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Discussion Starter · #1 ·
I am running this SP12-24000-CNC- A 210/64 cylinder head for my 383 but i am not happy with performance and it had valve leak .
engine information 350 block 4 bolts main. 030 bore .3.75 crank .5.7 rod .lt4 hot cam .dual plate intake .600 cfm marine cab (1409) +18 CC piston and this engine I build for boat. compression 9.5:1
so with cylinder head would I buy. i thinking 210 cc intake runner is too big .
 

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what rpm range are you planning to run? What is the purpose? What power range are you looking for? Is the exhaust dry or wet? What other components are you using? etc
 

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“Not happy“ is not exactly a technical term. Aside from a “valve leak“ there isn’t much to go on. Need more specific information about how it performs for what purpose it gets used for against what performance was expected?

Bogie
 

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Discussion Starter · #4 ·
what rpm range are you planning to run? What is the purpose? What power range are you looking for? Is the exhaust dry or wet? What other components are you using? etc
I plan at 5500rpm ,pull ski ,tubing , wet exhaust ,use 91 fuel, Delco Est marine ignition .
 

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210 is a fairly good match with the LT4 cam on the street, but 210cc likely has crappy velocity where you need it most - 1800-3000 rpm.

Can we assume it's an I/O? Jet is a whole new ballgame. Vessel weight and hull design is also a huge factor

It's really hard to beat stock Vortecs on a boat. You're pretty much capped at 5500 RPMs with most outdrives. 6000 can kill a good Alpha pretty quick.

I would think 190cc tops. I'm also a little concerned with wet exhaust and LT4 cams. That's way too much overlap for my comfort zone. If I'm building a marine engine with wet exhaust, I will push it to 210/220 with a 113 LSA, but I'd hate to see you destroy heads with reversion.
 

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Discussion Starter · #6 ·
“Not happy“ is not exactly a technical term. Aside from a “valve leak“ there isn’t much to go on. Need more specific information about how it performs for what purpose it gets used for against what performance was expected?

Bogie
For what i thinking my 383 build is something go wrong .I install stock vortec cylinder head at first time it make great power ,than I try it get light weight on engine than I bought set aluminum head install on it run but I think I lost torque ,boat start weak hard to get on plane .
 

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Discussion Starter · #7 ·
210 is a fairly good match with the LT4 cam on the street, but 210cc likely has crappy velocity where you need it most - 1800-3000 rpm.

Can we assume it's an I/O? Jet is a whole new ballgame. Vessel weight and hull design is also a huge factor

It's really hard to beat stock Vortecs on a boat. You're pretty much capped at 5500 RPMs with most outdrives. 6000 can kill a good Alpha pretty quick.

I would think 190cc tops. I'm also a little concerned with wet exhaust and LT4 cams. That's way too much overlap for my comfort zone. If I'm building a marine engine with wet exhaust, I will push it to 210/220 with a 113 LSA, but I'd hate to see you destroy heads with reversion.
I was use stock vortec head it make great power but it is iron it heavy ,that why i bought this cheap aluminum head . it make my engine weak the boat hard to get on plane .my boat is 17 ft it is I/O boat run 23 p impeller i read on line lt4 hot cam is same XM270HR . My 383 run lt4 hot cam does not reversion water to engine.
 

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First whether I’d use aluminum or not would depend on the cooling system. A closed system that protects the engine from direct contact with the water the boat is floating in can warrant the use or aluminum, otherwise aluminum is too reactive especially for salt water. The other issue is operating temperature, the power advantages of aluminum are in running it hotter than iron, this is harder to do with an open cooling system.

Iron is much less reactive, though I’d never pump salt water through an engines cooling jackets, but it is done. So if this boat uses an open cooling system I’d use an iron head as they are much less sensitive in power output to the cooling medium‘s temperature being under 200 degrees. Running iron cooler enhances its anti-detonation properties yet the power drop is not as severe as when running aluminum this cool because the iron does not transfer combustion chamber heat near so fast as aluminum so more heat is used to increase pressure on the piston than warm the surrounding coolant.

I would not consider a GM production L31, Vortec head. The GMPP competition versions ( Bow Tie Small Port Cast Iron Vortec Bare Cylinder Head, 185cc Intake Ports or Small-Port Vortec Bowtie Cylinder Head Assembly) would be on the table along with aftermarket iron versions of their heart shaped chamber heads because these castings are more robust than the production head that was used on trucks back when and is available on crate motors and is the bottom cost version of SBC Vortec sold by GMPP. The production derived head is a thin casting that is crack prone when worked hard and due to the thin casting will transfer chamber heat to the coolant much quicker, so if your using the surrounding water for direct cooling, as with aluminum this is a thermal step in the wrong direction.

