your cam based on this chart and your engine's static compression ratio.

Also, the Wallace Racing calculators are handy for obtaining some of the numbers you may want to compare when selecting your cam: http://www.wallaceracing.com/Calculators.htm

The above assumes you want to run on pump gas and avoid detonation.
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#3
what is your gear ratio?

what trans?

what tires?

do you want bottom or top end power?

smooth, moderate or rough idle?

lite to lite drag car or freewy flier?
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#4
I stay close to old grind specs for the Boss 351 hydraulic version D1ZZ-6250-BX you mentioned.... Or a similar Comp Cam split duration grind. That is for a street motor with 3.25 gears, 4 speed top loader or C6/FMX auto with high stall CJ torque converter. Ford knew how make these 4V heads work on the street.

290°/290° duration @ 0.004"
0.505"/0.505" lift
Exhaust valve opens at 84° BBDC
Intake valve closes at 74° ABDC
62° overlap
219°/219° duration @ 0.050"
114° lobe separation angle
Intake lobe centerline = 109° ATDC
  Reply
#5
basstrix;249893 Wrote:4v heads with a 4* don't necessarily mean an open chamber head. The only way to know for sure is to either pull the intake and use a mirror to check the casting number or pull the heads. I suppose a 3rd way would be to CC the cylinder at BDC and TDC but that's getting a little elaborate. D1AE-GA heads are 4v closed chamber with the dot.

The compression numbers you're reporting are fairly high for an open chamber/stock piston setup. I am thinking it's more likely you have close chamber heads.

As far as cam grind goes, you really want to know what you have for heads (compression) and then read this article paying particular attention to dynamic compression: http://pantera.infopop.cc/eve/forums/a/t.../319104265

There's a chart which lists the static CR vs the dynamic CR vs Intake valve timing (valve closing). Select this aspect of your cam based on this chart and your engine's static compression ratio.

Also, the Wallace Racing calculators are handy for obtaining some of the numbers you may want to compare when selecting your cam: http://www.wallaceracing.com/Calculators.htm

The above assumes you want to run on pump gas and avoid detonation.

Basstrix,
Was thinking those numbers were a little on the high side as well,
Snap-on comp tester, known good numbers.
I am keeping in these things: factory rebuild will almost always have the deck and cylinder heads trued, what pistons were used and is the camshaft in there now contributing to increased cranking compression.
Since intake manifold will come off for cam change, I will get a chance
to get a look at the casting numbers on the heads.
Was also going to replace valve seals while checking valve springs.
wonder if one could get a good enough look at the combustion chamber thru an intake port with a valve open (with proper precautions) to determine piston usage and open or closed chamber, just a thought.
Barnett468,
3L91 gears, a little steep for my taste, possibly changing to 3L50, supposedly professionally rebuilt C4 transmission, 2800 rpm converter, magnum 500 14'' wheels will be needing new tires.
I do not want this to be a drag car, but have at least be at the power level of my previous 4V engines I have built
KT69, been on the Pantera website quite a bit for reference, that is where I came up with my part numbers, wish I would have been a good note taker in my younger days.
For now, I am leaning towards a copy of the D1ZZ-6250-BX if I find closed chambers and copy of D1ZZ-6250-A or B if I find open chambers.
Looks as I will have to determine for myself if I get a copy of the CJ camshaft , if it is early or late valve timing as I cannot get verification
from SEALED POWER (CS650) , HOWARDS CAMS (237211-15) or LUNATI (10321004) of their valve timing events.
any additional info or suggestions would be greatly appreciated.
Boilermaster

Also,
I am seeing that Comp Cams makes a flat tappet hydraulic lifter with a diameter listed at .875'' as opposed to the advertised OEM diameter of .874''.
My 1972 shop manual lists standard diameter as 0.8740''- 0.8745'' with a clearance to tappet bore of 0.0007'' to 0.0027'' and a wear limit of 0.005''.
Thinking of the additional .001'' tappet diameter as (oil control loss prevention ) as well as these lifters have a patented metered oil orifice to the pushrod and rocker.
looking at comp cams #832-16 on Summit racing site.
anyone ever use these and care to share results ?
Boilermaster
  Reply
#6
I agree with the others, your compression numbers are likely too high for stock open chambers. You may have either CC heads or domed pistons from the previous rebuild. Also, seems a little odd that a single plane manifold would be placed on an engine with a mild cam. I agree with your comment about the 3.91 gears with a non-overdrive transmission. I have 3.73 and while fun around town or on windy roads it's not great on the open highway. 3.50 sounds like a good compromise.

I don't believe you'll be able to get a look at your pistons through the intake runners and past the valves. An inspection camera is probably the best way. Harbor Freight has them fairly reasonable. I have one of these and it works pretty well, better than I expected:
http://www.harborfreight.com/digital-ins...61839.html

When you get a look at your casting numbers take a look here:
http://www.7173mustangs.com/thread-casti...gine-codes
If yours isn't listed or you see a discrepancy please let me know.

