what to do with an old engine block before building

204Angler · **Posted:** Sat Jun 23, 2012 12:10 am

I have an '87 Fourwinns Sundowner 195 with a 4.3 (OMC) with a cracked block. I got another OMC block to replace it and when I take it to the machine shop I am going to ask they hone the cylinders and true the deck if it needs it. (also a cleaning). Question is; other than that, what else should I ask them to do??
Thanks!

rodeochow2 · **Joined:** Thu Jun 21, 2012 7:46 am **Posts:** 10

I would let them rebuild it. crank polished,rods checked,fit new pistons,cam bearing,etc thats what they do. Take you old heads in too and let them dip them and regrind valves..you can take it from there...remember to add zddp to your oil during breakin...flat tappet cams will likely fail during run in without zinc additive...google flat tappet cam failures.
For me I would get newer block with vortec heads with roller cam...more power and lot less worries.

ric · **Posted:** Sat Jun 23, 2012 10:23 am

All that.. or just buy a 4.3 longblock for like $600 with warranty and pick up some vortec heads/manifold and enjoy 200hp.

The vortec heads fit any 4.3, you just need the updated intake manifold. The exhaust is the same as the old ones.

The 4.3 is Chevy, not OMC. Plain ole astrovan/s10 engine. They made two kinds. Non Vortec and Vortec. It's just head design and gives more HP.

204Angler · **Posted:** Sun Jun 24, 2012 12:31 pm

I am probably not going to pay someone else to build it for me since I can do it and have more time than money but the last time I did it was a while ago (17 years or so) and the 440 block that I got was already reconditioned. I have another ski boat to use while I work on this one. Also not going to buy a long block...and for $600 you are probably looking at a non-marine engine? I know 4.3 is chevy but it is an OMC powerplant....just wanted to be clear on that just in case there was a difference between a mercruiser and an omc. Not gonna worry about vortec heads and gaining a few more horses with this boat...as long as it will pull a wakeboard I'm happy. I dont need to do more than 40....I have a bass boat for that

So you'd have them grind the valve seats as well? May as well right. Was just thinking about the crank...that sounds like a good plan having it turned and polished. You think I should go with new pistons regadless of condition of the existing ones? I haven't seen them yet so they could be burnt up but, i have no idea. I will give everything a good check before reinstall, but am about to bring the block into the machine shop. Also drop heads off later once I pull them and have them grind valves/seats. Thanks!

ric · **Posted:** Sun Jun 24, 2012 1:37 pm

There is no such thing as an OMC engine. It's a standard chevy non-vortec 4.3. Brass freeze plugs have been standard in car engine since the 80's. They're like $12 anyways. Volvo Penta, OMC, Mercruiser... all the same. The only differences are in the exhaust manifold designs. Put VP exhaust manifolds on a Mercruiser engine and it bolts right to a Volvo Penta outdrive or vise versa or OMC or whatever. It no make no difference.

204Angler · **Posted:** Sun Jun 24, 2012 3:28 pm

Yeah, I know that's why I said the only reason I said OMC is because I wasnt sure if there was a difference between that and a mercruiser etc... The power plant is called an OMC however

97_245_sd · **Posted:** Sun Jun 24, 2012 9:32 pm

I think you're on the right track with block and heads. The crank might only need polishing. As for the pistons, if they're in good shape and the block doesn't have to be overbored, no need to spend money, just get new rings. You could have them dye checked if you're worried about cracks but I'd check on how much that would cost vs. a new set before spending the money.

I don't know the difference between a non-marine and marine long block but they might have different cams. If I were to have to spend the money I'd check part number and casting numbers before I'd substitute anything. Marine duty cycles are much different than a car, much similar to a truck but I'm generalzing. I think the 4.3 was only used in trucks and vans so maybe they didn't have pass. car parts that were different.

Borchik · **Posted:** Mon Jun 25, 2012 6:51 am

There are differences between marine and automotive blocks, marine engines have a number of refinements because they are meant to run in different situations. For the most part they are all based on truck blocks. They are all coated inside and out with a anti-corrosion coating. The water passageways in most marine blocks are larger than their automotive counterparts. The cams and cranks are not standard automotive units.

You are on the right track with the block. Have them check everything. Deck it if necessary, line hone if necessary, bore if necessary. These are all things a good machine shop would check for anyways if you tell them what you are doing. While the heads are off always have a valve job done and magged for cracks. Its much cheaper to do it the first them than to pull it back off and have it done again!

ric · **Posted:** Mon Jun 25, 2012 9:20 am

I have searched the interweb for hours. I can not find a single shred of photographic or measurement evidence that supports any claim that marine engines are different then automotive evidence, not even a cam profile difference.

