erroded valve seats

[Ralph Savarese]

I just finished disassembling my SB Chevy all the engine components were perfect but the two middle exhaust valve seats on both heads nearest the cross over were rotted i have never seen anything like it . This engine ran fine would have never known.
Should the intake manifold gasget cross over have restrictors on both sides . It looks like the seats rusted away but no water any were else .Odd? I would think if it was getting water in it would have beeb effecting oyher cyl?

[GEOO]

Ralph, I've been told that reversion starts at the inner two piston's as you discribe. You may have a slight reversion problem at idle. GEOO

[Ralph Savarese]

well it was a stock motor is it still possible for reverson

[GeneD]

Ralph baby,
I don't know what year you have, but the replacement of exhaust valve seats is very common.
It might be that you don't have any valve seat inserts in those heads if they are older ones. With today's lousy fuel, we need hardened exhaust valve seats and any machine shop can do this procedure.
I just had one replaced (got eaten up and spit out!) in my '95 motor last month. Cost $30. But normally if you bring the heads in to have them re-done, this will be included in the price and I think that $125 per head is the going rate to have them completely gone over.
And in the past, I have had to have the valve seats retro-fitted for hardened seats. This was on my 1968 fuelie heads in the Corvette. They didn't have any back then, and the seats would have burned out had I not done that.
Not to worry Donzi Boy!
Oh and yeah, the crossover should be restricted. Maybe this is why the seats are destroyed?

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GeneD
007
Melbourne, Florida

[This message has been edited by GeneD (edited 10-25-2000).]

[Forrest]

Also, remember that since the two exhaust valves in the center of a SBC head are next to each other, those two get much hotter than the exhaust valves at each end of the head.

On more thing, if you are running popular Chevy 882 heads, the exhaust crossover on these heads connect to both center exhaust ports rather that just one. For that reason, 882 heads tend to have more heat related problems than do other Chevy heads.

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Forrest

[This message has been edited by Forrest (edited 10-27-2000).]

[GEOO]

Ralph, What type of stock motor? Marine or Auto? I think the cenerline on the cam causes the reversion. 112-114 is good. 106-109 not to safe. Also if an exhaust valve is not closing all the way it can cause reversion. GEOO

[AVickers]

Interesting...

Lead in older formulations of gasoline coated & lubricated the seats of older engines so they didn't need stellite/stainless valves and stellite or induction hardened seats. Nowadays, w/ unleaded fuels, exhaust valve/seat wear is a given w/o hardened surfaces.

HOWEVER, I was told by an old boat engine builder that putting inserts in older raw water-cooled Chevys and Fords is risky -- even if they are staked in. His opinion is that because of the rapid cooling cycle when the thermostat opens, a seat might come loose. It made some sense to me, so on this overhaul on my Chris Craft, I replaced the 1.5" exhaust valves w/ 1.6" valves and will run a lead substitute... (Hell, it went 30 years the first time! I don't think it'll be a problem for me in 30 more...)

The other choice would have been to get some heads w/ hardened seats, but there are some funky pads on the heads on these engines and I couldn't find any modern heads w/ pads to bolt accessories to...

Anybody else hear anything about seats dropping out on raw water-cooled engines???

[This message has been edited by avickers (edited 10-26-2000).]

[Ralph Savarese]

This was an automotive crate motor i bought new in 95 i just find it very unusual to have only the inner seats and valves get so bad we are only talking two chambers Why ?
All others are perfect . I have another set of heads i already re did with 68 cc chambers so i dont have to run as large of a dome to get to 10.0:1
Ralph

[GeneD]

I have heard of seats dropping out on a new Merc motor. That is how I got mine. Did an engine swap for a guy with twin 1995 350 cu in. Mercs, and one of them dropped a seat in number 3, or was it number 5? Either way, it was one of the two inner valves.
Now guys, I have a question...
What kind of compression 'reading' do you see on a motor that has 10:1 compression? For instance, if I want to 'guess' at what kind of compression I am running in my motor, and I have 165-167 lbs. on the gauge, with flattops and the 76 cc heads, what do you think I have?
Reason I want to know is that I think I have the low HP camshaft in this bitch. I just can not beleive that this motor is less powerfull than the old one. Of course, the old one (260 HP) was pretty much the same thing, with the exception of the camshaft, and could have been a freak of nature.
I just can't get over the difference in performance. I feel as if I am running my old 305 in there.

