Long story short, I have a '94 Roadmaster Estate with an intermittent main knock, a pair of 4-bolt LT1 bottom ends from C4s and a long, cold winter coming up, so I'm looking at a 383 build to kill the boredom. Given that this is a heavy pig of a car, it's used to tow things and it has a 2.93 locker in the rear, I'm wanting to focus way more on torque than on big horsepower and high-RPM.

So, the first real question I have is, what would you look for in a cam? This is my first GM engine build, though I've built and ported a handful of Mazda rotaries in the past, and a couple of Volvo redblocks, though those all had a very different set of priorities.

Tentatively, I'm thinking something around 12:1 or 12.5:1 static compression, if that'll help the cam choice.

Thoughts?

 

I'd leave compression stock. That CR you're flirting with having to run more than pump gas. If it were me I'd do a LPE 211/219 cam and ported heads. With a stroker you'll looking at well north of 400ft lbs of torque. Change up the gear ratio to 3.42's and you'll be able to pull an oak stump out of the ground in January. However if you are wanting more aggressive to the point of a lopey idle you'll want something more aggressive.

 

OP

you can go 11;1 if you want to bump up the compression over stock some on a 383. You will want to keep your quench about 35. There are off the shelf cams like the LPE211/219 as noted but also the Crane 227 is regarded as a VERY good TQ cam for the LT1

Your B body has iron heads so swapping over to LT1 aluminum or aftermarket heads that are ported is 1/2 the power/TQ equation

You should look into Lloyd Elliott (Elliott Portworks) H/C package. He is highly regarded and one of his packages would be what you are looking for.

Agree you will need/want more gear in the Roady. 3:42, IMHO, with a 2200-2400 stall would be a great street package. What I had in my B body when it was a automatic. With the kind of power/TQ the 383 will make your stock, likely tired, 4L60E will need rebuilding with better parts or it will shiat the bed under the 383 power

With a small cam you "may" get away with the stock 24 lb injectors but 30 lb would be better. Stock TB will be fine or you could get a 52mm

Whatever cam you do get you will need a PCM tune to allow the motor to not only run/idle right but take advantage of the higher rev the cam will allow and more HP the motor will make. For the type of motor you describe a mail order will be fine. moehorsepower.com would be one source for that

 

Honestly, a lopey idle isn't a huge factor, either way. Being able to live with it, both as an occasional tow rig and on the freeway is, though.

Good news is, I have two sets of the aluminum LT1 heads sitting on a shelf. That said, I'll take a look at Elliott's H/C packages.

I'm going to hold off on more gear until after the engine and transmission, since there's a 4L80 hiding in the garage, behind the eternal Volvo project from Hell...

I was anticipating an injector upgrade, and the PCM tune was a given. The computer is only as good as the data it's programmed with, and adding 33 extra cubes, along with more cam and a 4L80 is just asking for trouble otherwise.

 

While Lloyd offers other "brands" of heads for the LT1, most send him a set of GM LT1 aluminum heads to port and get one of his custom grind cams suited for their purposes. Also people include their intake so it can be port matched to the heads

 

Any cam will love steeper gears and so will you

 

I would say something around 230 deg. on the intake and a touch more on the exh. with a tight (108-110) lsa...
should be all done by 6k rpm
my $.02

 

What you're looking at will result in a high RPM, high performance motor with most of it's notable performance above 4000 RPMs. Not the engine you want in a 4600lb car with granny gears that's gonna be towing.

If it were my car, and I had your goals; this is what I'd do:

383ci, stock compression (about 10.5:1), fairly low duration cam, 3.42 gears, stock torque converter or aftermarket with no more than 2400 stall. Cam specs that I would go with:

220*/232*, 111* + 4* LSA, about .570"/.570" lift.

IVO = 3* …….. IVC = 37* ……. EVO = 51* ……. EVC = 1* ….. 4* Overlap.

This is a cam that will hit hard off throttle but will still carry RPMs to 6000 RPMs.

Plenty of low RPM torque means towing will be no problem....at all.
Strong revving for the occasional 'get you in trouble' highway blast.
Low overlap means it'll be streetable as hell and easy to tune.
Stockish compression means it can be tuned for any grade fuel you want (regular to premium)....with no problem.
3.42 gears for additional torque multiplication.
Low stall TC....because you won't need a higher stall, and you won't want the tranny heat generated by a higher stall TC when you're towing....especially if you're going up an incline (hill/mountain).

This is what I'd do....you do what you want.

Best of luck!

KW

 

Maybe just a shot more compression and a slightly steeper gear. 3.73 is a hard gear set to beat for a ride you want to do many things well.

