stage one of 3.7 dissmantle

[aussie]

first check was compression 175---150--155-- 145 may be broken rings or leakey valves . ok guys the head is off 7 tips of the valves r badly worn no sighns of why the push rods bent no marks on pistons . checked top off pistons there 30 plus so i t has been rebuilt and the exhaust manifold is not old . the pistons have a dish in them like a bath tub any one no wether they run flat tops or them. seen some used pistons on ebay of a 3.7 and they looked flat as far as the head goes the valves look too big for a engine that only turns to 4500 rpm and the exhaust ports r so restricted u could gain some horse power by porting them what were the thinking leaving those big humps in there . so next stage is to get the block out may be a few weeks till i do it

[aussie]

these r the pistons i saw i yhink this engine was rebuilt wrong maybe the camshaft is the wrong spec

http://cgi.ebay.com/ebaymotors/MERCR...ssoriesQ5fGear

http://cgi.ebay.com/ebaymotors/Marin...ssoriesQ5fGear

http://bpi.ebasicpower.com/pc/FEDH535P/MER37ENG

[aussie]

well done some figures looking at 250hp at the flywheel and 220 at the prop at 5200rpm

[aussie]

well just worked out what compression ratio the old engine had 8.5 to 1 when it should be around 10.5 to 1 well but using flat tops i should have 10.5 to 1 . with the head i decided to stay with the stock head using a aluminum head could lead into more problems with oil and water leaks as these aluminum heads do have problems with head gasket leaks on cast iron blocks so puting one on a aluminum block i would be asking for trouble cast iron heads can be overheated with out damaging them not like the aluminum ones u get the reall hot and there gone. so the plan is for me to port the head and fit new stainless vavles and replace valve springs retainers and locks fit screw in studs and guide plates and teflon vavle stem seals tripple springs and a thicker 3/8 pushrod and roller rockers also im using a head stud kit instead of bolts so my mind is made up on the top end

now the bottom end speed pro hyper tech pistons and rings new big ends and main bearings thje con rods will get cleaned up resized and new hd rod bolts the bores r perfect so a rebore is not needed a full engine balance as well

now with the camshaft i dont think i can get a new billet one for it if anybody knows where i can get one please let me know so at the moment i will regrind it it will be a solid grind not a race one but something that will make good tork from 2000 to 5000 rpm the reason im going solid is the head will be set up for it and with a sloid u make more power than a hydrulic of the same spec

now the intake im just going to cut it and weld a 4 barrel flange on it and fit a holley 600 that i will mod and jet to suit the engine they way im doing this is to fit a air and fuel ratio metre on the exhaust to get a readind of fuel mixture i fit them on alot of car engines i build and u will be surprized how learn most engines run so all jeting can be done on the water i also am getting a petronix kit as well as suggested by u guys
i also need a bigger valve cover cause i dont think the rollers will fit under it
ok guys u probly wonder why im always on here well i havent work for 17 years due to health so i get pretty bored so thats what im up to on my engine
i also got a quote from summit racing and im giving the guys down here to try and match there price have i bored u yet well im not lol

[Road King Cole]

Originally Posted by aussie

ok guys u probly wonder why im always on here...

I'm only here for the free beer...

[RidgeRunner]

Aussie, Your going about a mile a minute. (That is 60 MPH here in the states.) I ain't saying it won't work but 10.5 to 1 compression is kinda high for 87 octane and the motor you are dealing with IMO. I know manufacturers use 10.5 to 1 in modern autos all the time but the engines have computer controlled fuel injection, timing, and various other sensors that sense spark knock, air and water temp as well as air flow, O2, MAP and even barometric pressure. So these engines continuously adjust for the proper air/fuel ratio and timing based on load and the environment. You will have to play with the distributor and settle for less total timing to make it work.
What kind of petrol do you have access to down there?
Solid lifters, as you know require adjustment and often. Hydraulic lifters are adjusted once and your done til' its time to rebuild the motor or you bend a pushrod.
I am guessing the valve stems were wore from lack of lubrication. Did the motor have good oil pressure? Was it full of sludge? You are going to grind the cam? You have that kind of machinist background and the equipment to make it happen? Grinding on the exhaust side of the heads helps the motor to flow more exhaust but it can also affect your low end torque. Grinding in the right places on the intake side with a flow bench yields the most increase in flow and is well worth the effort if you are going racing.
You need to post some pictures. This sounds interesting.
Free Beer, I am all in...

