351 Rebuild - Need Opinions/Suggestions!!

So after rebuilding the transom, all new bellows/seals/gaskets for everything, getting the linkages hooked up and the starter rebuilt: we have locked up engine! We had found water in the left rear cylinder right before we put the engine back in, but we syphoned the water out put in some PB blaster/WD40 but it apparently did no good. Normally, I might just part out a boat with this issue, but with a new composite transom, all new seals, new bimini top, outdrive in good shape, new floor/carpet, reupholstered interior less than 2 years ago why not just rebuild the engine and have a new boat?!!

So, in rebuilding a 351W with about 750 hours (engine is a 75-76 model), what suggestions do you guys have for the rebuild?

Things I have in mind:
* Original Compression ratio per Seloc is 8.0, was wanting to go up to 9.0 if possible as we only run 91 octane and it is available dockside most places on the lake.
* Going to a 4bbl carb from the factory 2bbl Rochester and likely an Edlebrock performer intake.
* Should we stay at stock bore (just have cylinders honed) or go .30 over?
* Any particulars on regrinding the cam or crank? Possibly an upgraded cam, I know reversion is an issue, but how aggressive can we get without running into that problem?
* Any particulars on having the heads rebuilt? We will be getting all new valves, rods, lifters, etc as we might as well just make it a new engine to go with the "new" rest of the boat.
* We will likely be getting new exhaust manifolds/risers with all new hoses.


Anything else to keep in mind, suggestions, tips, tricks? I know there isn't a whole lot of knowledge on the 351 marine engines, but I need some guidance!

edit: We aren't looking to create a monster, just a solid engine to give another 30 years of trouble-free use! The outdrive is a 233 (pre-alpha) and original rated at 233HP, so I don't want to go above 300HP which isn't likely anyway, but just for your reference!

Re: 351 Rebuild - Need Opinions/Suggestions!!

So nobody has any suggestions for a marine rebuild? I have seen the US Engines and Rapido Marine options, but they are half a continent away shipping-wise. Anyone know what type of pistons were in the marine engines from the factory? Cast,Hypereutic, Forged, dished, domed, flat?

Re: 351 Rebuild - Need Opinions/Suggestions!!

I think Bubba's suggestions are right on, with just a couple exceptions,,, only bore it if you need to, then replace the pistons with slightly higher compression, if possible, if not, no big deal,,, as you'll be close to your target with just the 4bbl, manifold, a mild cam, and a good ignition system.

Re: 351 Rebuild - Need Opinions/Suggestions!!

this is just a thought,
750 hours does not sound like a lot of hours for a gas pot 351w.
did water just come in through the intake manifold? (rain)
are you sure its only one cylinder on one bank only?
pull the head on the side you found water, visually see how bad the rust has set up around the rings.
if minor rust, apply a rust/lubricant juice let sit. apply preasure to crank and tap piston head with rubber mallet or piece of wood to free, clean cylinder wall with very fine emery cloth (Put a rag on top of piston), bring piston to tdc blow out crud from top of ring/piston take to bdc wipe cylinder walls with lots of oil and rotate, wipe and repeat.
AND HOPE THE RINGS ARE NOT HOOPED
this would be the cheap easy fix if it works.
other wise drop the pan and pull the piston, hone and replace rings and piston
just a thought
rob

Re: 351 Rebuild - Need Opinions/Suggestions!!

rbh said:

this is just a thought,
750 hours does not sound like a lot of hours for a gas pot 351w.
did water just come in through the intake manifold? (rain)
are you sure its only one cylinder on one bank only?
pull the head on the side you found water, visually see how bad the rust has set up around the rings.
if minor rust, apply a rust/lubricant juice let sit. apply preasure to crank and tap piston head with rubber mallet or piece of wood to free, clean cylinder wall with very fine emery cloth (Put a rag on top of piston), bring piston to tdc blow out crud from top of ring/piston take to bdc wipe cylinder walls with lots of oil and rotate, wipe and repeat.
AND HOPE THE RINGS ARE NOT HOOPED
this would be the cheap easy fix if it works.
other wise drop the pan and pull the piston, hone and replace rings and piston
just a thought
rob

Click to expand...