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GeneD
007
Melbourne, Florida

[Jamesbon]

I'm gonna guess that flat tops and 76cc heads will put you between 8.5 - 9.0:1. My very first modification on the Donzi some 8 years ago was to remove the 76cc heads, and stick on a pair of 64 cc fuelie heads. It was worth about 500-600 rpm on the top. I believe my last 355 was 9.75:1 using 63 cc heads, and forged TRW flat tops w/4 valve reliefs.

[rayjay]

GeneD,
By 165 - 167#'s do you mean "cranking pressure"? This is from taking out the spark plugs, sticking the gauge in the spark plug hole, and cranking the engine. Cranking pressure is a function of static compression (what you call "10:1") and the timing of the intake valve closing. Cam duration and lift, unless radically too small, will not materially effect cranking pressure. The earlier the Intake closes the higher the cranking pressure tend to be. Assuming your gauge is accurate, 165 - 167#'s seems very high for a non "race only" motor, and could be the result of a high compression (doubtful if it starts on 93 octane) or very early valve closing, or a bit of both. From other things you have said I would vote for very early valve closing since you describe it as pulling good but running out of poop on the top end. rayjay

[GeneD]

So...what? Are you telling me that all engines have this cranking pressure of 165 lbs?
See? I'm confused over all this. I used to think that a high compression motor was just that, HIGH compression. Where else can you measure compression but on a cranking pressure test through the spark plug hole?
Yeah, the gauge is accurate, better be, it's only a couple of months old. I'll re-check, but I'm sure that's it. They were all like that...165-167.
So, here we are, I've got the same "cranking pressure" as the old motor. Same type of heads, same type of pistons, and I got 4600 Max RPM's. This isn't right!
I'm sitting here with no job, low static compression, and a boat that only goes ~60 MPH. What to do? Might as well run my head into the wall.
I do not want to change out the heads. They are perfect even though they are the bigger chambers. Let's not forget, the old motor had the same cc heads!
WHAT IS THE PROBLEM?

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GeneD
007: Going slower every minute.............
Melbourne, Florida


[This message has been edited by GeneD (edited 10-31-2000).]

[GEOO]

Gene,
I still have that NOS kit!!!! 50,75, 100,125,150hp!!! at the push of a button!!
It will give you a boost.

http://albums.photopoint.com/j/View?u=1265596&a=9365167&p=30609331

GEOO

[This message has been edited by GEOO (edited 10-31-2000).]

[This message has been edited by GEOO (edited 10-31-2000).]

[RickR]

GEOO
NICE!!!!

Gene
Static cranking pressure has very little to do with compression ratio. Like rayjay said cranking presure with a bigger cam is actually less than with a torquer type cam. Thats one of the reasons you want taller pistons with a radical cam.
The bigger cam comes into play with your Dynamic pressure.
To get your compression ratio you need to cc the heads, know the piston dome size, measure the intake gasket, figure stroke and bore.

I think it was Forrest that had a more in depth explination a few months ago.
Forrest?

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RICKR
mailto:riggerb@aol.comriggerb@aol.com</A>

[This message has been edited by RickR (edited 10-31-2000).]

[Ralph Savarese]

Gene D,
According to my catalog the regular old flattop pistons shood give you about 8.5:1 with 76cc heads .
I was going to use my 76cc's with.275 domes to get 10.0:1 according to the PAW catalog i have but after finding out that i had a bad valve seat i am going to use the other heads i have.
The second set i have are 68cc heads so i had to get .125 dome pistons to get me to 10:1. to answer you Question i dont know exactly what my pressures are going to be . When ever i always did a compresson check i always used the comparison method rather than actual pressures for diagnosis purposes.
Ralph

[BigGrizzly]

GeneD Don't panic binging your head against the wall will wake the people next door or crack the wall. You said the heads and pistons are the same- are you sure? If so the cam is only difference. Do you know your actual full advance timing, has the harmonic balancer slipped? Cam may be a tooth off or just mild. Check the timing for real. Find real top dead center with the positive stop method. This will tell you if the balancer has moved and how much. If the cam is too small and compression is low we can fix that with rhe right cam. First check timing then move it up to about 37 degrees. then check plugs. Start with a - one- new plug. save on cost. Always check that one if ok check the test drive wide open for at least 1/2 mile befor shutting down and checking the plug. Then get back to us. This procedure works providing engine has good integrity.

