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Sending 8.1 heads to the shop.
I have a stock 8.1L Volvo Penta turning a jackshaft connected to a VP DP-E drive on a Carolina Classic 25 (think heavy boat for its size; 8500 pounds). I'm not looking to race the thing but would like to see if I can squeeze some power from the heads when I sent to the machine shop to refresh. Anything I should consider? SSmarine exhaust manifolds and risers will be used to fix the water reversion problem that caused the 2 center valves and ports to get eaten away. The manifolds will be part of the FWC this time. Still good compressions on all holes.
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Which 8.1? GI or GXi?
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Gi-BF
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Originally Posted by lmannyr
(Post 4927062)
I the 2 center valves and ports to get eaten away.
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Originally Posted by BillK
(Post 4927296)
Without a picture its hard to say but if the ports actually did get "eaten away" I think I would look for a replacement set of heads. Your machine shop should be able to tell you for sure. Those heads shouldnt be too hard to find used. Plenty of them in Chevy trucks. Dart had a cast iron version but I dont think they are available.
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Wow,
Those are junk. I would not waste a second on them. I have done a lot of marine heads and I dont think I have ever seen anything that bad :( :( The bare heads are still available new from GM Not sure why but the right hand one is almost 3 times as much as the LH one RH 12581476 LH 12581477 |
looks like the acid water destroyed them
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I’m glad I posted here. I was actually contemplating installing the new SS Marine set on them. Thanks for the advise.
Do machine shops have remans on the shelf? I’ll want the bronze guides installed as well. I’m assuming I’ll need new head bolts. Any suggestions on brand for a stock application? I’ll grab new intake and head gaskets as well. The exhaust manifolds will come with their own. |
Originally Posted by lmannyr
(Post 4927307)
Do machine shops have remans on the shelf? I’ll want the bronze guides installed as well..
I dont know where you are located but I would try and find a machine shop that is familiar with Marine or Performance heads. They are not that different but just need to be set up right. If you are going to try and get a set of remans then see if you can find a marine dealer that has them. Stock head bolts are fine. Either from GM or Fel Pro if they have them. Fel Pro marine gaskets have always worked fine for me but you really dont even need them because those engines are fresh water cooled so the stock truck gaskets are fine. Thats all that came on them from Volvo. |
As far as I’m aware, Ther are no guides in the 8.1 stock heads. It’s just the reamed out steel and valve. No guides. Not that the manifolds will be switch to also be FWC withe the new set, it should be ok, but would like the extra protection of added corrosion resistant guides.
I’m in no rush. I’ll search online for new GM and then used. What is a fair price for a used set? Car-parts has plenty for about $200 a side. I would send it to the machine shop to be refreshed of coarse. |
Originally Posted by lmannyr
(Post 4927311)
As far as I’m aware, There are no guides in the 8.1 stock heads. It’s just the reamed out steel and valve. .
If you think about it paying $200 for a used head makes no sense if you can get a new one for $350 Its probably going to cost you at least $600 plus parts to refresh a set of used heads. If you buy new all they will have to do is clean and reface your valves if they are ok and check everything else on the new heads and put them together. Depending on how many hours yours have it would probably be a good idea to put new springs on them. It seems like every single time one of my customers buys a used head or other engine parts they regret it in the end. Usually costs as much to fix the old junk than to buy new. |
Originally Posted by BillK
(Post 4927313)
That is how every cast iron GM head in the world is :) They work just fine. How long have yours lasted ? I did a Mercruiser 8.1 about a year ago that had almost 1300 hours on it !!!! Had never been touched and the guides were still fine. Depending on the application a lot of times the factory setup is a lot better than people think. No need to rethink it.
