marine vs. automotive - Vortec

[Beech2000]

I have a 5.0 vortec installed in my 98 sea ray and would like to rebuild a 1999 5.7 removed from 1 ton work truck I was given if possible.

I understand the intake, carb, and exhaust being marine application as well as the electriacal components but I read Marine heads for vortec, I read marine 5.7 liters. What gives?

What differances can I expect from the basic Chevy long Block? (i.e. Oil Pan, front timing cover, cylinder heads etc...).

Great forum and I look forward to responce.

[stonebreaker]

There's not really that much difference in the long blocks. It's mainly the accessories and the fuel system that are different, and if you're re-using them, you'll be OK. As far as the oil pan, does your original engine have a one piece or two piece rear seal? If it's a 98, I would assume it's a one piece, like the truck engine, so you should be able to reuse your marine oil pan.

Judging by GM's power curves, the boat cams are somewhat in the middle between car and truck cams, in terms of torque curve and peak horsepower. The car cams make more horsepower, the truck cams make more torque.

GM's main weakness is their valve springs. If I were in your place, I'd use the Comp Cams beehive springs, pn 26918, and then go with either a Crane marine cam, p/n 109811, or else the GM cam 14097395. The GM cam is used in both the high torque 383 engine and also the Ramjet 350, and is very similar to my stock impala cam. You can go here and see the torque curve on the Ramjet 350 crate engine page.

[Beech2000]

Thanks for the reply Stone,

I took a look at the main seal and verified to be one piece on both engines.

So the truck block and heads are not specific to Marine application?

The parts guy at my local marina say's the cylinder walls are thicker, the internal water passages are differant and as you mentioned the cam is marine.

My goal for this project is following:
1) More bottom end torque using same 19 pitch prop for pulling 2 skiers/slalom.
2) More upper end speed without changeing prop. Currently boat speed with 4 people is around 45mph at W.O.T. 4200RPM. (Would like 50 or better at W.O.T.)

I realize changing to a ski boat sounds logical but I don't like the way true direct drive / Flat bottom ski boats ride or look.

Plus I feel I could build the truck engine for very low cost due to friend at machine shop who will boil block, true deck, bore cylinders .010" to .030" and rebuild heads at no cost. That is of course with me to supply the parts.

The biggest problem with all of this is the fact that the current 305 engine in boat is basic 2brl carb. So I have been shopping E-Bay and net for Vortec 4brl intake and carb for Mercruiser. As of now I have found lots of Pre-vortec manifolds only. That is with out spending 300 or more just for intake.

I am bugeting around 1,500-2K total for rebuild, carb and intake combined.

That is of course if 350 engine passes NDT and is not cracked. I know the history of these engines and all get replaced with new crate engines at 100K. I cut the 350 oil filter open and paper was clean as a whistle. I could almost get by running it as is but want a little more HP out of it as well and up to the challenge.

So I shouldn't have any bolt on or integrity issues?

Kevin

[stonebreaker]

Yeah, I hear a lot of that too - that marine engines are some sort of magical beasts and no automotive engine could possibly stand up to the strain

Yet, if you go to gmpowertrain.com and look at the marine engines, they use cast pistons, cast cranks and cast 2-bolt main caps. They even still use forged rods, despite the modern powdered metal rods being both stronger and better balanced.

The real difference between marine and automotive isn't in the strength of the parts. The real difference is corrosion protection and some marine safety issues. For example, the marine engine uses head gaskets with stainless steel inserts, and brass freeze plugs. My LT1 engine has brass freeze plugs in it, so you may not have to change the plugs in your block. As you mentioned, the accessories and the carb are specialized for marine use, but the block and heads are just the standard block and heads.

On the prop issue, it sounds to me like you might be a little overpropped as it is - 4200 seems a little low for max rpm. GM lists peak hp for both the 305 and 350 marine engines at about 4800 rpm. So if you build the engine with 5000-5500 as the target rpm, you should see 50 mph easily. 5500 rpm is well within the stock bottom end's capability, so where I'd focus my efforts would be the valve train. As I mentioned before, either the Crane or the GM cams would work well in this application, both peak at 5200 on a 350, although I favor the GM cam. Spend the extra bucks for a good set of springs (I like the Comp behives), and make sure your pushrod length is correct for the cam you eventually go with. If you can afford roller rockers, so much the better. Since you mentioned you'd be machining the block, make sure you fit the timing chain correctly so there's no slack in it. You know, details...

[Beech2000]

Stone,

I can get 4800 WOT by my self in boat but not with 4 adults. Should I be able to?

