63mako

a 350 will easily make 350-425 HP. Will it work well with a 2.87 rear gear ratio? If you want that much HP with that rear gear ratio Cubic inches and low to midrange power is your best friend. That don't need a forged crank.
This kit (about 1/2 way down the page) would work. Comes internally balanced, 6" rods, with forged pistons (only $100 upgrade) for $1125
9-350-3750-6000 2-ICR6000 FORGED
(DISH) 4.030 10.4 9.8 9.2 N/A - 1-90505 $979 1-90505BI $1125

http://flatlanderracing.com/scatsr-chevysbcast.html

gkull

this is not a good plan............ roller cams trap so much that they are detonation prone with such small duration cams. I had ping rattle with 232/238

DucatiDon

No offense, but your comment makes nonsense to me.

Many folks have said this cam is too big.......I guess we shall see.

63mako

Cam is not too big. That cam has 286 advertised duration. If your exactly 11 to 1 your DCR figures 8.48 to 1. That needs good premium fuel, great quench, low gear differential, Manual trans would be best, Really good A/F ratio and good cooling. Theoretically it should run on pump gas fine but 11 to 1 is 11 to 1 and tough to cam for pump fuel.
DCR is a guideline not an absolute.

Edit: I seen your other post.
If your running this cam: http://www.summitracing.com/parts/HRS-110635-10/
And Static is 10.89
Your golden!

gkull

I'm speaking from experience. Most people posting have had little or
no experience actually building and driving their own high compression 383's equipped with roller cams. I probably put 30,000 miles on my 383 roller motor with various ARF and Dart heads. I also thought 232/238 was kind of mild even with my 3500 stall and 4.11

I even had thermal ceramic coated pistons from Swain Tech. They are said to give you an additional 1/2 point of compression without detonation.

I to didn't want to go over board with my first roller 11:1 383. So I fought it for a year with every kind of octane booster and altered advance curves..... limiting vac advance. It actually rattled going down the freeway at 70 mph light throttle. Corvette forum was even different back then. It was an honest to goodness sub .040 quench even.

The fix was a bigger cam. I pulled my old refreshed 383 out of the box and put it in my Vette this year. It is kind of nice having a spare motor. Just adjusted all the valves because I remove the rockers for storage. It is actually kind of fun. No more octane booster and I can drive it 1000 miles in one day.

My advice is that when somebody gives you cam advice on a forum is question them if they are driving what they recommend. I've also had 3 different roller cams in my 427 sbc and various heads and intakes. From each one I learned something before having my own design custom billet cams ground.

Every once in awhile I even professionally build small blocks and big blocks

L88Plus

There is only one original engine for that car and it's a 2-bolt block. Once you've rebuilt it correctly (which many, including myself, includes decking the block), the stampings on the deck will be gone. There will never be any way to prove it's original again.

Pull it, drain it and store it. Find a 4-bolt later model Vortec long block with provisions for roller lifters, mechanical fuel pump and 1-piece rear main seal. Build it and drive it like you stole it from Harbor Freight, never worrying about what happens if it's destroyed.

I wouldn't build a stroker out of a 2-bolt block and there are many that feel the same way.

Build something you can whoop on without fear of losing the original. Won't cost much more - cost of the block - and you can build it without pulling the original until it's complete and ready to go.

The '81 with it's L81 was the only year the "L" designation matched the year model. It's the only engine that was available in the '81 Corvette and the engine was only available in the '81 Corvette.

jb78L-82

Build it into a high performance 355 like I did with my L-82 with AFR's and roller cam..you will not be disappointed. I did not deck the block and the numbers on the block are still there obviously. You can deck the block preserving the number pad…..

DucatiDon

Yep. Thats the one.

That needs good premium fuel, Check!
great quench, 0.39 Check
low gear differential, 3.73 Check
Manual trans would be best, RS500 Check
Really good A/F ratio (TBD with tuning....)
and good cooling Check!

63mako

Your 3.55 rear gear and manual trans allow a lot more leeway for a moderately aggressive build with a higher powerband.

jb78L-82

3.70 rears with my 4 speed….

gkull

DCR question

what would have been the dcr with my original roller cam? 232/240 112 286 296 I 11, 45 E 59, 5 valve timing events. 4.030 X 3.750 .035 quench -4 cc two valve relief flat tops. dart 227 cc 64 cc heads .021 MLS gasket block surfaced to .014 piston to deck.