Bogie
 

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what curtis andbogies said are very good points.
fresh water only then use aluminum heads or if cooling system is closed.
I would use a solid roller cam with specs like they use in the LS 427.
LSA at 115º or more. 204-210º duration. .58 valve lift with 190-195 cc Profiler heads.
750 cfm on an rpm intake (850 if the air cleaner system is restrictive)
headers with 1 5/8s long tubes.
if you cannot use a header then you will need a little more exhaust timing
9.5:1 to a max of 10:1 CR
steel crank/quality rods, super precision balance
 

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You went from 170cc Vortec to 210 cc un-named aluminum.....you killed velocity, no wonder it is a turd.

210cc head on 383 is still a 7000+ rpm head, and you don't get anywhere close to peak power rpm, you are barely getting above the peak torque rpm which is going to be somewhere around 4200 rpm.

If you want an aluminum head, I'd be in the 180-185cc range.
ProMaxx Maxx 183cc would be a good fit on a budget.
Flo-Tek has a 180cc in the same price range but doesn't flow as good.

Want the best, ProFiler 185cc or AFR 180cc
 

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Boats are a tough one. You pretty much have to get speed with displacement, not cam/flow. If you shift the torque peak to above planing RPM, it will be an absolute dog. I've seen guys take their freshly-built twin-454 26-foot baja out for it's initial run and it won't even plane because they went too hot with cam and flow.

You absolutely MUST have a torque peak that is at or below planing RPM or you'll lug the engine which can superheat pistons, cause inaudible (or audible) detonation, and generally a big no-no.

Regarding reversion, I'm glad you haven't had any... yet. The exhaust flow has harmonics just like intakes. When you have big overlap you are not only creating micro pulses where it's pulling water backwards, at or near peak VE you are making huge secondary harmonics that double that effect. If you suddenly pull a half teaspoon of water back and it touches a valve seat or the valve, you can likely kiss the head goodbye, or at the very least have to rebuild the head and replace valves. I'm not going to beat a dead horse, but IMO, it's too much cam for a 383 in a wet exhaust and it's begging for a big-money repair sooner rather than later.

I have nothing against aluminum heads in a boat application. I don't even worry about open cooling in fresh water with aluminum heads. It's just the ones you've chosen are killing low and midrange torque.

You also have to remember that in your boat, doubling the hp will only get you about 10-15 mph more top speed. So going from what you have now (let's say 350hp) and swapping to Vortec heads (now 325hp), you're only giving up 2-3 mph, but you can actually USE the boat.

The difference in weight is negligible in a 2100-lb boat. Use a lighter anchor and a smaller battery and you're back to fighting weight.
 

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My go-to recipe (on a 350 anyway) for heavier I/O boats is Vortec heads with flat-tops (9.5:1 which can easily run 87 octane), and a Melling 22124 for flat-tappet (203/214 - 110 LSA) or a Melling 22135 for roller (206/214 - 112 LSA). The flat tappet will make a good solid 280-290 and the roller will make a good 315 hp with no reversion.

For an I/O, getting 1hp/ci and having it still have any holeshot takes very careful parts selection and a pretty light boat. 0.85 hp/ci I would think is a valid target for a 17' I/O depending on weight and deadrise.
 

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Put it this way... if you can "hear" that it has a cam, you're risking reversion. Period.

In a car if you shift the torque peak higher you can always change gearing, stall speed, or make it lighter. You don't have that option in a boat. You get one gear, one prop, and your weight is relatively fixed. You absolutely cannot apply traditional street hp/tq techniques to a boat or you'll be disappointed like you are right now.
 

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Discussion Starter · #14 ·
You went from 170cc Vortec to 210 cc un-named aluminum.....you killed velocity, no wonder it is a turd.

210cc head on 383 is still a 7000+ rpm head, and you don't get anywhere close to peak power rpm, you are barely getting above the peak torque rpm which is going to be somewhere around 4200 rpm.

If you want an aluminum head, I'd be in the 180-185cc range.
ProMaxx Maxx 183cc would be a good fit on a budget.
Flo-Tek has a 180cc in the same price range but doesn't flow as good.

Want the best, ProFiler 185cc or AFR 180cc
How about Edelbrock 5089.?
 

