302 teardown

Well, I had a great talk with John from the Machine Shop here in Des Moines. He's much more knowledgable with marine application that I expected.

I asked his opinion about Stroking the motor and 331 vs 347. He said after seeing the condition of the crank, rods and my Cam he doesn't see a reason to justify stroking the motor unless I want to get a lot more power out of the motor.

Obviously, it's my choice and it would give me more power but at the same time I don't think at this point I NEED the extra power. Bored 30 over, heads, intake and a cam will be plenty of upgrade for me and won't break the bank. A $400-600 difference between stroking and stock makes me lean towards staying with the stock bottom end and using new forged pistons.

If I can get somewhere between the 270 and 280 mark I'll be a happy guy.

Tim you are 100% correct, the idea of another 40hp is very appealing. I just have a few concerns with going to a 347. One is durability of the block. I don't want to get into something I cannot maintain or worry I am going to break. Most of this stuff is way over my head anyway, I just know enough to be a little dangerous.

A more mild stroke at 331 is an option, but like John said, if your going to pay the $ to stroke the motor you might as well go up to a 347.

Doing just the top end seems like it would be more manageable but if I am wrong please correct me. Like you said earlier, I need to do some more homework and I don't want to get into something I don't fully understand.


The other is a question I guess I have to ask myself, what is the purpose of the boat and the rebuild?
-I am going to be using it as a travel boat of sorts, going to reunions and taking it on weekend trips around Iowa. It doesn't have to be a screamer but it would be fun to get up into the 55 MPH range.

The 4-600 bucks could be used somewhere else like upholstery or in the bank for other projects some day.

I'm not sure which way I'll go yet, I may need more persuading.     

I still would only go with a 331 versus a 347 due to the piston speed and all the other points we mentioned.

Yep yep yep, a million ways to skin the cat.

If I was looking at a bottom end rebuild and therefore needed to pop for new bearings, crank service, connecting rod service, machinging, new pistons and rings.. then yes I would say to myself.. for a few more bucks I could also get a new 331 cast crank and a decent set of rods and end up not only with a few more cubes but also a new crank and a set of rods instead of reconditioned crank and rods. A pretty good payback on the investment.

Nothing wrong with a well built 347.. but if I was building a 347 I start to think about a forged crank (+300 over cast), balancing (+200), and a stud girdle (+100 if it fits without new oil pickup and drain pan mods). Well now I am starting to talk about real money, wait if I am getting it balanced shouldnt I think about the condition of the flywheel and harmonic dampner before I put more money into them.. and next thing you know you are broke.. or maybe you do it cheap and you are broken?

I say the cheapest 331 you can get built, gt40p heads (be careful here the spring and valve selection could do you in), a used performer rpm intake, and don't let those guys at cam research give you no tractor puller cam.. the boat dont weigh nothin and has a v8.. you will get out fo the water just fine.

Or the cheapest 331 you can get built and the top end you have now.. cause as the man said you can always do the top end stuff later without even pulling the engine out of the boat. It might make sense in this case because you need new heads to just go right to the gt40ps even if you didnt want the cam and intake bill at this point. That way you can plan the right pistons to match the heads with the right compression ratio from the begining.

While we are here..great things are possible even with stock bottom ends with bigger badder heads, intakes, exhausts, and rpms. But that is where the drivability issues come into play. They can be taken out of play with fancier fuel and ignition systems, but when you start talking like that you have left the realm of bang for the buck in my skiboat and gotten into the realm of engine hobbyist.

This is a cool discussion thanks guys!

Chris forgive me if I missed it, but what ended up being the cause of the problem.

What is your ballpark estimate for the rebuild if you don't mind me asking?

Tim, what should I expect as far as a price range for what they are doing. I thought it was pretty fair considering they have time in taking the motor down, cleaning everything up, will be boring the block 30 over, magnifluxed and putting everything back together. The estimated labor cost was going to be about 700 bucks to do the entire thing.

Only reason I am price sensitive to the 400 is that I literally just put in an offer on a house not more than 10 min ago! Not sure what will come out of that but it may effect my thought process on this project. Good news is, it's the one with the big shop I told you about!

What new parts are part of this (new rod and main brgs)? What machine work is a part of this (Crank polished or turned and polished)? It's apart is it going to get hot tanked? When its bored is it going to get power honed for the correct fits?

I guess what I'm saying is I'd be asking for an itemized list of of parts and services I'm getting for my thousand bucks.

Whatever you decide to do, get the most you can for your money, and get it done right. If not it will cost you more in the long run.

Tom, as stated above, the rods and bearings are in great shape, this motor only has 400 hours. They've already had everything in the hot tank and cleaned up. Yes, the cylinders will be honed as well as bored. Not sure about the crank, I'll have to check with John on that one.

I'm going to go ahead and call on the Gt-40p's today so we can hopefully see them next week? Intake and cam will follow shortly after.

One thing we haven't touched on yet is ignition. I know some like to stay with points but I am open to suggestions.

TRBenj wrote: Chris, congrats on the house (and shop!).

Thanks Tim, we'll see what happens. Could be a great situation if it ends up happening, if not I'm in no hurry to take on any debt!

TRBenj wrote: Tom makes a good point- you want to fully understand exactly what youre getting. What services will be included, what parts he's using. Then you can figure out where your money is best spent. 351w with upgraded top end = 320-330hp 331-347 stroker with upgraded top end = 300-330hp 302 with upgraded top end = 260-280hp 302 with head upgrade only = 240-250hp stock 302 = 220hp

If you all think that heads and a 331 are my best option with the stock cam and intake then I am open to that option although I would really like to have this thing done and not have to tear into it again. (I have a Skier that is dying for my attention!) If my math is correct, I would be around 270hp with the heads and a stroker kit, basically the same as a stock bottom end and an upgraded top end?

That sounds very appealing to me as well Tim. Since it will be used as a workhorse when it's at our home lake towing kids and visitors around....and efficiency is always a plus. I'd really love to just dive in and do the whole thing right now, but the responsible side of me is saying to take it one step at a time.

If I can get this thing dialed in like it was before I think I will be in great shape. It fired up faster than any boat i'd been in and was smooth as silk, just a little noisy!

With these upgrades would I still be looking at an ACME 1210?

Tim, I'm going to try and get the prop pulled and check everything out next week. Was busy finishing up a trailer for the Chris Craft this week so I can drag it up to Wisconsin today.

I talked to Reid last night about his Mustang and 347. His opinion was to go with a stroker, heads and a cam to get the most bang for my buck. In his opinion, stroking with out a cam wouldn't utilize the $ spent in the stroker kit as much. He also mentioned there are other options for good cam's at a cheaper rate, I'm going to do some looking outside of Cam Research just to be sure. If anyone has any good leads I'd appreciate the heads up or a better description of what I should look for.

Chris, when's your birthday? Oops, saw where we just missed it in Dec, but what the heck, if you stick with the stroker route and I'll give you one of those Speedpro-type cams, in exchange for all the beer I can drink at our next outing we both attend. And I saw a brand new intake on ebay for $109.00, IN IOWA, of all places. 331 vs. 347, I'll stay out of that one for now.       

This must be the intake?



Thoughts? It's in Ames, Iowa. I've got a buddy up there who can snag it for me an bring it back over the weekend.

if you look at it this way, "347 is only 4 cu in's away from a 351"