Difference in the 351 engine packages?

[SpeedRacer0125]

I'm wondering what the major difference is between the early 90s 351 engine packages? Different Carb, Heads, Intake, or ???? I'm wanting to know how much trouble would it be to pep up one of the lower hp 351s to a HO. Thanks in advance for the help!

[east tx skier]

The only difference when it comes to power is that the 351HO had GT40 heads. The fact that the carburetor was a 4010 on the 351HO instead of a 4160 on the 351 made no difference in power, and a lot of people have retrofitted a 4160 to the 351HO.

The stock intakes on these two motors were the same, but if you're upgrading the heads, you'd be well advised to put a higher flowing intake on the boat like an Edelbrock Performer. These offer a very nice midrange torque bump. This will decrease the clearance under the motorbox, however. So you need to plan for that by finding a low profile flame arrestor, removing the spacer, or otherwise creating room under the box (collar under the motorbox).

Lastly (or firstly), upgrade the prop to a CNC milled prop like the Acme 541 or OJ XMP 13x11.5 or 13x12, assuming you aren't running at a very high altitude.

Good luck.

[drschemel]

I have to agree with ETS. The prop made a huge difference on my boat. A previous owner or maybe the original dealer had put a 13x15 prop on my boat and when I changed to the 541, the boat came alive! More pulling power and better top end despite being 13x12.5. And without lugging the motor when pulling, the exhaust sounds better too!

[SpeedRacer0125]

Thank you both for the info! I assume you're both running a 1:1 with that prop.

[SpeedRacer0125]

The only difference when it comes to power is that the 351HO had GT40 heads. The fact that the carburetor was a 4010 on the 351HO instead of a 4160 on the 351 made no difference in power, and a lot of people have retrofitted a 4160 to the 351HO.

The stock intakes on these two motors were the same, but if you're upgrading the heads, you'd be well advised to put a higher flowing intake on the boat like an Edelbrock Performer. These offer a very nice midrange torque bump. This will decrease the clearance under the motorbox, however. So you need to plan for that by finding a low profile flame arrestor, removing the spacer, or otherwise creating room under the box (collar under the motorbox).

Lastly (or firstly), upgrade the prop to a CNC milled prop like the Acme 541 or OJ XMP 13x11.5 or 13x12, assuming you aren't running at a very high altitude.

Good luck.

I appreciate the info! So, basically I can take any 351W, even an 85, that's not a HO and change the heads to GT40 heads to knock it up to the 285 hp rating then. Correct? Any other mods that you recommend?

[tockit]

I appreciate the info! So, basically I can take any 351W, even an 85, that's not a HO and change the heads to GT40 heads to knock it up to the 285 hp rating then. Correct? Any other mods that you recommend?

Can't go wrong with a hotter camshaft

[Guest]

Can't go wrong with a hotter camshaft

except remember that with a hot cam, sometimes you lose some vacuum......your power brakes might not work as well..

[Engine Nut]

The HO engine got GT40 heads and a different cam. The heads only will get you part way there.

[JimN]

I'm wondering what the major difference is between the early 90s 351 engine packages? Different Carb, Heads, Intake, or ???? I'm wanting to know how much trouble would it be to pep up one of the lower hp 351s to a HO. Thanks in advance for the help!

If you want to see which engine changes make the most difference, go to the websites for performance parts- they often have guides for this. An intake manifold often adds torque, as Doug posted and about 15 HP. A cam adds some, roller rockers/lifters in addition to a cam that has a more aggressive profile make more of a difference as a group. Heads can add more but if you stay with the existing ones, they can be made to breathe better (grinding and polishing the ports and re-grinding the valves). Make it breathe better and it will perform better- think of an engine as an air pump.

If you have a speed shop near you, they can be a good resource, too.

[waterlogged882]

..........

[SpeedRacer0125]

I keep seeing where the 92 still had the standard output engine and 1993 was the first year for the 285 HO being the production motor. Is this true that pre 93 the 285hp 351 was just optional or was it standard in 92?

[woodrowskis]

I did similar to a 1986.
I put "GT40 similar" heads, an edelbrock manifold (as much because the old one was really corroded as for power), the lifters and such were worn so I added roller rockers. A friend who was a much better mechanic (hot rod guy) did get some heads they were similar power and less money than the GT40s. So there are some choices out there.

There was a significant power increase. You'll like it. The GT40 boats are heavier so power to weight, you will probably be ahead of them. The hole shot was crazy.

Adding the new top end components increasing the power on the old engine, it would be advised to overhaul the lower 1/2 while you are it unless it has been done (mine had not been.

But after all those components looked new I couldn't handle that 1986 alternator. I had already gotten rid of the points with one of the modules you put in to top half of the distributor. But I bought a new marine distributor (just a Mallory, not like an MSD or anything.) I was really surprised how much smoother and precise the throttle response was. There is a lot of wear in old alternator and the technlogy for consisting firing got a lot better. You do this stuff it will feel like driving a brand new boat. And f budget is an issue, it doesn't all have to be done at once. Of course lot of extra work not do heads and intake at same time.

[CantRepeat]

I keep seeing where the 92 still had the standard output engine and 1993 was the first year for the 285 HO being the production motor. Is this true that pre 93 the 285hp 351 was just optional or was it standard in 92?

My 92 was factory 285hp.

[MIskiboat]

I think 240 was std in 91 and 275 in 92 with the 285 option.
What was the 240-275 change?

[SpeedRacer0125]

I think an 83-85 with a pepped motor and the awesome handling, that they're known for, would be amazing. I'm seriously leaning towards doing that.