383 rebuild - old dyno results & new cam ideas

Thank you both for the replies.

I installed the cam on a 104 intake centerline. Installing the crank gear using the straight-up keyway gave me an incorrect intake centerline, so I repositioned the crank gear to the keyway for advancing the cam timing. After repositioning the crank gear, I degreed the cam again and the intake centerline was 104.
 
I've been second guessing my cam choice lately. Install the thing, then second guess yourself....perfect timing .

Earlier in the thread it was mentioned that my dyno results looked like I could use a little more duration, I agreed so I went with that. Looking at the specs of the new cam again I'm concerned about the added duration and overlap. I don't have any vacuum accessories to worry about but don't want to wreck the drivability completely.

I don't go on 100 mile cruises and the car has not seen a freeway since I've owned it. I usually cruise from town to town, 20-30 miles apart, max speed 70 mph but average about 55 mph. With the 26" rear tires, 3.73 gear, and TH400 I'm usually not below 2300 RPM when cruising. FWIW the old cam with 236/248 duration didn't bother me, or have any issues, when driving the car before.

I looked at some Bullet lobe profiles today and played around with the calculators at the Wallace Racing website. I came up with a few options but liked the one listed below. Same intake duration as before but with much less exhaust duration.

Intake: 236 @ .050, .562 w/1.5 rocker
Exhaust: 240 @ .050, .562 w/1.5 rocker
108 LSA
IVO - 42
IVC - 70
EVO - 80.5
EVC - 36.5
78.5 degrees of overlap, vs. 85.5 with installed cam

In y'all's expert opinions, do you think my current cam will work for my intended use? How does the cam above look? And if you have any recommendations, please include them as well.
 
Do you know the advertised duration?

Can't you just drive the car and enjoy or does it have to be perfect, you might be over thinking this cam thing!
 
Advertised duration is 292/297.

You're probably right, I tend to overthink these things. It's worse now that I have a bunch of extra time on my hands waiting for the transmission to be rebuilt. Doesn't have to be perfect.

I'll run what I have. If I absolutely can't live with it a cam swap isn't difficult.
 
just some loosely related info, in my 1985 corvette I had tested a crane 119651 in my 11:1 compression 383 with a 3.73:1 rear gear and a 3200 stall converter and 1.6:1 roller rockers, 36 lb injectors a dual 58 mm ,1000 cfm throttle body and hooker headers and ported trick flow twisted wedge heads,
while it was not ideal to drive in traffic it did produce impressive power
now to be fair, I used a holley distributor and a 150hp wet nitrous throttle body plate, similar to this linked below but a different brand
www.hawksmotorsports.com

85-92 Tuned Port EFI 100-150 HP adjustable fuel injection nitrous oxide system, "Wet", NOS

85-92 Tuned Port EFI 100-150 HP adjustable fuel injection nitrous oxide system, "Wet", NOS
www.hawksmotorsports.com www.hawksmotorsports.com
the results produced frankly more power than the vettes suspension and tires could easily control.

Products specifications​

Advertised Duration​

306 INT./314 EXH.

Advertised Intake Duration​

306

Basic Operating RPM Range​

3,500-7,000

Cam Style​

HYDRAULIC ROLLER TAPPET

Duration at 050 inch Lift​

240 INT./248 EXH.

Exhaust Duration at 050 inch Lift​

248

Exhaust Valve Lift with Factory Rocker Arm Ratio​

0.558 IN.

Grind Number​

HR-306-2S-10.86 IG

Intake Duration at 050 inch Lift​

240

Intake Valve Lift with Factory Rocker Arm Ratio​

0.558 IN.

Lobe Separation (degrees)​

110

Quantity​

SOLD INDIVIDUALLY.

