Here We Go: My 383 Stroker Winter Project

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

of the manifolds, imco powerflows make the most, eddy marine's are close to a copy of the imcos and make a little less. stainless marine are on par with the emi's, the long tube headers a bit more than the imcos but only at higher rpms. I don't remember the specific numbers for the comparison or even if he told me exact numbers. If buying new, the imcos were enough better to be worth the coin, the headers weren't enough better to spend the extra. they were all run on a 383 with about 10:1 compression, iron heads, single plane intake and around 400-425 horsepower. I wound up with a set of powerflows. new manifolds I found on craigslist for 600, used risers off ebay for 200. They run great and have held up well. stainless headers sometimes crack and are a bear to repair or so they tell me. and they didn't make a lot more power on the dyno according to the man...

btw. project looks like it's coming together well!

Thanks Tim. It looks like Eddie Marine and IMCO Powerflow are at about the same price, which makes sense if they put out about the same power. On CP Performance it looks like the CMI Headers with a satin finish are only 200 more than the Powerflow system ($1995 vs $1799). If I'm going to spend $1799 I'll probably just go for $200 more and buy the headers - they look too good to pass up. I'll probably keep this engine even if I don't keep the boat so I'm willing to put some more $ into it. I just have to make a decision at this point, and it's getting close to boating season so it needs to be quick.

Greg: How fast were you before this build?

I gained 18-19 MPH gps. But my comp cams xtreme Marine 262 poops out (floats valves) at exactly 5000rpm. Which might actually be safer for myself AND my Alpha. Although Ive heard of people spining them alot higher.

I used to get 52mph by GPS on a good day with the 350. I was hoping for 70 when I'm all done but I'd be pretty happy with 65. I think 5000 rpm is probably a good bet for the alpha - although Tim has mentioned spinning his as high as 6500. I see you have a 1985 Chris Craft - are you running an Alpha gen 1 or gen 2 behind your 383? I would assume gen 1 unless it was changed out. How has it handled the extra power?

 

[wca_tim]

Re: Here We Go: My 383 Stroker Winter Project

you're better off to spin it higher with a little smaller (lower pitch) wheel than keep the rpms down and run a bigger wheel - the torque is what will kill it and having the drive turn a little faster (with fresh, high quality lube) is probably better. I routinely spin an alpha drive 5500-5700... I've scattered a couple of them, BUT each time I could trace it to my own mistake (primarily water in lube). 20 mph = gain of 200-250 horsepower, eh?

and the powerflows do make more horsepower than the emis according to the builder here. he also told me that for longevity, I would be better off with manifolds. he sees a lot of the cheaper headers crack... and there goes the engine when they do. I also had a clearance issue. I had to be really creative to get the engine and imcos in there - headers would have been a biotch. Also note that tall valve covers will fit under the imcos... not a minor issue if you're running aftermarket heads, rockers, etc...

btw. valve float with that mild cam at 5 krpms??? what spring pressures? surely not with new aftermarket springs? I can see that cam crapping out hard at 5k depending on the heads, but if the valves are floating at 5k there's something else running amok isn't there?

anyhow, enough rambling and living vicariously through the boating of others. in another couple weeks I'll be freed up enough to put things back together and go play. have fun!

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

you're better off to spin it higher with a little smaller (lower pitch) wheel than keep the rpms down and run a bigger wheel - the torque is what will kill it and having the drive turn a little faster (with fresh, high quality lube) is probably better. I routinely spin an alpha drive 5500-5700... I've scattered a couple of them, BUT each time I could trace it to my own mistake (primarily water in lube). 20 mph = gain of 200-250 horsepower, eh?

and the powerflows do make more horsepower than the emis according to the builder here. he also told me that for longevity, I would be better off with manifolds. he sees a lot of the cheaper headers crack... and there goes the engine when they do. I also had a clearance issue. I had to be really creative to get the engine and imcos in there - headers would have been a biotch. Also note that tall valve covers will fit under the imcos... not a minor issue if you're running aftermarket heads, rockers, etc...

btw. valve float with that mild cam at 5 krpms??? what spring pressures? surely not with new aftermarket springs? I can see that cam crapping out hard at 5k depending on the heads, but if the valves are floating at 5k there's something else running amok isn't there?

anyhow, enough rambling and living vicariously through the boating of others. in another couple weeks I'll be freed up enough to put things back together and go play. have fun!

