Okay, I know that this is not your typical LM4 application but I thought you guys might get a kick out of it. Plus it's not easy to find a lot of info on LM4's. I am also looking for some cam advice. I have a custom motor builder who is suggesting a custom cam grind of 220/228 duration 581/588 lift. Keep in mind that this is a 2000lb car. What do you think of this cam?
My SSR: 05 6 sp. with 4.56 gears, ZR1 clutch, Edelbrock intake, Lunati cam, Crane rockers, C6 modified pan
At only 2k# cam selection is certainly easier than in the 5k# SSR. If you're more than satisfied with the low rpm power now, then that cam should be great for more high end power. The problem with the LM4 is the low static compression. At 9.5-1, it's easy to really kill the low end with excessive int. duration. The intake closing point is what you need to look at closely. The further past BDC that the intake valve closes the more low end you will sacrifice. What you'd ideally like for that 5.3 is a very aggressive int. lobe with a very quick closing rate to retain the cylinder pressure. Tighter lobe centers will help as will installing the cam advanced. Also big ratio rockers will move the valve real hard with out changing the actual opening and closing point. The drawback to real aggressive lobes is the need for more valve spring pressure to control things. If you're currently running the stock cam, that cam that you listed is substantially larger, and would certainly swing the torque curve upward.
At only 2k# cam selection is certainly easier than in the 5k# SSR. If you're more than satisfied with the low rpm power now, then that cam should be great for more high end power. The problem with the LM4 is the low static compression. At 9.5-1, it's easy to really kill the low end with excessive int. duration. The intake closing point is what you need to look at closely. The further past BDC that the intake valve closes the more low end you will sacrifice. What you'd ideally like for that 5.3 is a very aggressive int. lobe with a very quick closing rate to retain the cylinder pressure. Tighter lobe centers will help as will installing the cam advanced. Also big ratio rockers will move the valve real hard with out changing the actual opening and closing point. The drawback to real aggressive lobes is the need for more valve spring pressure to control things. If you're currently running the stock cam, that cam that you listed is substantially larger, and would certainly swing the torque curve upward.
Wow - the knowledge on this site continues to amaze me.
You can come work on my engine anytime!!!!!!
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snip~ If you're currently running the stock cam, that cam that you listed is substantially larger, and would certainly swing the torque curve upward.
I shouldn't think a sand digger would want to sacrifice much bottom end torque. Although with relatively less traction to a street car, maybe a higher rpm is a more normal range.
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At only 2k# cam selection is certainly easier than in the 5k# SSR. If you're more than satisfied with the low rpm power now, then that cam should be great for more high end power. The problem with the LM4 is the low static compression. At 9.5-1, it's easy to really kill the low end with excessive int. duration. The intake closing point is what you need to look at closely. The further past BDC that the intake valve closes the more low end you will sacrifice. What you'd ideally like for that 5.3 is a very aggressive int. lobe with a very quick closing rate to retain the cylinder pressure. Tighter lobe centers will help as will installing the cam advanced. Also big ratio rockers will move the valve real hard with out changing the actual opening and closing point. The drawback to real aggressive lobes is the need for more valve spring pressure to control things. If you're currently running the stock cam, that cam that you listed is substantially larger, and would certainly swing the torque curve upward.
Thanks for the knowledge and feedback. I hear what you are saying but how does this info compare to my cam (I am very cam illiterate)? Are you saying my cam will not close quickly and therefore I will loose low end torque? This cam has a 113 lobe center which I was told helps keep low end torque. I am also planning to add an LS6 intake at the same time, currently I have an LS1 intake. Will this help to regain some of that low end torque?
A ton of torque is not necessary in a 2K# sand car. However, it is nice for cruising and just punching it when needed. I have also just lowered all my gears quite a bit so I will be higher in the RPM range more often.
My SSR: 05 6 sp. with 4.56 gears, ZR1 clutch, Edelbrock intake, Lunati cam, Crane rockers, C6 modified pan
Hey N2, I forgot to mention in my first post that your ride is way way Cool and looks like a blast! We went sand dragging for about 10 yrs. as it got real popular for a while in the midwest. We also went dune running some with it, as there's some great sand dunes on Lake Michigan. We were using a Jeep though with a 2.08/1 transfer case, so we had some crazy gear ratios to play with. I see you've lowered your gearing, so that should really help in regards to that camshaft. If it were me, I'd probably still install it 4 degrees advanced to build a little cylinder pressure. What also is helpful is if you would consider installing a solid lifter roller cam & lifters. Then if you miss slightly on the cam profile, by adjusting the valve lash you can change the cam timing somewhat. I don't think the LS6 intake is going to help you much on the small heads you're running. It might just make for some soggy throttle response and lower mid range power. If you went to LS6 or LS2 heads then the intake would be of some benefit. All in all it would seem to be pretty hard to mess up badly, with only 2,000# to drag around!! Where do you run that thing?
Thanks Topspin. I run this sandcar in Glamis, just over the border from Arizona.
I spoke with the custom engine builder and he said there is absolutely no need to advance their cams. He also said the LS6 intake will provide positive gains on the 5.3. I am holding off on the intake though. I had a stock LS1 in my last sandcar and hope that this motor with the cam will give my about the same performance. That's my goal anyway. What do you think?
My SSR: 05 6 sp. with 4.56 gears, ZR1 clutch, Edelbrock intake, Lunati cam, Crane rockers, C6 modified pan
N2, your 5.3 will be close to the stock LS-1, but the -1 made 350 hp with 10.1-1 compression and had slightly better breathing heads on it. The 5.3 has only an 1.89" intake valve, while the -1 has the standard 2.0" intake valve in it. The larger bore of the -1 is also beneficial in unshrouding the valves to allow better intake swirl. The larger the bore, the better the LS heads perform! Your 5.3 has only 9.5-1 compression and that's why I keep harping on advancing the camshaft. Horsepower will increase directly in line with a compression increase up to about 12-1.
How much do you think the LS6 heads will help, especially with this cam? I see that they are only 3.5cc's larger than what I have now so compression wont change much. Is there any concern with the smaller bore size of the LM4? Also, what is a fair price for a used set?
The spec that caught my attention is the cam LIFT. .580" is a LOT of lift, that will require very stiff valve springs and will shorten valve spring and valve seat life. Some of the hottest street cams for LS series engines hve only .550" lift, and that's plenty.
I shouldn't think a sand digger would want to sacrifice much bottom end torque. Although with relatively less traction to a street car, maybe a higher rpm is a more normal range.
Being an old Sand Rail Dude, I can tell you; you need to think High Torque.
Otherwise these engines just fall on their Face in Sand.
Topspin is thinking Low End Power for this Machine. That is correct.
By the way, That Dune Buggy, does look like a Kick to drive.
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