LT4 Production cam vs Hot cam?
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LT4 Production cam vs Hot cam?
Hey all,
So I never knew, but I heard there are actually two different versions of the LT4 cam. The one used in the factory LT4 Vette's (And I think some 4th gen F-bodies?), and the "Hotcam" version, which is supposed to be more aggressive, is this correct?
If so, I'm mainly asking which one would be a better choice for the motor I'm planning to swap into my car. How does the drivability of the two differ, mainly? What I'm dropping in will basically be a stock L31 longblock, with the exception of having the heads machined and valve springs upgraded for a higher lift cam. Just basically a fun street car build to replace the tired L03 I have now with.
It will be fed by a modified TBI system upgraded w/the EBL Flash, if that makes any difference (i.e, it's staying EFI, no carb). I have a GMPP TBI Vortec intake on it's way I will be using.
Also, if there are other cams I should consider, don't be afraid to mention those as well.
Thanks!
So I never knew, but I heard there are actually two different versions of the LT4 cam. The one used in the factory LT4 Vette's (And I think some 4th gen F-bodies?), and the "Hotcam" version, which is supposed to be more aggressive, is this correct?
If so, I'm mainly asking which one would be a better choice for the motor I'm planning to swap into my car. How does the drivability of the two differ, mainly? What I'm dropping in will basically be a stock L31 longblock, with the exception of having the heads machined and valve springs upgraded for a higher lift cam. Just basically a fun street car build to replace the tired L03 I have now with.
It will be fed by a modified TBI system upgraded w/the EBL Flash, if that makes any difference (i.e, it's staying EFI, no carb). I have a GMPP TBI Vortec intake on it's way I will be using.
Also, if there are other cams I should consider, don't be afraid to mention those as well.
Thanks!
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Re: LT4 Production cam vs Hot cam?
First part: correct. But you'll get better results from your proposal if you use the ZZ4 cam.
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Re: LT4 Production cam vs Hot cam?
We put in GM part number 14097395 in a crate 350 which used to be known as "the 383 cam". You got to remember you can't ignore the SCR of a engine when choosing which cam. The customer was very happy with the amount of bottom end this cam provided with a TBI. And no matter what cam you choose,the cam needs to be degree'ed in.
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From: Macon, GA
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Re: LT4 Production cam vs Hot cam?
I'd skip the LT4 cam. You already have a factory sized cam, if you are going to bother changing it out, get a big one. The LT4 hotcam is a pretty decent medium cam. Not super cutting edge, but decent. Works great with Vortec heads too. I'd probably expect around 325-350fwhp, which is good enough for 12's at the track if you can get the TBI to feed it.
Degreeing cams:
Grumpy is a guy I listen to when it comes to these matters, and he suggests that it's super critical. Very smart fellow and very experienced:
http://forum.grumpysperformance.com/....php?f=52&t=90
And then here is Ron Iskendarian speaking his mind on the matter:
http://www.dragracingonline.com/tech...sion/ii_4.html
And our favorite pal... sofa:
It's not that its a bad idea, if you can do it, do it. But at the end of the day, for people like us I just dont think it's worth it to get hung up on slight discrepancies of tiny measurements that lead to small power band nuances. Running a factory block and heads under a TBI in a streetcar, you're not trying to win any sanctioned races, just have a fun car. Peak torque happening 100 RPMs sooner or later just isnt going to matter.
But if you just want to verify your cam matches the specs and they didnt accidently send you an RV cam, go for it.
Degreeing cams:
Grumpy is a guy I listen to when it comes to these matters, and he suggests that it's super critical. Very smart fellow and very experienced:
http://forum.grumpysperformance.com/....php?f=52&t=90
when your degreeing in a cam your verifying that the cam card figures , you purchased the cam for MATCH what the cams going to be doing in the engine , if everything is correct a dot-to-dot install will be almost identical, but the fact is that due to manufacturing tolerances a dot-to-dot install will frequently be a few degrees off! now most guys might never notice, but it can and frequently does effect the engines power band so getting it correct helps and eliminates one potential source of problems
And then here is Ron Iskendarian speaking his mind on the matter:
http://www.dragracingonline.com/tech...sion/ii_4.html
Now Kurt, to answer your specific questions. Of the four timing events, the intake closing point is by far the most important because it regulates your cranking compression. (Reference Tech Tips #2001 and #2002 on the Isky website www.iskycams.com) As to whether you should move the cam to the calculated 104-degree intake centerline or change the intake opening point to 33 degrees Before TDC — to accomplish this 4 degree advancing of the camshaft, use either method you are comfortable with. As the story above points out, in one’s pursuit of higher performance, splitting hairs with valve timing is not a panacea. Your time and energy would be better focused elsewhere.
