stage one of 3.7 dissmantle

[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!

[aussie]

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
hey sorry about the caps lock was half way threw when i realized and i have to look at the keys while i type

[aussie]

im at 70mph now

[RidgeRunner]

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..

[aussie]

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

[aussie]

Originally Posted by 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.

well it will be stock in the sense of camshaft and the comp is 10.1 only makinf it breath better and raise its tork

[spareparts]

Sounds like you are on the right track. use the KISS method, Keep It Simple Stupid, or the way I usually do it, Keep It Stupid Simple. BTW, if you go to the machine shop with this motor, have them look at the cam shaft bores. One of the issues with the 3.7 motors is they loose oil pressure after they get hot. the problem is the cam rides directly in the block, no cam bearings. There is a service replacement cam bearing that has to installed by a machine shop(cam bore has to be overboared then new bearings installed). Might be worth checking into see you're going this far

[aussie]

Originally Posted by spareparts

Sounds like you are on the right track. use the KISS method, Keep It Simple Stupid, or the way I usually do it, Keep It Stupid Simple. BTW, if you go to the machine shop with this motor, have them look at the cam shaft bores. One of the issues with the 3.7 motors is they loose oil pressure after they get hot. the problem is the cam rides directly in the block, no cam bearings. There is a service replacement cam bearing that has to installed by a machine shop(cam bore has to be overboared then new bearings installed). Might be worth checking into see you're going this far

well thanks thats good to no i havent pulled the block out yet so they run the cam directly on the block like ohc engines well the oil pressure was good on the engine but will measure the bores of the cam to see how much clearance and i hope there not worn the could put a a big expense on the engine well thanks for that info i wouldnt even of checked them