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SBC 383 cam selection

Started by _Terrible One_ , Sep 18 2011 10:03 AM

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17 replies to this topic

#1 _Terrible One_

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Posted 18 September 2011 - 10:03 AM

So im putting together a nice little 383 for my LJ, just struggling with camshaft selection now. Ive been following LXCHEV's thread on his 383 build as it reads similar to mine but Im still no closer to a decision. Basic specs are as follows:

350 block 30 over
Scat 3.75 crank
Scat I beams
Forged Pistons
Alloy heads around 200cc intake
Edelbrock RPM
750DP
Around 10.5 comp
MSD 6AL programmable and MSD coil

The car is gonna be used for mostly street with the odd test and tune and events like Powercruise etc. Ive got a Zex perimiter plate gas system on order so it will be copping around 100 shot of gas on the odd day. Still must be streetable. Id like to go with a solid cam. Usable rpm range up to 6-6500. Ive been looking at cams with around 244 duration at 0.050" , am I way off the mark or is this ballpark ok? Too big or too small?

Will have 3.55 gears and undecided on gearbox still.

Help!

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#2 LXCHEV

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Name:Brett
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Car:'76 LX - 383 Chev
Joined: 08-November 05

Posted 18 September 2011 - 09:37 PM

Hey mate. Are you gonna go solid flat tappet, or solid roller?

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#3 _Terrible One_

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Posted 19 September 2011 - 07:24 PM

Solid flat tappet, from what ive heard solid rollers are too hard on the rest of the valve train and not really suitable for street. I dont mind adjusting valves once in a while.

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#4 axistr

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Posted 19 September 2011 - 07:45 PM

My 383 is running 232@50 flat tappet hydraulic(anti pump ups), 195 AFR heads 10.6 comp.022 quench area from head to piston top, edlebrock R.P.M performer manifold and 770 holley 1"7/8 extractors. Power from 1,500- 6,200 R.P.M

Just remember for 383 you will need a cam with small base circle other wise you may have the conrod bolts touching on two cam lobes. Very inportant to check on 383s as many cams & engines fail due to people/engine builders not knowing of this problem with long stroke engines.

Very streetable a bit lumpy at idle, still has decent vacuum at idle. I wouldn't go any bigger for street use. Gets off the mark ok with 3.08 gears. 5 speed manual.
Pulls hard from 2,000-5,700 and will pull stumps out of the ground.

Hope this helps

Lenny.

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#5 _Sandman_

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Posted 25 September 2011 - 02:29 PM

I've got a Crane CC278 solid cam in a 383. Has worked well for years. Great on the street, have towed trailer etc. Best 1/8th mile time NA was 7.6 in 3600+lb HQ panelvan. It clears 400gm conrod no worries and is easy on the valvetrain.

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#6 _Terrible One_

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Posted 25 September 2011 - 06:01 PM

I pulled the motor down this arvo to send the block away for some work and it turns out its got the lugs in the valley to run OEM roller lifters. Its got me thinking, should I run a hydro roller instead? Ive never really considered going a hydro roller but seeing that its only going to cost me $250 for the GM Performance roller lifter kit its kinda tempting.

Thoughts?

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#7 _Bomber Watson_

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Posted 25 September 2011 - 06:12 PM

Dunno much about chebbies but it seems rollers open the valve faster and close it faster, which means that for the same duration you get more valve lift for more time without increasing your maximum lift, = more flow for longer...........So YES lol

Prolly insure your heads have enough meat under the spring seats to cope with the extra spring pressure required??

Cheers.

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#8 rodomo

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Posted 25 September 2011 - 07:59 PM

Dunno much about chebbies but it seems rollers open the valve faster and close it faster, which means that for the same duration you get more valve lift for more time without increasing your maximum lift, = more flow for longer...........So YES lol

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#9 _Bomber Watson_

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Posted 25 September 2011 - 08:02 PM

You would not agree Brodo???

Keen to hear your take on the matters.

Cheers.

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#10 _Sandman_

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Posted 25 September 2011 - 08:09 PM

You don't need heaps of valve spring pressure for a hydralic roller. 120-140lb is usually enough. Solid rollers you would need 200+lbs, depending on how big the cam is.

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#11 _oldjohnno_

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Posted 25 September 2011 - 08:15 PM

There's actually a little bit more to it than that. A roller does indeed allow higher lifter velocities, but a flat tappet actually allows higher acceleration rates and higher changes of accel. rates (jerk), especially in the early stages off the ramps. In other words you can "slap" a lifter with the flank of a flat tappet lobe and get very high initial acceleration rates.
What this means in the real world is that for more moderate profiles (very roughly 0.4" lobe lift or less) you can actually get more area under the curve with a flat tappet. With the big stuff however, a roller leaves a FT way behind.

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#12 _Bomber Watson_

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Posted 25 September 2011 - 08:20 PM

Well in that case i'll shut the frOck up

Cheers.

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#13 _Terrible One_

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Posted 26 September 2011 - 03:33 PM

Thanks for the feedback.

I understand that there is more area under the curve with a hyrdaulic roller. They do seem very popular in the USA, for good reason I think. I think thats the way I'll go.

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#14 _sbc57lx_

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Posted 26 September 2011 - 04:29 PM

I pulled the motor down this arvo to send the block away for some work and it turns out its got the lugs in the valley to run OEM roller lifters. Its got me thinking, should I run a hydro roller instead? Ive never really considered going a hydro roller but seeing that its only going to cost me $250 for the GM Performance roller lifter kit its kinda tempting.

Thoughts?

Is it a Chev VORTEC ??? I was just curious about the GM Performance lifter kit ??

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#15 _Terrible One_

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Posted 26 September 2011 - 08:03 PM

I dont believe so. I checked the casting numbers and the bottom end belongs to a late 80's car and the heads were either 307 or 327 from the late 60's. The bottom end was still fitted with a flat tappet hydraulic cam but has lugs for the roller cam. The casting number from the block says its either from a Camaro or there were a bunch of Chevy trucks fitted with these blocks that had the roller cam mounts but werent used with a roller.

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#16 _oldjohnno_

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Posted 27 September 2011 - 07:12 AM

Thanks for the feedback.

I understand that there is more area under the curve with a hyrdaulic roller. They do seem very popular in the USA, for good reason I think. I think thats the way I'll go.

There are some very good reasons for choosing a hydraulic roller. But don't kid yourself that a street hydraulic roller grind will have more area under the curve than a good mech. flat tappet of similar lift. Even Comps own tech guys will admit to this when pressed. Higher lift solid rollers are a different story of course, but then they're not really suitable for long term street use.

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#17 LXCHEV

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Name:Brett
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Car:'76 LX - 383 Chev
Joined: 08-November 05

Posted 01 April 2012 - 08:45 PM

Hey Terrible One, what cam did you end up using?

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#18 _Terrible One_

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Posted 05 April 2012 - 07:37 PM

Still havent bought one! Most of the parts are there but I just booked a 2 month long trip to Europe with the woman so it may have to wait for a bit. I decided to go a hydro roller but havent really nutted out an exact grind. After the trip Ill spend some time working out the best combination of bits for the top end and possibly get the whole top end put on a flow bench to aid cam selection. Its not worth spending big dollars on good shit if it doesnt work togethet properly.