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C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Marine Cam & Heads

 
Old 05-06-2019, 01:26 PM
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bpan
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Default Marine Cam & Heads

Hi guys, I have been browsing these forums for a little while, but this is my first post. I have a new to me 1990 C4, with the L98. I am looking at some performance modifications. I have headers, full exhaust, K&N filter etc. I have some questions regarding cylinder heads and camshafts.
I have a set of repellent condition marine heads with the casting number 059 stamped. From my understanding these are Vortec style heads, that should flow pretty well, maybe not as good as the 062 Vortecs. I also have the camshaft from this motor. The reason I am trying to use all of this, is because the parts were free. My question is has anyone had experience, or what are your thoughts on this. The only specs I can find on the camshaft, is below.

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Old 05-06-2019, 02:31 PM
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Being 305 parts not worth the trouble. You have better parts already. Trade or sell the marine for something you can use.
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Old 05-06-2019, 03:30 PM
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I wanted to add, here is the camshaft. I'm having a hard time pulling up the full specs anywhere online though.
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Old 05-06-2019, 03:35 PM
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Mercruiser dealer may help. Marine engines come in both clockwise and counter clockwise rotation. You need to know what it's for.
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Old 05-06-2019, 03:37 PM
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Here are also some flow numbers on the heads. It appears the 059 has a smaller intake valve, but the numbers seem to flow better?




I got these numbers from this site.
http://users.erols.com/srweiss/tablehdc.htm#Chevy
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Old 05-06-2019, 03:39 PM
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Originally Posted by Kevova View Post
Mercruiser dealer may help. Marine engines come in both clockwise and counter clockwise rotation. You need to know what it's for.
Thanks for the help Kevova, I actually work at a marine dealership, the parts came from a boat with a frozen block. The motor is a clockwise rotation.
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Old 05-06-2019, 03:40 PM
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Only Direct drive inboards had reverse rotation. All Stearn drive use regular rotation.

I see a few problems with this plan:
1. IF those are Vortec heads, they'll be iron, so heavier.
2. You'll also need a Vortec specific lower intake manifold which will run you $4-500. So "Free" goes away, there.
3. If those are head for a 305, they're smaller combustion chamber and may be too high compression ratio for your car/combo.
4. That cam looks pretty lame.

If it were ME, and I were on a 'free' budget, I'd hand port my stock '90 heads and throw a used cam and/or rockers at it.
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Old 05-06-2019, 03:56 PM
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Originally Posted by Tom400CFI View Post
Only Direct drive inboards had reverse rotation. All Stearn drive use regular rotation.

I see a few problems with this plan:
1. IF those are Vortec heads, they'll be iron, so heavier. - Yes, I am aware of this, but any aluminum performance heads are big $$, even if I bought new heads, they would most likely be iron.
2. You'll also need a Vortec specific lower intake manifold which will run you $4-500. So "Free" goes away, there. - Yes I am aware of this as well, I was figuring on if this worked it would still be considerably less than a set of performance heads.
3. If those are head for a 305, they're smaller combustion chamber and may be too high compression ratio for your car/combo. Thank you, this is exactly the type of information I'm looking for.
4. That cam looks pretty lame. Again, good information, thank you!

If it were ME, and I were on a 'free' budget, I'd hand port my stock '90 heads and throw a used cam and/or rockers at it. I gave up most machine/fab work a long time ago. Mechanical sure, but I'm not good enough at this type of work to justify doing it myself.
Thanks for your input. My thoughts are above.
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Old 05-06-2019, 04:25 PM
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Originally Posted by Tom400CFI View Post
Only Direct drive inboards had reverse rotation. All Stearn drive use regular rotation.

I see a few problems with this plan:
1. IF those are Vortec heads, they'll be iron, so heavier.
2. You'll also need a Vortec specific lower intake manifold which will run you $4-500. So "Free" goes away, there.
3. If those are head for a 305, they're smaller combustion chamber and may be too high compression ratio for your car/combo.
4. That cam looks pretty lame.

If it were ME, and I were on a 'free' budget, I'd hand port my stock '90 heads and throw a used cam and/or rockers at it.
So you seem to know what your talking about here. If you had to do a set of heads, and camshaft, without doing any DIY porting, what would you suggest I go with?
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Old 05-06-2019, 04:45 PM
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Tom400CFI
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I guess I'd look for used heads.

