Looks like it is Time for a rebuild Chevy 350

[ponyman460]

I have been diagnosing this "No Start" condition wit this boat that I just got. Firts we started with the solenoid....then the starter. As I got the manifold/riser off to get better access to the starter I noticed a significant amount of rust on the inside of the #8 exhaust port. I was thinking "damn...water in the motor it must be locked up." PUlled all the plugs and got it turning over pretty easy by hand....cool deal right? Nope. I pulled the valve covers to make sure everything looked good and noticed #7 rocker not moving. Found a bent/broke push rod.... I didnt know why it was bent, so I went to the store and bought a new one... After I put the new one in I found that while turning the motor over that the exhaust valve is rusted in the head and locked up. WONDERFUL!

At a minimum the heads need to come off and get refurbished. I want to pull the whole motor and go through it but I have to say that it intimidates me. I am a car guy...and have never messed with boats much so I just dont know all the ins and outs of that system.

Any suggestions? Just the heads? Whole motor? Are there any detailed write ups on pulling a chevy 350 or anything to look out for?

My buddy reccomended getting some newer chevy VORTEC heads bc you can get complete heads for 450ish ready to bolt on, and they should pick up some power. Has anybody done the head swap and found an intake to fit? Do they exhaust manifolds still line up if I swap the heads?

Thanks in advance@

Rick

 

[Fishermark]

Re: Looks like it is Time for a rebuild Chevy 350

At a minimum the heads need to come off and get refurbished.

That's true. But very easy to do if you have good access. You will know more when the heads are removed.

My buddy reccomended getting some newer chevy VORTEC heads

I would certainly second that motion. You would also need a new intake as well.


The basic engine is the same as a car. Same basic mechanical info / skills are needed.

While you are at it, be sure to remove the outdrive and check the condition of the bellows, gimbal bearing, shift cable, etc.

 

[HT32BSX115]

Re: Looks like it is Time for a rebuild Chevy 350

Howdy,


Have those manifolds and risers been on the engine a few years?

Since you indicated that you have a rusted valve, I would suspect a bad exhaust manifold, riser, gasket, etc.

It could have allowed some salt water to run back into that exhaust valve and you know the rest.

So as a minimum, you should probably plan on replacing/rebuilding the heads and maybe replacing the manifolds and risers.

You'll see when you get the heads off..... If the manifolds and risers are fairly new, you should at least, break the risers from the manifolds and inspect/replace the gaskets.


regards,


Rick

 

[ponyman460]

Re: Looks like it is Time for a rebuild Chevy 350

That's true. But very easy to do if you have good access. You will know more when the heads are removed.




I would certainly second that motion. You would also need a new intake as well.


The basic engine is the same as a car. Same basic mechanical info / skills are needed.

While you are at it, be sure to remove the outdrive and check the condition of the bellows, gimbal bearing, shift cable, etc.

Heads should be real easy to get off....nothing obstructing the access at all.

I understand that I will need a new intake...and know that I either need a cast iron piece, or an aluminum one with the water passages coated.

I am good with cars....have removed and replaced the motor in my mustang at least 5 times (anther story for another time) and have plenty of help from friends that are huge into chevy 350 specific stuff.

Removing the outdrive is where the intimidation comes in. I dont know anything about it really. I have been trying to read as much as I can here and have learned, but dont want to get it apart and not be able to reinstall it correctly.

 

[HT32BSX115]

Re: Looks like it is Time for a rebuild Chevy 350

Removing the outdrive is where the intimidation comes in. I dont know anything about it really. I have been trying to read as much as I can here and have learned, but dont want to get it apart and not be able to reinstall it correctly.

That will be the easy part.... It can take as little as 30 min to pull an outdrive... Bondo can do it in 15!!

 

[ponyman460]

Re: Looks like it is Time for a rebuild Chevy 350

Howdy,


Have those manifolds and risers been on the engine a few years?

Since you indicated that you have a rusted valve, I would suspect a bad exhaust manifold, riser, gasket, etc.

It could have allowed some salt water to run back into that exhaust valve and you know the rest.

So as a minimum, you should probably plan on replacing/rebuilding the heads and maybe replacing the manifolds and risers.

