454 Mag MPI gen v rebuild help
 

It looks like i have a new winter project. I need to rebuild my gen v 454 mag mpi. i have a few things I want to do while Im in there but the purpose of this thread is see if there is a good kit for marine engines instead of using Merc stuff and maybe to discuss pro's and con's of adding a bigger cam. Minus machinist work Id like to find a complete rebuild kit. I think I ll need main rod and cam bearing, oil pump, marine gasket kit, piston rings, cam and lifters stock vs bigger?, timing chain, and that should be everything. Im hoping ot hear from someone that has rebuilt there and have gotten reliability out of it. I dont want to put cheap parts in it but I want it reliable. My main goal is to cruise, maybe ski, and short full throttle burst. Probably need a crank but if I can have it turned and put in oversized bearing I probably will.

Ive seen so many "marine cams" that supposedly replace the stock cam but does it really? Anyone else know a good cam to replace stock? If Im going stock I dont want to do computer work because the cam isnt just right. If Im going to upgrade I can expect to do computer work but reliability and other work may be needed. Wouldn't mind having something that sounds better. Either way I believe the cam will need to be replaced as some of the lifters had heat spots and with the RPMS believe its probably best.

I have a great machinist that is very cheap so if i can get away with spending $1000 on all parts and machine work vs $2500 for performance upgrade and have to worry about fuel and reliability Ill take the cheaper option.

Seems like if Im going to buy a Merc special cam for $400 then a after market cam lifters and computer upgrade might be beneficial?

What about the crank in this engine. At this point Im going to assume I have a spun bearing so has anyone ever tried oversized bearing in a marine engine?

cb,
Most of the internal parts are no different than a GM truck engine. The parts are all readily available aftermarket and very good quality. Gaskets are definitely different but Fel-Pro makes very good marine gasket sets. Your machine shop should be able to get you a complete kit with everything you need in it.

Not sure how "cheap" your machine shop is going to be but That figure would not even come close to touching the machine work on most marine engines I see with any kind of hours on them. If you need a crank they are $900 from GM and if you regrind yours it will be $250. Then you need some rods by the sounds of it, they are $100 a piece. And so it goes. If the block needs boring an engine kit with pistons and just a stock camshaft will probably be in the $700 range.

You get the picture :(

If you're trying to do this on the cheap I have a set of gm "dimple rods" and stock pistons out of my 525 sc...pistons won't do you much good since the 525 sc's are low low compression but the rods are better than what you have I'm sure...nothing wrong with any of it was just time for me to rebuild and up the power....PM me if you're interested

Other than that...like bill said no way you're going to get parts and labor for a grand unless you buy used and know a guy at a machine shop...I had well over double that just in machine shop labor and I disassembled my old motor myself and took them all the parts....plus mine was a fully running functioning engine just wanted to up the power...don't mean to sh!t on your parade but those are just facts lol

Think I have the stock 525sc cam laying around somewhere too...its a flat tappet not a roller but its a little more than what you have I believe...I'll let this stuff go for next to nothing so lemme know

In your other post you mentioned Tyler Crokket. He has a nice package assembled for a 502Mag.Cam.lifters,springs,fuel pressure regulator,ECM reprogram. You would have to call him to see if it is compatible with your 454. If you start down this road know you need to improve exhaust. Manifolds and risers 3k-4k. With different cam and lifters you need to be able to adjust the valves which means you need screw in studs and guide plates, and new rocker arms. Your stock valve covers won't clear the roller rockers. Will have a clearance issue between valve covers and exhaust depending on what exhaust you use and which tall valve cover you buy. Silent choice? Might have to say goodby to that. Noise restrictions where you boat? Everything you do to add power affects something else. It gets expensive fast. It's all cool if you are prepared for it. Thats why I said rebuild it stock. Feed it gas. Have fun.

there are 4,523,652 454 build threads on here. Search and read, search and read some more, Figure out what exactly you want , then what its going to take to achieve it. As had been said...it's easy to make more power, but then you get to change the fuel system from 3/8 to 1/2 inch, and increase you oil system, bigger lines, new cooler, better oil pump. then you need better exhaust. Screw something up in the recipe and start over. So take some time and read.learn from the mistakes and successes of others.