And our favorite pal... sofa:
What timing set are you using?
Does it have adjustment provisions?
Do you know what the cam's intake centerline is designed to be?
Since you can't change the ICL with the timing set you have (in smaller increments than one tooth of the chain anyway), what would you do if you found that the cam wasn't where it was supposed to be? Do you know if that would even be a bad thing?
That's the downside of "degreeing" a cam for most people. Not that it's a bad idea in and of itself; but, if it's off, there's basically not a thing you can do about it except send the cam back or buy an adjustable timing set. All you're really accomplishing, is doing the cam mfr's QC for them, after the fact.
If it's an off-the-shelf cam from a major mfr (Comp, Crower, Isky, Lunati, Crane, etc.), and a good quality timing set from a reputable mfr as well, then your odds of it coming out within a degree or so of its design are probably 99% or better. On the other hand, if you're using a cheeep "roller" timing chain, the $20 kind that we call "bushing roller" or "truck chain", it will stretch about 6° within the first 1000 miles anyway, no matter what you do; so does it really matter how accurate you get it? since it's not going to stay where you put it anyway. "Measure with micrometer, mark with chalk, cut with axe".
So there's no "right" answer to that question, either "yes you must" or "don't bother"; it's all about what YOU feel comfortable with, and how much you want to spend on tools if anything, and what you think you might do if it turns out different from what you think you want.
Does it have adjustment provisions?
Do you know what the cam's intake centerline is designed to be?
Since you can't change the ICL with the timing set you have (in smaller increments than one tooth of the chain anyway), what would you do if you found that the cam wasn't where it was supposed to be? Do you know if that would even be a bad thing?
That's the downside of "degreeing" a cam for most people. Not that it's a bad idea in and of itself; but, if it's off, there's basically not a thing you can do about it except send the cam back or buy an adjustable timing set. All you're really accomplishing, is doing the cam mfr's QC for them, after the fact.
If it's an off-the-shelf cam from a major mfr (Comp, Crower, Isky, Lunati, Crane, etc.), and a good quality timing set from a reputable mfr as well, then your odds of it coming out within a degree or so of its design are probably 99% or better. On the other hand, if you're using a cheeep "roller" timing chain, the $20 kind that we call "bushing roller" or "truck chain", it will stretch about 6° within the first 1000 miles anyway, no matter what you do; so does it really matter how accurate you get it? since it's not going to stay where you put it anyway. "Measure with micrometer, mark with chalk, cut with axe".
So there's no "right" answer to that question, either "yes you must" or "don't bother"; it's all about what YOU feel comfortable with, and how much you want to spend on tools if anything, and what you think you might do if it turns out different from what you think you want.
It's not that its a bad idea, if you can do it, do it. But at the end of the day, for people like us I just dont think it's worth it to get hung up on slight discrepancies of tiny measurements that lead to small power band nuances. Running a factory block and heads under a TBI in a streetcar, you're not trying to win any sanctioned races, just have a fun car. Peak torque happening 100 RPMs sooner or later just isnt going to matter.
But if you just want to verify your cam matches the specs and they didnt accidently send you an RV cam, go for it.
Last edited by InfernalVortex; Sep 1, 2012 at 09:50 AM.
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Re: LT4 Production cam vs Hot cam?
The quality single roller heavy bike style chains do stay where they are put. Cams are cores before they are ground and pin locations are located before they are ground. Lots depend on the same cores used by many. GM during the smog yrs on purpose built their timing gears retarded. To use those veritable adjustment timing sets is a bad idea because the adjustment doesn't stay where it is set.
It was Ed himself yrs ago during a dinner we had after a Indy Drag Racers auction that told us too many things come into play to install a cam right out of the box. That it needs to be degree'ed. And John Lingenfelter confirmed the same with us telling us not one of his engines leaves his shop without it. And yes that is his main business is street engines.
But aside from throwing out names. I am telling you that with over 40 yrs of building,selling,and racing engines. It's in the details that matter. So say it's only a street car,is sour grapes. I suggest you have to make a decision if your building a car or not where every dollar you put in you want back in power output. To say cam timing events don't really matter,in my opinion is just wrong.
LOL-just to throw out one more name. A for-runner in the trades Engine Builder Mag has many,many,authors of articles with no less David Vizard supporting degree'ing cams.