Valve Lift with Factory Rocker Arm Ratio​

0.558 INT./0.558 EXH.
thmotorsports.com

Crane Cams 119651 Crane PowerMax Hydraulic Roller Camshafts

Crane Cams 119651 CRANE SBC Hydraulic Roller Cam
thmotorsports.com thmotorsports.com
 
Last edited:
@Drew Pedersen
Do you happen to have the part number and grind number?

Average HP/TQ from 3000 to 6600 RPM is
Sim08 = 410/451 [70cc Chambers]
Sim08 = 412/453 [68cc Chambers]
Sim09 = 413/455 [68cc Chambers]

DPSim09_vs_Sim08.jpg
 
the 236/240 duration cam should produce impressive power, and while I doubt it would be really easy to drive in traffic,
when I drove a similar combo, it impressed me with the power, but I felt the daily drivability was marginal at times.
a great deal of the drivability depends on the rear gear ratio, cars weight, where you program the trans shift points, the tire diam, and converter stall speed,, and your engine/trans cooling capacity,
and your induction and exhaust matching the cam power range.
I know several guys who have similar or even longer duration cams in a 383, that say its no problem to drive.
obviously part of this is your personal perception of what your willing to put up with/endure
RICK, with the light weight T-bucket could more easily tolerate the extra duration than a car that was lets say 3200 lbs,
having built lots of similar engines, in the past for many people and getting their opinions,
I value durability and a broad easily and nearly instantly accessed torque curve in a street combo,
more than bragging number peak power at the cost of other characteristics,
obviously if the cars rarely street drive other than too the track,
you would much more easily swing the choice, in the cam toward a longer duration/ race cam selection.
 
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Rick,
I don't have a part or grind number for the cam. I was just looking at the individual lobe profile list on Bullet's website and and chose those 2 lobes. Following the format of my current cam's PN, the grind number would be CHS 292/297-08HR.

Grumpy,
Thank you for your insight and opinion, I appreciate it. I agree, it's all a matter of what the individual is willing to put up with in their combo. I'm going to try this cam and see how I like it. Until then I'll be looking around and bench racing smaller cam's to have a "plan B" just in case.
 
Quick update:

My transmission is rebuilt and ready to install, I picked it up from the builder last week. While chit-chatting I mentioned not being able to find a shop with a dyno that would run a non-customer built engine. Luckily for me, he's good friends with the owner of a machine shop and dyno that will run my engine. I'm waiting in line behind customer engines but should hopefully get my turn later this week. This dyno is a DEPAC equipped Stuska, the previous tests were done on a Superflow SF-901. Not sure if that will make any difference.
 
The isky I ran in my 355 was 246/ 246 @.050 274/274 on a 106 it was a circle track solid lifter cam. It needed a vacuum canister and would get chuggy below 2k but had a 2600 converter so was fine to drive like grumpy said the rest of your combo has to accommodate.
 
Dyno day was yesterday, all went well. I'm at work and forgot to bring my dyno sheet but peak numbers were 498.5 HP at 5900, and 489 LB/FT at 4800 (IIRC). I'll post the printout later after I make it home.

The only issue I had was both of my intake end seals were leaking. I always use a large bead of RTV (Permatex Ultra Black) for this vs. the cork/rubber molded seals that come in the kit. This is the first time I've had a leak using only RTV. I made sure both the intake and block were clean and dry before applying the RTV; after installing the intake the RTV was compressed properly. Any ideas on what could have caused the RTV to not seal?
 
first congrats on decent dyno results

obviously I was not there when you installed the intake ,
but its common for those cork or rubber end tab gaskets to pop out,
use of solvent to remove oil film and dimpling both surfaces helps retain end tabs
either just silicone or silicone on the tabs
dimple both the matching lower intake and china wall upper surfaces helps retain the silicone
most people DIMPLE and clean the matching surfaces with a solvent to remove oil film
that can prevent the silicone gasket sealant from sticking
yes many people just use a long bead of sealant without the gasket end tabs, but it will depend on the application

guide too re-installing the intake manifold /distributor

Guy
garage.grumpysperformance.com

correctly re-install an intake

step 1 pull and carefully clean and degrease the intake mount surfaces...after bring the engine to TDC on the damper tab and ballancer and verifying the distrib rotor is pointing at cylinder #1, then throw the rubber front and rear intake seal bars in the new intake set in the dumpster step 2...
garage.grumpysperformance.com