If you think about it paying $200 for a used head makes no sense if you can get a new one for $350 Its probably going to cost you at least $600 plus parts to refresh a set of used heads. If you buy new all they will have to do is clean and reface your valves if they are ok and check everything else on the new heads and put them together. Depending on how many hours yours have it would probably be a good idea to put new springs on them. It seems like every single time one of my customers buys a used head or other engine parts they regret it in the end. Usually costs as much to fix the old junk than to buy new. $350 for new? Where? Have a link? At that price, I would prefer to get new. Is this bare or all the valves, springs etc..? 1300 marine hours on a no guide head? Nice! Thats great. Doesn't sound like a really need the guides then....especially with FULL FWC system. |
Head Casting is the same on both sides? 12558162 One head has F202 the other has F282. Would think the longer number would be different for left and right.
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New Bare GM heads on order. Ordered no valve stem seals, valve cover bolt grommets (many were ripped), Head bolts, head gasket, intake gasket.
Currently stripping the valve cover, and cross over pipe for prime and repainting. Cleaning up the engine bay as much as possible with only the block in the way now. Injector baskets on order, cleaning fuel rail. New "Paintless" fuel cell on order. I plan to reuse the same valves, springs, retainers, keepers and move over to the new head myself. Anything I should be careful about this process? I'm more concerned with proper seal of the valves. I'll clean up the valves with a scotch brite and carb cleaner. |
Originally Posted by lmannyr
(Post 4927444)
I plan to reuse the same valves, springs, retainers, keepers and move over to the new head myself. Anything I should be careful about this process? I'm more concerned with proper seal of the valves. I'll clean up the valves with a scotch brite and carb cleaner. |
Maybe 500 hours on engine.
Whats the best way to clean the intake manifold and the the block gasket surfaces? Will take the heads to the shop and have them reface/replace valves and springs as necessary. I’ll have them replace the keepers as well. I appreciate the help. Should I remove the old valves and take them in or have them do it. I like doing as much as I can my self. I enjoy tinkering and working with my hands. I don’t mind saving a few bucks while doing some work myself. |
8.1L Marine application.
After soaking in diesel, chucking in a drilling wiping with a Terry cloth. Thoughts on these valves? Whats the cause of the pitting? The back sides are all nice and smooth on both intake and exhaust valves. The pitting is only on some the intake valves. One in particular has some chips on the edge. I'm assuming the pitted valves need replacement. Since its at least 4 of 8 intake valves, the plan would be to replace all the intake valves. Thoughts? https://cimg9.ibsrv.net/gimg/www.off...3f7538aae.jpeg https://cimg1.ibsrv.net/gimg/www.off...eff905eaf.jpeg https://cimg2.ibsrv.net/gimg/www.off...e49e3fe99.jpeg https://cimg3.ibsrv.net/gimg/www.off...8b2e99412.jpeg https://cimg4.ibsrv.net/gimg/www.off...bb527c2e8.jpeg https://cimg5.ibsrv.net/gimg/www.off...f94d847d0.jpeg https://cimg6.ibsrv.net/gimg/www.off...777dd32bb.jpeg https://cimg8.ibsrv.net/gimg/www.off...337d55f96.jpeg https://cimg9.ibsrv.net/gimg/www.off...69d91d92d.jpeg https://cimg0.ibsrv.net/gimg/www.off...c8fac0fe5.jpeg https://cimg1.ibsrv.net/gimg/www.off...bdc98b093.jpeg |
Holy cow, that's a lot of pitting... I also noticed in the pictures of the block, there is quite a lot of pitting on the deck surface... you might want to remove the head gaskets and see if that pitting is under that surface as well.. If it is, you might have to pull the block and get it decked... This almost looks like it sat full of water for a long time...
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Dropped off the new heads, old valves/springs, seats, retainers, etc… to the machine shop today. They will call me when the valves are cleaned up and we. An go from there.
the block deck is good. It had not been cleaned yet. Started on cleaning the old gasket with CRC gasket cleaner. Comer right off. Tedious but it works well. Trying to be careful not to let debrie fall into the water jackets and oil holes. Cleaning the pistons in place as well. |
I'm no expert in engines but.... cleaned off the block deck in preparation for the heads, then decided to also clean up the pistons.... The pictures speak for themselves. Looks to me some detonation. This is in a 25' Carolina Classic, so not trying to break any speed records. Usually I'm cruising at about 35-40mph at about 3300 RPM area. (can't remember....it's been about a year). Thoughts on replacement pistons? Pulling block out and will disassemble and send to the machine shop. Would be nice to get a bit more power out of it. The Volvo DP-E drive has a 425HP limit though. Not looking for more than that.