[This message has been edited by BigGrizzly (edited 10-31-2000).]

[GeneD]

Do not know the full advance timing.
I got the tape out to do the job, and after the motor was started, I just plain forgot.
I am still at the 10 BDC mark. I do not think the balancer has moved, it was all very nice when it was put back together. It was all practically brand new.
I am very sure the pistons were the same. I brought the pistons with me when I bought the new ones.
Now that I'm thinking about it, there is ONE difference, but I think it would be negligible...the intake. It is the same thing as I took off, except it is drilled for the new type heads.
Also guys, I haven't taken out the boat since I bought the new coil. Could be a factor.
It HAS to be the cam.
Hey, here is another factor...would the remote oil filter be playing a role here? More oil to pump around? The oil pressure is fabulous, but does fall off after an extended run. A bit under 40 lbs. when Rob R. and I ran it for about 20 minutes. But nothing really dramatic.
I have no problem replacing the cam, in fact, I would get the biggest I could run if I were going to buy a new one.
Big G, what is the beef with the spark plugs? I checked them recently, and they were beautiful. I was encountering a rich condition, but I found that the choke was closed! Since it got cold here, it wasn't rigged for anything but 90+ degrees of ambient temp. Not to mention the fact that even after it was warmed up the thing stayed closed. Fixed that though.
Could be it'll wake up with the new coil. Haven't had the fuel money to try it yet. I'll try to talk one of my buds into paying for some fuel this weekend.
Someone please come up with the PN for the Merc. Magnum roller cam, or maybe a Crane?
I do not see Merc. running domed pistons on any of their SB's. In fact, I would be interested to know what their compression ratio is on their present motors.
The motor I took apart had dish pistons with the 76'ers. Wonder what HP that was? I of course replaced those with the flattops, with the thinking I was reproducing the exact configuration of the other engine.
Who knew?

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GeneD
007
Melbourne, Florida

[This message has been edited by GeneD (edited 11-01-2000).]

[woodsy32]

Gene, Big Grizzly has it right. It definitely sounds like a timing issue. Probably a combination of a bunch of small things. Definitely follow Griz' advice. One other quick thing you can check that was not mentioned, check that your distributor was installed correctly. Bring Cylinder #1 up to TDC. Take off your distributor cap. The rotor should line up perfectly with the #1 position on the cap. It is extremely easy to install the distributor off by one tooth. I have chased that gremlin before. I am sure it is something really simple. Just my $.02

Dave

[GeneD]

Dave,
With respect, there is no way the dist. can be off one tooth and affect the timing once installed and timed using the light.
Timing is timing once the motor is running and the light is put on the balancer and the dist turned to the proper degrees.
While it is true that chevy changed out the balancers way back when and in turn changed out the timing mark.
Oh but wait! This 'might' be an issue. I did use the old balancer from my old motor. if the marks are different from the old to the new, that 'might' make a little difference.
But if you remember from one of my old posts, I changed from 8 BDC to 10 BDC with no appreciable difference in speed or RPM. And again, that was with the lousy coil. I'm hoping that the new coil will make some difference.
Let us go through it again.
1995 crank (original), 1995 roller camshaft (new, specs unknown), 1995 intake (used, cleaned up in and out), 1995 heads (76 cc?, machine shop valve job with clean-up mill, 4 bbl valves - 1.98 intake dia), NAPA camchain (new), 1995 cam gear (new), 1995 crank gear (new), 1986 Thunderbolt IV ignition, Clevite 77 bearings (new), Z-28 oil pump (new), Badger pistons (flattops - 4 valve relief), Speed-Pro Single Moly rings, SST ($5 ea.) projected tip spark plugs, Mercruiser wire set. I think that is about it.
I CAN see the cam or crank gear having the wrong timing slot for this engine, that is a strong possibility. I didn't know what the timing spec should be, so I didn't do a cam time on it.
Thing is again...the engine runs so damn good, it's just incredible to think it is anything but the cam!
I think the thing is just under-cammed.
I like to build at least one engine that is totally stock. They run very reliably. This is one reason I never thought to run a pop up piston. I always was under the impression that the compression would be too much for the fuel that we can get.
I would like to try some, when I get the money. Don knows I have enough engines in my shop to try just about anything I want.
Just got to screw around a bit more I think.