You'll see when you get the heads off..... If the manifolds and risers are fairly new, you should at least, break the risers from the manifolds and inspect/replace the gaskets.


regards,


Rick

Rick, thanks! I have no idea how long they have been on there, and they are getting replaced for sure. I found some on ebay for ~500 plus shipping.

They are very rusty, and I dont want to take the chance with those.. It is strange but I found the same amount of rust inside #'s 7 and 8 but nowhere else. Are the rear cylinders prone to going bad first?

What I would like to do is pull the heads/ recondition them/ put on new manifolds and risers and then diagnose everything else as I go.

I just got the boat 4 weeks ago, and if it means anything the last time it was registered was 2007, so I have to assume it has sat for at least 3-4 years.

RIck

 

[ponyman460]

Re: Looks like it is Time for a rebuild Chevy 350

That will be the easy part.... It can take as little as 30 min to pull an outdrive... Bondo can do it in 15!!

wow! that makes it sound easy!

 

[Alpheus]

Re: Looks like it is Time for a rebuild Chevy 350

Pulling an engine in a boat is 10 x easier than in a car. Put your shift lever in forward,remove the 6 nuts on the outdrive and the 2 nuts holding on the hydraulic rams and pull pull it off.

Here are links for your engine and outdrive service manuals along with an engine Remove and Replace manual. Read them. You will see its not that hard to pull the engine. For your first time it should take you no more than 2 hours...

Engine R&R Manual

Alpha One Outdrive Manual

Engine Manual

 

[Fishermark]

Re: Looks like it is Time for a rebuild Chevy 350

I understand being apprehensive, but like mentioned above - it is a very easy thing to do.

Do some reading up for sure... but basically you simply put the outdrive in forward gear (that's necessary to line up the shift shaft)... remove the trim rams.... remove the six nuts holding the outdrive on.... pull off outdrive.

That's the basics. It may be stuck, in which case you can come back for more tips.

 

[ponyman460]

Re: Looks like it is Time for a rebuild Chevy 350

you guys are awesome! Thanks.

 

[John_S]

Re: Looks like it is Time for a rebuild Chevy 350

I suspect your 70's motor has flat-top pistons. If so, the 64cc vortec heads will put the compression fairly high (for a boat). If the block needs boring, you can just get the right pistons to keep the compression reasonable.

 

[ponyman460]

Re: Looks like it is Time for a rebuild Chevy 350

I suspect your 70's motor has flat-top pistons. If so, the 64cc vortec heads will put the compression fairly high (for a boat). If the block needs boring, you can just get the right pistons to keep the compression reasonable.

ok, thanks. I have to keep reminding myself that I am not building a car....

In my mustang, high compression is king.....we are doing a 10.5:1 compression motor with 17lbs of supercharger boost for the car......

what is maximum compression that i would want on a boat? I want it as high as I can get away with safely because compression make torque

 

[Fishermark]

Re: Looks like it is Time for a rebuild Chevy 350

I realize a car is not a boat, but the engine in my car - the 56 Chevy in my avatar - is a 350 as well. I built it from a 1988 Suburban engine. I bored it 30 over and put in flat top hypereutectic pistons with valve reliefs. I have the stock cast iron Vortec heads with an aluminum Edelbrock Performer manifold and carb. I don't know the compression ratio, but it runs fine on regular gas. It has a basic vacuum advance HEI distributor - nothing fancy - no computer controls to limit or retard timing due to knock.

And just to be clear, I am not suggesting you put in a vacuum advance auto distributor.... I am simply pointing out that a 350 can be made to run, and run well, with flat top pistons and Vortec heads. You simply have to watch that you do not advance the timing too far.

 

[John_S]

Re: Looks like it is Time for a rebuild Chevy 350

I realize a car is not a boat, but the engine in my car - the 56 Chevy in my avatar - is a 350 as well. I built it from a 1988 Suburban engine. I bored it 30 over and put in flat top hypereutectic pistons with valve reliefs. I have the stock cast iron Vortec heads with an aluminum Edelbrock Performer manifold and carb. I don't know the compression ratio, but it runs fine on regular gas. It has a basic vacuum advance HEI distributor - nothing fancy - no computer controls to limit or retard timing due to knock.