 

I pull a 6,000 lbs travel trailer with an 11:1 aluminum head 350 Vortec in my Express van. I have a 4L85E with a high str 2,800 rpm converter. I run a 5.13 geared 10.5" corporate 14 bolt and LT265/75R16 tires. The commercial chassis LT1 D cars used a 9.5" 14-bolt, might be worth finding one. I believe they were either 3.42 or 3.73 gear. The 215/224 comp custom grind cam I am running with 1.7 rockers degrees 218/228 @ 0.050, .578/.578 lift, 110 LSA, 106 ICL and has Rhoads VMax lifters. My intake manifold is a dual plane mercruiser MPI with a low profile Edelbrock intake plenum and an 87mm drive by wire Trailblazer SS LS2 throttle body. Thorley Tri-Y headers to boost torque in the low-midrange. The heads are assault racing heads with roughly 215cc runners that were ported by Lloyd Elliot. 2.02/1.60 valves, double springs, 7/16" screw in-studs and guide plates. It pulls my 6,000 lbs travel trailer down the road at 70 mph @ 2,850 rpm locked up in overdrive. I am able to run 28° of timing on 93. 34° on E85. Quench ended up being 0.041" with a GM 0.028" compressed head gasket. I have Megnetti Marelli injectors that came factory on the marine intake that flow 56 lb/hr @ 58 psi.

 

Here are a few pictures of the engine in question. Along with the intake when I was mocking it up on the 305 sitting in my shop floor.

 

I run a triple disc lockup 2,800 high str converter. More torque multiplication off the line to get rolling far more easily. Lock it shortly after the 1-2 shift and keep it locked. I have the in radiator trans cooler and a massive Trucool 40K auxiliary cooler in front of the radiator. I run 5.13 gears with my tallish LT265/75R16s for added torque multiplication. It pulls away nicely from a stop at 12,500 lbs GCVW.

The specs on your cam are very close to what I run in my Express van. With the 1.7 rockers its 218/228 @ 0.050", .578/.578, 110 LSA +4°. Makes peak HP right at 6K. With Rhoads lifters it idles and drives like the stock cam on the bottom end. The torque curve is flatter and the lifters seem to fully restore the lift and duration around 3,000-3,500 rpm. I did alot of research on how they work and modeled them on a couple of engine building software programs. I tried what I learned with the software. I currently have them set to give full lift/duration decrease on the intake valve and half on the exhaust valve. As the engine revs up the intake lobe is slower to restore than the exhaust lobe. Since they work off bleeding away pressure the cam becomes asymetrical closing both the intake and exhaust valves sooner. The Intake closing point and LSA actually change at idle as well. In Park/Neutral I pull 22 in/hg of vacuum at 650 rpm. 24 in/hg @ 2,000 rpm.
The lifters make the cam like having a cam specing 198/214 @ 0.050, .548/.563, 114lsa, +6° around idle.

Unloaded I shift at 6,200, loaded it shifts at 5,200 in Tow/Haul mode. One should be able to program the LT1 PCM for Tow/Haul using the performance mode shifting tables.

My 6" rods lower the dynamic compression ratio a bit.

 

Phoenix'97, My build has a 215/224 cam with stock unported heads that have been milled for more compression and a good valve job. I also have 1.6 roller rockers and a meziere electric water pump.

My car makes tons of torque with this cam even under 2500 rpm. I can roll on roast my 315 rear tires in 2nd gear so the torque is great and the engine pulls great right up to 5800-6000rpm. I wouldn't go with any smaller of a cam ! If anything a step up would be nice.
I am also a torque fan. I even went with 1 5/8 headers instead of 1 3/4 headers to try and keep low end torque.

 

I ended up changing the cam in that 11:1 383
recently to a Bootlegger 232/244 that is more like 236/248 with the 1.7 rockers. Ended up with 0.627" lift on both sides. The torque still comes on strong in the low-midrange with the Rhoads lifters and it makes a massive torque number with the dual plane PFI intake and thorley tri-ys. I had considered a XFI 292 rather than the Bootlegger. From the looks of the software model I am glad I choose the Bootlegger grind. Model shows about 540 ft/lbs @ 4,400 and 530 hp @ 5,700. I have the rev limit set at 6,200 rpm and shift WOT in the 6,100 rpm range. Light blue/red curves are the results of the current cam/rocker combination negating the Rhoads effect under 4,000 rpm. I am not sure why the model is showing such an extreme drop-off after peak with the 1.7 ratio rockers though. The ports had not stalled even at .700 on the flow bench. I feel in reality the torque curve with 1.7s probably still has the same curve on the top-end with a similar increase all the way to redline. With the 5.13 rear gear and the 2,800 rpm stalled 4L85E this setup hits hard. I was running 70 mph on the open highway the other day and some crap box of a BMW 328I tried to keep me from passing him. After speeding up to about 75 mph and being paced, I shoved the pedal to the floor. The trans dropped to 3rd, brought the engine a little over 4,000 rpm and I was at 100 mph and 5,500 rpm in about the distance it took to overtake said 328I. A few miles down the road, accelerating from a slow down here is this BMW again. He floors it from about 40 mph. I floored it again and put a bus length on him by 70 mph. 6,200 lbs Express van moves out with this little hotrod of a 383. It is pulling about 440-450 gms/sec through the MAF at 5,500. From lower speeds it pulls harder than my girlfriends Infiniti Q50 twin turbo 3.0L which impresses me because its a red sport 400 with 400 hp and 350 tq and very quick.