Aside from being side tracked with this debate,I don't want you to over look the cam I am suggesting. I am guessing at your compression ratio,but if it is what I think it is,that cam is pretty well matched up for your engine. GM build it for their crate engines.
It was Ed himself yrs ago during a dinner we had after a Indy Drag Racers auction that told us too many things come into play to install a cam right out of the box. That it needs to be degree'ed. And John Lingenfelter confirmed the same with us telling us not one of his engines leaves his shop without it. And yes that is his main business is street engines.
But aside from throwing out names. I am telling you that with over 40 yrs of building,selling,and racing engines. It's in the details that matter. So say it's only a street car,is sour grapes. I suggest you have to make a decision if your building a car or not where every dollar you put in you want back in power output. To say cam timing events don't really matter,in my opinion is just wrong.
LOL-just to throw out one more name. A for-runner in the trades Engine Builder Mag has many,many,authors of articles with no less David Vizard supporting degree'ing cams.
Aside from being side tracked with this debate,I don't want you to over look the cam I am suggesting. I am guessing at your compression ratio,but if it is what I think it is,that cam is pretty well matched up for your engine. GM build it for their crate engines.
Last edited by 1gary; Sep 1, 2012 at 11:42 AM.
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Re: LT4 Production cam vs Hot cam?
Checking the install is very important. Having it exactly on spec is relative. For a 400 HP 350, one degree off either way is not a big deal. In fact, re-degree most cams on all 16 lobes, you'll find precious few that are all on spec. But nobody is going to degree one cam 16 times. I only did it twice, and won't be doing that ever again. Lesson learned. Exactly on spec is more of a concern with canted-valve engines using huge lobes and huge domes. Then a degree can make a world of difference.
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Re: LT4 Production cam vs Hot cam?
You guys are either trying to win races or trying to sell performance engines and cars. Different goals, different means. For guys like you and Lingenfelter and so forth it's stupid not to go through that extra trouble.
Definitely not a bad idea to degree it in, but we're just trying to build fun street cars, you know?
Definitely not a bad idea to degree it in, but we're just trying to build fun street cars, you know?
Last edited by InfernalVortex; Sep 1, 2012 at 12:54 PM.
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Re: LT4 Production cam vs Hot cam?
You guys are either trying to win races or trying to sell performance engines and cars. Different goals, different means. For guys like you and Lingenfelter and so forth it's stupid not to go through that extra trouble.
Definitely not a bad idea to degree it in, but we're just trying to build fun street cars, you know?
Definitely not a bad idea to degree it in, but we're just trying to build fun street cars, you know?
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Re: LT4 Production cam vs Hot cam?
The factory LT4 cam is only a smidge bigger than the factory LT1 cam, which itself is basically the same as the old L98 TPI cam, but with more lift. They are all pretty similar, differing more in lift than duration. I duobt you could tell them apart without a dyno.
The LT4 HotCam is about 10-15* more duration than the production line LT4 cam (specs in at 218/228* @ .050 on a 112* LSA and .525/.525" lift using the spec'ed 1.6 rocker arms). Works great with Vortecs but I think it might be a bit much with a factory TBI setup and mild 9:1 compression of the Vortec longblock. If killer low end torque is your goal I think you'll find it a bit mushy down low.
The factory Vortec truck motor cam is something like 194/202* @ .050, if memory serves. So it's considerably smaller than the LT4 HotCam. The production line LT4 cam would be about in the middle of the two.
The LT4 HotCam is about 10-15* more duration than the production line LT4 cam (specs in at 218/228* @ .050 on a 112* LSA and .525/.525" lift using the spec'ed 1.6 rocker arms). Works great with Vortecs but I think it might be a bit much with a factory TBI setup and mild 9:1 compression of the Vortec longblock. If killer low end torque is your goal I think you'll find it a bit mushy down low.
The factory Vortec truck motor cam is something like 194/202* @ .050, if memory serves. So it's considerably smaller than the LT4 HotCam. The production line LT4 cam would be about in the middle of the two.
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Re: LT4 Production cam vs Hot cam?
Well, based on what everyone has said so far, The LT4 hot cam sounds like a great choice for my build, but 1gary, what kind of performance differences would the GM cam 14097395 make vs the LT4?
Overall, I'm after a fairly consistent powerband vs just gobs of low end torque or screaming top end, and something around 350 FWHP, give or take a few ponies. Something I can drive around and enjoy on a nice day, but that's also alot of fun when you open it up.
As far as the TBI being able to feed it, I will be upgrading the ECM w/EBL Flash, and using bigger injectors and a higher flow fuel pump, so I'm not too worried about being able to properly tune/feed the motor.
