Performance Boats Forum banner

1 - 20 of 25 Posts

·
Registered
Joined
·
1,001 Posts
Discussion Starter #1
Okay I'm no professional like several of you guys. I'm just a garage hack and build my own motors. I was not aware that the guides needed sized different for marine use, and I'm not suggesting that they don't need special clearances. However, given the number of engines I have built over the years, without any guide failures, leaves me wondering why they need special sizing, or why I haven't had any guide issues? My latest build (http://www.performanceboats.com/dyno/58837-dyno-results.html) used AFR heads but my head guy supplied the valves and springs. Since the new motor currently has less than an hour of run time, off the dyno, do I need to pull the heads to check the guides?
 

·
steelcomp was here
Joined
·
26,516 Posts
[HR][/HR]
Okay I'm no professional like several of you guys. I'm just a garage hack and build my own motors. I was not aware that the guides needed sized different for marine use, and I'm not suggesting that they don't need special clearances. However, given the number of engines I have built over the years, without any guide failures, leaves me wondering why they need special sizing, or why I haven't had any guide issues? My latest build (http://www.performanceboats.com/dyno/58837-dyno-results.html) used AFR heads but my head guy supplied the valves and springs. Since the new motor currently has less than an hour of run time, off the dyno, do I need to pull the heads to check the guides?
AFR specifically says in their tech sheet (included with the heads) that their guides are on the tight side and for blown/Nos or marine use, they advise more guide clearance.
Last year I had to do a complete rebuild on a set of AFR 325 heads for a customer who had someone else build the heads, supplied the ex valves, and didn't check the guide clearances. There were clear signs of the ex valves running hot and dragging in the guides. Fortunately (his was a centrifugal blown engine) he hadn't really stuck his foot in it yet, because from what I was seeing on the ex valve stems, he was one hot-foot run from sticking an ex valve. I tell you this in detail to let you know your engine can be running, but you could still be risking sticking a valve which we all know can be catastrophic. Also note: the valves AFR uses are a few tenths smaller than, say, a REV or a Ferrea, so when you stick an aftermarket valve in the head, like this last case scenario I explained, you end up with even less clearance than what AFR is already telling you is minimum.
As far as other heads, most have generous enough clearance that it's not an issue, but for me, it's always a good idea to check.
HTH
 

·
Registered
Joined
·
383 Posts
pistons need more clearance in marine motors because the block never gets hot enough to expand to size, valve stems only care about guide material & fuel, ex valves that don't have enough clearance stick pretty quick, intake valves need to be on the tight side to keep oil out of the combustion chamber. valve stem seals are suppose to be a controlled oil leak. ski boat motors valve guide seals should be a pc on the intake & umbrella seal on the ex.
 

·
Registered
Joined
·
1,544 Posts
pistons need more clearance in marine motors because the block never gets hot enough to expand to size, valve stems only care about guide material & fuel, ex valves that don't have enough clearance stick pretty quick, intake valves need to be on the tight side to keep oil out of the combustion chamber. valve stem seals are suppose to be a controlled oil leak. ski boat motors valve guide seals should be a pc on the intake & umbrella seal on the ex.
Wow....... Some smart mofo's on this site.......:D keep the info coming!!!!!
 

·
steelcomp was here
Joined
·
26,516 Posts
pistons need more clearance in marine motors because the block never gets hot enough to expand to size, valve stems only care about guide material & fuel, ex valves that don't have enough clearance stick pretty quick, intake valves need to be on the tight side to keep oil out of the combustion chamber. valve stem seals are suppose to be a controlled oil leak. ski boat motors valve guide seals should be a pc on the intake & umbrella seal on the ex.
Guide expansion is effected the same as cylinder wall expansion. Cold water in the heads will lessen ex guide expansion especially, and increased egt's in marine engines can exaggerate the condition.
 

·
Gone in a Flash!
Joined
·
221 Posts
What valve stem to guide clearance is considered to be "marine spec" for your typical lake ski BBC motor. More Specific, Aluminum heads with bronze guides and Inconel valves? (Darts/Brodix):idea: Does the spec change when we start talking about "GM iron" 990's, 781's?