This is the NON HO 8.1L from Volvo Penta. Rated at 375HP. https://cimg4.ibsrv.net/gimg/www.off...3ff044b1b.jpeg https://cimg5.ibsrv.net/gimg/www.off...7268ade47.jpeg https://cimg6.ibsrv.net/gimg/www.off...ccf34a857.jpeg https://cimg7.ibsrv.net/gimg/www.off...c852f72c5.jpeg https://cimg8.ibsrv.net/gimg/www.off...9ce2c7a87.jpeg https://cimg9.ibsrv.net/gimg/www.off...bed2639db.jpeg https://cimg0.ibsrv.net/gimg/www.off...2c378fcf4.jpeg https://cimg1.ibsrv.net/gimg/www.off...a8caaa7ba.jpeg https://cimg2.ibsrv.net/gimg/www.off...f911f9e09.jpeg https://cimg3.ibsrv.net/gimg/www.off...ed862d058.jpeg |
Yikes... you may want to think about getting a price to bore over your block while replacing pistons... looks to me like there's also some pitting in the cylinder wall in your 8th picture.. maybe it's an illusion.. but going thru the hassle of replacing pistons and rings is a lot of work.. is be inclined to at least have the shop take some measurements of the bores, and crank journals and see if everything looks usable.. just my .02
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Originally Posted by ashipshow
(Post 4928067)
Yikes... you may want to think about getting a price to bore over your block while replacing pistons... looks to me like there's also some pitting in the cylinder wall in your 8th picture.. maybe it's an illusion.. but going thru the hassle of replacing pistons and rings is a lot of work.. is be inclined to at least have the shop take some measurements of the bores, and crank journals and see if everything looks usable.. just my .02
After disassembly, the block will go to the shop and have them do their thing. I'll wait for them to see what they say before ordering anything. This is all just incidental findings. From the corroded exhaust ports to now this. All I planned to do was upgrade from the stock manifolds to aftermarket to end reversion. Looks like reversion did the damage long long ago with a previous owner and I'm now finding all this now. Glad I'm seeing this now vs having it break apart while running. |
Originally Posted by lmannyr
(Post 4928068)
Yup...
After disassembly, the block will go to the shop and have them do their thing. I'll wait for them to see what they say before ordering anything. This is all just incidental findings. From the corroded exhaust ports to now this. All I planned to do was upgrade from the stock manifolds to aftermarket to end reversion. Looks like reversion did the damage long long ago with a previous owner and I'm now finding all this now. Glad I'm seeing this now vs having it break apart while running. https://cimg3.ibsrv.net/gimg/www.off...02006a8fe.jpeg not sure if you're interested, but keeping in the back of your head I do have a brand new block never been used. It's been all machined ready to go. I've had as spare that I've never used. |
To answer your questions on pistons, Wiseco has forged pistons specifically for the 8.1 in various sizes. I've used several sets, they run good. (part #s PTS524AS, PTS524A3) These pistons use a traditional piston pin size of .990 like earlier big blocks, so you'd need to replace the rods with 6.7" big block chevrolet aftermarket rods when you do that. There's lots on the market for 6.7" rods. (example Scat 2-ICR6700-7/16)
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The valves should be changed out. The pitting will increase they're operating temps.
The piston pitting is classic water corrosion/erosion. Guides: for the most part, the best wear resistant guides are cast iron. Pressed in iron guides may be a better iron for guide wear vs the head iron. Alternatives are bronze liners or full bronze guides. Liners are cheap, and can last a long time if setup correctly. Less valve to guide clearance is better for wear, but the valve also need to be setup correctly. Chrome valve stems etc. Guides need to be sized correctly and straight. Broached to size is not sufficient. They need to be honed. |
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