LT1 Weaknesses
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Re: LT1 Weaknesses
Originally Posted by chrism400
Yes I would agree. I didn't know the advertised duration of the Hotcam and still don't (trying to find that out.) If the advertised duration at .006 is more than the XE grind, then overlap can be more depending on valve opening and closing events. As far as I can see, Z95M6 may be right on this one. But I wouldn't say I'm your "Bitch" though. The score is 2-1 in my favor. Shame on me for not checking the advertised duration on the Hotcam.
Originally Posted by chrism400
Cam help for Z95M6, Jerm, & chrism400 
:
Since we talking degrees, I might as well cover duration. Duration is the amount of time that the valve is open in relation to crankshaft rotation. It is expressed in crankshaft degrees. If we have a cam with a duration of 300 degrees, the valve will be open for 300 degrees of crankshaft rotation. There are two methods used to describe duration. Seat-to-seat or Advertised duration and at .050" duration. The advertised duration is the measurement from the very beginning to the very end of the lobe ramps. It is difficult to get an accurate measurement using advertised duration. Theoretically, you should be able to find zero lift of the lobe ramps, but it is harder than it sounds. To simplify this method, cam grinders pick an arbitrary number unique to themselves. It could be anywhere from .002" lift to .008" lift. Because cam grinders wont get together and give us consistent advertised duration lift points, they came up with a standardized method of @.050" lift. When the lobe is at .050" lift, the duration starts and ends when the lobe is at .050" lift on the other side of the lobe. When comparing cam profiles, it’s best to use the .050" duration numbers.
Duration is probably the most important aspect of a cam’s profile to pin down when selecting a cam. Cubic inch displacement, cylinder head characteristics, EFI, NOS, aspiration, compression, drive train, vehicle application and weight, desired peak power, desired engine operating rpm…….etc are all factors to consider when picking a cam. I’ve found that it’s usually a task best left to the cam grinder to make. I’m not going to get into cam selection in this article, but I should talk a bit about the effects that duration has on an engine.
:Since we talking degrees, I might as well cover duration. Duration is the amount of time that the valve is open in relation to crankshaft rotation. It is expressed in crankshaft degrees. If we have a cam with a duration of 300 degrees, the valve will be open for 300 degrees of crankshaft rotation. There are two methods used to describe duration. Seat-to-seat or Advertised duration and at .050" duration. The advertised duration is the measurement from the very beginning to the very end of the lobe ramps. It is difficult to get an accurate measurement using advertised duration. Theoretically, you should be able to find zero lift of the lobe ramps, but it is harder than it sounds. To simplify this method, cam grinders pick an arbitrary number unique to themselves. It could be anywhere from .002" lift to .008" lift. Because cam grinders wont get together and give us consistent advertised duration lift points, they came up with a standardized method of @.050" lift. When the lobe is at .050" lift, the duration starts and ends when the lobe is at .050" lift on the other side of the lobe. When comparing cam profiles, it’s best to use the .050" duration numbers.
Duration is probably the most important aspect of a cam’s profile to pin down when selecting a cam. Cubic inch displacement, cylinder head characteristics, EFI, NOS, aspiration, compression, drive train, vehicle application and weight, desired peak power, desired engine operating rpm…….etc are all factors to consider when picking a cam. I’ve found that it’s usually a task best left to the cam grinder to make. I’m not going to get into cam selection in this article, but I should talk a bit about the effects that duration has on an engine.
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Re: LT1 Weaknesses
Originally Posted by Jerm
The advertised duration is listed at .050" on every cam I've seen, how are you supposed to find that out?
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Re: LT1 Weaknesses
Originally Posted by TQdrivenws6
That is not necessarily true. Overlap is affected by the opening and closing rates also, so if the valve timing is more or less aggressive around the seat, then you can have the overlap change also.
.The way I understand it if the valve opening and closing points are identical (same adv duration on the same LCA) the open period would be the same reguardless and thus the overlap would be identical ,for instance if both cams open the intake at say 20 BTDC and both close the exhaust 15 ATDC and they both have a 110 LCA but one has 230 .050 and the other has 224 .050 they would both still have 25 degrees of overlap right?
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Re: LT1 Weaknesses
Originally Posted by WS Sick
I can't understand what youre saying here, please explain in simpler terms for me please .
The way I understand it if the valve opening and closing points are identical (same adv duration on the same LCA) the open period would be the same reguardless and thus the overlap would be identical ,for instance if both cams open the intake at say 20 BTDC and both close the exhaust 15 ATDC and they both have a 110 LCA but one has 230 .050 and the other has 224 .050 they would both still have 25 degrees of overlap right?
.The way I understand it if the valve opening and closing points are identical (same adv duration on the same LCA) the open period would be the same reguardless and thus the overlap would be identical ,for instance if both cams open the intake at say 20 BTDC and both close the exhaust 15 ATDC and they both have a 110 LCA but one has 230 .050 and the other has 224 .050 they would both still have 25 degrees of overlap right?
