5.7L head question

[1slow5ltr]

right now i have a 5.7L mercruiser engine in my 1989 21ft larson senza a friend of mine sold me some alum sb chevy heads complete with dual valve springs and stainless steal valves for $400.00 complete i know i have to use marine head gaskest and i am replacing the carb and intake with edelbrock ones, my question is the heads have 2.02 intake valves will they hit my pistons with the stock cam and some roller rockers that are the stock 1.5:1 ratio? any help would be awesome as i am new to the marine inboard world

[PAR]

The 2.02 valves are the diameter, which isn't an issue with piston interference. Stock rocker ratios, again is a none issue. The concern is two fold, deck height and cam lift. The easy way is to assemble and turn it over real slow by hand to see if it hits. The proper way is to use a dial indicator, check cam lift and the amount of "squish" area at TDC to insure you don't smash a valve into the top of a piston.

[Frosty]

If you are not changing the cam or the rocker ration then your valve lift will be the same.

However if the valves are at an angle then they could touch due to the combustion chamber difference, as said turn over by hand very carefully to be sure, and/ or use plastecine (play do) on the piston top to see just how much gap you have.

Don't forget the piston will travel higher up the cylinder at higher RPM, accommodate this.

If its a closed fresh water cooling system a stainless gasket is for what?

[El Sea]

We were low-tech back in the sixties, so we would use modeling clay to check for clearance. Remove the heads, place a layer of M/C on the top of your piston, re-assemble upper end of engine. Rotate crank and cam through serveral revelution. Dis-assemble upper end of engine and check for traces of valve imprints in the clay. Like I said 'we were low tech in the sixties'.

El Sea

[PAR]

I've used "Plummer's Putty" and done the same thing El Sea. The real check is the amount of clearance, which is difficult to check accurately with putty. If you expect tight tolerances or the head has been decked (milled to increase compression or remove warp), then you're best off with a dial indicator and "indexing" everything properly.

This is a common task for an engine builder or automotive machine shop and shouldn't cost much to have preformed, if you're uncomfortable with the technique.

[Fanie]

Most of the new pistons come with valve pockets in them especially for higher valve lift, check which pistons you have in there. My 2 chevy motors both had 1.6 ratio's and 2.2" valves. If your timing is right you won't have a problem. I would strongly suggest you get a book on how to build those motors up, some good tips are usually showed in them.

On that stock cam... yuk, the thing could perform better with a broom stick. There are cams made for marine motors, but you cannot just run off and get a hot cam, a hot cam alone will give you more problems.

The whole motor has to be designed to work with certain parts, there is a relationship between them that makes the motor more efficient and more fuel friendly while at the same time give better performance.

[1slow5ltr]

thanks for the help guy's i think i am going to try to do the heads and intake and new carb soon, i may also go with some 1.6rr and msn ignition i have built my share of motors for mustangs (302 ect.) just wasnt sure if there were any diff,. in marine motors, my next question is where could i get some headers for this engine it has through hull exhaust now but the manifolds and risers need to be replaced any suggestions?

[rasorinc]

Here is one site out of dozens on the internet. http://www.ebasicpower.com/

Here is another http://www.glenwoodmarine.net/ Stan

[1slow5ltr]

ok one more question how can i determine which rotation my motor is i was just going to order my msd from summit and they asked which rotation my engine is? the distributor rotates clockwise on my 5.7L sorry guys i am not a chevy person only really worked on fords...thanks again

[rasorinc]

Most transmissions, newer ones at least can accept either rotation. Look up marine transmissions on the internet and they will tell you how to determine rotation, Maybe even one of the sites I gave you. Stan Just google a question how to determine V 8 engine rotation

[Fanie]

There are parts designed for marine applications. Most of your spares shops should be able to help you with that and should be able to explain what the difference is between automotive and marine spares.

[rasorinc]

Check out the difference between marine carbs and auto carbs. I know marine air filters stop the excape of flame if an engine backfires and marine starters are different from auto for the same fire potential and if the coast Guard checks you out they will know the difference and be looking for it. Also there are venelation requirements.
Stan http://files.dnr.state.mn.us/education_safety/safety/boatwater/backyardboatbuilders.pdf CC regs for backyard builders

[PAR]

Marine carbs also prevent fuel vapor (what actually blows up) from escaping into the compartment. The throttle and choke shafts usually have O rings to prevent leakage, the bowl vent is looped make to the venturi, plus other, marine specific refinements.

Headers only can be used on a fully exposed engine (no engine box). Your application uses a "wet exhaust" which precludes the use of headers.

Engine rotation is determined by how the flywheel turns if you're looking directly at it from behind. Clockwise is right hand, counter clockwise the other way. If you can't see the flywheel, then from the front of the engine the crank pulley rotates counter clockwise for right hand, etc.

Cam selection is very different for a marine engine then automotive. Don't put a hot, big overlap, high lift cam in a boat, unless you really have a clue about what you're building. Unlike a car where the engine uses 20% of it's available power 90% of the time, a marine engine uses 90% of it's available power 90% of the time. This means a high lift, auto cam engine will take a dump pretty quickly in a boat. You want to build a high torque engine, not an easily revved, high HP engine.

[Frosty]

The cam you can use would be a 4 wheel drive application for torque. A good dual plane manifold again for torque, torque torque.

You really dont want overlap on the valve geometry or you will get reversion, not good with a wet exhaust.

If you look at the front of the engine the crank turns which way Par?

[george allard]

If the front pulley turns clockwise, it is a right hand engine. Right?

[PAR]

No, if the crank pulley rotates clockwise, the engine is left hand rotation.

[darrellp88]

you really need some compression with the 202 valves it won,t run any better you will hurt it more then help the performance.good luck comp cams has a great marine high energy cam i instaled it in a 350 mag pull,s alot harder with it that,s all i changed!went from 42mph to 53mph!