Auto cam water suck?

[erikgreen]

Hey all -

In a chevy 350 (Mercruiser 5.7/260) how critical is the cam? I've heard that you want to keep the power band of the engine adjusted toward the lower RPMs, so you have starting torque, but are there other problems with using a car cam? I seem to remember hearing something about water aspiration?

Erik

 

[Haut Medoc]

Re: Auto cam water suck?

Yup, the overlap on an auto cam can cause water ingestion.....​

 

[erikgreen]

Re: Auto cam water suck?

Thanks Haut.

One more question - I'm having trouble fitting some parts on this (admittedly cheap) 350 I have... so I'm wondering if the model year is wrong. The intake I'm trying to fit is from a mercruiser 228 from 1983, and the block is an auto block, casting number 3970010, which according to the info I have is a:

3970010....350...69-80...2 or 4 bolt main

Can you or someone tell me if I have an ok block to use with the old parts? I'm attaching the intake and external bolt-on parts from the 305 (alternator, starter, etc), but I'm using the 350 block, heads, fuel pump, and internals.

I'm buying new marine gaskets, freeze plugs and (now) a camshaft and the parts to put it in.

Erik

 

[Dakota47]

Re: Auto cam water suck?

I hear that a RV cam for trucks will work??

 

[whywhyzed]

Re: Auto cam water suck?

I have seen the 3970010 block in a lot of boats.

 

[whywhyzed]

Re: Auto cam water suck?

I'm using the 350 block, heads, fuel pump, and internals.

I'm buying new marine gaskets, freeze plugs and (now) a camshaft and the parts to put it in.

Erik

Don't use an automotive fuel pump, but the rest makes sense - you wouldn't want to put 305 heads on a 350 but it looks like you know that already

 

[erikgreen]

Re: Auto cam water suck?

Cool, thanks, it's good to know I'm not trying to do something that just flat won't work.

Since I have to install a marine cam (I could just get a truck cam I think, but a marine cam is only a hundred bucks or so) I'll tear this thing down, clean its parts, maybe touch up the orange paint here and there, and then assemble it all using the marine gaskets and bolt-ons (and the marine fuel pump from the 305).

Wish me luck.

Erik

Edit: Duh, the 305 camshaft will probably work, provided I switch over all the lifters too...

 

[180shabah]

Re: Auto cam water suck?

If you reuse the cam, keep track of which lifter came from which location, and install them exactly the same way in the new engine, otherwise you will be replacing the cam anyway.

If you decide to go ahead and get a new cam, the key is keeping the LSA (Lobe Seperation Angle) 112deg or lower, this keeps the water in the exhaust from getting sucked back into the cyl through the exhaust valve.

 

[erikgreen]

Re: Auto cam water suck?

Good information, thank you.

Just for kicks I'll try and ID the cam inside the engine (gotta be marked somewhere, but maybe not on the ends) to see if I can just leave it in... I really want to get this thing fixed and on the water, and I can swap in something like a Comp 268H in the fall or next winter.

Erik

 

[Coors]

Re: Auto cam water suck?

Good information, thank you.

Just for kicks I'll try and ID the cam inside the engine (gotta be marked somewhere, but maybe not on the ends) to see if I can just leave it in... I really want to get this thing fixed and on the water, and I can swap in something like a Comp 268H in the fall or next winter.

Erik

Degree wheel, and dial gauge, and a book.
But you can probably find the instructions on-line, with the gear-head forums.
Interesting to know, check your cam.

 

[Coors]

Re: Auto cam water suck?

I forgot; you will need a piston stop, also.
If you have a welder, and taps, you can make one.

 

[erikgreen]

Re: Auto cam water suck?

I do.. sounds like a fun project. Dunno if I wanna take it on right now though. Turns out my motor is a "stock" truck motor, so I should be ok on the cam it has.

Now if I can just manage to put it back together