Need Help Finding Spec's On Merc 350 Mag
 

Hello To Everyone

This is my first time posting on OSO. The info and topics on this site are awesome.

Can anyone help me find out the spec's on a 1987 or 1988 Merc 350 Mag. I don't have access to the motor or the Merc tag numbers. I need to find out the cam specs, the size of the heads, what type of carb(CFM rating), what type of intake, and what type of valve train.

I would really appreciate any help or a push in the right direction.


Brian Englert

Keep The Good Stuff Comming!!!!!!!!!!!!!!

I've got what you need.

Cam
Depending on the actual S/N of your engine it could have either a flat or a roller cam. Some time in '88 Merc switched to the roller cam in all 350's.
My 350MAG has the flat lifter cam, specs and part numers are:
Merc p/n 431-5943
GM p/n 340284
Duration Int 200*/Exh. 212*
Lift @ .050 Int .400/Exh .410
Lobe C.L. 108*ATDC/112*BTDC
Lobe seperation 110*

Heads
Standard GM 350 SBC cast iron, non-vortec type, small valve.
I think the valves are 1.94" and 1.50" diameter.

Carb
Should be a Rochester Q-Jet, 750cfm.

Intake
Cast iron version of Z-28 aluminum high rise.
GM p/n 14096242


If there's anything else, just ask.

IGGY

Thank You so much.
I have one more questine for you. The piston's. Can I get away with putting head's on that are 2.02/1.6. I'm wondering if the piston's have valve relief's big enough to handle the bigger valves. I would be bummed to put them on and turn it by hand, only to find out they hit.

Brian

Sorry I didn't get back to you yesterday. Just wasn't time to go online.

You shouldn't have trouble with clearance depending on the cam you decide to use. If sticking with the stock cam, no problem.

There's two things to watch out for though.
One is the size of the combustion chamber. On the high performance heads it's smaller and will raise compression ratio. Stock heads have a chamber size of about 74cc's, hi-po heads are around 64cc's.
The other item is the center two intake manifold bolts.
On all heads made up to 1986 they're all the same.
From 1987 to 1996 the bolts are at a different angle and require a matching manifold. You could take an older style manifold and drill the center holes oversize and at the correct angle to make it work.
From 1997 up the Vortec heads don't have any center bolts and the intake ports are different shape/size. Again, a matching manifold is required.

BTW you should pick up a copy of Dennis Moore's "Small-Block Chevy Marine Performance", around $18.00. Most of my answers came from it.

OK, what about std SBC 260 HP..I hear it has the Z-28 style intake but lame in the Cam and heads area...I am going to ge the book..18.00 is a cheap investment. thanks

I'm not sure since it's only 10hp less than ours (270hp).
I think the HP version took the place of our 350MAG when the 350MAG went to EFI.
As for the intake, check the p/n cast into it against what I posted above.
FYI GM still offers the cast iron version in their performance parts catalog. Same goes for the cams.

ttt

I was told the only differance between the 350 (260hp) and the 350 mag (270hp) was the intake. Tha mag motor had the high rise intake..

350Mag= Four bolt mains, forged crankshaft, and forged pistons. Uses a cast iron version of the Z- 28 high rise manifold. Also slightly larger primary jets and secondary metering rods than the standard 260

350- (260) 2 bolt mains, cast crankshaft and pistons, standard height cast iron intake manifold.

Heads, valve sizes and camshafts are shared by these models, as well as the standard 750CFM QuadraJet.

Just do what I did......

sit your 350 in the corner and built a big ole fat mighty mouse :D :D


and spend millions trying to catch the big boys :D