bad news.. need a new motor. Help me plan the new one :)

I believe alpha 1's are rated to 300hp - I think you will be pushing that with a 400.

LK
 
I'd call the Cam companies and ask them. Aboat requires a much different profile than a car. I believe CompCams has a specific cam for marine applications.
 
Summit racing can match parts for performance in either auto or marine. Watch over carbing the engine. Many use a tall cam and large carb and flood the engine on start. My son hung an 850 dominator and large cam on his 350 only to push gas out the tail pipe, pull rocker studs and would not idle under 1000 rpm. I'm sure you'll watch this but its worth mentioning.

Let whoever you use know what rpm, HP, and power band you want to operate in. 383 strokers are great for yanking the arms off a skier if you so desire.LOL.
You can regulate the rpm with correct prop placement. Once the motors in check the top end rpm. Should be around 4500-4800 WOT. If to high then add some prop, Too low then less prop. The prop angle will raise or lower the rpm around 200 per pitch angle as a rule of thumb.

I was going to up Old Skools performance but I'm not ready to hang a new Bravo on the back just yet.

I know there are a lot of folks here that have much experience and will add their comments too. Good luck.
 
well I'd think you'd be pushing pretty hard on that alpha with a 400, it's definately not as much torque as a BBC pushing on it but still walking the line a little bit. just would need to watch your hole shots and be careful on your reentries. I'd love to give dynamite advice but honestly I've never built a 400ci or known anyone with one. so I'll be honest I'm shooting a bit from the hip that said;I'd say if your going with the vortec heads you should look into something like that edlebrock air gap performer intake manifold, lots of guys running those on 350's with vortec heads have raved about the combo. the standard performer is nothing special (trust me I know:/) not sure on a cam although I've read the vortec heads are limited to around .480 lift I blieve. maybe something like an LT4 Hotcam would work well, especially if your going with a roller rocker setup? I think in terms of carb I wouldn't go any bigger then a 750 cfm and even that is probably pushing it.
 
so you guys think I would need to step up to a bravo with said setup? If so do you guys have a link to that swap? I really only do cruise with the boat, so I would be pretty gentile on the hole shots. I'm newer to boats and more used to Mustangs lol. I know in a car you can nurse a t-5 tranny in a very powerful mustang as long as youre careful with the launches. Would that hold true to boats or am I wayy off?
 
Someone already mentioned it, but you just can't use a steep cam on a boat like a car. It won't work. What are you looking to do? How fast do you want to go? It's a 25' Amberjack, not a Cigarette, so you really ought to think about what you're trying to accomplish. I'd be aiming for a good cruise with decent efficiency.

You'll probably straighten out that Alpha with 400hp.
 
I did the 383 motor with Vortec heads, cast iron intake and a mild marine cam with a rejetted q-jet. Can not beleive the difference from the stock 260 hp motor in the amouint of torque, I now only have to use the trim tabs to level the boat, not help get it on plane. This was one of the best things I did performance wise and like you I mainly cruise with it so hole shots are not an issue.
 
390x said:
Someone already mentioned it, but you just can't use a steep cam on a boat like a car. It won't work. What are you looking to do? How fast do you want to go? It's a 25' Amberjack, not a Cigarette, so you really ought to think about what you're trying to accomplish. I'd be aiming for a good cruise with decent efficiency.

You'll probably straighten out that Alpha with 400hp.
Click to expand...

Oh yea definitely not looking for a big cam. Just something good for mid range cruising. Just wondering what brands people have gone with?
 
Flat Rate said:
I did the 383 motor with Vortec heads, cast iron intake and a mild marine cam with a rejetted q-jet. Can not beleive the difference from the stock 260 hp motor in the amouint of torque, I now only have to use the trim tabs to level the boat, not help get it on plane. This was one of the best things I did performance wise and like you I mainly cruise with it so hole shots are not an issue.
Click to expand...

Ahh I found someone with almost my desired setup!

a few questions if you don't mind.

-Are you on the alpha 1 or MR drive and is it holding up well?

-Do you remember what cam you went with?

-What is your cruising speed and top speed with new combo?

-What should I expect to pay for a similar setup with the longblock being set up by someone else?

Thanks!
 