I'm just a DIY garage hack that builds his own motors for fun and education too. This forum gets read by me every morning over coffee and is chalked full of great info.:)coffee There are a lot of astute individuals that post here and much can be learned if one pays attention.:)hammers Thanks for all the replies and good posts!:D
 

·
Premium Member
Joined
·
25,975 Posts
Ashumtoy, couple of reasons you may not have had any problems is, one your lucky. But as much as anything, it could be the way you drive the boat. Not to say you don't hammer the sumbitch. But you do it after its good and warm.

When water cooled 2 stroke bikes first came out, they had a bad problem with sticking the piston big time. What was happening was that the rider would "warm" up the bike, and them hammer it. Well the water wasn't warm, and really, neither was the cylinder. But when it got hammered, the piston would go to temp in a heart beat and the thing would stick. An exhaust valve and guide isn't a whole lot different.
The whole engine has a much better chance of surviving less than ideal clearances if the thing is fully warmed up before the fuel is layed to it.

Your heads may have simply been looser without you knowing it. Steelcomp had an issue with loose guides from Patriot heads, even after returning them.
Also, long overlap cams and high compression helps alittle. Low compression and short overlaps tend to create more exhaust heat combined with less intake cooling during the overlap event. Also, even though the guide doesn't expand as much in a lake cooled engine, a huge part of the exhaust valve's heat is rejected thru the seat and the stem. Both are much cooler in a marine engine. Even though a marine engine generates alot more combustion heat due to load, the exhaust valve is able to reject much more heat due to the cooler seat and guide.

Bottom line, all marine engine should have the guides set accordingly, but blower and NOS marine engines seem to be much more problematic than N/A deals. JMO.

I try not to worry too much about this crap and just let Steel handle it. That way if I stick a valve, I know whos ass needs whooping.:wink2:



100% free webcam site! | Awesome chicks and it is absolutely free! | Watch free live sex cam - easy as 1-2-3
 

·
Registered
Joined
·
383 Posts
the really fun guides to size are my buddy's 383 that he drives daily & run at the brackets, icing the intake between rounds.
 

·
Registered
Joined
·
1,001 Posts
Discussion Starter #9 (Edited)
Okay, you've convinced me. I'll make the 260 mile trip to Havasu and pull the heads to check the clearances. What should the clearances be?
 

·
steelcomp was here
Joined
·
26,516 Posts
Okay, you've convinced me. I'll make the 260 mile trip to Havasu and pull the heads to check the clearances. What should the clearances be?
Int. should run about 0013-.0015, exhaust .0016 -.0018 and I'll "allow" as much as .0020 on big power adder stuff. Like to try to keep it about .0018.
 

·
Registered
Joined
·
166 Posts
Int. should run about 0013-.0015, exhaust .0016 -.0018 and I'll "allow" as much as .0020 on big power adder stuff. Like to try to keep it about .0018.
Will these clearances work for both cast iron and aluminum heads? I have 049 irons that need to be sized for marine use. I will be running e85 if that makes a difference.
 

·
steelcomp was here
Joined
·
26,516 Posts
Will these clearances work for both cast iron and aluminum heads? I have 049 irons that need to be sized for marine use. I will be running e85 if that makes a difference.
IMO, yes.
 

·
Registered
Joined
·
123 Posts
I bought a set of assembled heads from afr (bbc 325's) and told them i was running marine with a blower. After reading a few threads on here I took them to Tim at Morgans Machine since he is right down the street from me. He said the guides were way too tight and probably wouldn't have lasted long on my application. So again thanks to the guys here on performance boats for the the helpfull advice. So i would also recommend having the heads checked out by a professional.
 

·
Premium Member
Joined
·
25,975 Posts
I bought a set of assembled heads from afr (bbc 325's) and told them i was running marine with a blower. After reading a few threads on here I took them to Tim at Morgans Machine since he is right down the street from me. He said the guides were way too tight and probably wouldn't have lasted long on my application. So again thanks to the guys here on performance boats for the the helpfull advice. So i would also recommend having the heads checked out by a professional.
I may take some smack for this, but if you want to buy a set of ready to bolt on AFRs, the best place to get them is thru Teague. He gets them bare, does all prep, and final machining, uses manely Severe intakes, Extreme exhausts, and Isky springs and retainers, and they are only slightly more than getting them from Summit, Jegs or AFR.