The engine ran perfectly about 2 years ago, but we ended up with a rotten transom. So I pulled the engine, and it sat in the garage for 2 years while I rebuilt the transom. Upon reinstalling the engine, I pulled the spark plugs and put new plugs in and sprayed WD-40 in the cylinders for start up lubrication. Upon removing the starboard rear spark plug, there was water in the that cylinder, which I was surprised at, and promptly syphoned out. The water was "clean" not rust colored. I simply figured the tilting and swinging around we did of the engine when removing it let the little bit of water left in the rise/manifold get back into an open exhaust valve. We tried to start it, it wouldn't budge, so then I used a pretty stoud 1/2" socket wrench on the crank bolt and it wouldn't budge. There was also a small bit of water in the oil upon draining it before reinstalling the engine. Not milky, just water drained out first for 3-4 seconds, then regular oil. This is why a rebuild is likely in order.

While 750 hours in itself is not a high number, when the engine is 30+ years old and is only run for a 10-20 hours a year it certainly doesn't help extend the engine life. I pretty much figured if I was going to pull the engine, I might as well just rebuild it completely. We always use 91 or better octane, so the stock 8.0:1 compression could be raised to take advantage of it, say to a 9.0:1 or close to it.

Anyone think the water was related to something else?

Re: 351 Rebuild - Need Opinions/Suggestions!!

Also, when trying to get the motor to turn over by hand, I sprayed both WD-40 and PB blaster in via the spark plug hole to try and break up any rust on the cylinder. It sat overnight and I tried it again the next day to no avail. It gives me the chance to up the HP a bit (not really essential as it had 233HP stock and would plane out fast and run 50mph empty.) Going to a 4bbl carb from the stock 2bbl Rochester would be a step up as well.

Re: 351 Rebuild - Need Opinions/Suggestions!!

FWIW

I would let the engine tear down determine my course of action.

It might be that the pistons are undamaged and only need rings and a honing of the cylinder wall. That was what I found on mine.

Your crank might need to be turned or it might polish up std/std and just need a fresh set of bearings

You should replace the following in any engine overhaul( at least in my opinion) all gaskets, casting plugs, cam bearings, rod and main bearings, oil pump and of course a complete gasket set.

Additionally, I would replace a timing gear and chain set if it wasn't a double roller type and in perfect condition. Lifters are another cheap safety item to replace, but if you keep them numbered and return them to the same location they can be reused if you reuse your cam. If you replace the cam, replace the lifters. If you replace only the lifters, make sure and lube them and the cam and follow the break in procedure for a new cam.

If you need new pistons, the hypereuteric are a great choice, though many motors run long lives on cast pistons. Forged are nice but of no advantage in a mild application as compared to the hypereuteric.

Compression increases will help with horsepower but going from 8:1 to 9:1 isn't going to do a whole lot. the biggest place to find horsepower is in the exhaust side of the heads. There are a ton of aftermarket heads that outflow the factory heads-stay with the cast heads, not the aluminum and the GT-40 heads are a pretty good choice and fairly reasonable. Stick with a good marine cam. A new intake and 4 barrel carb will help to wake the engine up and will work very well with either performance heads like the GT-40's or stock heads with a little exhaust port work from a head shop.

I am convinced that many people think they can bolt on real horsepower with an intake and a carburetor, and while you can to some extent, unless you work the heads to let the exhaust out easier, you just can't pump enough additional air through the engine to take advantage of those new parts. (An engine is a big air pump-it can't suck in more than will flow though the intake and it can't pump out more than will go through the exhaust) A change on one side will only benefit the engine to the extent that the other side already had excess capacity.

The edelbrock 1409 is a particularly easy carb to set up on your engine.

Check the mechanical advance on your distributor and have it rebuilt is necessary. If converted from points you are in good shape, if not-put a fresh set of points (and condenser) on and make sure they are set right.

One thing I do recommend with a ford engine is stay away from high dollar spark plugs. Standard Champion or Autolite seem to run best in every small block for I have owned that would be 8 so far and not one ever suffered an engine failure no matter how hard it was flogged (transmissions are another story )
Good luck

Re: 351 Rebuild - Need Opinions/Suggestions!!

J. Mark said:

FWIW

I would let the engine tear down determine my course of action.

It might be that the pistons are undamaged and only need rings and a honing of the cylinder wall. That was what I found on mine.

Your crank might need to be turned or it might polish up std/std and just need a fresh set of bearings

You should replace the following in any engine overhaul( at least in my opinion) all gaskets, casting plugs, cam bearings, rod and main bearings, oil pump and of course a complete gasket set.

Additionally, I would replace a timing gear and chain set if it wasn't a double roller type and in perfect condition. Lifters are another cheap safety item to replace, but if you keep them numbered and return them to the same location they can be reused if you reuse your cam. If you replace the cam, replace the lifters. If you replace only the lifters, make sure and lube them and the cam and follow the break in procedure for a new cam.