Overall, I'm after a fairly consistent powerband vs just gobs of low end torque or screaming top end, and something around 350 FWHP, give or take a few ponies. Something I can drive around and enjoy on a nice day, but that's also alot of fun when you open it up.
As far as the TBI being able to feed it, I will be upgrading the ECM w/EBL Flash, and using bigger injectors and a higher flow fuel pump, so I'm not too worried about being able to properly tune/feed the motor.
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Re: LT4 Production cam vs Hot cam?
I think Summit still sells the cam I am referring to.Nice spec's if you look it up there for the compression ratio engine you have.Not a huge 500 lift,but the timing events lend it's self to a good performer. We too used a 350 crate with a TBI and some slight mods to the TBI with that cam. Kind of took me by surprise how wide the power band was. The customer still to date comments on how happy he is with it.
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Re: LT4 Production cam vs Hot cam?
Checking the install is very important. Having it exactly on spec is relative. For a 400 HP 350, one degree off either way is not a big deal. In fact, re-degree most cams on all 16 lobes, you'll find precious few that are all on spec. But nobody is going to degree one cam 16 times. I only did it twice, and won't be doing that ever again. Lesson learned. Exactly on spec is more of a concern with canted-valve engines using huge lobes and huge domes. Then a degree can make a world of difference.
You guys are either trying to win races or trying to sell performance engines and cars. Different goals, different means. For guys like you and Lingenfelter and so forth it's stupid not to go through that extra trouble.
Definitely not a bad idea to degree it in, but we're just trying to build fun street cars, you know?
Definitely not a bad idea to degree it in, but we're just trying to build fun street cars, you know?
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Re: LT4 Production cam vs Hot cam?
I keep leaving out one very important thing.As for the two of you,I have read a number of threads that you two have posted on. You should be two of the respected members of this forum along with many others. Alot of what I read from both of you I say hell ya, now that something to think about,kewl.
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Re: LT4 Production cam vs Hot cam?
The factory LT4 cam is only a smidge bigger than the factory LT1 cam, which itself is basically the same as the old L98 TPI cam, but with more lift. They are all pretty similar, differing more in lift than duration. I duobt you could tell them apart without a dyno.
The LT4 HotCam is about 10-15* more duration than the production line LT4 cam (specs in at 218/228* @ .050 on a 112* LSA and .525/.525" lift using the spec'ed 1.6 rocker arms). Works great with Vortecs but I think it might be a bit much with a factory TBI setup and mild 9:1 compression of the Vortec longblock. If killer low end torque is your goal I think you'll find it a bit mushy down low.
The factory Vortec truck motor cam is something like 194/202* @ .050, if memory serves. So it's considerably smaller than the LT4 HotCam. The production line LT4 cam would be about in the middle of the two.
The LT4 HotCam is about 10-15* more duration than the production line LT4 cam (specs in at 218/228* @ .050 on a 112* LSA and .525/.525" lift using the spec'ed 1.6 rocker arms). Works great with Vortecs but I think it might be a bit much with a factory TBI setup and mild 9:1 compression of the Vortec longblock. If killer low end torque is your goal I think you'll find it a bit mushy down low.
The factory Vortec truck motor cam is something like 194/202* @ .050, if memory serves. So it's considerably smaller than the LT4 HotCam. The production line LT4 cam would be about in the middle of the two.
191º/196º dur @ 0.50" lift lift is 0.412"/0.428" on a 111ºLSA
1996 Vette LT4 manual trans/1996 COllectors Edition Manual trans/1996 Vette Grand Sport and 1997 LT4 Firehwak and LT4 SS Camaro cam spec was 203º/210º 0.476"/.480" with 1.6:1 rockers(stock full roller fulcrum and roller tipped rockers-ONLY GM engine to ever use a full roller trunnion and tip)0.446"/.450" lift with 1.5:1 rockers on a 115ºLSA.
ZZ3/4 cam 208º/221º lift 0.474/0/510" 112º
ZZZ-ZZ2 engines roller cam235º/235º dur@0.50" 0.489"/0.480"114ºLSA
HT383/Ramjet 350 and MArine roler cam 196º/206º 0.431"/451" 109ºLSA
95-97 dual Cat LT1 F-body 201/208º 0.447"/0.459" on
1987 TPI 350 206º206º 0.403"/0.415" 115ºLSA
Just a few GM roller cams off the top of my head. I orget some of the earlier Y body and F body LT1 cams.
peace
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