HOWEVER...if Steel is up and running yet, getting AFRs thru Cstraub is another excellent place as well. Well Scott, are you doing heads yet???? Are you sitting up Canfields yet?



100% free webcam site! | Awesome chicks and it is absolutely free! | Watch free live sex cam - easy as 1-2-3
 

·
steelcomp was here
Joined
·
26,516 Posts
I may take some smack for this, but if you want to buy a set of ready to bolt on AFRs, the best place to get them is thru Teague. He gets them bare, does all prep, and final machining, uses manely Severe intakes, Extreme exhausts, and Isky springs and retainers, and they are only slightly more than getting them from Summit, Jegs or AFR.

HOWEVER...if Steel is up and running yet, getting AFRs thru Cstraub is another excellent place as well. Well Scott, are you doing heads yet???? Are you sitting up Canfields yet?
Hey Bob, yes I am, thanks for asking. Just sold a set of Canfields last week and probably valve jobbed over a dozen sets of heads in the last few weeks. I have a customer's set of AFR's here and another set on the way, and three engines to do.
 

·
Registered
Joined
·
123 Posts
I may take some smack for this, but if you want to buy a set of ready to bolt on AFRs, the best place to get them is thru Teague. He gets them bare, does all prep, and final machining, uses manely Severe intakes, Extreme exhausts, and Isky springs and retainers, and they are only slightly more than getting them from Summit, Jegs or AFR.

HOWEVER...if Steel is up and running yet, getting AFRs thru Cstraub is another excellent place as well. Well Scott, are you doing heads yet???? Are you sitting up Canfields yet?
If i was to do it all over again, definitely would have gone that route. Whish i would have found this forum a little sooner. Trying to get my pops to upgrade the heads on the hallet, and if he does will deffinetly got through steelcomp.
 

·
Strap on the JATO
Joined
·
305 Posts
I bought a set of assembled heads from afr (bbc 325's) and told them i was running marine with a blower. After reading a few threads on here I took them to Tim at Morgans Machine since he is right down the street from me. He said the guides were way too tight and probably wouldn't have lasted long on my application. So again thanks to the guys here on performance boats for the the helpfull advice. So i would also recommend having the heads checked out by a professional.
I've been hammering my junk for 3years & Tim did the same w/ my 990's. They're all too tight
usually if not machined for a marine config. Good info here...Like always!! Ol' Tim Morgan does
some good work!!
 

·
Living in a cage of fear
Joined
·
16,462 Posts
On a related note, I'd like to hear the pros opinion on valve stem seals and guide material.

I quit running positive seals years ago. When I was still doing heads for customers.
I had seat and guide machine and full Winona bronze guide tooling, in conjunction with a Sunnen guide hone to finish size. Those heli-coil type guides needed oil, it seemed, or they would destroy a valve stem.
It seemed that on anything that didn't get tore down every week, I would see stem wear from the seal/ top of guide area.
I just do my junk now, but on my Brodix with SS valve stems I run only an umbrella seal on the intakes and no ex. seal at all.

They were at .002 +- .0002 this winter, after 2 summers (maybe 40 hours actual run time? All hard running). Started at .0018 last head service. (I checked them when changing springs earlier this year.)

when I pull the heads this winter, what type of replacement guide/ insert would the pros run in these Brodix heads? They are Brodix bronze originals now.
I have guide drivers still, and can change solid guides but will have to farm out the finish hone.

Lake jet, 454, Hyd roller, 4000 - 5400 RPM at all times except idling in no wake zones.
 

·
Registered
Joined
·
4,318 Posts
I likes 2 run mine on the loose side of loose. I cans tell just how loose by the tone of the clunk :p:p


And yes, it ran that way....with no obvious problems. Even had decent compression. Best guess it was caused by a poor finish on the valve stems local machine shop missed it twice. All 8 intakes were like that.
 

·
Registered
Joined
·
1,299 Posts
I likes 2 run mine on the loose side of loose. I cans tell just how loose by the tone of the clunk :p:p


And yes, it ran that way....with no obvious problems. Even had decent compression. Best guess it was caused by a poor finish on the valve stems local machine shop missed it twice. All 8 intakes were like that.
that's not loose guides..... that's NO guides at all!:))eek:))
 
1 - 20 of 25 Posts
Top