PDA

View Full Version : What about this combo?



Cuda
09-07-2003, 08:44 AM
I found some of the build sheets for the engine I bought two years ago for my 20 foot Formula. Let me know what you think of this combo. I may use it for a guide on the engine for the Minx. Actually, I'm going to go ahead and drop that engine in the Minx, then rebuild the other one so I can get on the water right away.

350 4 bolt block .30 over
Votech heads
Keith Black KB 142 piston package
Pink rods
Edelbrock intake
600 cfm Edelbrock carb
12495490 arm kit (???)


For the cam it has listed part number 24502476. I don't know if this is a Gm part number or what. The specs written say:

T @50 Lift
I - 318 212 .435
E - 327 222 .460 112.5 CL

What do those first numbers relate to?

Any idea how much power this set up is making? Stock Merc manifolds and risers.

BUIZILLA
09-07-2003, 01:55 PM
I'd say it's probably 320-325 hp, depending on compression.

The cam duration at .050 tappet left is 212/222, valve lift at the stem with stock 1.50 rockers is .435/.460

112.5* is the lobe seperation degree #, so I would degree the cam in at about 110* intake centerline, or maybe leave it at 111*-112*. If the cam has 4* advance built into it, it will degree out to 108.5, which is still pretty torky up top. Idle should be excellent at 650 in gear, peak rpm should be 4800,5000 tops, good cruise rpm should be 3200-3400.

What I would definately do, is get a set of Erson roller rockers in 1.6 ratio for the intake and 1.5 for the exhaust, and put it together. Those rockers should fit under the stock valve covers.

J

Cuda
09-07-2003, 03:51 PM
You're the second person to suggest going to the 1.6 rockers. How much improvement would they make?

BUIZILLA
09-07-2003, 04:48 PM
If you have stock 1.5 slotted ball rockers now, and you go to the same ratio in a true roller style, you'll gain about 15 hp and 10 lbs-ft of torque. Going from a stock 1.5 slotted to a true 1.6 roller would net you about 22-24 hp and 15-18 in torque. Pretty cheap horsepower gain, and the upper rpm geometry is MUCH more stable. Since we all like to *buzz* our motors pretty good it seems, it becomes a no-brainer required upgrade to me. I think running 1.6 intake and 1.5 exhaust rockers makes a little more torque overall, and evens out the valve lift in your situation. An unported Vortec head is basically *all done* at .480-.500 valve lift anyways, so keeping the valve lift in the .460-.480 theatre makes perfect sense.

Your cam probably has .290 intake lobes and .306 exhaust lobes, based on the net lift numbers you stated above. Multiply each of those numbers by 1.5 or 1.6 for your true lift, at the valve stem.

Keep in mind if you run a solid lifter cam, your ACTUAL valve lift numbers are less whatever the valve lash spec is.

Also, you gain a proportional amount of cam duration OVERALL gain, since the valve opens earlier and closes later, with a larger aspect ratio rocker. For instance, your 212-224 cam becomes a 224-236 with only a 1.6 rocker change. That 12* gain interpolates into about a 24 hp gain at the flywheel.

J