84 Scarab

I'm sure this question has been asked to death, but I gotta do it anyway because I'm a gearhead and I like to tinker with my stuff.

Is there anything to be gained by using "bolt on" performance parts for an 84 Merc 260? For instance, upgrading from a 3 inch riser/manifold combo to a 4, maybe installing some 1.6 roller rockers to give the stock cam more lift, or a freer flowing flame arrestor? I have noticed that most boaters either leave their boats with a stock engine or build something rediculous, not too much in the way of bolt ons, I'm wondering why that is? I really think that a couple more hp are available from this, but I'm a newbie so I could be wrong.

Any replies are appreciated, and yes I am the same idiot that asked about supercharging it last week lol.

FIXX

iTrader: (2)

vortec heads,rpm airgap intake holly 650 dp and a xtreme marine by comp cams..you eill be around 330 hp..

Wes Burmark

I changed the heads on mine to World Products, added the magnum iron high rise, rejetted the Quadrajet, magnum flame arrestor, added a Crane Cam, and roller rockers. I had to go 2" up on the prop pitch. Gained 4-5 m.p.h. If you are fresh water cooled I would go with aluminum heads and intake. You will probably save 100 pounds alone! I used 76cc heads as I was afraid of having too much compression and having to use 89 or 92 grade gas. As it was 1986 when I did my build I know I could get a lot more power today. I'd go to a 383 cu. in. setup with aluminum heads and intake, and a roller hydraulic cam. I would think you could make an easy 380-400 h.p. Enough to break your drive!

GPM

Cast crank, cast pistons, make it a winter project and do a 383.

befu

iTrader: (2)

Just got done with a similar one. I ended up replacing the whole engine, but the old short block to new is pretty much the same setup except for the roller cam.

I was able to buy two 350 long blocks from 97-99 pickups with spun main bearings, less than 100,000 miles either engine, for $500 total. Used those vortec heads and brackets on my engines. Went with the aluminum dual plane intakes and the mercruiser roller cams. Should be right at 300 HP I am guessing, but that is just using mercruiser numbers. Still using the same carbs, they aren't bad actually and changing out secondary rods is real easy to play with air/fuel ratio. yeah, I left HP on the table with the merc bump sticks, but I had one already and didn't want to fork out another $500 for new cams.

so you can get vortec heads for $300 or less per engine, then a new aluminum intake manifold will push almost $200, then a gasket set which is pricey for the vortecs, I think around $180ish, can't remember. About $700 an engine with a few extra parts thrown in. Wake it up with a new cam and lifters for another $100 I would guess for non roller.

my build is in the formula section, go figure huh?

Good luck, Brian

Mr Maine

There may be different opinions on this, but mine come from experience. At the 260 (270 mag) horsepower level these heads are maxed out. I have put bigger cams on them and better induction and exhaust and have seen very little improvement in performance. The heads are just not up to the task.

That being said, throw on a pair of vortec heads and a good roller cam and results are instant. Either search them or I can tell you common combinations for small block power.

Of cousre you can also go big (AFR, Dart, etc.) and stroke to a 383, but you seem more interested in moderation and fair prices.

You won't be disapointed in a build vortec 350 and it wont cost verly much relatively speaking.

dereknkathy

nobody directly answered your question, yet they all did. the 1.6 rockers won't magically make the stock 260 cam into a bob madera custom grind. the 4 inch risers and bigger flame arrestor won't change a thing. unless and until you go heads-cam-intake-exhaust you will see very little improvement. what you need to do first is make sure everything is right with the motor and it is putting out the 260 it is supposed to. plugs, wires, clean all the black gunk off the flame arrestor. make sure it is timed correctly.

Full Force

iTrader: (5)

I had a 24 Chris Craft 245 Limited years ago, stock 260 it went 42 mph gps, I used my buddys 350 from his camaro with a ZZ4 roller cam, edelbrock aluminum heads, edelbrock performer intake and a 650 Holley, boat went 53 mph gps after that, I would say that was a good gain over the 260 it was for the money spent...proven combo without going broke... the shortblock held up fine with stock internals..

befu

iTrader: (2)

Derek is correct, none of us answered directly.

Like he said, no bolt ons are really going to make a difference until you swap the heads. Stock cast iron vortec is the biggest bang for the buck, but that also requires a new intake due to bolt pattern. but you should get rid of that cast iron intake anyways. So a minimum: used gm vortec heads and intakes, which means top end gasket set. My gasket set was whole engine, so maybe heads up would be less, but it is the intake that was pricey I think.

And if you do that, you owe it to yourself to do the cam since the intake is off anyways. Once you see the price of intake gaskets for the vortec, you will not want to do the cams later.

And you are at that minimum number of $700 or more.

Are you willing to spend the $1500 ish it will take to do both motors? If the answer is yes, then do as suggested and get them running in top shape and beat on them for a bit to make sure they hold together before adding more HP.

Brian

Sam007

Just put a weiand 144 blower on it. Run 5# of boost, you should get an easy 350hp and be able to run close to 60mph. All you will have to do is replace the intake and rejet the carb and plugs. You wont have to take the motor apart and it will idle like stock and run like stock till you get in it and start making boost.