Where to start?

[SleepyMerc]

I'm trying to find out all I can about my Merc Grand Marquis. Things like how the engine is dfferent from the HO mustang ie: Is the intake just turned around or is it different in runner length and cross-section? Is the cam flat tappet or roller? Cam specs? Compression ratio?Are the pistons cast, hyperteutectic, or forged?

You know, basic stuff. Assuming the rear is an 8.8, is it 28 or 31 spline axles?

I've been searching for a quick reference type thing and I can find everything in the world for Mustangs but squat for the GM.

Any nudge in the right direction will be appreciated.

[Paul_]

welcome to GMN!

the differences between a ho motor and the lo-po your GM has are pistons, heads, intake has been swapped around, and i believe the cam is different as well. somebody else will chime in with more details. the rear on all cv/gm/tcs is an 8.8 and they have 28 spline axles. hope this helps. like i said welcome, and the more knowledgeable people will chime in as well

[Mercracer]

With the exception of the cam profile, the GM/CV motor is identical to the 1986 Mustang/Capri motor.

Pistons: Cast flat top with no reliefs 8.9:1 CR

Heads: E6AE "fastburn" It had a masked itake valve design which was intended to produce swirl.

GM/CV/92-93 Truck Cam: Lift .237/.244 Duration 244/256
HO Cam: Lift .278/.278 Duration 266/276
94+ Truck/Explorer/Van: Lift .264/.280 Duration256/266
302 & 351W

The cross section of the upper intake is different on CV/GM/TC motors.

[SleepyMerc]

With the exception of the cam profile, the GM/CV motor is identical to the 1986 Mustang/Capri motor.

Pistons: Cast flat top with no reliefs 8.9:1 CR

Heads: E6AE "fastburn" It had a masked itake valve design which was intended to produce swirl.

GM/CV/92-93 Truck Cam: Lift .237/.244 Duration 244/256
HO Cam: Lift .278/.278 Duration 266/276
94+ Truck/Explorer/Van: Lift .264/.280 Duration256/266
302 & 351W

The cross section of the upper intake is different on CV/GM/TC motors.

So if I want this 127k engine to wake up, there's not much sense in a stock rebuild. If the rockers are the same 1.6 ratio that puts valve lift at less than .4", so the cam is pretty much worthless without forced induction, the pistons limit lift to about .44'', and the heads would be marginal on an old 221. If memory serves me correctly.

Here's what I'm thinking, let me know how it sounds. I want a fresh engine, and I'm thinking it would be easier to stick with the low deck 5.0 instead of the 351. The block should be OK with a .030 overbore and a 3.4'' crank kit would make the 347. That would be a good size for the midrange torque this heavy beast needs. Hypereutectic pistons would allow better oil control and save few bucks, though forged would allow adding a power adder later.

A cam in .500-.525 valve lift range and 230ish duration @ .050 lift should give good power from 3000 to 6000 rpm. AFR185's should flow plenty of air. I don't know which aftermarket manifolds work in a full size, but I would think an extrude honed and port matched explorer manifold would work if you can't use an Edelbrock or Trick Flow. I'd prefer long tube headers but I don't yet know what fits the chassis. Whether they're shorites or long tubes there's plenty of room to follow them up with a catted x-pipe and 2.5'' true duals.

The Mustang 3.27 gears and posi should bolt up. I've got a supposedly fresh 91 Mustang AOD. I think a 2000-2200 stall converter with lock-up would work well. Then convert the SD to Mass Air and tune it with SCT software.

What do you guys think? Am I missing anything? Is this a good rcipe for a Sleeper Merc? :evil:

[Mercracer]

A cam in .500-.525 valve lift range and 230ish duration @ .050 lift should give good power from 3000 to 6000 rpm. AFR185's should flow plenty of air. I don't know which aftermarket manifolds work in a full size, but I would think an extrude honed and port matched explorer manifold would work if you can't use an Edelbrock or Trick Flow.
The Mustang 3.27 gears and posi should bolt up. I've got a supposedly fresh 91 Mustang AOD. I think a 2000-2200 stall converter with lock-up would work well. Then convert the SD to Mass Air and tune it with SCT software.
What do you guys think? Am I missing anything? Is this a good rcipe for a Sleeper Merc?

Sounds like you are looking for serious power if you are looking at AFR 185's. 230ish duration @.050 is way too much with a heavy car, 3.27 gears and a mild converter.
Trick Flow Stage I cam would fit the bill and retain decent manners for you in a 347. You will still need 3.55's or 3.73's though. If you are switching converters, go with a 2500-3000 rpm stall.

[SleepyMerc]

I was thinking of the 3.27s cuz they'd be handy, but if I go any steeper I'll just go to 4.10s. I could care less about top end and I don't think they'd be any worse for gas mileage than 3.73s since it will have OD. With 4.10s the 2500-3000 converter would be awesome. i was figuring the 2200 would produce a lot less heat with the 3.27s. I'm not sold on AOD durability.

And yes, I do want power! I figure that combo should be good for 350+ hp and around 400 lb/ft torque at the flywheel, maybe more. Should be good for low 13's in street trim. All I want to do is keep up with the local ricers!

I'll check into that cam. thanks. I like some of the Ultradyne profiles for hydraulic lifters, but I'm not decided yet. Cam selection will be one of my last decisios. Years ago a buddy had 67 396 SS Impala. Everyone thought the L88 cam would be way too much for a 3900 lb car. But it worked great--with a four speed and 4.56s!