Am I Going To Be Happy With This Camshaft?
- Thread starter Bodyperson
- Start date
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I get it with the headers. I always understood the asymmetrical profiles were for factory manifold cars. I can real back my order but I think we are splitting hairs at this point.
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It’s more to do with the 108 LSA than the dual pattern grind. It would perform stronger across the entire rpm range.
You would be correct. There's nothing written in stone that says a split pattern is best for manifolds and single pattern best for headers. That's an unknown that cannot be known until you hit the street, drag strip or dyno. And yes, it's splittin hairs. I wouldn't sweat it a bit.
I'm just trying to soften up up the hit on the low end. Pump gas for me. 93 these days.
Dale Davies
Well-Known Member
The 0.465" lift spec is I take it with 1.5:1 rockers. With 1.6:1 rockers your lift will be about 0.495". Depending on compression and intake valve diameter are, it should work out fairly well for a street engine with some grunt.
270 - 180 = 90
90 ÷ 2 = 45° overlap
That is in the middle for hot street use. Should be a bit of lope but not bad.
Dale Davies
Well-Known Member
Dual pattern usually have more duration on the exhaust to compensate for a restrictive exhaust, whether from port design or the manifolds. Frequently have less lift as that is not a big problem on the exhaust.
With good exhaust ports and headers a single pattern tends to provide a bit more low speed to mid range torque.
You are correct Rusty, kind of splitting hairs.
These days though, a lot of them have more lift and duration on the intake side. I've never been convinced that works as well and Doug Dutra proved it did not with the slant 6.
Revisiting this thread. 6 months and no cam from Howards. I reckon you all know about the cam shortage. Going for the regrind. I would have sent one to Oregon but I'm dealing with a builder and expecting a cam with similar specs from Bullet.
So you ordered a stock high stall converter. That's basically a 340 converter. Is that what you wanted?
Uncle Bob
Shiny paint causes stress.
That's nuts. I ordered a Howard's cam through Jeg's about a year ago. IIRC it had a 30 day lead time and I got the cam in about 2 weeks. Then it took me another year to get the project running LOL.
Uncle Bob
Shiny paint causes stress.
That's exactly what I have. Note that it didn't come in one of the nifty plastic cases, just a heavy duty box in a box.
I just have limited run time on it because some Gomer got the pushrod measurement just wrong enough to make it a tapper. Still waiting on a set 1 turn longer.
Nice little chop there. Great Mopar sound!
Newbomb Turk
Well-Known Member
Here's what I know from the math I use.
That as the bore to stroke ratio gets closer to 1.0 (the bore and stroke are the same) the more exhaust timing it will want.
As the rod to stroke ratio gets lower, it will want more exhaust timing.
Running the math for my 340 my math calls out a single pattern cam.
If I run the math for a 4.1 bore, 3.79 stroke it calls for a 14 degree split.
I know the math is very close because I had an engine on the dyno that used it and the torque and power peaks were exactly where the math said they would be.
I used to be pretty much opposed to a split like that. I'm still against buying a shelf cam with the de facto 4 degree split.
That's some marketing ****. I've run the numbers on lot cams and I've never seen this math call for a 4 degree split.
The least I've seen is 6 degrees and that was a Pontiac I ran the numbers on.
The other exception may be high RPM stuff that may be way over square and with a reasonable R/S ratio. They look like they want a bunch of split.
I also think that valve size plays a big roll in duration splits.
The smaller the exhaust valve the more split it will want.
I remember when I started building engines a 1.94 exhaust valve for a BBC was standard. By the mid 1990's I was going no bigger than a 1.88 and later on I tried to stay around 1.84.
That big exhaust valve takes up space that's better used for intake valve diameter.
Of course all this is NA stuff.
Yeah but what about under square stuff like the slant 6? Doug found it didn't add anything.
Newbomb Turk
Well-Known Member
Do you have a link to what Doug did? I don’t remember reading anything about it.
Edit: hopefully it has the engine specs in it. If it does I’ll run the numbers and see what I get.
I'd really have to dig for it. It's been forever ago. He got with Erson on it and they ground it for him and even had the camshaft available. But now, they don't have anything for the slant anymore and hardly anything else. I think the advertised was something like 280/270, I honestly cannot remember. I was actually going to try one and then he posted their results showed it gained nothing. I think it even lost some. @Jim Kueneman might know a little more.
Newbomb Turk
Well-Known Member
I don’t remember the bore, stoke and rod lengths for a slanty any more. I used to.
If you can remember that stuff and how many rpm peak power is at and I’ll do some math.
This is fun!
Ok, on my long rod build sittin on the stand.
Bore- 3.445
Stroke- 4.125
Rod Length- 7.005
I don't know about peak RPM power, but the camshaft grind I chose is .495/[email protected] on a 108. FWIW, static compression is 10.5. I know dynamic will be around 8.5, but this is with the closed chamber head and flat tops with one valve trough and I can get "around" .027" quench distance. I ain't skeered to go down that far, because my red line will be 6K at the absolute most and it'll likely never see that.
Newbomb Turk
Well-Known Member
Yes, if I’m understanding what the question is correctly, I was talking with Doug a lot about camshafts before the forest fires took his place a few years ago. He didn’t find splitting the durations to be any more or less effective than the same duration on both intake exhaust. I ran about 1 million simulation runs on performance trends with various camshafts that he’s tried and I’ve got similar results to what he saw. If you’re looking for that 0.1s difference to win a drag race yeah maybe but if you’re just driving it for fun on the street. You’ll never see the difference .
All stock specs for a slant: Bore is 3.40, rod is 6.70, and stroke is 4.125.
BSB67
Well-Known Member
That’s an interesting overlap calc.
Newbomb Turk
Well-Known Member
Do you feel like running the numbers I’m going to post about Rusty’s engine through PT?
I’d love to see what it says.
As long as Rusty doesn’t care we are posting about his stuff.
Newbomb Turk
Well-Known Member
Oh crap…hold on…
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