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GeneD
007
Melbourne, Florida

[This message has been edited by GeneD (edited 11-01-2000).]

[BigGrizzly]

GeneD just trying to save you money with the one plug bit. If you installed a late model cam gear it has probably been advanced for emissions. Take your old cam gear set to NAPA and compare to the new ones and see if the slots or holes are lined up the same if not RayJay is right. If they are the same do the timing and plug thing.

If none of this works get the darn six in that truck, call RayJay, and get your butts up here. I got the room, the hoist, Pizza and beer. We will fix yours, then you guys can help me with mine.

[This message has been edited by BigGrizzly (edited 11-01-2000).]

[BigGrizzly]

Just more information, flatop pistons with closed chambered heads run better than popups with open chambered heads. That is if the compression is the same on both.
Randy

[rayjay]

GeneD,
Like BigG said, if we had your engine in front of us we could figure out what is there and what can be done to get you what you want. That is the problem with a board like this, we ae all trying to diagnose the problem without having the problem in front of us.

Yes, 165#'s cranking pressure is high for a "stock" engine, 135 - 150#'s being a more normal or expected range. With the piston and head combo you describe, 165#'s leads me to believe your cam is closing to early. As BigG said this could be caused by a mis-match between your timing gears and your cam. Does your cam gear have a number of key ways? If it does you may have inadvertently used the "emissions" one that advanced the cam, but again, that is only speculation on my part. If you want, I'm sure BigG and I can figure a way to get you on the phone with us and maybe we can help you zero in on the problem.

Well, now back to figuring out how to get a ZX12R up to 200.... Ah, sweet dreams. rayjay

[GeneD]

Okay,
I've done a little research, and by no means have figured out what is going on, but I got the info to begin to figure it out.
First of all, the total advance for this computer, and that is exactly what the Thunderbolt igntion is, a computer, is a whopping 24 degrees total.
So with an intial timing of of 8 BDC, or in my case, a 10 BDC intial, we would get 32-34 degrees of total advance. The only way to get the total advance higher, is to advance the intial timing higher. Remember, the Merc dist has no mechanical advance, and no vacuum advance.
So to get the total to be the suggested total advace of 37-38, I would have to bump up the initial to 14 BDC.
The engine DOES seem to want it. As all Chevy's do. This problem seems to be very strange in it's complexity(?).
Think about it.
The timing on the Corvette is 8 BDC with the vacuum hose for the advance disconnected. As soon as you connect that hose, the timing goes way up. What that BDC number is, I don't know, but I DO know that the timing mark disappears from view (when the timing light is on it) when you connect that hose.
Now this advance has to be compensated for by the transmission. A factor we don't have in the boats.
Now the motor I have is a hybrid. It came originally with dish pistons.
Merc says that the 350 Mgnum engine comes stock with 9.3:1 compression ratio. This is with the flattops and the 76 cc chamber heads. (go figure) It also came stock with the roller cam.
I believe that this is what I built.
The motor I got from Merc to replace the one I took from this guys boat was a 5.7 Alpha. It came with dish pistons and the roller cam. I took the roller cam with it's gears and lifters, and put it aside for my use. I used the old cam and lifters in the crate motor and installed it into the guys boat. With the thinking that the roller cam would give a different RPM range than his old bump stick. (he's got twins)
So when it came time to build my new motor, his old engine, I changed out the dish for the fattops and used the roller cam. With the thought that I was reproducing a Magnum.
So I'm thinking that I got an Alpha cam, and not the Magnum cam.
If this is the case, it would account for the marginal performance.
Remember guys, this thing runs great. It is just not the get up and go motor that I envisioned.
To answer some ques. from above. The cam gears did not have any extra slots in them. Totally stock from Merc.
I am willing to try one of those special crank gears with the three slots. And maybe we'll try that. But I think I would rather change out the cam.
Anyone got one?
I guess I could always pull out my racing stick and throw that in there. I just don't want to screw with plunge milling the piston heads on this great engine. I should probably save that for the 400. If that ever gets off the ground.