Port Matching Procedure (Step-by-Step Guide with Pictures)

Tools and Equipment: Make fixture with 1/16", 3/32"** and 1/8" holes in a 3/4" x 2" x 2" steel block Drill Bits: 1/16", 3/32", 7/64", 1/8", #36, #37, #38 and #39 3/32" Roll Pins, 1/2" Long 1/8" Roll Pins, 1/2" Long Grinder and/or Dremel Tool (Dremel Tool in not required, but does make...
garage.grumpysperformance.com
 
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Here's the dyno printout. When I arrived I was surprised to see a SuperFlow 902 dyno. Apparently the Stuska dyno listed on the shops website was replaced with a SuperFlow last year.IMG_20230622_212238.jpg
 
just a tip when looking at dyno print outs
you do know that at 5252 rpm the tq and hp should match?
That all comes down to the variable of time. This is the reason for it all.
Horsepower is a calculated number from torque and RPM.
Because of this equation, horsepower will always equal torque at 5,252 rpm.
(yes yours looks fine) but if the numbers are not close the dyno is miss adjusted
 
I read about that years ago in a magazine article. Since then the first thing I look at on any dyno graph is where the two lines converge. Especially on dyno graphs used in advertising.
 
why not post as complete a parts list , and machine work you had done,
now in one place so someone can find the details easily in one place,
list block, bore/stroke, compression, rod bolts, used, bearing clearances, piston to bore clearances,
heads, cam, rockers, lifters, timing chain set or gears used, rods, crank, rings, pistons, intake, carb, you used, etc.
and anything else you remember
now that you have dyno results to prove the combos both valid and got impressive results,
thus listed components that you used on your engine as well as you can remember,
so someone who wanted too could duplicate your results or maybe improve on using your base info,
on it if you find improvements you list later, thus allowing further duplication,
or avoiding mistakes you might make and regret, of your on going project.
(yeah we all tend to make changes , good or less than ideal, over time)
and it helps to keep records of changes and results
index.php
 
Grumpy,

Great idea, I will definitely post a complete parts list with results sooner than later.

I noticed an unexpected issue this morning when preparing to fix the oil leaks. My valve seals and the ends of my plugs have rust on them. I've never seen this before. No signs of water intrusion into the oil or cylinders that I found.

I told the shop this was a pump gas motor but didn't confirm that's what was ran.

- Could this be from using a leaded race fuel?
- Do the heads need to be pulled and disassembled to clean the valve seats, or is there a way to correct this without disassembly?
- If I remove the heads, can the head gaskets be re-used?

Thanks in advance.
IMG_20230624_134610.jpgIMG_20230624_134055.jpg
 
well thats the first time I ever saw that!
it looks like there was a great deal of moisture in the area when they ran the engine,
but obviously it could be from an internal coolant leak,
is there any indicators of moisture, or a gasket leak in the lifter gallery?
any way you can do a leak down test and watch for air bubbles in the radiator?
 
I haven't see any indications of a coolant leak yet. The lifter valley, heads, and oil all looked great with no signs of moisture.

After I posted earlier I did a search online. Several people mentioned the same issue with valve seat and plug rust after running VP race fuel. They recommended fogging the engine after a race or dyno run to prevent this problem. I'm thinking that may be where my issue came from but don't know for sure.

For now my plan is to pull the heads, disassemble them, clean the rust and hope it didn't pit the seals beyond repair. I'll look for signs of coolant leaks between the heads and block.

Assuming all is well after all that; would it be ok to reuse the head gaskets, or best to replace them?
 
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