There is one thing I know. You do one thing and there are three other expenses others you have to do. I was looking for a cam and ecm reprogram but apparently no one makes a 50hp improvement that don't require 10k dollars. I'll build it back stock but I have to ask why do people keep thinking I need new rods? I think I spun a main bearing. Why change the rods if they've live 650 hard hours on this boat. Are they weak?

I am interested in the cam but yeah my machinst is old school and will turn the crank for $150 with bearings. Vat it, replace cam bearings, check the rods and pistons and sell me the complete master rebuild kit for $750 total... if he's not completely retired.

Probably because it is pretty rare for main bearings to fail before rod bearings so when you said the crank would need turning we probably all took it to mean that you had messed up a rod bearing. If you did indeed "spin" a main bearing then you might as well include a block in your estimate.

As far as your machinist turning a crank and supplying bearings for $150 . . . . unless he is a friend and doing it for you for no profit tell him he is not doing our industry a single bit of good by being that cheap. Those are 1960's prices. Is he going to magnaflux the crankshaft for that price too ?

Why would i have to include a block for a spun main bearing? I assume its a main bearing because the knock I hear only happens once coming of a hard rev. A rod bearing usually knocks every rotation. I havent broke into the engine yet and Im think of taking it to the lake again to see if it might be something else.
He is semi retired and does it for fun. Yes his prices are 1960's and he is a honest man. Hes not trying to rape people but simply keep the doors open when he feels like working.

Looks like a expensive upgrade. My boat isnt worth what you have in this motor. Guess I stick with stock. Man if it sounds as good as it looks im jealous.

What are some of the must do's while im in this engine? Im not trying to build a very expensive engine. It's going to be a budget build and other than machine work im doing it myself. If the rods are weak I'll replace them.

Called Tyler Crockett today and they have a special ground cam and ecm chang that should yield a easy 50hp. I assume no other change was necessary.

Called comp cam and they have a cam but man did they not seem to know anything about mpi engines. Stated they have a cam but couldn't tell you how aggressive it was and they don't give out hp numbers. Also stated no computer change was necessary. Stated it would increase hp but couldn't tell you much about it.

What Boat?

They know nothing but the computer does not need reprogramming ? WTF ? I can't believe this would be an answer today in 2019 and it wasn't an acceptable answer back in 1989 !

Always talk to a computer programmer, like you have, that has experience with the engine and computer in question, + can tell you what cam(s) they have programmed for successfully.

If you are using stock cast iron exaust i would build it as a stock rebuild. Most larger cams are gonna require better exhaust to avoid reversion issues.

You seem to be stating that in a pretty negative manner.

My opinion is that if a camshaft company is telling you that their cam will add #### horsepower to your engine I say they are full of it. Unless they have built your exact engine with that camshaft and have put it on a dyno before and after there is no way they can tell you a horsepower figure. They might be able to take an educated guess but that's it.

I can guarantee you that if you don't slow down, figure out what's wrong and take the appropriate steps to correct, and deal with somebody that knows what he is doing, you WILL be back this spring posting " I spent $xxx dollars on a new motor ,it does t run right, my boat goes slower and my engine builder ripped me off "

X2

Honestly slow down. I mean this in a bad way but you are all over the place. Im not sure you have a knock in your engine at this point. If I remember one of your recent posts it did not knock when you had it out checking fuel pressure. If that is the case a bearing knock will be constant.
I would take your oil filter off and cut it open to see what is inside at this point.

That's what I said back when he changed oil, don't know if it happened. My heads spinning on this one too. Cableguy....you got all winter man take your time like they said and just do it once. Tyler Crocket is a good dude,very smart, and will answer the phone and talk to you. The advantage with his package is it is known and tested, and he already has a tune for the ECM. He can reprogram it for you, he can also service your fuel injectors which you should do if it's apart.

Im keeping it stock but will do the Tyler Crockett custom cam hoping to add 50hp. I heard you take it slow.