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in terms of the alpha holding up from what I've seen it's a complete crap shoot, I've known guys push 400hp for years through an alpha with lots of abuse and never have a problem , but I've also seen guys with less power baby them only to have them blow. sure you can nurse the alpha along, will that make for fun relaxing day on the water though? if you are just into cruising why do you need the extra power?
a bravo swap is getting pretty involved and it can get to be pretty pricey, your talking a new drive, new transom plate, and you'd need to use a IMCO shorty lower unit to hold the same x dimension. honestly if you're going through the trouble of swapping over to a bravo then I'd ditch the small block all together and go big block. at which point now you're investing alot of money that you'll get almost no return on come resale time. again just something to think about. to me it sounds like your torn between reliablity and more speed, all I can say is welcome to the club:smt001 I'm not the dali lama of boats and would never tell anyone what they should and shouldn't to do with their boat but if big power and more speed is what you want maybe this isn't the right boat for your needs. could always move into something like say ohhhh I don't know a Pachanga 27 :grin:
 
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A friend of mine has a 1977 SRV240. They’ve had it since new. That boat has had numerous different SB builds in it through the years. Some were better than others but they never felt they were powered right for that boat and their type of boating. The last time they put a stock 454 in it and switched to a Bravo 3 drive. It planes very quickly now, has a top end almost 50mph but the biggest improvement was seen in in rough water conditions. It stays on plane at slower speeds and doesn’t get pulled down by every large wave it meets. Before they were even finished putting the stock 454 in they were already discussing future modifications:lol: but it has performed so good with the bravo3 that everything has been left stock since.
 
I had a 406 (.030 over 400) in a 70 Chevelle I sold a couple years back, Torq cam, headers, 650 Edy carb and a good tune and that thing was the best motor I ever drove (as far a small blocks go) Man, Now I am missing it. :( - Watch your piston selection if you go with the Vortec heads as they have really small (58cc?) chambers and the stock 400 heads are in the 70's

LK
 
I don't understand what a Siamese bore has to do with a marine application? ALL 502's have a Siamese bore.


That shouldn't be a problem at all.
 
Not sure if you are looking forward to building an engine or buying one with a warranty but you may want to check these guys out: http://www.michiganmotorz.com/

I personally have not worked with them but a friend and cousin have, one a short block and the other turn key.
5 and 6 years on them and they are both running excellent.

Less time rebuilding and more time on the water - something to think about. :huh:
 
OldSkool said:
Summit racing can match parts for performance in either auto or marine. Watch over carbing the engine. Many use a tall cam and large carb and flood the engine on start. My son hung an 850 dominator and large cam on his 350 only to push gas out the tail pipe, pull rocker studs and would not idle under 1000 rpm. I'm sure you'll watch this but its worth mentioning.

Let whoever you use know what rpm, HP, and power band you want to operate in. 383 strokers are great for yanking the arms off a skier if you so desire.LOL.
You can regulate the rpm with correct prop placement. Once the motors in check the top end rpm. Should be around 4500-4800 WOT. If to high then add some prop, Too low then less prop. The prop angle will raise or lower the rpm around 200 per pitch angle as a rule of thumb.

I was going to up Old Skools performance but I'm not ready to hang a new Bravo on the back just yet.

I know there are a lot of folks here that have much experience and will add their comments too. Good luck.
Click to expand...
Sage advice indeed. "Matching parts" is the key to sucess.

If every kid with his first car and wanting to go fast followed OldSkool's advice,they might avoid much disappointment.
 
390x said:
I don't understand what a Siamese bore has to do with a marine application? ALL 502's have a Siamese bore.


That shouldn't be a problem at all.
Click to expand...

I'm just going by what I read on a few other forums. I'd prefer to go that route though if I can, it's cheaper!
 
I'll have to check the cam specs and get back with you but it was a mild Crane marine grind. The motor was originaly put in front of a Cobra drive in a 26 ft Bayliner Sunbridge (6000 pounds) with no problems, just now going into the 240 Hardtop with an MC drive so no data yet for you. I was able to reprop the Cobra and get better planeing speeds and more top end. I had a machine shop do all the bottom end work (put the 400 crank in a 350 block and install pistons, rods, brgs) and I assembled the rest. 5 years ago the cost was slightly over 2000.00 for their work and parts (I supplied the block, cam and heads). Total I have approx. 2700.00 in the motor but that was using some parts I already had (heads) and my own time. I beleive I had about 150.00 in cam, 200.00 intake, 150.00 gaskets. Machine shop/engine builder estimated the HP at about 320 to 330 and I know that I'll have to be easy on the drive with that but it is not a hot rod boat and should be OK if I behave myself, if not I switch over to something a little stronger later on.

Hopefully I'll have the transom back together later this month and start putting the motor in so if my luck holds out I may have some more info in a couple of months.
 
Well, I don't know if there's something special about a 400, but the 502 is a Siamese bore, and there are obviously tons of them running around in boats without problems, so that alone shouldn't stop you.
 
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