The cam that cured detonation is a 238/242 300/304 I 12, 46 E 56, 6

This is what I've been driving around lately and it is not radical. I think it is something like .628/.644 valve lift and AFR ported 210 cc heads 2.08/1.60 valves

DucatiDon

With my math your first cam would have been 11.4:1 with a DCR of 8.47

Your current cam calcs out at 8.05 DCR

Mine splits the difference at 8.2

MrJlr

California here too.
I looked at the numbers and went with a Blueprint 383.
432hp/461tq - $3700.

63mako

Hydraulic roller and hydraulic flat tappet figure advertised duration and intake closing point @ .004 or .006 lift. Using these figures is fairly accurate using the DCR calculators. Solid roller skews the DCR calculation because of lash. A Solid roller cam from comp has an intake closing point and advertised duration figured @ Theoretical .015 lift. The cam has a .020 lash @ .015 the events haven't started yet. The advertised duration is narrower and the intake closing point is earlier than shown @ .006 actual lift which increases actual DCR in a running engine. If Comp gave you advertised duration for this cam @ .026 lift or if you could safely reduce lash to .009 it would figure correctly in the calculator. http://www.compcams.com/Company/CC/c...?csid=302&sb=2
Extra DCR safety margin needed with Solid cams if you use the numbers given depending on the difference between lash and posted timing events which varies from grind to grind, manufacturer to manufacturer and lash setting to lash setting. Your crane cam intake closing point @ .006 actual lift is different than your posted cam card info = higher DCR than the calculator shows = detonation. It would be way easier if every cam of every type used .006 actual lift for their timing events.

DucatiDon

Now that is something I was not aware of.

good info.

63mako

I get the same numbers. George, See previous post for reason why you have detonation issues using the solid roller. Your build will likely run actual 8.5 to 1 DCR with no problem.

63mako

With any solid cam you also have to subtract lash from the advertised lift numbers to get actual lift. The comp cam I just listed has a posted lift of .550 - .020 lash measured rocker to valve tip = .530 actual valve lift. You can adjust your duration wider and intake closing point later with tighter lash adjustment to a certain point. Can't do that with hydraulic.

DucatiDon

So...in theory, increasing rocker arm ratio would reduce DCR slightly, due to the increased duration.

So what pinged with 1.5 might not with 1.6 rocker arms?

F22

I've been following this thread with interest, as I'm building a 383 as well. I have an 87 block, that's set up for factory roller lifters and am going to order a balanced rotating assembly from Scat using the KB-102 pistons (which yield 9.7:1 on 64cc heads. My engine guy doesn't want to go to 10:1, as we have 91 Octane, but I'm not sure about that. This is going to be street/strip car and will see the drag strip regularly.

I have recently purchased a set of the new MAXX series heads from Promaxx and they come with 183 cc runners, 2.02 intakes and flow 249.2 CFM at .500 lift.

http://www.jegs.com/i/ProMaxx-Perfor...ductId=2944747

I had Howards Cam do an analysis on what I'm running. 1974 C3, with a T-10, 3.50 rear end, old Edelbrock Performer, with headers and 17" wheels (235/17's). 3,400 pounds est. weight. The carb is a Holley 650 Mechanical DP. I'm going to be running the Comp Cams Ultra Pro Magnum XD rocker arms, with a 1.5 ratio.

http://www.summitracing.com/parts/hrs-180325-10



They recommended the Hydraulic Roller Cam, 180325-10, which has an RPM range of 2,200 to 5,800 RPM, 225/233 duration Int/Exh. The advertised duration is 278/266 Intake/Exhaust lift is 0.525/0.530 with a 110 LSA.

It's described as "Rough idle, street/strip performance, strong midrange, 2,500+ stall."

My question is, reading this thread, I'd actually like to get 10.1 out of it, using flat tops, versus the D-cups of the KB-102 and I'm not sure about what DCR I'd end up with, using the combination that I have.

63mako

No. Lobe lift is unchanged so intake closing point would still be almost exactly the same and with the valve open more cylinder fills more. Effective duration changes slightly @ .100, .200, .300 ect but valve events stay virtually the same. .006 / 1.5 x 1.6 = .0064
4/10,000 of an inch difference at valve at intake closing.

With the solid less lash gets you on the ramp faster, opening the valve earlier and off the ramp later, closing the valve later. Actual duration and valve events change. George might have been able to tighten intake lash and get out of detonation if it was really, really close but increased lift also increases filling. Change from .020 lash to .012 gets you .006 difference at original intake closing, before and after, across the board.
6/1000 of an inch at intake closing point or 15x the difference going from 1.5 to 1.6 at .006 lift