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GeneD
007
Melbourne, Florida

[rayjay]

GeneD,

I would resolve the issue with the cam timing before changing anything else. If you have a mis-match between the cam and the timing gears, then changing the cam may or may not correct the mis-match. You may have a good cam that is just not in the correct position to work properly. Getting an adjustable cam drive, either gears, bely, or chain, is a good idea, but wait until you know the whole problem.

I am sure there is a fix for the ignition timing issue, either a chip or box, that allows some adjustability. This will just take research. Your Corvette probably just has a very high / good vacuum at idle and / or one of the GM vacuum advance units that allow the vacuum advance to come in at a lower vacuum. If it works, then it is okay. rayjay




[This message has been edited by rayjay (edited 11-02-2000).]

[GeneD]

RJ,
What you say it true, but I can't see the gears being mismatched.
Like I said, they came with the 5.7 Alpha engine. And that was all hooked up to the factory roller cam. AND...the gears for the flat tappet and the roller cam are different. You can not interchange them. So the gears that I have now, are made specifically for the roller cam. Now, which roller cam I got is in question.
I continue to forget to bring home the spec sheet for the motor. I have it hanging on my wall of fame in the shop, and whenever I am there, I have a load of things on my mind and always walk around just prior to leaving saying "did I forget anything?" And always do!
The computer for the Thunderbolt IV is sealed and non-adjustable. They DO however make a Thunderbolt V that has more kick and more advance.
I've been kicking around the idea of 1.6 rockers, but only Comp Cams makes them (stamped steel, the roller rockers are around $350/set) and they charge $198/set.
I'll bet if I call my local rip-you-off place they will sell me the cam and gears out of that Magnum, and I could be on my way!
But...no job, no money, no cam.
Anyone want to buy my 400? (I also have a 1995 Merc 305 long block that appears to be in good condition. No tin. (I guess I could come up with a timing cover.)
BTW, the Corvette's vacuum advance is stock, and the hose-off timing procedure is SOP. In 1975 anyway.
And here is another interesting Merc thing. The main metering rods for the Alpha (Quadrabog) is designated as "CL", the main metering rods for the Magnum is "CH".
Now, my spark plugs look to be very dry and tan, I wonder if I need some more fuel? PaulO was having perf problems with the stroker, and changed out his carb (Quad) for a 750 CFM with no appreciable perf difference. So I wonder if this would even be a factor?
I'm spinning!


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GeneD
007
Melbourne, Florida

[BigGrizzly]

I thought you said you put on new gears from napa. Get the cam specs including opening and closing,get lobe lift and i can figure the rest out with the exception of the ramp actuation. the distributor will need more timing.
GeneD you have no money but you do have time and you have some great friends here on this board. All of us want to help. So lets put this bitch to bed. Do some measuring give us some figures do the testing for us. You are our eyes and ears we can only make suggestions. You find the need to find the answers for us so we can help. All you will lose is a little time.
If you have a Holley carb either 600 or 750 cfm use it. the meatering needles are too hard to deal with in this situation .

[GeneD]

BigG,
Perhaps I didn't make this clear enough, Don knows I have been talking about it long enough to have confused everyone!
When I did that guy's motor, I had to use the cam chain from the new motor. The old cam chain was worn, not appreciatively, but worn just the same. So when I built this engine, I needed a new chain.
Only the chain is from NAPA.
The gears...one came with the roller cam and was new from the factory, the other - the crank gear, was on the crank already and appeared to be in good condition.
Okay, so you want cam specs. I'll try. I do not want to start pulling valve covers to measure the lift, ect. So I'll try to call the factory and see what they sent me.
Still haven't been to the shop yet this week. But I just talked to one of my buds and he is throwing for beer and fuel this afternoon. So looks like 007 will be out terrorizing the manatees today.
We'll know soon enough if the coil wakes this thing up.
BTW, I have put this engine up for sale on BoatTrader.com. I really want that Magnum I saw recently.
Guys, this thing runs perfect. Just not fast enough for the old 007 Racing Team.


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GeneD
007
Melbourne, Florida

[This message has been edited by GeneD (edited 11-03-2000).]