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Re: LT1 Weaknesses
Originally Posted by Z95m6
See obviously you need to look at some cam specs. The Xe's have more duration at .05 lift but actually have less advertised duration. So actually the lobes are smaller than a standard lobe of similar duration at .05 lift. They just spend more time at higher lifts so they make more power from a smaller lobe. Look at just the intake lobes. The hot cam intake lobe has 280 degrees of advertised duration vs the 224's intake lobe of 276 degrees of duration. Hmm it seems the hotcam's lobes are bigger. Even though the 224 has more duration at .050 lift. What did i tell you the Xe lobes are actually smaller than standard lobes yet they make more power. You said in your own post that more duration = more overlap. Read, learn, understand what you are talking about before you post. You are Owned B!tch.
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From: newton, kansas, USA
Re: LT1 Weaknesses
The Xe lobes are designed to do more in a smaller lobe. Ex. CC306 intake lobe VS 230/236 intake lobe.
.050 duration Advertised duration
CC306 intake 230 290
230/236 intake 230 281
Since both of these are Comp Grinds they would be using the same measuring devise (tolerances) to measure the Advertised duration. The Xe lobe still has smaller advertised duration so it will provide less overlap provided the exhaust lobes were the same size. I believe i remember Phil at AI telling me that you can look at the Advertised duration vs the .050 lift to see how aggressive the ramps were. I wanted a lunati 227/233 cam instead of the XE but he said the ramps were so big and lazy by comparing Advertised duration vs .050 duration, that it would have overlap like the CC306. So i went with the XE grind instead.
.050 duration Advertised duration
CC306 intake 230 290
230/236 intake 230 281
Since both of these are Comp Grinds they would be using the same measuring devise (tolerances) to measure the Advertised duration. The Xe lobe still has smaller advertised duration so it will provide less overlap provided the exhaust lobes were the same size. I believe i remember Phil at AI telling me that you can look at the Advertised duration vs the .050 lift to see how aggressive the ramps were. I wanted a lunati 227/233 cam instead of the XE but he said the ramps were so big and lazy by comparing Advertised duration vs .050 duration, that it would have overlap like the CC306. So i went with the XE grind instead.
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From: Dayton, OH
Re: LT1 Weaknesses
[QUOTE=Z95m6]The Xe lobes are designed to do more in a smaller lobe.
Yes, I get that much. It's good to have a shorter duration lobe with high ramp rates to open and close the valve quickly. It lets the engine get the job done with less cylinder pressure loss etc...I'm unsubscribing to this thread because I haven't eaten in 4 days, my hair is falling out, the wife says I'm ugly, and my kids don't recognize me anymore. I just don't care anymore and I think my life is over.
Yes, I get that much. It's good to have a shorter duration lobe with high ramp rates to open and close the valve quickly. It lets the engine get the job done with less cylinder pressure loss etc...I'm unsubscribing to this thread because I haven't eaten in 4 days, my hair is falling out, the wife says I'm ugly, and my kids don't recognize me anymore. I just don't care anymore and I think my life is over.
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From: Kansas
Re: LT1 Weaknesses
Originally Posted by chrism400
I don't think anyone really knows what the heck the Hotcam really is. Still doing research...
This hydraulic roller cam is for service only for all V8 engines with roller camshafts. The duration at lash point in degrees (intake/exhaust) is 279/287; duration at .050" tappet lift (intake/exhaust) is 218/228; and maximum lift with 1.6 rocker ratio (intake/exhaust) is 525/525. Valve lash is zero/zero and lobe centerline is 112 degrees.
I got the specs from the gm goodwrench website. Are you a believer now?
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Re: LT1 Weaknesses
I went on the Canton site for an oil pan and came across a few things regarding the oil pan for the 96 LT1 fbody.
Was there any issue in dealing w/ the fitment of the pan?
STYLE: 7-1/2" shallow, fully baffled for road racing, this pan was designed to fit in late model (82-92) F Bodies, (93-Up) F Bodies might require the steering rack to be lowered or the engine mounts shimmed. Makes a great late F-Body Drag Pan. Can be used with cross-over exhaust. Pans can be notched for steering clearance on a special order basis.
Canton
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Re: LT1 Weaknesses
Originally Posted by Jerm
I went on the Canton site for an oil pan and came across a few things regarding the oil pan for the 96 LT1 fbody.
Was there any issue in dealing w/ the fitment of the pan?
Was there any issue in dealing w/ the fitment of the pan?
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Posts: 240
From: You know when they Quit Suckin that something is Wrong!!!!
Re: LT1 Weaknesses
Originally Posted by Z95m6
I wouldn't waste my money on a bigger oil pan the stocker works fine. That is money you could be putting towards a better cam or headers. Just my opinion
Originally Posted by Jerm
I did a search and have found a world of conflicting opinions.
The car sees a lot of road racing, so my goal in the rebuild is to make sure I cover all the LT1 weaknesses.
The car sees a lot of road racing, so my goal in the rebuild is to make sure I cover all the LT1 weaknesses.
It's not bigger and the reason why it interests me is to prevent oil starvation. Last time I checked, a dry sump system can get pretty expensive, so I definitely do not want to go that route
BTW, the best price I've found on Mac Midlenghts w/ dual cat is 675, can anybody beat that?
Last edited by Jerm; Oct 21, 2004 at 11:49 PM.
