Retarding the Camshaft
Melting Slicks
Joined: Mar 2001
Posts: 2,174
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From: Clarence N.Y.
Depending on the grind it may hurt bottom end power. If I remember correctly it will lessen exhaust valve clearance. I only retarded one cam once,it improved the upper rpm band a great deal. This was one
a roller cam in a dragster,not street driven.
a roller cam in a dragster,not street driven.
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From: Orange Park Florida
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Advancing the cam opens the intake sooner. Causing more reversion. Comp Cams grinds 4 degrees into their cams. It gives the car that choppy race idle. All show and no Go! Overlap/smaller LSA numbers create higher hydrocarbon emissions and poor gas mileage.
That is why factory cams even though mild have wide LSA like 114 - 116
I install my cams 4 degrees retarded for more top end. That is why I have lots of power out to 7500 rpm.
That is why factory cams even though mild have wide LSA like 114 - 116
I install my cams 4 degrees retarded for more top end. That is why I have lots of power out to 7500 rpm.
Melting Slicks
Joined: Mar 2001
Posts: 2,174
Likes: 56
From: Clarence N.Y.
mrvette advanceing the cam helps bottom end,retarding helps top end,
gkul hit it on the head about pulling hard in higher rpm's.
We used to advance the cam,along with other things,to increase bottom end power if a track had real good bite. If it was greasy we retarded the cam.
gkul hit it on the head about pulling hard in higher rpm's.
We used to advance the cam,along with other things,to increase bottom end power if a track had real good bite. If it was greasy we retarded the cam.
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From: All humans are vermin in the eyes of Guru VA
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So if I get a cam with a duration that creates the idle vacuum I need, I can retard it and pick up some top end power, perhaps get a wider lobe seperation?
Neat.
Neat.
Melting Slicks
Joined: Nov 2003
Posts: 2,362
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From: San Antonio TX
I have a wild way out thought lol. Ask the cam grinder what they think? Sure they will ask you questions about the car and how it is used. Weight,Transmission rear end gear and even questions about the engine. Other wise just install with a degree wheel by what the cam card says it should be.
as said before if you retard the cam it will increase the high end.
if you advance it will increase your low end.
And depending on the cam you can even play with rocker ratios. But that is another ball game lol.
as said before if you retard the cam it will increase the high end.
if you advance it will increase your low end.
And depending on the cam you can even play with rocker ratios. But that is another ball game lol.
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From: All humans are vermin in the eyes of Guru VA
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Because believe it or not. I enjoy learning more about concepts and the dynamics there in. I will probably end up calling a cam grinder at some point but, I also enjoy learning how things work and why things are done.
Melting Slicks
Joined: Nov 2003
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From: San Antonio TX
Race Director
Joined: Nov 2002
Posts: 12,142
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From: Taylor Michigan
Most of you have it right. Retard, top end. Advance, bottom end. But best bet for the street is straight up as most cams are dead on. Retard with domed pistons could be critical on overlap as the valves are hanging open in the cylinders and the piston is chasing the exhaust valve 
But if you have too much bottom end HP and would like to use it on top for MPH, you can retart it if you have one ot these. 
But if you have too much bottom end HP and would like to use it on top for MPH, you can retart it if you have one ot these.
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Joined: Jul 2004
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From: Pacific N.W. Warshington
I'm not a cam expert, but this was quite a bit different than previous experience and the only difference I could find (after the fact) was the wider LSA.
This is no fault of Summit and the cam/lifters broke in just fine: just me not paying attention to ALL the specs. I will change it again some day when time permits, in the meantime I rev it like crazy to keep up with what previously was normal.
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From: All humans are vermin in the eyes of Guru VA
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Racer
Joined: Oct 2004
Posts: 285
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From: Stockholm
If the intake valve will close later, will this mean that the some of the dynamic compression ratio will be bleed off?
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Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
This is my 383 cam valve event numbers installed straight up
Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 11.0 BTDC 45.0 ABDC 107 236 °
Exhaust 59.0 BBDC 5.0 ATDC 117 244 °
DD 2000 give my combination
558 @ 6000 and 536 @ 4500 and it drops to 487 hp @7500
Retard it 4 degrees and you get this: That is why I retard my cams.
Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 7.0 BTDC 49.0 ABDC 111 236 °
Exhaust 55.0 BBDC 9.0 ATDC 121 244 °
DD 2000 give my combination with 4 degrees retard
577 hp @ 6500 rpm and 532 TQ @5000 and it still has 532 hp @7500
Racer
Joined: Oct 2004
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From: Stockholm
Have you verified the DD2000 value with the dyno?
If I retard my cam let say 4 degrees and use a 0.028 composite head gasket as jackson recomended in this old thread http://forums.corvetteforum.com/show....php?t=1570164 , my DCR would be around 8.4 and the SCR around 11.1
If decking my block to 0.018, the quench dist would then be 0.046, which still should give me some quench benefits.
Now it evening here and I will forget about DCR/SCR/Quench and gaskets and go to the local pub nearby for a couple of beers, see you tomorrow guys!
If I retard my cam let say 4 degrees and use a 0.028 composite head gasket as jackson recomended in this old thread http://forums.corvetteforum.com/show....php?t=1570164 , my DCR would be around 8.4 and the SCR around 11.1
If decking my block to 0.018, the quench dist would then be 0.046, which still should give me some quench benefits.
Now it evening here and I will forget about DCR/SCR/Quench and gaskets and go to the local pub nearby for a couple of beers, see you tomorrow guys!
Last edited by gbak; Jan 12, 2007 at 11:53 AM.
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Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
No, because I live at 1500 meters and some of the local mountain passes are nearly 3000 meters. So if I spent the time and money to dial it in locally and then decide to enter some race near sea level non of the setting would be correct. The same thing I considered dyno tuning at sea level and writing everything down. so I would be good for racing at sea level and then retune for the majority of my driving.
I do know that it is a good time motor and when combined to a lightened car, it is really fun. With my 5 speed tranny it actually excelerates hard enough in 3 gear to actually feel it push me back in the seat from 4500 -7500 rpm. Even 4th gear is impressive how fast the speedo climbs to 140 mph and it's time to shift into 5th
I do know that it is a good time motor and when combined to a lightened car, it is really fun. With my 5 speed tranny it actually excelerates hard enough in 3 gear to actually feel it push me back in the seat from 4500 -7500 rpm. Even 4th gear is impressive how fast the speedo climbs to 140 mph and it's time to shift into 5th