[PaulO]

Gene,
I did find no difference when going from the Q-jet to the Holley 750DP except that it looks real cool. I did however find a huge difference when I re-rodded the secondaries on the Q-Jet prior to the Holley swap. Gained several hundred RPM. Off course, I went richer. Grizzly, what is the proper procedure for deterimining maximum total timing without blowing my motor to bits?
PaulO

[rayjay]

I could give you some funny (but true) ways to do it like keep turning it up until it makes less power or blows and then build the next motor with a couple of degrees less advance. But seriously, the only real way to do it is on a non-inertial dyno, and then try it under actual use. Very high amounts of spark lead help the cruise economy, and low and mid power. A lot of race engines actually pull the advance back as the rpm's increase. Also a good burning head / piston / engine combo will have good flame travel and need less advance to make the most power.

MSD has some kits that can provide the high rpm (or for nitrous or boost) retard or decrease in ignition timing. rayjay

[BigGrizzly]

I would start at about 32 deg with a known jetted carb. drive it till it was warmed up, then do a speed run and cut the engine. then read the plugs. if jetting is right then and plugs look good advance it 5 degrees and repeat the process. Remember watch the tach for changes. on a boat any thing past 37 degrees, is not worth it. The engine won't blow apart in short sperts.The dyno will get you real close then actual application testing is final test. One uear at Datona I spent Two hours dyno testing and jetting my race bike at AMI, just to have lean it out at the track ahich was less then a mile away. Your stuff is not that critical. Look how long it took GeneD to drop his and it was ,I belive 15 deg too adv. How about Geeo jetted it on dyno then had to lean it out in the boat. You see there is more then just bolting on parts.

[GeneD]

PaulO,
I'm interested in what rods you used to re-jet your carb. If I could get 200-300 more RPM's, I think I would be happy.
Took it out for a ride last night. Nice easy night, no full throttle runs till the end.
With the wind, WOT got us about 61-62 MPH on the speedo. My friend was screaming that something was wrong with the speedo, but I knew better. It is just not the animal the old engine was.
This thing runs so perfect, it's scary. It didn't miss a beat, starts right up. Oil pressure and temp were very stable. I don't like the way the voltage drops slightly at idle, then comes up with RPM increase, but, hey...that's life with the Mondo.
RobR,
No fan belt problems so far. Thing is though, now that this thing is totally in sync as far as the alignment goes, the adjustment bar for the alt is 'almost' hittng the stringer! I wonder if that is what threw that belt that night? We did do a few air shots. Maybe the motor came down and hit the bar and loosened the belt? We may need some kind of modification in that area if I throw another belt. We'll see.
But right now, she is running really fine. No real balls, but super smooth.
I still think I need a new cam.

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GeneD
007
Melbourne, Florida

[Gearhead99]

Gene,

I've been reading your posts about the power your engine is putting out. More cam and some head work should do the trick. Also, install 1.6 roller rockers. I have a friend at Crane and can get you a very good deal when you are ready. He will also spec it out for what you want and all that techno stuff. Let me know.

Dave

[Rob]

Gene, I think you are right on with your fan belt diagnosis. You noticed the power steering was gone right after we hit that big cruiser wake, and the temp started climbing right after that.

Time to get a shorter alternator belt???

[GeneD]

Don't know what to do at this point!
I'm not all that sure that a shorter fan belt will take care of business or not.
I just know that adjustment arm is very close to the stringer. It's hard to tell exactly how close, since I have that carpet in there. I'm not even sure how to cure it at this point. I would hate to go in there and have to rebuild the stringers again, but since the height on those babies were questional in the first place, that might be the only option. Also, I was thinking...perhaps my gimble bearing is so worn that it appears as if it is in alignment and really isn't? I AM experiencing a bit of rumble from the bearing.
So if we go with that assessment, maybe the motor is too low on the front motor mounts? All kinds of things are running through my mind.
Hey, and listen to this. Put the new coil in, and the thing is running great!
AND...the speedo tube WAS screwed up! I think perhaps I was doing maybe 65 the other night, but nowhere near the almost 70 numbers we were experiencing some months ago.
I got some things in the works, we'll see what happens. I am just very happy that the thing is running so good.
Hey, anyone live out in Tulsa OK? We might be neighbors soon!

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GeneD
007
Melbourne, Florida

[This message has been edited by GeneD (edited 11-05-2000).]