|01-11-2013 04:27 PM|
Here is a more modern camshaft by Crane that has simular duration at .050 numbers:
Crane Hydraulic Flat Tappet Camshafts 113531 - SummitRacing.com
It is a good engine building practice to degree your cam. Timing sets off,crank key off,etc. Rarely do you find the cam itself ground wrong.
The intake lobe on that speed pro cam is lazier than the exhaust lobe.
I do not know how that cam will perform in your 327 but I think the Crane will be better. Shoot for 7.5-8 DCR
|01-11-2013 04:01 PM|
You were replying at the same time as me. So you are saying this is not uncommon and could be correct. I agree that it does appear that it would make a durable grind as it is a low ramp rate equating into lower pressures on the lifter/cam mating surfaces, push rods, rockers and valve stems.
If the Pat Kelly DCR number is accurate, then is 6.7 DCR a problem?
|01-11-2013 03:55 PM|
Exactly! Yes, that is the number on the card.
I haven't contacted SpeedPro/Federal Mogul, because I can't find a phone number, but I've confirmed this number on several different websites of companies selling this cam. The other cams that appear on the same listing from Speed Pro do not follow this grind pattern.
Does anyone have a contact number you've found for SpeedPro?
Has anyone encountered a dual grind cam where the the intake duration is greater than the exhaust at .006 and vise versa at .050 lift? And if this is accurate and other manufacturers make a cam similar, then what is the purpose of this?
As cdminter59 mentioned, I'm kicking myself for not degreeing the cam when I installed it!!! Currently I'm in the process of installing a multiport setup on this and hope to have it done in a couple of weeks and then I'm pulling the trans for a rebuild. The more I think about it, I'm thinking I'm gonna pull the engine while I'm waiting for the trans to get rebuilt to degree the cam.
Like I mentioned in the original post, if you check my DCR using Pat Kelly's calculator, you'll see what my concern is. Basically, that is the reason for my starting this thread. I have to admit that I believe what TechInspector said, but......, I can't understand how two different and reputable DCR calculators could be so far off from each other.?.
|01-11-2013 03:46 PM|
|GMC boogie||I calculate a 9.63:1 CR and a DCR of 6.76 if those numbers are correct. That is using the Pat Kelly calculator.|
|01-11-2013 03:44 PM|
|01-11-2013 03:32 PM|
That is one low intensity cam lobe. Intake duration at .006 304
Intake duration at .050 220
That is a difference of 84. Sure that advertised number is at .006?
|01-11-2013 04:12 AM|
If at 1st you don't succeed, then read the directions and try again
|01-11-2013 04:02 AM|
DCR calculator conflict - by ALOT!
In this article by Pat Kelly he says the correct way of figuring the DCR is by using the cams advertised duration. That using the .050 reading is incorrect. But KB calculator is adding 15* so IDK who is right. I wish I had found these articles when my engine was on the stand so I could check for myself. He also says if the DCR should be in a range of 7.5-8.5. If it drops below 7.5 like you suspected the torque drops off and you also lose power on the top end. If it is in a higher range tha 8.5 no problem add racing gas. Dynamic CR
|01-11-2013 03:28 AM|
I would love to degree the cam, but it can't be done in the car due to clearance issues - we currently have about .5" from the water pump pulley bolts to the radiator (using electric fan). I could try doing it with timing tape, but I don't know if that would be very accurate with a small balancer.
|01-11-2013 03:03 AM|
The intake closing point is where my concern is. If I use the closing point, at .050, of 36 deg and then add 15 deg, then all is well, BUT if I use the actual closing point at .006 of 78 deg then all is not well.
Should I assume that the KB calculator is saying that the intake valve is closed at 15 degrees past the .050 lift point? If that is the assumption, then my DCR is actually much lower because, according to cam card, my intake valve isn't closed until 78 deg. Unless, the intake valve is considered closed for DCR calculations at 51 degrees.
What do you think?
FYI - I tried to word my question so that it isn't confusing - I can't say that I succeeded, but I tried.
When I put this engine together, I relied on the machine shop to recommend the cam and pistons. He thought the engine should easily make 1 hp/cube, but I haven't been able to pull it off. The best I've done is a little less than 310. The 310 was calculated from the dyno owner's software based on actual rwhp. I realize that all dyno's are not alike, but, this got me checking into the DCR just to see whether it was OK. When I found the discrepency between the two calculators then I thought this could be some of the issue. But I don't have a good enough understanding of exactly how DCR is calculated. And that is how I got into this conundrum.
Do any of you know what happens when the DCR is at or below 6.7:1? Will the engine still run well and be low on power, or will it run poorly all the time, certain RPM ranges, or what?
For some background, this engine was put together in the spring and driven for most of this last summer and fall - about 4000 miles. I can say safely, based on driving it, that I need more stall for launch, but other than that it seems like a rocket in the car. The is quite light, around 2600 lbs. At 40 mph it feels like it's shot of gun when you lay into the throttle.
Thanks - Jim
|01-11-2013 02:18 AM|
DCR calculator conflict - by ALOT!
64nailhead, the easiest way to check out what you want to know is to install a degree wheel and degree your cam. This way you can find out if the intake valve is closed at .050 or just partially closed. IDK about the brand of cam you have installed but Comp Cams valve opening and closing are at .006 on the cam card. Crane cams opening and closing are at .004 on their cam card. The Crower cam I have the opening and closing are at .050. It seems all these manufacturer just want it so confusing.
|01-10-2013 06:48 PM|
|hcompton||Oh crap i read that wrong. Ignore me.|
|01-10-2013 06:46 PM|
I see your problem.
I get 10.28:1 and 7:1 with .015 gasket.
You need to work out the deck height. If possible did you order your pistons yet. Get them so the deck will be .010 on down to zero if possible.
With .010 and .015 gasket i get 10.55:1 and 7.37:1 for dcr. Your engine will be alot happier with proper squish and scr. This should be happy on the street with good heads and proper setup.
Have you purchased the heads. 59cc will open up a lot of options to you. 59cc procomps is what i am using on my current build because the cam is so big.
|01-10-2013 06:40 PM|
OK, we have the following values.....
679.3 cc's in the cylinder
4.2 cc's in the piston deck height
8.7 cc's in the gasket
0 cc's in the piston crown (we sliced off the pop-up and put it in the chamber)
65.5 cc's in the chamber
Divide by 78.4 and find 9.66:1 SCR
On the KB calculator (only one I have used for years).....
compression ratio 9.66
rod length 6.250
intake closing point 36 + 15 =51.000
DCR = 8.398:1
Looks like a good build to me, except the squish at 0.059". I would have either cut the decks or used a thinner gasket to get closer to 0.040".
|01-10-2013 06:35 PM|
|hcompton||And did you put your piston dome in as - number or negative number. In the link i posted itnshould be neg if pop up.|
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