If you need new pistons, the hypereuteric are a great choice, though many motors run long lives on cast pistons. Forged are nice but of no advantage in a mild application as compared to the hypereuteric.

Compression increases will help with horsepower but going from 8:1 to 9:1 isn't going to do a whole lot. the biggest place to find horsepower is in the exhaust side of the heads. There are a ton of aftermarket heads that outflow the factory heads-stay with the cast heads, not the aluminum and the GT-40 heads are a pretty good choice and fairly reasonable. Stick with a good marine cam. A new intake and 4 barrel carb will help to wake the engine up and will work very well with either performance heads like the GT-40's or stock heads with a little exhaust port work from a head shop.

I am convinced that many people think they can bolt on real horsepower with an intake and a carburetor, and while you can to some extent, unless you work the heads to let the exhaust out easier, you just can't pump enough additional air through the engine to take advantage of those new parts. (An engine is a big air pump-it can't suck in more than will flow though the intake and it can't pump out more than will go through the exhaust) A change on one side will only benefit the engine to the extent that the other side already had excess capacity.

The edelbrock 1409 is a particularly easy carb to set up on your engine.

Check the mechanical advance on your distributor and have it rebuilt is necessary. If converted from points you are in good shape, if not-put a fresh set of points (and condenser) on and make sure they are set right.

One thing I do recommend with a ford engine is stay away from high dollar spark plugs. Standard Champion or Autolite seem to run best in every small block for I have owned that would be 8 so far and not one ever suffered an engine failure no matter how hard it was flogged (transmissions are another story )
Good luck

Click to expand...

Exactly he type of advice I am looking for. I run Autolite plugs in it and have had no issues. Also, the points/condensor were new 2 years ago, but dwell, etc will be rechecked upon disassembly. I will be talking to an engine builder who has built several engines for muscle cars like Corvettes, etc. to see what he will charge. A local shop quoted 5K for a new long block! However, the US marine has a 300HP long block option for $1899. New everything. Plus a couple hundred shipping round trip. If I can't get it done locally for less than $2K, then I'll just ship it to WA and get a 7yr/500hr warranty to boot.

I know cast pistons would work, but I'd just assume get hypereutic pistons (no need for forged) and have the cylinders honed. If they can do it without boring it .20/.30 over that's all the better. I may even be able to just have the heads reworked locally and just have the short block done. I am mechanically inclined, but have never messed with engine internals and don't have items like micrometers, piston-ring tools, etc.

Re: 351 Rebuild - Need Opinions/Suggestions!!

Went through rebuilding my 351 last fall. I ended up just honing out the cylinders as there was very little ridge. Bought a set of flat top KB hyper pistons. File fit the top ring a little looser than recommended. Put new main and rod bearings on it. Pressure washed the block and cleaned her up. Used auto gaskets except for head gaskets. My motor had Dooe heads on it which if i read right were a pretty good head for the time. I spent a day working the ports on them. I rounded and smoothed out the valve guide area, blended the bowls a little, ground out the exhaust bump, gasket matched the ports and polished the exhaust port and combustion chamber. Just got a couple of carbides and started working. Stayed with the 2brl and stock intake at the time due to funds. I figured compression around 9.5-9.8:1 and it runs on 89. I'm running a cam that has 218/224@.050 duration on a 112 lobe sep with a little over .500 lift. It runs total timing around 26-28 which it right in spec. Previous owner said boat had a hard time with a 14.5x19, only able to turn around 3800 rpm. After breaking motor in, i went for a wot test and only stayed in it to 4600 and then backed off. While running at wot i noticed my vaccuum gauge was starting to pull a vacuum after 3500. This boat has some definite get up and go. Shoots like a bullet on the hole shot with a little over half throttle. I'm very happy with the low to mid range torque the motor produces. I'm looking forward to this year with the addition of the 4brl and thru-hull exhaust. Should sound good and run even better. It's a new 35 year old Sea Ray.

This year i've updated to center riser manifolds/risers, captains call exhaust, 600cfm holley, edelbrock dual plane and roller rockers. The biggest gains should be the switch to the 4brl. From reading, the 4brl 351's were rated at 255hp. Just rebuild it to what you can afford and are willing to do yourself. I was fortunate enough to be able to do everything myself and rebuilt the motor for less than $700. Also, I wouldn't bore a raw water cooled block, especially one that been cooled like that for over 30 years. You'd be surprised of the amount of rust pieces that'll come out of the block. Just visit the local JY and get one out of a beat up old truck or something. Don't want to bore it .030 over and have the walls be to thin due to rusting.

