383 - 496" stroker cam question?
#2457546
02/25/18 10:10 PM
02/25/18 10:10 PM
|
Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
OP
master
|
OP
master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
|
Looking for camshaft suggestions for a 383 496" stroker. This combination is way different with the short 1.538:1 rod ratio. This is the flat top, 4cc valve relief, 84 cc head (RPM), so at 0.060" over I am coming up with 11.37:1 compression. Want to run pump gas, and this is a street car, not a racer so looking at street friendly lobe profiles.
With the lower rod ratio, will it want a cam with the wider LSA?
I am thinking a cam like the Comp XR292R but with 112 LSA and installed around 108 to 110 centerline?
The specs would be something like Advertised 292/297, 0.050" duration, 254/260, 112 LSA, 110 CL
In theory that calculates to 7.82:1 DCR compression and 159 cranking pressure?
Anyone build one of these
|
|
|
Re: 383 - 496" stroker cam question?
[Re: 451Mopar]
#2457548
02/25/18 10:16 PM
02/25/18 10:16 PM
|
Joined: Jan 2003
Posts: 31,051 Oregon
AndyF
I Win
|
I Win
Joined: Jan 2003
Posts: 31,051
Oregon
|
Did you read this article: http://www.hotrod.com/articles/dyno-tested-make-700-hp-trick-flows-new-fe-heads/We used a XR292R-10 street roller in it. It is roughly the same size of engine that you are talking about (482 vs. 496) and similar compression ratio (11.37 vs. 11) The XR292 works great in an engine this size. It is big enough to make plenty of power but small enough that the idle should be half way decent. It won't idle like a Caddy, but it should have decent vacuum and be driveable if you have 3.23 or 3.54 gears.
|
|
|
Re: 383 - 496" stroker cam question?
[Re: 451Mopar]
#2457635
02/26/18 12:07 AM
02/26/18 12:07 AM
|
Joined: Oct 2007
Posts: 4,209 New York
polyspheric
master
|
master
Joined: Oct 2007
Posts: 4,209
New York
|
will it want a cam with the wider LSA
Narrower: short rod makes piston motion faster around TDC.
LSA is just a number, it's derived from your cam choice - it doesn't determine your cam choice. You will see references to a big LSA, but it' not relevant - that's a cam with so much duration (280° @ .050") that opening it up makes the actual OL window closer to what you'd expect.
Vizard's guess as estimating the actual area when both valves are open: proportionate to the OL in nominal (not .050") degrees, squared, × .01. E.g., IO 40° BTDC + XC 50° ATDC = OL 90°: OL area = 81 "units". Small changes are important, going from that to IO 50° BTDC + XC 60° ATDC = OL 110°. Looks like +22% (110 ÷ 90)?, but the OL area = 121 "units", 49% larger.
Boffin Emeritus
|
|
|
Re: 383 - 496" stroker cam question?
[Re: 451Mopar]
#2457987
02/26/18 06:23 PM
02/26/18 06:23 PM
|
Joined: Aug 2003
Posts: 8,716 Baltimore/Denver
64Post
master
|
master
Joined: Aug 2003
Posts: 8,716
Baltimore/Denver
|
Jim,
Are you correcting your numbers for your altitude?
I've noticed your past builds were sea level type combos and always wondered why you didn't add at least 20% more mechanical compression. Your 11.3 theoretical is closer to 9.0:1 @ 5,000 D/A.
Last edited by 64Post; 02/27/18 09:55 AM.
|
|
|
Re: 383 - 496" stroker cam question?
[Re: 451Mopar]
#2458008
02/26/18 07:06 PM
02/26/18 07:06 PM
|
Joined: Aug 2011
Posts: 2,867 Pattison Texas
CSK
master
|
master
Joined: Aug 2011
Posts: 2,867
Pattison Texas
|
The off the shelf, 110 LSA cam looks OK to me?, but was curious about the wider LSA for a few reasons.
Just some ideas I'm throwing around: The engine has what looks like a good amount of compression at 11.37:1, but want to run it with EFI on pump gas. I think the lower rod ratio will help with the pump gas part because the piston is not going to be near TDC for very long? Backing off the installed intake centerline should also close the intake valve a bit later lowering the DCR?
I will get the suggestions from some cam grinders too. Just checking if I am way off base as this combination is a bit different than what I have done before.
A wider LSA can also have more detonation in the part throttle low to mid rpm, because it has less EGR affect of the overlap.
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
|
|
|
Re: 383 - 496" stroker cam question?
[Re: 451Mopar]
#2458015
02/26/18 07:18 PM
02/26/18 07:18 PM
|
crabman173
Unregistered
|
crabman173
Unregistered
|
Lots of street combos actually like wider LSA's and the wider units can surprise you on the dyno--most folks have always went with the old 108 stuff so it has that sound they all crave ( that being in a 440) in the bigger CI Mopars they soak up cam size pretty fast The older I get and with the way I drive now the wider I like them for great overall performance but for customers sake and getting that coveted "sound" on the bigger CI I usually end up with 110 and never go past 112 Your cam choice looks fine to me for a hot stroker I would not think about it more than three seconds based on rod length--the way I see it you will have less piston noise and that will be a plus you did not bank on compared to say a 7.100 rod hockey puck piston
|
|
|
Re: 383 - 496" stroker cam question?
[Re: 451Mopar]
#2458256
02/27/18 08:13 AM
02/27/18 08:13 AM
|
Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
OP
master
|
OP
master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
|
It's not my engine. My friend already has the heads and stroker kit, and wants to drive here and at sea-level on pump gas. Really, for the application, I would have gone with the 20cc dish pistons, about 10:1 compression and use a smaller cam.
The old 451 engine was a 11:1 engine with less quench, and a tad less cam (251 @ 0.050") than this one. It should make for a really strong engine, but the pump gas part is the question?
|
|
|
|
|