I did go on GM's many web sites regarding marine applications and the link you sent me to. I aggree now and very pleased that this will work.

The engine has double roller timing chain, roller lifters as well as 4bolt main caps. Wow this engine is very nice!!. Lot differant than 307 in my high school nova.

I am half tempted to just change do valve job with crane cam springs install GM marine cam and lifters and run it. I think I still see the hone marks on cylinder walls. Oh. Do marine application SB's use Stainless valves?

[Jango]

4800 RPM with driver only is exactly right. Your prop is correct.

Summit Racing sells an Edelbrock Marine 4 Brl for about the same cost as the Auto version. I use the 750 cfm unit on my boat - very good carb.

I believe S.S. valves are used on GM motors although not sure. By choice my marine Ford has S.S. valves.

If at all posible, use the Roller lifter/cam - an automatic 50 hp and 50 ft - lb even with the same duration/lift.

Good luck, sounds like you're on the right track.

Jango

[Beech2000]

I guess corrosion and higer tolerance to heat are the main advantages of the Stainless valve as opposed to the factory steel right? So its an integrity upgrade that is sounding very expensive...

Gee's Sky is the limit to the high quality parts availiabllity.

I will check into it though.

The truck engine appears to already have roller tappets. can roller tappets be reused? I know flat tappets are not reusable but on the other hand I don't want to jepardise quaility and integrity just to save a buck.

Thanks for the reply Jando and Stone. You have realy helped me alot.

[stonebreaker]

Agree with Jango, your prop seems correct if you can hit 4800 rpm with the boat light. Except now, you should be able to hit it with the boat full.

As far as the cams go, I couldn't find the actual specs on the current roller cam for the 5.7; however, I DID find the part number for the flat tappet cam and lifter kit, which is 12353918:

12353918 - Camshaft Kits


All "Marine" and off-road small-block Chevrolet V8. Compression ratio 8.75 - 10.5 to 1, 2600 - 3000 cruise rpm, basic rpm range 2000 - 4500 rpm, 6500 rpm attainable with proper valve springs and lifters.
Technical Notes: These are hydraulic flat tappet camshaft kits. The duration at .050 lift (intake/exhaust) is 214/224 degrees, and the valve lift is .442"/.465". Lobe centerline is 112. This camshaft kit is designed and manufactured by Crane Cam Cov.®. It contains one camshaft and 16 tappets.

This is extremely interesting, because GM sells a roller version of that exact cam, p/n 12370845. I ran that cam in my car for three years, and it is indeed capable of revving to 6500 rpm with the correct springs. It is an all-around bad ass cam. I have run a best of 12.6 at 108 mph with that cam in my 96 impala, at a race weight of 4400 lbs, and still get 22 mpg on the highway.

Having said that, I'd still opt for the ramjet 350 cam, as the 845 cam design is about 20 years old and isn't optimized for the vortec heads; the ramjet cam is. Hell, for all I know, the new marine cam may BE the ramjet cam, I won't know until I can find the specs. However, I suspect the current marine cam is still the older 12370845 cam, or 845 cam for short, for this reason: I went to the Crane website (all GM cams are manufactured by Crane) and looked up marine cams. Crane sells the GM 845 cam as part number 109821 in automotive applications; however, when you look up cams for a 98 marine engine, you get p/n's 109811 and 109831. P/n 109821 is strangely absent. This seeming oversight is explained, however, if Crane 821/GM 845 is still the current marine cam and Crane can't sell it in competition with GM.

Crane sells cams in families, with the exhaust lobe from the smaller cam becoming the intake lobe for the next larger cam. You can see this if you go to the http://www.gmperformanceparts.com/ website and look at cams 12370845, 846, and 847.

Let me know if I'm losing you.

[stonebreaker]

PS - the marine engines don't use stainless valves. Go back and look at the gmpowertrain site - while they are very careful to point out the stainless insert head gaskets, fuel rails, and injector tips, nowhere do they mention stainless valves.

Roller tappets can be reused. The stock roller tappets are good to about 6500 rpms.

[Beech2000]

Wow,

Definetly lots of info. You sure know your cams.

So. would you recommend the reuse of the roller lifters with the competion cams beehive springs and the GM RamJet 350 cam?

I fear noisy valve train should the truck lifters not pump up. Your thoughts?

[stonebreaker]

Originally Posted by Beech2000

Wow,

Definetly lots of info. You sure know your cams.

So. would you recommend the reuse of the roller lifters with the competion cams beehive springs and the GM RamJet 350 cam?