I guess I'd consider 350/L31 Vortec heads....but adding weight and then paying for a new lower? I don't think that I could convince myself to move on that.

I don't know where your priorities fall, but you could get some 350 Vortec heads cheap (you can get them at pick 'n pull yards here for about $35/head) and then double stack intake gaskets, keep your lower and get 15-20hp for less than $100 bux. I guess that would be a thing I could maybe talk myself into...since the investment is so low.

Cam? I'd search the classifieds for a used roller cam of about the right size. For ME, on a stock TPI that would be in the 2-teens duration.
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Old 05-06-2019, 11:24 PM
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Originally Posted by Tom400CFI View Post
Only Direct drive inboards had reverse rotation. All Stearn drive use regular rotation.

I see a few problems with this plan:
1. IF those are Vortec heads, they'll be iron, so heavier.
2. You'll also need a Vortec specific lower intake manifold which will run you $4-500. So "Free" goes away, there.
3. If those are head for a 305, they're smaller combustion chamber and may be too high compression ratio for your car/combo.
4. That cam looks pretty lame.

If it were ME, and I were on a 'free' budget, I'd hand port my stock '90 heads and throw a used cam and/or rockers at it.
So there are infact reverse rotation sterndrives... seen them myself actually. They're pretty much gone now but they did exist. So yes, a non issue.

Anyway, everything you said
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Old 05-06-2019, 11:31 PM
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Tom400CFI
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Huh. I learned a thing. Who brought that out? OMC?
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Old 05-07-2019, 02:29 PM
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84 4+3
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Originally Posted by Tom400CFI View Post
Huh. I learned a thing. Who brought that out? OMC?
They all did actually. Merc might have only used it with the blackhawk iirc which was a sterndrive but used a standard inboard gearcase for shifting.
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Old 05-08-2019, 01:19 PM
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Thank you all for the help, from the sounds of it I have a bunch of large paperweights. I will definitely look into other options for these areas.
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Old 05-08-2019, 02:35 PM
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Porting what you have is a good idea, they arent horrible.
Factory castings leavea lot to be desired so most anything will pick them up lol!
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Old 05-10-2019, 11:25 AM
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Originally Posted by Tom400CFI View Post
Only Direct drive inboards had reverse rotation. All Stearn drive use regular rotation.

I see a few problems with this plan:
1. IF those are Vortec heads, they'll be iron, so heavier.
2. You'll also need a Vortec specific lower intake manifold which will run you $4-500. So "Free" goes away, there.
3. If those are head for a 305, they're smaller combustion chamber and may be too high compression ratio for your car/combo.
4. That cam looks pretty lame.

If it were ME, and I were on a 'free' budget, I'd hand port my stock '90 heads and throw a used cam and/or rockers at it.
305 heads also have smaller valves that are needed to clear the smaller bore. I wouldn't bother with them.

That cam sheet is worthless imho, it doesnt list duration, overlap (which it wont have any because it's a marine cam) or valve timing. Save your money for better parts.
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Old 05-11-2019, 02:05 PM
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Originally Posted by 64Scout View Post
305 heads also have smaller valves that are needed to clear the smaller bore. I wouldn't bother with them.

That cam sheet is worthless imho, it doesnt list duration, overlap (which it wont have any because it's a marine cam) or valve timing. Save your money for better parts.
Thanks for the help, I am definitely looking into other options. I found these which look to be pretty promising at a pretty solid price.

https://www.flotekheads.com/store/Sm...4cc-p130678684
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Old 05-11-2019, 02:51 PM
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vortec heads have a lower limit for valve lift. The heads are a 8 bolt to manifold versus the regular chevy bolt pattern. Vortec heads have a center bolt valve cover.
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Old 05-11-2019, 08:15 PM
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cuisinartvette
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Limitmed by the guide. with someone who knows they can be picked up big time with a little :wink

Last edited by cuisinartvette; 05-11-2019 at 08:16 PM.
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Old 05-11-2019, 09:09 PM
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Originally Posted by cuisinartvette View Post
Limitmed by the guide. with someone who knows they can be picked up big time with a little :wink
Yea. They still are low lift flow heads though. Swapping to shorter retainers and locks will get you some as well. Cutting the guides will get you in the .55 range.
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