Do you know how tall the powerflows are compared to the original mercury manifolds/risers? I will run into some clearance issues as well. I've emailed someone on their website but am waiting for a reply and I'll probably call them Monday if I don't get one by then.

Also, Tim what kind of gear lube to you run? I definitely want to run something synthetic. You seem to be the alpha drive expert from the threads I have read of yours. What do you think will be a good lube?

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

I've decided I'm probably going to get the IMCO thumper system. I can get them for $990 and they offer a 5-7% boost in power over my stock manifolds, which could equal 20-28 hp. The powerflows appear to be too tall to fit in my engine compartment, and after all the $ that has gone into this project I really can't put another 2k into the exhaust. Same with EMI - they are $1750. I still need to buy a flame arrestor and a few more things, and probably save up some $ for what will eventually turn into the new outdrive fund. Anyone have any experience with the thumper exhaust? There are some posts on other websites that seem to suggest it is a good system.

 

[wca_tim]

Re: Here We Go: My 383 Stroker Winter Project

Just make sure the risers dump the water into the exhaust a bit further back then the factory exhaust. have you looked for a second set of stainless marine or imco manifolds? I see them for sale once in a while.

LOL expert? hardly. run merc synthetic lube to be safe. I've come full circle on this one. I don't know on te clearance. I do know that my flame arrestor with the airgap rpm and afr heads is the part that hit the hatch and required shimming it up... the risers are about to touch as well...

ps. check your pms, I'm sending you link to used set(s) for sale - not mine, just passing on info...

 

[Flysfloatsor]

Re: Here We Go: My 383 Stroker Winter Project

Im running Patroit Performance "Vortec" Style heads. I cant remember what the spring pressure is, but I remember the specs claimed to match up to the cam... Im not sure if there is something else up, or the springs werent up to the task as advertised.

I run a Gen 1 Alpha. IMO - better than Gen 2's because of their availability and price.

I also run a labbed 25" Mirage, which puts me at a decent crusing speed at friendly RPM's. I also have a stock 25" Mirage Plus with more cup, but I havent tested it much.

I think youll hit 65, but you'll have to work on boat set up for 70.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

Just make sure the risers dump the water into the exhaust a bit further back then the factory exhaust. have you looked for a second set of stainless marine or imco manifolds? I see them for sale once in a while.

LOL expert? hardly. run merc synthetic lube to be safe. I've come full circle on this one. I don't know on te clearance. I do know that my flame arrestor with the airgap rpm and afr heads is the part that hit the hatch and required shimming it up... the risers are about to touch as well...

ps. check your pms, I'm sending you link to used set(s) for sale - not mine, just passing on info...

Lol, I said expert because when I was doing my research on 383/alpha combos before I started this project I always saw posts from you talking about all the different drives/props you have run. I thought it was you who suggested the Redline lube in a post somewhere a # of years ago. I am leaning toward Amsoil or Mobil 1 synthetic at the moment just because I have heard so many good things about both. I have looked all over the place for used stainless marine, IMCO, CMI, etc without much luck. I love the stainless marine exhaust too but it's just as much as the CMI headers. If you happen to see any more please send them my may. That guy wanted too much $ for the EMI manifolds - there is a set on ebay, chrome, brand new for $750 right now. Still not that great of a deal when I can buy a kit brand new for $1200 including risers, gaskets, a shift bracket and plumbing.

Im running Patroit Performance "Vortec" Style heads. I cant remember what the spring pressure is, but I remember the specs claimed to match up to the cam... Im not sure if there is something else up, or the springs werent up to the task as advertised.

I run a Gen 1 Alpha. IMO - better than Gen 2's because of their availability and price.

I also run a labbed 25" Mirage, which puts me at a decent crusing speed at friendly RPM's. I also have a stock 25" Mirage Plus with more cup, but I havent tested it much.

I think youll hit 65, but you'll have to work on boat set up for 70.