The facts that I do know are.. Mercruiser uses 2 bolt main blocks and cast crankshafts. Not 4 bolt main or forged cranks. They are not "heavy duty" truck blocks, they are the dime a dozen car engines. They do not use the better PM rods (just cast) and use the base model cast pistons not the upgraded hypereutectic pistons.

They are base model engines.

Borchik · **Posted:** Mon Jun 25, 2012 9:40 am

You can search online all you want, just because you can not find it does not mean there is not a difference. I worked for many years for an engine builder on a part time basis. Marine engines have different cam profiles so that they make power in different ways than cars.

Take an unpainted marine block and it will not rust for quite sometime (especially in fresh water) because they are coated with an anti-corrosion material.

204Angler · **Posted:** Mon Jun 25, 2012 9:49 am

ric wrote:

I have searched the interweb for hours. I can not find a single shred of photographic or measurement evidence that supports any claim that marine engines are different then automotive evidence, not even a cam profile difference.

The facts that I do know are.. Mercruiser uses 2 bolt main blocks and cast crankshafts. Not 4 bolt main or forged cranks. They are not "heavy duty" truck blocks, they are the dime a dozen car engines. They do not use the better PM rods (just cast) and use the base model cast pistons not the upgraded hypereutectic pistons.

They are base model engines.

http://www.boatfix.com/how/marineeng.html

http://www.perfprotech.com/store/articl ... arine.aspx

All I have found out is the main differences is the components, cam shaft, head design. Did the 4.3 ever come with 4 bolt mains?? Either way, Ive got a 4.3 block that was used for an OMC marine application and all the components so, that's what Ill stick with. Boat for $300, block for $130...so far, so good

204Angler · **Posted:** Mon Jun 25, 2012 9:53 am

97_245_sd wrote:

I think you're on the right track with block and heads. The crank might only need polishing. As for the pistons, if they're in good shape and the block doesn't have to be overbored, no need to spend money, just get new rings. You could have them dye checked if you're worried about cracks but I'd check on how much that would cost vs. a new set before spending the money.

I don't know the difference between a non-marine and marine long block but they might have different cams. If I were to have to spend the money I'd check part number and casting numbers before I'd substitute anything. Marine duty cycles are much different than a car, much similar to a truck but I'm generalzing. I think the 4.3 was only used in trucks and vans so maybe they didn't have pass. car parts that were different.

Yeah I probably won't end up substituting anything...better safe. I think I am just going to go with a new set of rings because the compression is decent, but Id rather do it while I have it apart than pay for what you said, to have the dye checked and maybe break after assembly. What should I check for with the pistons? When I rebuild aircraft engines (continental, lycoming) we would always dye them but, if they werent scorched looking, they were most likely good.

204Angler · **Posted:** Mon Jun 25, 2012 9:56 am

Borchik wrote:

There are differences between marine and automotive blocks, marine engines have a number of refinements because they are meant to run in different situations. For the most part they are all based on truck blocks. They are all coated inside and out with a anti-corrosion coating. The water passageways in most marine blocks are larger than their automotive counterparts. The cams and cranks are not standard automotive units.

You are on the right track with the block. Have them check everything. Deck it if necessary, line hone if necessary, bore if necessary. These are all things a good machine shop would check for anyways if you tell them what you are doing. While the heads are off always have a valve job done and magged for cracks. Its much cheaper to do it the first them than to pull it back off and have it done again!

Yeah I am waiting to here recommendations on good machine shop in the area, hoping they can strongly recommend things to check, or accomplish. So, I will pull the engine when I can, remove the heads and take everything into them. Yes, I would not be happy if something failed after I assembled it just because I didnt think of having it checked or wanted to save a few bucks...

Good to hear you guys say I am on the right track so far

ric · **Posted:** Mon Jun 25, 2012 10:48 am

If you want that engine to never break again, get the block dipped and checked for cracks.. then...

GM Performance forged crank, forged rods, forged pistons, ARP bolts everywhere, vortec heads, roller cam, vortec intake, multiple layer steel headgaskets, timing gear set (no more chain).

It will outlast you, as long as you keep oil in it. That engine will cost you under what it will cost to have that 80's thing rebuilt.

rodeochow2 · **Joined:** Thu Jun 21, 2012 7:46 am **Posts:** 10

angler..300 dollar boat..where do I start..first cosmetics...how is the upholstery moreover hows the floors nearly rotten or totally rotten. transom ?..if any these are true I would run..not walk..remember you dealing omc..not merc or volvo parts. lets see some pics. not hating just sayin you can get buried real quick in these old boats. Hey I know I got 85 horizon. Its my mini libby (liberator)...and I love it.

www.iFourWinns.com

what to do with an old engine block before building

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