And just to be clear, I am not suggesting you put in a vacuum advance auto distributor.... I am simply pointing out that a 350 can be made to run, and run well, with flat top pistons and Vortec heads. You simply have to watch that you do not advance the timing too far.

Common for cars to get away with it. No where near the load of a boat. Merc/Volvo advertise a 9.3/9.4:1 ratio (vortec 350), but if you go through actual calcs with the known stock parts and clearances, it is less. Prior to vortec heads the static compression was 8.5-9.0:1 range. Do some searches on recommended compression ratios for heavy towing. Can you get away with it in a boat, yes... sometimes, and matching everything up. Might have to feed it premium, and or reduce total timing. Look at a few of the hp/compression ratio calculators. You are probably leaving less hp on the table than you think. If you are dealing with a stock marine engine, why risk it? If you are rebuilding it, the piston cost difference is nil.

 

[Fishermark]

Re: Looks like it is Time for a rebuild Chevy 350

If you are rebuilding it, the piston cost difference is nil.

Absolutely agree.

But that is IF you are rebuilding it.

If he is simply going to replace the heads, then I believe he can get away with simply retarding the timing if he has pre-ignition issues or running higher octane.

 

[John_S]

Re: Looks like it is Time for a rebuild Chevy 350

If he is simply going to replace the heads, then I believe he can get away with simply retarding the timing if he has pre-ignition issues or running higher octane.

If it was a fresh rebuild, maybe worth trying the risk with 0.051" head gaskets. If not, jumping compression on a worn motor, doesn't sound wise to me.

Water in the exhaust cavitity, frozen open valve, probably means heavy rust in cylinder. He currently can't do a compression or leak down to see what the condition is.

 

[ponyman460]

Re: Looks like it is Time for a rebuild Chevy 350

If it was a fresh rebuild, maybe worth trying the risk with 0.051" head gaskets. If not, jumping compression on a worn motor, doesn't sound wise to me.

Water in the exhaust cavitity, frozen open valve, probably means heavy rust in cylinder. He currently can't do a compression or leak down to see what the condition is.

I agree. I am thinking that due to those points I will just pull it out and rebuild. I would hate to go through all the work of swapping heads, intake etc and have the bottom end let go. It just doesnt make sense to me.

You guys have proven to me that it shouldnt be that bad, so I am going to try it out.

 

[Alpheus]

Re: Looks like it is Time for a rebuild Chevy 350

You can get a reman engine for about the same cost as the machine shop bill...

Rapido Marine

 

[nofuss]

Re: Looks like it is Time for a rebuild Chevy 350

I was reading through this thread waiting to see if anyone set u on the easy track but I see one guy did. I was doing some research on what it cost to rebuild a chevy 4.3 and the prices are just about the same and in some instances less for the 350. the difference in the cost of a reman engine, is often just about the cost of the rebuild, if you are doing it your self.
with an engine of suspect condition, that seems to have had questionable maintainence, i would not be supprised if the condition of the water part of the block is in a bad way too , so it may be an overall saving to just buy a reman engine. and with a reman you get a warranty which you are unable to build into yours
At least that way you start off with a casting in good good condition and could do your maintainence to keep from having stupid overheating problems after rebuilding a rusted out block.
Guy with a boat near mine actually rebuilt his engine and then found what appeared to be some porosity in the block and had to end up doing a second rebuild with a fresh block, cost him way more, he almost went to a reman instead of the second rebuild, but the mechanic worked with him to reduce the cost.
depending on where you are there is also the posibility of impropper winterizing too, and unless u are like me and dont need to know what that means, im sure u know where im heading......

My advice at this point is buy a reman engine and start fresh

note it seems cheaper to rebuild at first glance. but if u done it in cars check everything, and u will see.

No Fuss

 

[444]

Re: Looks like it is Time for a rebuild Chevy 350

Chevy 350 is the best supported, cheapest to upgrade, most generic v8 engine there is. Dealing with this should be easy for you. Once you get down to the nuts and bolts the marine version is basically the same as the car version.