porting heads for boat??

does anybody port heads for a boat?
just curious as my engine was cracked when i boat the boat ( I Knew)
but the heads are okay. now i have automotive heads on it.
seeing as a boat usually spends more time at higher rpms, would a port and polish job on the extra heads i have be worth it???

if not, why

Re: porting heads for boat??

Auto heads = boat heads

If you are going to spend money for extra power, skip the porting and buy a set of vortec heads.

Re: porting heads for boat??

Porting and polishing will be great, above 6,000 RPM.
Boats are lucky if engines make it over 5,200 RPM, most WOT
range is 4,200 to 4,800.

Re: porting heads for boat??

I would say porting and polishing would be great, but you need somebody that knows how to port for the running rpm of your motor. Many times just opening up the ports will not give you much more power for the money/time involved.

A boat motor is just about the same as a car motor will will work with the same performance enhancements, but normally boat motors are not made setup to operate at as high of an rpm, since they could be at that range for a much longer time than a normal car would.

Kim

Re: porting heads for boat??

what size and type of engine?
What size heads do you have?

On a small block Chevy porting small valve heads are not worth it. If you have 2.02 intake with 1.60 exhaust or 1.94 with 1.50 exhaust then porting will increase midrange torqe and top end hp. If you go for vortec heads you need to get the right ones which have three triangles at the front of the heads these are 2.04 intake with 1.60 exhaust valves. You will have to also install a Vortec intake. A edelbrock rpm airgap will perform great.

Hope this helps

Re: porting heads for boat??

porting IF done right (ie mild to medium by someone whon knows what theya re doing, has a flow bench and experience running the same kinds of heads on the dyno, etc...), can add a good bit of power. That being said, as is mentioned above, it is more cost effective to buy better heads first.

AND remember that as you get better and better flowing heads (typically sets the power you can get wiah a given set up), you will want to upgrade everything else along the way so it all works together.

for a reasonably "mild" upgrade, a set of vortec heads (no porting work) a matching cam, intake and carb, can net some significant gains.

after that head wise, the options are only limited by your pocketbook and imagination.

I'm dropping the heads off my smallblock off to have some porting work done on them in the next few weeks (as soon as they have time to fit them in the schedule), but they're aftermarket head with relatively large valves and ports already and I want more out of them... I gave the stock heads away long ago.

OH, and to get a decent porting job done by someone who knows what they are doing, is probably going to cost at least as much as a new set of vortec heads set up and ready to run...

Re: porting heads for boat??

It should also be mentioned that 20hp on the water doesn't yield the same result as 20hp on the street. Boats are very hull-shape sensitive when it comes to anything above about 50mph. At that point you start needing something with a shallow draft, big chines and speed in the design.

Re: porting heads for boat??

Yes it helps. I did my own and made some good gains. I like to tinker though. If I had to spend money I'd look into to some Dart Iron eagle or Vortecs which is the route I'll go this winter.

Also porting isn't just for high rpms and making the port bigger. It's reshaping for flow and velocity and if done right can make a significant difference over the entire operating range.

Re: porting heads for boat??

Two words:
Restricted Exhaust

Re: porting heads for boat??

mkast said:

Two words:
Restricted Exhaust

Click to expand...

AMEN!!!

one of the largest bottlenecks are the factory exhaust manifolds (and aftermarkets that are similar in design)... both from a reversion / cam overlap limitation standpoint and especially from a performance / flow standpoint.

imco, emi, stainless marine, dana, revolution.. all make good products.

I'm running imco powerflows...

The engine builder / shop I have been working with said they make more power than the others on his dyno...

On an aside, I would bet that the reason people don't see any difference for through hull exhaust in most situations is really because the manifolds are the bottleneck and changing the downstream backpressure doesn't make any difference until you deal with the manifolds.

would you build a hot rod and put the stock exhaust manifolds off a 1976 caprice wagon on it?

Re: porting heads for boat??

mkast said:

Two words:
Restricted Exhaust

Click to expand...

Yeah.. Just a little...
The stock manifold are a big chamber and have zero scavenging. Each cylinder is constantly trying to overcome another till it makes it out of the boat.

My next fix to the addiction is some decent aluminum manifolds...... Weight savings and better flow.

Re: porting heads for boat??

brunolund, the bases have been pretty well covered here. Boat motors, being limited in RPM and somewhat restricted by the exhaust will not benefit greatly from a classic port job.

What will make some difference, withing the limits of the exhaust system would be what is referred to as a 'gasket match' port job. That is simply matching all of the port openings to the gaskets. This would be for both the intake and exhaust side.

This is very easy to do yourself. You just need a high speed air grinder (ala Harbor Freight), a couple of 1/4" shank carbide grinding burrs and a sharpie marking pen. Just hog out all of the ports to the markings (made by overlaying the gasket) and make sure you fair them back aways so they are not abrupt. Can't get into any trouble doing this and it will give you as much benefit as can be used.

You can see my sharpie outline around the exhaust port in this picture.

Re: porting heads for boat??

I'll let you know in a few weeks how much of a difference a good port job makes on my set up anyhow...