How about an LS7 Cam in a 383? Tired of the Sewing Machine Noise!!!
01-26-2009, 08:21 PM
#1
How about an LS7 Cam in a 383? Tired of the Sewing Machine Noise!!! I would appreciate some advice regarding my 383 I recently built. I used an LS6 block, honed to match new Mahle 3.905" forged pistons, SCAT 4" crank and H-Beam rods. The heads are 243 castings, milled .020". I'm using Patriot Gold valve springs.
The problem I'm having is that despite trying several push-rod lengths, I still have that annoying "sewing-machine" sound from the engine. I tried 7.35", then 7.30" (much worse), and finally settled on 7.40". Since the heads were milled .020" and the block surface decked .008", I wouldn't think that any longer would be good for the LS1 lifters. I've tried measuring with the Comp Cams push-rod checker, but I just get more discouraged.
What I suspect is the cam lobes are just too aggressive, which is causing the valves to snap shut. The cam is a Comp Cams - 224 intake, 230 exhaust, .609 lift/.605" on a 114LSA. These are the XFI lobes.
What are the thoughts about going with a less aggressive cam like the factory LS7 cam? I know that I would need an LS2 front cover and cam sensor extension, but that's no problem. Would the motor sound stock again? Would the cam be sufficient for a 383?
Any other thoughts?
The problem I'm having is that despite trying several push-rod lengths, I still have that annoying "sewing-machine" sound from the engine. I tried 7.35", then 7.30" (much worse), and finally settled on 7.40". Since the heads were milled .020" and the block surface decked .008", I wouldn't think that any longer would be good for the LS1 lifters. I've tried measuring with the Comp Cams push-rod checker, but I just get more discouraged.
What I suspect is the cam lobes are just too aggressive, which is causing the valves to snap shut. The cam is a Comp Cams - 224 intake, 230 exhaust, .609 lift/.605" on a 114LSA. These are the XFI lobes.
What are the thoughts about going with a less aggressive cam like the factory LS7 cam? I know that I would need an LS2 front cover and cam sensor extension, but that's no problem. Would the motor sound stock again? Would the cam be sufficient for a 383?
Any other thoughts?
01-26-2009, 08:59 PM
#2
IMO it would be a complete and utter waste of your time and money to put a factory GM cam back in a 383 engine. Not too mention it takes some elbow grease on the LS2/7 conversion to use their cams. I've done the conversion once, and don't ever plan on doing it again. The gain wasn't worth it, nor what I got paid to do it.
Your main problem is the XFI lobe. If you backed down to an XE or XE-R lobe even, you'd notice a dramatic decrease in valvetrain noise. It won't be dead quiet, but will be noticeably quieter. One big reason I don't use LSK or XFI lobes is for this reason, that and their spring killers. Most of the cams I use are on XE or XE-R, and I've never once got a complaint on valvetrain noise.
How are you setting up the valvetrain? Are you using an adjustable pushrod, checking preload, using a checker spring, etc etc ? If you're just throwing diff. length pushrods in there hoping something will work, that's not how to go about it. Not trying to be a dick, just letting you know.
That cam choice could also be a tad better for your application. I use a 232/236 XE-R/XE 113+4 cam in the 383's I've done, and it's kicked major ***, the valvetrain is quiet
, and driveability is about perfect.
Your main problem is the XFI lobe. If you backed down to an XE or XE-R lobe even, you'd notice a dramatic decrease in valvetrain noise. It won't be dead quiet, but will be noticeably quieter. One big reason I don't use LSK or XFI lobes is for this reason, that and their spring killers. Most of the cams I use are on XE or XE-R, and I've never once got a complaint on valvetrain noise.
How are you setting up the valvetrain? Are you using an adjustable pushrod, checking preload, using a checker spring, etc etc ? If you're just throwing diff. length pushrods in there hoping something will work, that's not how to go about it. Not trying to be a dick, just letting you know.
That cam choice could also be a tad better for your application. I use a 232/236 XE-R/XE 113+4 cam in the 383's I've done, and it's kicked major ***, the valvetrain is quiet
, and driveability is about perfect.
01-26-2009, 09:13 PM
#3
IMO it would be a complete and utter waste of your time and money to put a factory GM cam back in a 383 engine. Not too mention it takes some elbow grease on the LS2/7 conversion to use their cams. I've done the conversion once, and don't ever plan on doing it again. The gain wasn't worth it, nor what I got paid to do it.
Your main problem is the XFI lobe. If you backed down to an XE or XE-R lobe even, you'd notice a dramatic decrease in valvetrain noise. It won't be dead quiet, but will be noticeably quieter. One big reason I don't use LSK or XFI lobes is for this reason, that and their spring killers. Most of the cams I use are on XE or XE-R, and I've never once got a complaint on valvetrain noise.
How are you setting up the valvetrain? Are you using an adjustable pushrod, checking preload, using a checker spring, etc etc ? If you're just throwing diff. length pushrods in there hoping something will work, that's not how to go about it. Not trying to be a dick, just letting you know.
That cam choice could also be a tad better for your application. I use a 232/236 XE-R/XE 113+4 cam in the 383's I've done, and it's kicked major ***, the valvetrain is quiet , and driveability is about perfect.
Your main problem is the XFI lobe. If you backed down to an XE or XE-R lobe even, you'd notice a dramatic decrease in valvetrain noise. It won't be dead quiet, but will be noticeably quieter. One big reason I don't use LSK or XFI lobes is for this reason, that and their spring killers. Most of the cams I use are on XE or XE-R, and I've never once got a complaint on valvetrain noise.
How are you setting up the valvetrain? Are you using an adjustable pushrod, checking preload, using a checker spring, etc etc ? If you're just throwing diff. length pushrods in there hoping something will work, that's not how to go about it. Not trying to be a dick, just letting you know.
That cam choice could also be a tad better for your application. I use a 232/236 XE-R/XE 113+4 cam in the 383's I've done, and it's kicked major ***, the valvetrain is quiet
, and driveability is about perfect.As for the pushrod length checking, I tried using the pushrod checker, but it's kind of hard to tell if the lifter plunger is all the way pumped-up or down in the lifter body. Then, it's a pain the *** to keep putting the rocker back on, checking for movement, etc. I guess I'm just getting lazy (lazier??) in my old age.
But, I'd be open to another cam to quiet things down. I'm at the point were I really don't want to even drive the thing. It's embarassing. tic-tic-tic-tic-tic-tic-tic........
01-29-2009, 03:08 PM
#4
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I think you have it backwards... my valve train noise is almost stock and I am running the same XFI cam. It's definately quieter than the XERs I've heard... not to mention it's easier on the springs, giving them LONGER life.
01-29-2009, 08:01 PM
#6
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Even though you mentioned it already, my guess is either pushrod length or lifter preload. With this cam, Patrick G recommended 7.425, but I got away with 7.4. You might want to try the 7.425 if you can't get the lifter preload correct.