Don't be afraid of the motor, research engine rebuilding, even youtube it. The key is following torque steps and numbers. Just take your time. It's just nut and bolts. You can pick up a digital mic from harbor freight for i think less that $10. It's actually pretty accurate. A ring compressor is cheap. I wouldn't skimp to much on a torque wrench. A nice 1/2" drive one would be perfect. You can rent a balancer puller from autozone. The bigger expenses would be a engine hoist and an engine stand. My other 2 stands had engines on them so I bought one last year from autozone for i think $50. I used a hoist that we've had for years that came from Northern. It's a pretty big one. Just barely had enough reach to get the motor out but it was all good. Once you rebuild your first engine and hear it fire up for the first time, it's one of the best feelings. Take good notes on how stuff goes together, get baggies and label where the fasteners went, dedicate an area to lay out parts and keep your work area as clean as possible. It's not as hard as it seems. Rebuilt my first motor at 17 and haven't looked back yet. Started with a 350 Buick, 350 Chevy, 351w Ford, 472 Caddy, and soon to be a 4.7L Jeep stroker. Not bad for only being 22 now and yes, it's an addicting hobby.

Jeramie

Re: 351 Rebuild - Need Opinions/Suggestions!!

Find a local machine shop. My heads needed 6 valves and with that added to the costs, overhauling the heads was 195.00.

All the machine work on the block and measurements on the crank and a polish was $300.00

I went ahead and let the machinist do the assemble to save time-he charged me $350.00 for the assembly and preset the valves (perfectly I might add) and I spent about $ 300.00 for parts. Mine was a chevrolet 350, so head work wasn't necessary, but if rebuilding a ford, the above posts description of how to do headwork is about what I would recommend though I would have the chambers cc'd to insure that they are all the same after the work.

a 351 block will tolerate a ..030 overbore if absolutely necessary, but any more and you should look for a block.

Getting everything spotlessly clean during the rebuild is just as important as any other step-it is why I elected to let the machinsit do the work that I am capable of (that and I had more money than time and preferred doing my hull overhaul myself.)

Re: 351 Rebuild - Need Opinions/Suggestions!!

I already gave good torque wrenches and have the engine stand/engine hoist as I bought them when I removed it the first time. I have done lots of work with auto's, especially DOHC engines which are a bit more complicated in theory, but just never been beneathe the heads on an engine.

Yeah, the .030 overbore will be a last resort and I have no doubt that the block will have plenty of rust in the coolant galleys. The HP rating for the US engines base 351 rebuild (1600 bucks) is 260HP, for a hundred more they get you the 300HP version. I will likely get a new coupler as well just to avoid having to pull the engine again because of a simple part. I won't bother with thru-hull exhaust as my boat would look akward with it, would sound nice though!

As far as the heads go, I will have them port-matched by a machine shop as well as have a 3 or 5 angle valve job done too. New valves, lifters, springs, etc. No point in having a brand new bottom end and reusing the 30 yr old top end. RDJ, I had looked at the KB pistons as well, I assume the pisonts are a flat top with the valve dish? I am in the same situation you were with a 30+ yr old boat with everything new except the powerplant, including my composite transom, so I don't see any reason why the boat won't last another 30 years.

Re: 351 Rebuild - Need Opinions/Suggestions!!

I was actually pretty impressed with the KBs. That's correct, the piston are flat top with 2 valve reliefs so piston orientation maters with these. I made that mistake but caught it after installing 2 pistons. Another thing i did was clean up any burrs or casting flash on the tops of the pistons. Also polished them up as best as i could. They were pretty good though compared to some other pistons i've dealt with.

What's the hold up! You got all the tools to get the job done. Get going! Just messing. You'll be fine. Everything just goes back the same way it came off.

You can do it.

Jeramie

Re: 351 Rebuild - Need Opinions/Suggestions!!

Will be yanking the engine this coming weekend and begin dissassembly. I think we will be going with the KB's as well. Pretty cheap for a full set, and I think we can have the block machined pretty cheap as well as have the block dipped to clean off the grease and coolant galley rust as much as possible. The heads I still haven't decided on whether we will attempt to rebuild ourselves or not, but I'll have to see the casting numbers to find out which heads we have anyway. Anyone happen to know what size the valves are in these heads? I just need to make sure on valves sizes and the CC's for the head so I can match the pistons without getting too high a compression ratio.