390 Ec Engine overhauls with increased HP

[hottoddie]

The 454350HP Crusaders will be coming out for overhaul in Sept. One developed an internal rap on Sunday, most likely a wrist pin or rod bearing. Anyway are there any CSR members that have had their 454's rebuilt with some extra HP and with what results? The 454's in a 390 are borderline adequate and I would like to get them up to 380-400HP with some minor modifications. I am fortunate to have 3 qualified machine shops around Boston that I know will do a good job on the motors but I am curious if any of you have done this type of modification and what were the results.

 

[dpmulvey]

Balanced and blueprinted a fellow got 525 out of his. Don't know if he had it bored and stroked or not. How much do you want to spend.

 

[Air O'Nautical]

I just funished that delemina. What to repower with? So many choices and different cost levels. After alot of thought and weighing the options 8.2, 8.1, 7.4, diesel or rebuild mine?? I elected to repower with brand new 7.4L long blocks and replace everything else with new parts while I was at it. Originally, I planned to refurbish many pieces but, replacement was just quicker and easier.I ended up creating new 7.4L Mercruisers that aren't available in a complete package anymore.
I was happy (enough) with the performance and simplicity of the gas motors and didn't feel the upgrade to larger more complicated engines was going to be worth it....to me.
We cruise anywhere from 18-23kts depending on how much fuel we want to burn.
The boat tops out at 29-30kts WOT and we have done some longer distances in calm water at 6kts.


This isn't our last boat but, plan to have it for a good while longer because, it works for us.

Just a thought of what to do..
Good luck with your repower,


Mark.

 

[hottoddie]

Balanced and blueprinted a fellow got 525 out of his. Don't know if he had it bored and stroked or not. How much do you want to spend.

Don't need to go any more than 400HP. All the external accessories are 1-2 years old except the circulating pumps and heat exchangers. I will replace the circulating pumps, thermostats, flex plates and have the heat exchanger's cleaned and pressure tested. I may also replace the Prestolite distributors with Delco HEI electronic units. Based on a couple of initial phone calls I estimate each long block will run 4k to have reworked. I will do all the R&R and along with the misc. items I think the repower will cost 10-11k total. I am curious as to whether the stock 19X18 three blade props will need to be changed.

 

[Jimmy Buoy]

Keep in mind that a bump in HP doesn't always mean a similar bump in torque. HP numbers help sell a new boat but torque is what gets you up and away!

 

[270win]

Want torque? Bore and stroke the 454s out to 496. Have a marine cam specialist spec a cam to your build for torque, the stroke with give you more torque and you should be able to turn bigger props. I would go for 400 hp max, you probably don't want longevity to be cut down.

 

[hottoddie]

Today I decided to investigate where the "rap" in the Starboard engine was coming from. Removed the left cylinder head on the starboard engine and found a small piece of metal embedded in the top of the #7 piston and it had been bouncing around in the cylinder and sounded like a rod or wrist pin wrapping. Fortunately it appears the damage is minor and once removed and the top of the piston is cleaned up a little the engine will be fine. While 'm at it I'll have the valves done and the heat exchanger will be cleaned and pressure tested and I'll put in Delco Voyager EST distributors. Wish I knew where that piece of metal came from. Just dodged a major bullet.

 

[Pyrojodge]

Maybe, where did the piece of metal come from? What else failed to create that? Best of luck...

 

[wileecoyote]

Take a pic of the metal piece, maybe we can figure out what it was/is.

 

[270win]

I'd really be interested to know where the metal came from...obviously something broke on top of the combustion chamber or above the ring land on that piston. I'd find out where that came from before doing heads and putting it back together.

 

[hottoddie]

The metal fragment is magnetic and the top ring land of the piston is completely intact. The compression in that #7 cylinder was 135# before disassembling. I think something got ingested thru the carb. I am going to closely examine the quadrajet toady the see if any small part may have come loose in the throat area of the carb. The inside of the block and the condition of the cylinder walls are still like new.

 

[electricaldoctor]

A nut or washer used to secure the flame arrester???

 

[270win]

The metal fragment is magnetic and the top ring land of the piston is completely intact. The compression in that #7 cylinder was 135# before disassembling. I think something got ingested thru the carb. I am going to closely examine the quadrajet toady the see if any small part may have come loose in the throat area of the carb. The inside of the block and the condition of the cylinder walls are still like new.

That's entirely possible, if that's all it was and it did no real damage then you're doing good!

 

[Jeepers]

454 is known to develop a tick in the area of the fuel pump. No harm to motor or performance. Even after rebuilds the tick remains. Some blocks tick, some don't. Still....it's aggravating.
You still going through with rebuild ?

 

[docofthebay]

Sometimes part of the spark plug tip will break off ( the part you bend when setting the gap). This could then embed into the top of the piston.

 

[hottoddie]

454 is known to develop a tick in the area of the fuel pump. No harm to motor or performance. Even after rebuilds the tick remains. Some blocks tick, some don't. Still....it's aggravating.
You still going through with rebuild ?

In this case the fuel pump is not the culprit. I remove the fuel pump and started the engine and the rap was still there. Also removed both drive belts and same result. See next post for more.

 

[hottoddie]

Sometimes part of the spark plug tip will break off ( the part you bend when setting the gap). This could then embed into the top of the piston.

Removed the right cylinder head today and the top of #6 also had some minor damage. The shape of the damage looked like a 1/4" lock washer like used on the flame arrestor. I am very cautious when removing and installing the flame arrestor so if that what it is it may have been sitting in the intake manifold for quite a while until last weekend it decided to move while under acceleration. The Quadrajet check out fine.

In any case the heads are off and going to the machine shop tomorrow for a valve job and inspection of the valve guides and a .010" shave of the heads. New gaskets, heat exchanger cleaned and pressure tested and maybe new Delco Voyager EST distributor. Maybe pick up 20-30hp in the process. If all goes well then the port engine will get the same treatment over the winter. Hope to back up and running next weekend.

 

[wileecoyote]

So you had 2 pieces of metal floating around in the engine, one on each side??
Has someone been doing some work on that engine? It's odd to find one piece of metal on top of a piston, let alone both sides. It's very unlikely that this is a freak accident. Something is either coming apart, someone is very careless, or someone has a real axe to grind with you.

 

[270win]

So you had 2 pieces of metal floating around in the engine, one on each side??
Has someone been doing some work on that engine? It's odd to find one piece of metal on top of a piston, let alone both sides. It's very unlikely that this is a freak accident. Something is either coming apart, someone is very careless, or someone has a real axe to grind with you.

I agree, not sure about he axe to grind though, there are much better ways to be sure to sabotage an engine if you wanted to.

 

[hottoddie]

Re: 390 Ec Engine overhauls with increased HP Updated

Just got done putting the reworked heads back on yesterday and today. Engine fired right up and the knock is gone. Found a damaged 5/16" steel lock washer in the starboard outer bilge yesterday morning that had a small piece broken off and it matched the imprint of the lock washer on the top of #6 piston. The other small piece that was embedded on the top of #7 piston appears to be the broken off piece of that washer. I think the 5/16" washer got blown out of #6 cylinder during the compression test and ended up in the outer starboard bilge area. The end result is positive as the damage to the top of 2 pistons is minor and will not cause any problems down the road. Just very happy that the job cost me 1 boat buck and about 30 hours labor. Will do the same to the port motor at end of season but not looking forward to it. Thanks for the input and chock another one up to experience. :smt038