I also run a gen 1 alpha and I may even just buy an SEI drive at the beginning of the year so I don't lose a week when the drive eventually does go. I have a 21" Mirage prop right now and have access to a 25" laser II that my uncle keeps as a back up for his Fountain. He's going to let me borrow it for testing. I figure I'll end up in the 23-25" range. I'm not really sure what WOT RPM I am shooting for. Probably somewhere in the range of 5000-5500.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

As luck would have it, I found a used set of Stainless Marine risers, and just bought the manifolds. $1400 total for a $2000 exhaust system - not a bad deal. The Thumper or EMI would have cost me $1250 so I am happy with what I got.

 

[Flysfloatsor]

Re: Here We Go: My 383 Stroker Winter Project



Can you post a picture of what you bought? I lucked out on a set of "Stainless Marine" manifolds and risers when I was doing the engine build. If they are the same ones I bought - I wont tell you how much I paid... But I have $200 in the powder coat stripping and polishing.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

View attachment 141772

Can you post a picture of what you bought? I lucked out on a set of "Stainless Marine" manifolds and risers when I was doing the engine build. If they are the same ones I bought - I wont tell you how much I paid... But I have $200 in the powder coat stripping and polishing.

Once they come in I'll post a picture. I'm pretty sure they're the same ones you have in that picture - just the standard hi-torque manifolds. They should be in in a week or so but I won't be able to put them on until early May.

 

[Flysfloatsor]

Re: Here We Go: My 383 Stroker Winter Project

The Stainless Marine manifolds and risers are nice. Youll save about 100lbs over cast iron. Dont bother getting the powder coat removed, they tarnish in a few months if polished.

Youll have to hook up your cooling system a little different than stock.

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

The Stainless Marine manifolds and risers are nice. Youll save about 100lbs over cast iron. Dont bother getting the powder coat removed, they tarnish in a few months if polished.

Youll have to hook up your cooling system a little different than stock.

Yea I noticed that there appear to be only 2 water inlets in the whole system. My thermostat housing has 4 hoses coming from it that connect to the stock exhaust setup. How is it done differently?

 

[Flysfloatsor]

Re: Here We Go: My 383 Stroker Winter Project

There are 3 openings (one Bottom, two top) on the manifolds and one on the risers.

Fresh water typically enters the bottom and exits one of the top ports. The problem is, if the fresh water hits the manifolds before the risers, they get real hot. So you could do 1 of 2 things. Open the back top manifold port and dump through a thru hull fitting or do like I did and use a Tee system, so the hot water from the manifolds and a fresh supply of cool water dumps into the risers.
(thise are just brass plumbing fittings used, you get them at a supply house - not a big box store) I will get anodized aluminum or stainless Hardin Marine ones if I feel like wasting money sometime later. Either way, you will have a plug in one of the 3 holes on the actual manifolds.
I have an engine Pic if you follow that link on my profile. Its not uploading right now for some reason?

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

There are 3 openings (one Bottom, two top) on the manifolds and one on the risers.

Fresh water typically enters the bottom and exits one of the top ports. The problem is, if the fresh water hits the manifolds before the risers, they get real hot. So you could do 1 of 2 things. Open the back top manifold port and dump through a thru hull fitting or do like I did and use a Tee system, so the hot water from the manifolds and a fresh supply of cool water dumps into the risers.
(thise are just brass plumbing fittings used, you get them at a supply house - not a big box store) I will get anodized aluminum or stainless Hardin Marine ones if I feel like wasting money sometime later. Either way, you will have a plug in one of the 3 holes on the actual manifolds.
I have an engine Pic if you follow that link on my profile. Its not uploading right now for some reason?

I followed the link from your profile - your engine looks real nice. Either one of those options for the exhaust sounds like it would work just fine. I'll probably end up using the Tee system because I don't want to drill any more holes in the transom for thru-hull fittings. The manifolds should be coming in this week. School is done on May 2 so I'll be able to finish everything up by then.

Flysfloatsor, since you have the stainless marine manifolds, I assume you know how tall they are. Do you by any chance know what the difference in height is between this system and the stock mercruiser manifolds/risers? I know I am going to have to raise my engine hatch but I'm not quite sure how much, and I can't find it anywhere online. If you knew, that would be awesome.