I fear noisy valve train should the truck lifters not pump up. Your thoughts?

Yeah, I think the ramjet cam is the better cam for your situation, but only a little better than the 845. It makes a little more torque in the midrange, a little less horsepower up top. If you usually run with a full load, the ramjet is going to be a better choice, although the difference between the two cams is going to be less than 5% at any given rpm. My gut feeling is that the ramjet is going to be a little more fuel efficient, but I really don't have any data to back that up.

I've run the stock lifters out to 6500 with no problems. However, you'll want to examine both the cam and the lifters before re-using them. Look for any pitting or cracks on the rollers and the cam lobes. If you see ANYTHING suspicious, dump them and get a new set. Every time I swap cams, I like to go over everything both by feel and with a magnifying glass. Here's a pic of a cam that was about to cost me a lot of money if I hadn't been planning on swapping it out anyway. Turns out I had a broken spring that was allowing the lifter to bounce across the top of the lobe. I never heard anything - just got lucky I decided to swap that cam when I did.

I caught the crack just right in the second pic. That cam was made by Erson, btw, and is not a GM cam.

[Beech2000]

Stone,

Do you know what the lobe centerline angle is on the RJ Cam?

I fear anything less than 110 might jeopardize idle and acceleration from low speed high load.


Hey Stone, in referance to the quote from GM Performance brochure I read the following,

Quote:"The Ram Jet 350 makes it easy to have electronic fuel injection on any 1976 and older vehicle originally equipped with a
carburetor. The secret is the industry leading MEFI 4 controller. This new controller fits in the palm of your hand and was
originally developed by GM Powertrain engineers for marine applications."

Wonder what GM sells this set up for? How could I find cost out or does it only come with crate engine only>

[stonebreaker]

Originally Posted by Beech2000

Stone,

Do you know what the lobe centerline angle is on the RJ Cam?

I fear anything less than 110 might jeopardize idle and acceleration from low speed high load.


Hey Stone, in referance to the quote from GM Performance brochure I read the following,

Quote:"The Ram Jet 350 makes it easy to have electronic fuel injection on any 1976 and older vehicle originally equipped with a
carburetor. The secret is the industry leading MEFI 4 controller. This new controller fits in the palm of your hand and was
originally developed by GM Powertrain engineers for marine applications."

Wonder what GM sells this set up for? How could I find cost out or does it only come with crate engine only>

The LSA on the ramjet cam is 109 degrees, vs. the 845's 112, but because its duration is smaller, it actually has less overlap than the 845, so it will idle smoother than the 845, although the 845 already idles pretty smooth - you can't hear the lope unless you know what to listen for. The stock cam on my 96 impala - my STOCK, FACTORY cam, has a 111 deg LSA. This gives it huge torque in the midrange, and is another reason I like the ramjet cam - my stock cam is basically the ramjet's little brother.

ON the mefi controller, here you go: http://www.sdpc2000.com/search.asp?s...mefi&doquery=1

[Beech2000]

Not seen or heard about after market Port fuel injection out side of OEM. Mercrusier included. I Need to toss this idea altogether as safety and durablilty needs to be first concerning marine toys.

Just in the preliminary stage of gathering info for the best bang for the buck. Guess I'll continue my search of great deal on vortec cast 4bbl manifold and carb.

Thanks for the research on the MFI set up.

I like the sound of the RJ Cam though. I just fear overcaming like I did once upon a time to a Ram Air 400 years ago. this is a family boat and not off shore racer.

Looking for good balance. A friend of ours bought one of the new Baja's with merc 5.7 FI that has this balance but with a 50K price tag. Ouch!

This lit up another light bulb in my head. Wonder if any detail specs are publically published on High performance merc's.

If so I wonder if the same specs on the RJ Cam you mention and speak so highly of might not match similure profiles of that in the marine GM engines.

I much appreciate your input and quick responce and who knows, maybe the back side of this project will prove to be benifical to all of us weekend water racers.

[stonebreaker]

A couple of suggestions. Would that mefi controller be cheaper than a carb and manifold? YOu could use it on the stock truck manifold and throttle body.

Did you happen to get the wiring harness and computer off the truck along with the engine? If not, maybe price one at a junque yard. Then have the stock computer reprogrammed for the boat. These guys can reprogram your stock computer for not too much. They can also tell you what computers would work best on your engine, so you don't have to try and track down just your model and year. I would imagine any Gen I or Gen II v8 computer could be made to work. Then you can take a wiring harness and strip out the fuel injection part and chuck the rest.