burtonrider11

Understood. I don't expect to gain much if anything on these headers. Just figuring if I do pick up at least a little horsepower and shed 70-80 pounds from the stern, it's still a net gain. Stock manifolds are 20 years old and the corrosion is into them pretty good right now, so they are getting replaced either way. If I'm going to replace them, I figure I might as well do so with something that is an upgrade? Otherwise, I did see a GLM OEM replacements that had individual runners versus the stock manifolds. But these are cast iron as opposed to alum, so no weight savings. But 1/3 the cost of the IMCO/EMI etc...

I'm curious on the heads, at 20 years old and 600 hours, should these be pulled and inspected? Is it time for new gaskets either way? I did speak to one machine shop and they said it would be good to pull them and inspect them. He didn't really recommend a 3 angle valve job, he said these heads flow well for stock and there probably wasn't much advantage to this. He seemed very reasonable for cost to inspect, pressure test and resurface for $245 for the pair.

Just trying to get the best spend to take care of any maintenance that should be done. I understand the limitations of the hull we have and I'm okay with it

If anyone has any lightly used IMCO thumpers or EMI Thunder exhaust, I'd be interested

Gimme Fuel

If you aren't looking for horsepower, what makes you think at 600 hours the engine needs refreshing? They have a 1000 hour design life. You did the right thing with Smitty's replacement injectors, I run them in my 1000 hour 502MPI motors, AFTER burning a piston from bad injectors. I just pieced the bad one back together and went through the fuel systems including the new injectors and that was 3 years and ~100 hours ago and they still run like swiss watches, however a bit of extra blow-by.

If you are worried about the motor, do a compression and leakdown test then go from there. There is still way more life in that thing at 600 hours if tests check out.

As far as exhaust manifolds, yes if getting crusty it would be a good idea to change them. You would be fine with any of the Imco Thumper or EMI systems with the short aluminum riser versus the longer stainless risers to save money.

burtonrider11

Is this Krawdad??? It's Geoff from Facebook/PQ Owners Forum, you helped me a ton last offseason by the way.

I don't know that there is anything that needs replacing/refreshing aside from the exhaust. I didn't know if people normally did head gaskets at specific intervals or not. My thoughts were that since I was going to have the manifolds off, now would be a good time to have the heads gone thru. And I meant to do a compression test, but just didn't get to it. I still have the batteries in the boat, so I probably still could do that first. Can I do a compression and leakdown test with the exhaust manifolds off? I still have them on right now. Probably need to disconnect the fuel pump as well? The only thing I can't do is start up and run the engine to normal operating temp, so maybe that's a spring thing.....

Gimme Fuel

Haha yes it is Geoff!

You can do the tests without manifolds, easier access anyways haha. Will just be cold readings which would be lower than hot so take them with grain of salt. Looking for balance/consistency between all cylinders, not what absolute PSI reading is though.

Just unplug injector harness and take coil wire of distributor so no fuel/spark when cranking.

You can certainly have the heads redone as a winter project since you have manifolds off, just a bunch of extra work. Frankly at that point it is almost easier to work on engine out of boat on a stand than climbing in and out of a bilge. And when the engine is on a stand.....thats when the snowball effect of adding HP parts begins haha.

I will be doing manifolds on my boat this winter and eliminating silent choice since I now have two sets of EMI manifolds with long SS risers. Several other upgrades planned over winter as well. Just finishing up my barn addition this week so the big beeotch will finally have an inside home with heat.

TomZ

Trust me. If it's running well, don't mess with it!

Exhaust and injectors are the things needed to live a long and happy life with these engines. You've done the injectors so you're good there. You cannot go wrong with Stainless Marine. Their parts will probably outlast the boat. Great people to deal with too.

articfriends

IF your keeping the stock cam (which is tiny) I would NOT invest alot in getting your heads "ported and polished" as you mentioned. I would use the porting/polishing money for a decent cam if your going to pull the heads and going to manifolds that are less prone to reversion than cast iron, Smitty
IF your feeling industrious and pulled the heads yourself, you COULD take a sand roll to ridges that shroud the valves in chamber , easiest way to pick up 10 to 15 cfm and wont hurt airflow anywhere!

articfriends

And IF you do a exhaust sytem, get o2 bungs installed, at least one, and we can get together and fine tune your boat on the water !