Re: Cam break in is done!....Now more questions!
[Re: mopfried]
#1493024
09/21/13 01:22 AM
09/21/13 01:22 AM
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Joined: Feb 2010
Posts: 18,493 Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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I do hope that all of this stuff ends up helping others as well as myself. I have read archived threads on this and many other subjects in the interest of learning. My understanding is that while Mopfried has a good point about the bigger cam making more cylinder pressure at high rpms, maybe the short time span at that high rpms makes detonation less likely?? Don't worry about anyone thinking your post was hijacking anything. I am open to all points of view. Anyhow.... I found a Dynamic CR calculator that has that odd "Intake closing PLUS 15 degrees" bit: https://www.uempistons.com/index.php?mai...e30f95974e64ff7Using that calculator, the '509 gave me a 7.91 Dynamic ratio. The Lunati gave a 8.09. I was told that a dynamic at 8.0 or below was good enough for pump gas. Maybe they mean 93 octane?
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Re: Cam break in is done!....Now more questions!
[Re: Kern Dog]
#1493027
09/21/13 03:30 AM
09/21/13 03:30 AM
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Joined: May 2003
Posts: 6,566 Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,566
Downtown Roebuck Ont
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Quote:
If I could go back and visit myself in 2004 I would have ordered dished pistons and zero decked the block. This would have put me in the mid 9s with quench. I probably could have run 87 octane while still making plenty of power. I could still do this, but that would be another $1000 in parts, machine work and down time.
Just an FYI my 493 has zero deck with IIRC 34cc dish. 8.9something:1. Basically makes 500hp and 600 ft/lbs with a .509 cam and it is quite happy to do it with 87 regular on all but the hottest of days.
Kevin
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Re: Cam break in is done!....Now more questions!
[Re: Twostick]
#1493028
09/21/13 04:44 AM
09/21/13 04:44 AM
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Joined: Feb 2010
Posts: 18,493 Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
How did you arrive at 10.73:1 compression? Did you actually measure/CC everything yourself? I ask because when I plug in the numbers for a flat top 493 into my calculator with an 84 cc head, .039 1009 4.410 bore gasket -4cc valve reliefs and -.017 deck I get 10.86:1.
The heads were new when I bought them in 2003, so the 84 cc number should be pretty close.
My pistons have a 6 cc valve relief. When I enter the numbers, they tell to put a minus sign before the number if it is a DOME but use only the number if it is a dish or a valve relief. I checked # 1 cylinder to measure the piston height at TDC. It was between .017 and .018 so I err to the high side on that one.
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Re: Cam break in is done!....Now more questions!
[Re: Twostick]
#1493029
09/21/13 04:48 AM
09/21/13 04:48 AM
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Joined: Feb 2010
Posts: 18,493 Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
Just an FYI my 493 has zero deck with IIRC 34cc dish. 8.9something:1. Basically makes 500hp and 600 ft/lbs with a .509 cam and it is quite happy to do it with 87 regular on all but the hottest of days.
Kevin
That is fantastic. 500 HP is enough to blow off any street tire! It would be great to be able to run on any available octane without worry.
There has always been something "off kilter" with this engine. When I ran it on a chassis dyno in 2005, it only made 369 HP at the tires. Even accounting for a 20% loss through drivetrain etc, thats only 443 HP. I've wondered if the 2 1/2" exhaust is a bottleneck.
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Re: Cam break in is done!....Now more questions!
[Re: Kern Dog]
#1493030
09/21/13 09:48 AM
09/21/13 09:48 AM
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Joined: Feb 2005
Posts: 4,318 Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,318
Prospect, PA
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I cannot help to think that possibly there are still a couple pieces of mis-information that keeps this thing going in circles. My opinion (I think ) is that you are on the edge with this combo being pump gas friendly, but have believed up to this point that you could get there by tweaking the details. 2 1/2 exhaust is not the problem, unless it has a failed muffler, but some one already brought this up and you concluded that this was not the problem. When you get to the point (may be there now) that you just want to fix the problem, or symptom, here is my suggestion: Take the heads off and have someone with a cnc program (like MCH) cut the chambers to the desired cc's, and put it back together with the 0.027 gaskets.
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Re: Cam break in is done!....Now more questions!
[Re: Kern Dog]
#1493032
09/26/13 09:29 AM
09/26/13 09:29 AM
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Joined: Feb 2003
Posts: 1,238 Nevada
dezduster
pro stock
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pro stock
Joined: Feb 2003
Posts: 1,238
Nevada
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I have been following this thread from the beginning. Reading every post every idea and watching for results from those suggestions. The one suggestion from SUPERBEEDAVE asking about cam timing was the only one that I feel was not addressed/double checked. I am not a know it all, or a done it, seen it, sailed it, scaled it, dove deeper come up dry guy. But I have seen the result of a cam installed improperly timed.It ran soft down low had crappy idle characteristics pinged until higher in the rpm range then it ran unimpressively. Oh it needed premium fuel at 4500ft elevation at 9ish compression. Exhaust would glow, required weird jetting and timing settings. The timing set was an edelbrock set their markings are vague as are the directions. You have stated this is your first serious performance build perhaps a mistake in cam degreeing has you here. This is not a slam nor me criticizing you your efforts or anyone else's. Just trying to help. Some have said your engine is defying normal logic that logic applies if valve/cam timing is correct if not??? Who knows. Good luck.
Last edited by dezduster; 09/26/13 09:32 AM.
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Re: Cam break in is done!....Now more questions!
[Re: Dodgem]
#1493041
10/08/13 11:45 PM
10/08/13 11:45 PM
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Joined: Feb 2010
Posts: 18,493 Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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I got the left head off today. Looking at the head gaskets again, I found that while the fire rings were not burned, there were a few rough spots. I'm unsure if the detonation could have worn them rough or if they became rough, then the detonation began. I have read the term.. Unshroud the valves before. Does this mean to clear material away from the valves to lessen restrictions?
Last edited by Frankenduster; 10/08/13 11:54 PM.
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Re: Cam break in is done!....Now more questions!
[Re: Kern Dog]
#1493042
10/09/13 12:11 PM
10/09/13 12:11 PM
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Joined: Jan 2003
Posts: 75,062 U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,062
U.S.S.A.
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Quote:
I have read the term.. Unshroud the valves before. Does this mean to clear material away from the valves to lessen restrictions?
Yes , put the head gasket on you plan to use with dowels in the holes and lightly scribe the head gasket pattern onto the head, open the chamber up on either side of the valves to just inside the scribe line and blend it into the chamber.
Then replace the pistons with a zero deck dish piston to lower your compression and gain quench
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