stage one of 3.7 dissmantle

aussie

aussie

Senior Member
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
 
well done some figures looking at 250hp at the flywheel and 220 at the prop at 5200rpm
:love:
 
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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
 
Slow down brother

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...
 
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
 
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.
 
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.
 
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!:nice:
 
WELL NO ONE HAS YET TOLD ME WETHER THESE ENGINES COME OUT WITH FLAT TOPS OR NOT I DO UNDERSTAND WHAT U R SAYING IM NOT TRYING TO BUILD A RACE MOTOR JUST A STRONGER AND BETTER ONE LOOK ALL THESE COMPONETS IM PUTING ON IS WHAT MERCRUISER COULD OF DONE BUT COST IS ALWAYS A PROBLEM JUST LIKE THE EXHAUST PORTS A FEW HOURS OF WORK ON THEM GIVES A BIG RETURN JUST LOOK AT THE SIZE OF THE INTAKE PORTS WHAT GOES INTO THE INTAKE PORT MUST COME OUT OF THE EXHAUST PORTS AND IF U HAVE EVER LOOKED AT THEM THERE IS A BIG RESTRICTION IN THE EXHAUST THE CAM WILL BE CHECKED FOR ITS PROFILE AND REGROUND THE SAME IN A SOLID GRIND NO BIGGER JUST A WIDER TORK RANG AS FAR AS THE COMP GOES ALL THE INFO I HAVE SEEN SAYS THEY HAD FLAT TOPS IN THEM SO COMP WILL BE THE SAME PROVE TO ME THAT THEY DONT HAVE FLAT TOPS STANDARD AND I WILL GO FOR THE DISS TYPE ITS A GOOD IDEA ABOUT THE HEAT EXCHANGER MORE POWER FROM THE ENGINE THE MORE HEAT IT PRODUCES I MISS THAT ONE STOCK IS NOT ALWAYS THE BESY WAY ITS THE CHEAPEST WAY AND COMPANYS LOOK AT THE CHEAPEST WAY TO GIVE U A PRODUCT FOR MORE PROFITS WELL U HAVE TO CONVINCE ME DIFFERENT AND WITH THE COMMENT OF A LONGER CONROD YES IT GIVE U A LONGER DWELL TIME AT TDC AND HELPS WITH HP BUT THE COST OF BUYING RODS AND OISTIONS WITH A DIFF PIN HIEGHT DONT WIEGH UP TO HP TO DOLLARS
:nice: hey sorry about the caps lock was half way threw when i realized and i have to look at the keys while i type
 
The longer rods increase dwell and change the angle of attack. Essentially giving the rod more leverage to move the crank and less side loads on the pistons to their bore. It is costly for all modifications and the end result is sometimes less than one would like. I agree with your decision 100% to make it better, especially in the valve train but you need to ensure it is as reliable as possible. That was what I was suggesting earlier. If your car doesn't want to start (like my old 11 to 1 SBC) you just step out onto terra firma and give them shoes a chance. On the water it is a little more complicated. Your approaching terminal velocity..
 
i agree totally im not building a race engine just trying to get a better tork range and as i said 10.5 to one was just a guess there not much info on deck hiegts when i get the bottom end together with the new pistons i will have a better idea of compression ratio i dont mind using high octane pump fuel in it at the end of the day it will still be cheaper than running a 2 strokeand if u no 2 stroke engines there pritty flat on low rpm so i cant see how a mild solid cam will afect bottom end power all the mods r to increase strenth ans reliablitiy read a few forum post on other site and some guys r having oroblems with bending pushrods too ill put some picks up of the heads and the bad condition of the vavle tips and rockers and also i read that the blocks were made by volvo


no one has yet told me if 3.7 use flat tops pistons
 
well i just changed my mind again must sound like women well i just ordered a new head edelbrock proformer I did think about what u guys said about better to have 2 aluminum parts together expansion rate wil be the same as there is proff of head gasket issues on the 3.7 dont no why merc didnt just make one from the start costing would of played a big part so the project cost just stepped up another $700 when u deduct the price of rebuilding the old head getting the bigger chamber 93cc migh be still too much comp but the plan is to go zero deck hieght and macihe small dish on the piston top to get rite compression ratio well i have till november to finish it so i have time to save my some money well i could save $ 100 a week from not smoking but i dont see that happening
:love:
 
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