You can also play around with compression numbers in the spreadsheet at:
http://www.7173mustangs.com/thread-engin...lculations
Get a rough idea of what your compression ratio is:
http://www.7173mustangs.com/thread-compr...lculations



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
  Reply
#7
Don C;249919 Wrote:I agree with the others, your compression numbers are likely too high for stock open chambers. You may have either CC heads or domed pistons from the previous rebuild. Also, seems a little odd that a single plane manifold would be placed on an engine with a mild cam. I agree with your comment about the 3.91 gears with a non-overdrive transmission. I have 3.73 and while fun around town or on windy roads it's not great on the open highway. 3.50 sounds like a good compromise.

I don't believe you'll be able to get a look at your pistons through the intake runners and past the valves. An inspection camera is probably the best way. Harbor Freight has them fairly reasonable. I have one of these and it works pretty well, better than I expected:
http://www.harborfreight.com/digital-ins...61839.html

When you get a look at your casting numbers take a look here:
http://www.7173mustangs.com/thread-casti...gine-codes
If yours isn't listed or you see a discrepancy please let me know.

You can also play around with compression numbers in the spreadsheet at:
http://www.7173mustangs.com/thread-engin...lculations
Get a rough idea of what your compression ratio is:
http://www.7173mustangs.com/thread-compr...lculations

Don C,
got off my butt and removed intake, took more time to clean off the grit around the ports and vacuum it up than it did to actually remove the intake itself.
The casting numbers D1ZE- DA with a born on date of 2E25 should make them open chamber.
suspecting now some block clean up and or head clean up.
Who knows what pistons are being used ?
Good thing is CLEAN but with that Holley street dominator, what a port mismatch , I believe it when they state that this manifolds ports are smaller than 2V.
That manifold will be on the must sell list.
Machine work and stock length pushrods may explain why there was so much lifter preload. (averaged 1-3/4 turns.
Now that I have it this far, might as well pull the front cover and radiator, will be time to order up parts on Monday.
Boilermaster
  Reply
#8
Agreed on the open chambers, with that date code I was sure they were, the casting number verifies it.

Good luck on your build, keep us informed as to your progress, always interesting as well as educational.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
  Reply
#9
Don C;249919 Wrote:I don't believe you'll be able to get a look at your pistons through the intake runners and past the valves. An inspection camera is probably the best way. Harbor Freight has them fairly reasonable. I have one of these and it works pretty well, better than I expected:
http://www.harborfreight.com/digital-ins...61839.html

I thought of the bore scope option after I posted. I bought one similar to this last year when I needed to inspect the cylinders on an outboard I rebuilt. It's small enough to fit through the spark plug holes and has a mirror allowing you to see the combustion chamber. I spent ~$40 on the one I bought because it didn't come with the mirrors.

http://www.amazon.com/Waterproof-Boresco...ion+Camera

I believe this is the same as the one I bought...it's a little more expensive than the one linked above: http://www.amazon.com/Supereyes-Inspecti...RQSC8A94N1

THe nice thing with this is that you can use your laptop's screen....I've used the cheapo with tiny display and found many more benefits to the USB/Laptop style. Of course, the downside is, you have to have a laptop to use it.
  Reply
#10
For the 4V Cleveland you have to verify what head piston combo you have as maximizing compression is an absolute must do. Back in the day first thing to do to a post 71 351 Cleveland was to pull the open chamber heads and swap for a set of 4V 70/71 closed chamber heads with the thin gasket to overcome the anemic compression ratio Ford bestowed on post 71 Cleveland's. Anything else you do will be minimized until you verify you have achieved 9.5:1 - 10:1 compression ratio. To little and you will not achieve the torque required for this combo to take advantage of the head design and required ignition timing. To much and you risk detonation or retarded timing to compensate.

Those of us who experienced 11.5 to 12:1 compression ratio and leaded gas know how much compression effects the seat of your pants and how an engine can pull throughout the power band.


3.25 rear gears with larger diameter tires than the OEM 25.9" will be about right for overall city/highway driving with only a 3 speed auto transmission. Tire wheel combo's in the 27-28" diameter range you could perhaps go with a 3.5:1 rear gear. I ran 3.79:1 and 3.90:1 back in the day with 26.6" diameter tires which were great for cruising the local strip or loop and stop light drag racing...top end speed burst max'd out (wrapped out) around 100 mph. Cruising the interstate at 55-60 mph and 3,500 rpm was a real drag and totally sucked. With those steeper gears I ran a BOSS 351 or Torker intake dual point distributor and 700- 750 Holley carb. One could purchase BOSS components over the counter back in the day. I also owned a white BOSS 351 from 74-77.....bought it used for $4K one hell of a muscle car!!!! I put Keystone wheels on it..air shocks, traction bars and N50's on the back for rubber. I will forever love a BOSS 351, Top Loader, Hurst shifter and ZZ-Top. Spent the rest of my life trying to recapture a bit of that magic ya just don't know what you got till its gone.
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