Decent cam choice for a 383 build?

[L31MaxExpress]

My 383 cam is 271/284 @ 0.006, 218/228 @ 0.050, 108 LSA, 106 ICL and 0.578 lift with 1.7 rockers. I have Rhoads V-Max lifters cold lashed with a 0.014" feeler gauge off the bottom of the travel. With open exhaust it sounds a bit choppy. With a quiet muffler it sounds near stock and it is dead smooth running at 750 rpm. Throttle response is instant.

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Valvetrain does make a bit of noise but alot of that is the full roller rockers. They always have a well oiled sewing machine noise to them, even factory roller fulcrum rockers on a LS with a 0.550 cam is about the same.

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[L31MaxExpress]

The old 350 running years ago with a stock LT4 cam, 1.6 rockers, shorty headers and a magnaflow muffler. 383 is every bit as tame as that 350.

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Brothers 99 Suburban running with factory exhaust and a 1995 F-Car LT1 cam.

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[Erik the Awful]

I had my eye on the Lunati CAM V262HR12, but they said it was for an LT1 and wouldn't fit a vortec...

Who said? Lunati recommended that cam to me for my engine when I originally built it for my Suburban.

There is a member on the Forum (Erik the Awful) who has that cam and says it runs well in MPFI with a tune, poorly in TBI, and definitely a truck cam. It says LT1/LT4 but with Lunati it's either that or retrofit roller and with a cam retainer you don't want a retrofit roller.

Yep, it's a direct fit with the cam retainer, and it's true you don't want a retrofit cam. The Lunati 20080720 is absolutely a truck cam. I need to get some video of driving and towing with it. It has great torque without being a "race" cam.

As far as the timing chain and oil pump, I went with a Melling stock-style link chain for durability. I bought the standard Melling oil pump, and I've seen it dip under 60 psi once on a hot day.

 

[L31MaxExpress]

Who said? Lunati recommended that cam to me for my engine when I originally built it for my Suburban.


Yep, it's a direct fit with the cam retainer, and it's true you don't want a retrofit cam. The Lunati 20080720 is absolutely a truck cam. I need to get some video of driving and towing with it. It has great torque without being a "race" cam.

As far as the timing chain and oil pump, I went with a Melling stock-style link chain for durability. I bought the standard Melling oil pump, and I've seen it dip under 60 psi once on a hot day.

I run the GMPP or Cloyes style single roller for added durability over the link style. The link style wears on the sprocket teeth and stretches over time. In 50K it will have noticeable wear, the single roller will not. I have pulled apart 200K mile single roller chain equipped engines and re-used the timing chain and sprockets. GM used the same setup in the 8-lug trucks, the industrial/marine engines as well as the ZZ series of crate engines. GMPP says its reliable to 6,500 rpm. The GMPP setup comes with hardware and both sizes of cam retaining plates.

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[383Dreams]

I emailed my shopping list to Jegs tech support to double check for me, and they flagged the Lunati cam in the list incompatible. It made no sense to me either. These are all great tips! Thank you so much. I will certainly adjust the timing chain to either the Cloyes 9-1157 Street, or the GMPP single roller. One thing I am having an issue with at the moment is finding a machinist. I got a quote today of $2200 for preparing the block and assembling the bottom end of a 383 with me furnishing all the parts. I am not sure I want to do that. That could go a massive distance upgrading something else. I am still checking around. Does that sound reasonable to anyone out there?

 

[JeremyNH]

Quote at $2200 seems high but you should get an itemized list and see what their per unit costs are and also to define what their scope of work is. I was looking at your rotating assembly and that kit uses 5cc dished pistons. Assuming your shop zero decks (which they should and at $2200 better be) and you use a .040 thick head gasket that puts compression at 11:1. Even with aluminum heads that will be tough to pull off if you're planning to use pump gas. My pistons are 19cc dished and come in at 9.6:1 which for aluminum heads is about the limit at 87 octane which is the aim for my build.

 

[L31MaxExpress]

Quote at $2200 seems high but you should get an itemized list and see what their per unit costs are and also to define what their scope of work is. I was looking at your rotating assembly and that kit uses 5cc dished pistons. Assuming your shop zero decks (which they should and at $2200 better be) and you use a .040 thick head gasket that puts compression at 11:1. Even with aluminum heads that will be tough to pull off if you're planning to use pump gas. My pistons are 19cc dished and come in at 9.6:1 which for aluminum heads is about the limit at 87 octane which is the aim for my build.

I am running 91 on an 11:1 aluminum head engine with relative ease. However I do my own tuning and have for years. The only time I have even seen the knock sensor retard the timing is when I free reved it to the fuel cut at 6,200 and bounced it off it a couple times before I could lift the throttle.

My cranking compression. 225 psi

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[L31MaxExpress]

I emailed my shopping list to Jegs tech support to double check for me, and they flagged the Lunati cam in the list incompatible. It made no sense to me either. These are all great tips! Thank you so much. I will certainly adjust the timing chain to either the Cloyes 9-1157 Street, or the GMPP single roller. One thing I am having an issue with at the moment is finding a machinist. I got a quote today of $2200 for preparing the block and assembling the bottom end of a 383 with me furnishing all the parts. I am not sure I want to do that. That could go a massive distance upgrading something else. I am still checking around. Does that sound reasonable to anyone out there?

What is the exact part number of the Lunati cam? If it is a step nose cam it will 100% physically bolt in and work in a L31. As I mentioned before my van had a production 96 LT4 cam and my brothers suburban had a 95 LT1 cam. Just watch the dowl pin length. If it has an extended pin, cut it off or drive it further in to match the length of the L31 cam.

 

[JeremyNH]

I am running 91 on an 11:1 aluminum head engine with relative ease. However I do my own tuning and have for years.

My cranking compression.

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I said tough not impossible. At 11:1 he's not driving that truck very far absent perfect quench and a great tune. He's also not talking about changing heads just the bottom end. 11:1 doesn't work with iron heads no matter the tune.

 

[L31MaxExpress]

I said tough not impossible. At 11:1 he's not driving that truck very far absent perfect quench and a great tune. He's also not talking about changing heads just the bottom end. 11:1 doesn't work with iron heads no matter the tune.

Agreed. I have run 10.5 but had a fairly big, wide lsa cam to keep the cylinder pressure lower at low engine speeds.

At 9.6:1 my iron heads pinged enough to make the knock sensor pull timing with 0.042 quench and only 29° of timing on 91 octane. Swapped to 200cc aluminum heads on the same engine and ran 34° on 87. I was running the same timing advance I ran on E85 with the iron heads on 87 octane.