 

[Flysfloatsor]

Re: Here We Go: My 383 Stroker Winter Project

I havent put a tapemeasure on the risers BUT I would say they are about the same as stock cast ones. Maybe only slightly taller, less than an inch. As you saw in the picture, I have an edelbrock intake manifold with a Holley Marine Carb and oversized 5" tall Holley flame arrester. The flame arrester is taller than the manifolds, and all fit under the sun hatch without modification.

Id bet You will not have to do any special modificatins for the risers, the Flame arrestor will be the tallest part on your motor.

The manifolds are nice, the manifold to riser clamping system is well engineered for easy installation. Which makes it really easy to install the manifolds with the engine IN the boat because they are light (without the riser attached). You would appreciate this even more if you've ever changed out a cast iron manifold with the engine in the boat...

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

I havent put a tapemeasure on the risers BUT I would say they are about the same as stock cast ones. Maybe only slightly taller, less than an inch. As you saw in the picture, I have an edelbrock intake manifold with a Holley Marine Carb and oversized 5" tall Holley flame arrester. The flame arrester is taller than the manifolds, and all fit under the sun hatch without modification.

Id bet You will not have to do any special modificatins for the risers, the Flame arrestor will be the tallest part on your motor.

The manifolds are nice, the manifold to riser clamping system is well engineered for easy installation. Which makes it really easy to install the manifolds with the engine IN the boat because they are light (without the riser attached). You would appreciate this even more if you've ever changed out a cast iron manifold with the engine in the boat...

Perfect - that's exactly what I was hoping you would say. I have about 2 inches of clearance from the top of the stock risers to the hatch, so I may not need any extra clearance at all, unless I want a larger flame arrestor. Hopefully everything will work out just fine without any changes. I have replaced a few sets of cast iron manifolds with the engine installed in a few different boats. I agree that it's no pleasure to do.

Just out of curiosity, could you notice the weight difference when you switched from iron to aluminum? Some people say it is very noticeable, others say not so much. I've switched both the exhaust manifolds and intake manifold to aluminum from iron, so I should have somewhere around 100 lbs less weight in the back.

 

[wca_tim]

Re: Here We Go: My 383 Stroker Winter Project

The Stainless Marine manifolds and risers are nice. Youll save about 100lbs over cast iron. Dont bother getting the powder coat removed, they tarnish in a few months if polished.

You'll have to hook up your cooling system a little different than stock.

if you want to polish them and have it last, polish, treat with metal prep and shoot several heavy coats of por-15 Glisten on them giving plenty of flash time between coats. after they harden for a few days, wetsand and buff any trash or runs out. Mine look great three years later. even after running in pretty salty brackish a good bit last year.

ditto on cooling system, have to swap outlets (assuming you're going regular freshwater cooling rather than closed...)

 

[greg82255]

Re: Here We Go: My 383 Stroker Winter Project

I personally like the black stainless marine finish, so I'll probably stick with that for now. Maybe at the end of the year polishing them could be a winter project. I don't have the $ to switch over to closed cooling right now so I'm going to go with raw water cooling. I'll post a picture of the cooling system setup once it's installed to make sure I've done it right.

 

[Flysfloatsor]

Re: Here We Go: My 383 Stroker Winter Project

Im not a good test case for the weight question. Because I went from a 200hp Mercuriser 305, to a 383 with the aluminum intake and exhaust. So, my power was way different. (I wanted Aluminum Heads, but didnt get them because Patriot Performance sold me cast ones for for a great deal because they had been ran on a Dyno test engine)

 

[Flysfloatsor]

Re: Here We Go: My 383 Stroker Winter Project

I personally like the black stainless marine finish, so I'll probably stick with that for now. Maybe at the end of the year polishing them could be a winter project. I don't have the $ to switch over to closed cooling right now so I'm going to go with raw water cooling. I'll post a picture of the cooling system setup once it's installed to make sure I've done it right.

Youll be able to tell in 10 min in the driveway if you hooked it up incorrectly. The rubber hose to the exhaust tips will get HOT.