21eagle

what does my drive have stock its a 1989 alpha 1 would replacing with a 1.32 gear ratio help with my set up now??? let me kno thanx a lot i am spinning a 21 pitch at 4600 prop is a little dinged up i have a 22 lab finished prop im going to try this weekend let me know if u think the 1.32 with the 22 prop is worth a shot

bobl

Personally, I'd stay with the 350. I've built many of these engines for customers. Install good heads, mild cam, intake and carb and you'll have a solid 350+ HP engine that won't break your drive. The GM Vortec heads are a good way to go, but they'll raise your compression ratio enough to require 91 octane fuel if you have flat top pistons. You'll need to limit RPM to a maximum of about 5200 with the stock rods. If you rebuild the bottom end and install good rod bolts you can turn it higher.

turbo2256b

Just going to port the stock heads on my 350s. Just did a set and was flowinng 240 CFM at .4 lift. Lower port volume than the vortec heads. I am not going to change the cam just a better flowing intake.

Nova 26

I agree with Bobl, the small block works great with the alpha drive. The big block can make the same hp as the small block with less stress on it, sure, but it also makes much more torque than the sb, torque kills drives. I think the alpha is at its limit with the 350/383.

21eagle

It is a stock 1989 350 mag plkease tell me what cam? what intake? and what carb what heads? the vortec heads with the vortec manifold im geussing but i cant find a metal intake only aluminum in the vortec what cam and carb would work best with these heads and intake ??? i currentl run 53 on gps stock with a 21 pitch could i see over 60mph with this set up?? 4600rpm is the max for this motor what needs replacing to turn it a little more?? roller rockers and lifters ??? Thanx all again for the help want to get all the parts together and then yank this motor out Once i do these upgrades should i go to the 1.32 gear to keep the rpms down??? Chris IS THERE ANYWAY ADDING SOME HP WITHOUT CHANGING HEADS MAYBE CAM INTAKE CARB ROLLER ROCKERS MOTOR RUNS GOOD WOULD HATE TO PULL OFF HEADS.ANY IDEA OF SPECS ON STOCK 350 MAGNUM CAM 1989

Ryan00TJ

I've ran 5 different small blocks now with my Alpha. A stock Merc 260, 355 w flat tappet cam, L98 aluminum heads,
355 w AFR heads, solid roller, intake and exhaust, 360ci w flat tappet cam, AFR heads, etc......

Keep the 1.50 gears, they are the best for small block performance. Remember power is made in the heads, skimp on them and you will not get the power you want. You can easily spin your 350 MAG more than 4600rpms. The bottom end can handle 5200-5500 for reasonable WOT runs. Watch oil temp and pressure.


Here are a few combo's you could use.....

Comp Pro Mag 1.5 roller rockers
correct length pushrods
aluminum Vortec dual plane intake
650 CFM DP Holley
Vortec 170cc heads modified for higher lift and with screw in studs and upgraded valvesprings
Comp XM270 hydraulic roller 218/224 .495/.503 112+2
Your choice exhaust I think you said EMI's?

Should idle fine with the Alpha, make good lowend and midrange torque and pull hard to 5200-5500rpms. With the above you should break into the 60's easily.

Or copy my old 355 combo.....

Crane 1.6I and Lunati 1.52 roller rockers
Holley 750 DP
226/230 .537/.511 112+2 hyd roller
AFR 190cc aluminum heads 73cc 10.1SCR
Edelbrock Performer RPM
Glenwood Magnaflow manifolds and Fastglass long risers

Motor spun 5700rpms with a 23p labbed 3 blade cleaver @ 76.2GPS best speed I ever saw. Made 400hp.

jrz

I do not know if the link is going to work, but this is a new CMI small block header to be released in Miami.

Dangerous Dave

Ryan,
what bottom end were you spinning 5700?
I'm going to assume it was forged but please correct me if I'm wrong.
Thanks

Ryan00TJ

4 bolt block, Eagle 4340 crank, GM forged rods, ARP rodbolts, TRW forged pistons. Rotating assembly was balanced very well. FluiDamper harmonic balancer.

For what it's worth I spun my old 360ci Jasper marine shortblock to 5500rpms for 365 hrs before I pulled the motor. Internals looked great and I kept it for a spare. It was nothing special just a cast crank, stock rods, rodbolts and cast pistons. Jasper did balance it very well though compared to a stock GM shortblock.

kornegle

I have a 1990 Wellcraft 216 Eclipse Cuddy. Slow Family Cruiser with a 260HP (230 propshaft HP) Alpha drive. Almost stock with roller tip rockers, K&N stack, and Nose Cone (that did nothing) it ran about 52 - 53 mph on GPS turning a 21 Mirage around 4600 rpm. (high slip). Pulled the engine and installed Vortec heads with only outer Z28 valve springs, Comp Cams flat tappet XM 256 cam (212/218@ .050) 1.5 aluminum roller rockers, Edlebrock dual plane intake for the Vortec heads,30* timing and new Mercruiser HiPo manifolds and risers.Put the K&N stack back and the first run I quit at 5500 rpm with the 21mirage. Installed a 23' Mirage (not a plus) and hit 5100 - 5200 rpm and the GPS said 60.4 mph. There is a bit more left if I play with props.Comes up on the plane easy.Tried various props but the 23 Mirage was best so far. Idles like stock doesn't sound like it has a cam, runs like stock but about 7 - 8 mph quicker.