[aussie]

ok well i do have a mechanical background and as u said porting heads isnt childs play u can hurt down low power very easy and with the camshaft im going to use my bench grinder to grind the cam lol no i have to people i use for cam grinding crow cams and wade cams sa for the solid and hyd cam debate the engine will have a broader tork curve with a sloid cam than with a hyd in other words to get the same power as a solid cam the hyd one i have to use will loose alot of bottom end tork and as for the adjustment maybe i will have to do it once a year with the oil change and its on a four and how much do u use a boat not like a car nearly all cars have solid lifeter now well there shimed and most of them the engine dies before they get adjusted
as for fuel side of it yes we do have high octane fuel at the pump and the dizzy will more and likely get recurved for the new cam specs
no has told me wether the 3.7 come with flat top pistons i posted some pics of some but it would be good for some one to say yeas they did
high commpression is not the only thing that make engines ping its bad chamber shape and and piston deck hieght

well i really think its a good trade of for some extra tork just to adjust tappets once a year

have i slowed down 59mph

[RidgeRunner]

Yes, You have been clocked at just under 55 now.
I just read your other thread. Sorry, been out of town. Not trying to be a dick. The dizzy, LOL never heard it called that before. You are right on the money about combustion chamber design, deck height and quench. I built a small block chevy 350 and hogged out some 305 closed chamber heads (as a teenager) before I really knew what I was doing. I ended up with 11 to 1 compression, and a doctors bill for removal of metal from my eye from all the grinding. Motor Ran Good, had to always leave the automatic tranny in gear to shut it off (to prevent engine run on). I also had to pony up for a high dollar gear reduction type starter. Bugger wouldn't start when the factory starter got hot. It got great mileage. Last project was a small block 400. Used longer rods from Summit, flat top pistons and Trick Flow Aluminum heads at 10.5 to 1 with no problems. Aluminum dissipates heat better than iron and you can get away with a bit more compression. Ran into a big problem on the final valve adjustment, adjusted five or six valves and then I couldn't turn the motor over by hand. One of the rods interfered with the lobe on the camshaft. Had to disassemble the motor and take it back to the machine shop to have them clearance the rod(s) and re-balance the entire assembly. The only other option was a small base circle cam and they only make them with solid lifters, unacceptable for my daily driver.
I like the idea of installing longer rods. Smokey Yunick Power Secrets -"Install the longest connecting rod possible that will still allow a good ring package".
I do not know what pistons the 3.7 is supposed to have. My guess would be a small dish. Mercruisers idle great and have pretty small cams as a rule. Beware, if you make too much power you will end up breaking that Alpha drive.

[spareparts]

Aussie, build that motor back stock. Don't raise the compresion any above fatory. They had issues with preigniton back when we had good gas and revised the spark timing back 4 degress. Leave the cam alone, use a good rocker system. The performer head is a good idea, you won't have dissimular expansion rates like the cast iron head to aluminum block. You may have to increase the size of the heat exchanger to handle the increased heat transfer from teh aluminumhead. Recurving the distributor isn't going to help as most of the total timing is in before you get to cruising rpm, increasing the curve below planning speed can cause preignition. Buy those other two motors you had listed, use the 4bbl intake and oil cooler off of one of those. Put a pertronix igniton in the distributor and a 1 step colder plugs. You will be happy at the peformance with the 3.7 in its stock form. If you want to go faster, put a V8 in the boat. Most of the mods you have listed will work great if the engine was in a car, but in a boat, you will have longevity issues, along with peaky peformance(especially with a heavy boat like a V), don't try to turn the motro any higher than 5000 rpm, the drives don't like high rpm. You'd be surprised how well the boat will perform in stock good condition. I understand your desire to build it bigger and better, but I don't think you are going to get the return from your time and money you are looking for with this combo.

[step up here]

mate that is the best advice for you . whether you like it or not . sorry but i have mentioned similar advice. the one thing i know is the factory [mercruiser] has more research and development on that motor then anyone else. once again not trying kick you in the nuts. maybe just hoping you get to enjoy your V20 LIKE OTHERS DO!