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I have a simular situation, I just bought a 1997 20 ft Muriah boat, 350/Alpha 1, gen 2. The previous owner did not winterize it properly and it has cracked block and one cracked head (casting 217). I have a rebuilt .030 vortec 1pc rear seal block with pm rods and flat top 345np pistons, I also have a set of 193 casting truck tbi heads (swirl port), Would this be a good head with a vortec stock truck roller cam for power from idle to 4200 rpm. Any suggestions from you boat guys, Just want a pleasure cruiser, not a race boat. Budget is a concern here....
 

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The Swirl Port head is just about ideal for what your doing. They emphasis power from idle to 4000 RPM. Given the port has the restrictive swirl vane they are more sensitive to duration increase changes than increased lift. The chamber on the 193 head is 64 cc and it is more the similar to the L31 Vortec than not, the only thing missing is the beak extending between the valves from the squish/quench step. This chamber is identical to the L98 head of the same era used on the Corvette and Z28 option engines but in cast iron instead of aluminum. There is a cast iron version of the L98 head that Mercruiser used on their 350 marine engine it is the same head configurationally but carries a different casting number as the 193 but is cast without the swirl vane in the port pocket. You can find them on Ebay but like all marine parts are pricey for what they are.

The aftermarket makes a lot of iron head’s that are identically configured as their much more costly aluminum heads, this is worthwhile checking out if you haven't already spent your money. These tend to be more robust castings than comparable GM production head’s.

Wish you guys would ask questions here before shredding your wallet on parts.

Bogie
 

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and it had valve leak
Your engine build should be about perfect... I suspect leaking valves and/or misadjusted valve lash is possibly your problem...
Do a compression test on all 8 cylinders and then get back to us...
Your little boat should jump up onto a plane in its own length with that engine!
My boat does that and it's a bigger boat with a smaller engine! Similar sized cam...
What is your 23 pitch prop? 14 1/2" diameter stainless steel or 16" diameter aluminum?
Also, your carb. is kinda too small for that engine and the secondaries are prolly, thus, opening at too low an RPMS! Giving a bog when trying to get on plane... But that is adjustable via different secondaries springs... I use a 750 CFM marine Holley... looks just like a 600 marine Holley as it's single feed... can prolly find one on a 351W engine in a ski boat in the boat junkyard...
You should have about #70 - 74 primaries jets...
BTW, here's a video of how a smaller SBC 355" runs with 210cc Asian heads:
 

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flat top 345np pistons, I also have a set of 193 casting truck tbi heads (swirl port),
The 345 pistons have shorter compression height than claimed and sit low in the cylinders, hurting engine quench effects. Some D-dish pistons of stock compression height would be better. I'd use the Vortec heads and a ZZ3-ZZ5 roller cam. Let your throttle arm decide how much power/speed you want.
 

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Discussion Starter · #20 ·
Flow chart is pretty much the same as the Flo-Tek
Your engine build should be about perfect... I suspect leaking valves and/or misadjusted valve lash is possibly your problem...
Do a compression test on all 8 cylinders and then get back to us...
Your little boat should jump up onto a plane in its own length with that engine!
My boat does that and it's a bigger boat with a smaller engine! Similar sized cam...
What is your 23 pitch prop? 14 1/2" diameter stainless steel or 16" diameter aluminum?
Also, your carb. is kinda too small for that engine and the secondaries are prolly, thus, opening at too low an RPMS! Giving a bog when trying to get on plane... But that is adjustable via different secondaries springs... I use a 750 CFM marine Holley... looks just like a 600 marine Holley as it's single feed... can prolly find one on a 351W engine in a ski boat in the boat junkyard...
You should have about #70 - 74 primaries jets...
BTW, here's a video of how a smaller SBC 355" runs with 210cc Asian heads:
I will do compression by this weekend. short story last three week took exhaust manifold out to change gasket .I look inside exhaust cylinder I saw my exhaust valve like dart black build up i know something go wrong with my engine I start remove cylinder head out also intake valve have dart black build up too. I do test like dump water inside intake runner and blow air at intake valve at compression champers I saw air leak in to water almost intake and exhaust valve leak .I bring to machine shop they cost me 350$ to re work on cylinder head and I am not do it I took cylinder head home clean it up and install back to engine with new gasket .engine idle good ,but I fell I did not get all power from 383 . I think some thing go wrong to my cylinder head , that why I come here to ask for help before I order new aluminum cylinder head .Thanks for reading sorry for my writing English.
 
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