I am heating up a valve in oven right now, 400 degrees and gonna see if it fits in guide stay tuned... Btw the lifter will not come out of the bore so one of 2 things happened...

Crap blew into intake and went I to each cylinder there is stuff all over

Anybody can look at the top of that piston and see detonation. You have carbon in the center and shiny all around the outside of the piston I highly doubt this was such a detailed build that you manage to push all the fuel to the center of the piston and ignite it. It's detonation see it all the time there are many reasons it happens timing is one of them...

That's normal a lot of times it ruins the carburetor also.

Tim so sorry to hear about your issues.

NONE of us deserve this to happen

Let's hope OSO can constructively help give ideas and pointers instead of 100% confidently diagnose an engine issue through a picture! Lol

[ATTACH=CONFIG]541411[/ATTACH]not bad timing at all....

BTW my new AFR heads valve guides are getting honed as we speak.........glad I spoke with more then one professional to help steer me in the correct direction.

Tells nothing about the timing.

Just an idea Tim, but I know you had some intake sealing issues with these motors initially. What are the possibilities that you had an intake leak from the valley on that cylinder? You might not see it on the wideband if it is only one cylinder running lean. Are you running widebands on both banks or only one per motor? I really can't imagine a tight guide seizing the valve that quickly, and if it was tight guides I would imagine you would see the failure on an exhaust valve first.

I take issue was fixed after first fire if engine no damage at all

Tim Full Force, posting on this thread is pointless. The entire thread is based on someone's butt hurt because someone said they could improve afrs exhaust port.

How dare you even mention guide clearance could be a possible issue with one of their out of the box heads. I bet it was because you didn't run 5w40 oil.

Yea I know I am on to 2 causes both not my fault....

As far as plug shown, I'm sorry not timing that shows NOT LEAN

Correct it shows pig rich.

Detonation was not the issue....

I put valve in oven at 400 degrees put in guide was very snug, yes a hillbilly test but makes ya go hmmmmmm

Now put the head in the oven and give it a try.

Valve runs hotter then the head especially in lake water in may....

I agree. But the head isn't going to be room temperature. So, if your going to waist your time putting the valve in the oven minus well go all the way and throw the head in also.

Tim, I did the very same thing last summer first time out. Only difference was 1000 more rpm it was detonation. My head was ten times worse. I ended up replacing valve seats in the other side of the motor. 2 Pistons bunch of valves and seats some welding and a bunch of grinding it was back together. Mine also hung the lifter in the bore. Polished the lifter re-used. Once I got it back in the boat I stopped paying attention to the wideband and tuned it from the plugs. Once I got the proper tune-up/ temperatures in the motor. You could push it wide open and go to sleep.

Exhaust valve 100 times more common to seize than intake...or more.

You ever find out what caused the 1/4" or more clearance from dist to dist pad on intake ? Reason for asking I never heard if you checked intake port flange to see if a bunch of material was milled off from last build....or deck was cut considerably....or ?

You ever check lifter bore to lifter clearance ?

How did you determine pushrod length ? Any pics of the rockers installed ?

Guide could be trashed now from the trama anyway. So, I don't think checking the guide vs valve right now would show accurate results.

Intakes were milled issues fixed with a .120 gasket...

Lifter bores .0012-.0015 on starboard, .0018-.0020 port engine bob m and Johnson both said .0012 -.0015 ok and was told "sweet spot" for them..

Pushrod length done half lift met kind I will see for pics... 5 people said I was ok there

I get many things can happen but this is not right I am lost but I don't see any sign at all of detonation here

It does with cylinder that was not damaged....

That will just show that valve with that gude.

Make sure to put some lube on the valve that won't burn off at 400F when you check it.

Tim, I would bring the heads to your machine shop. Have them check the guide clearances. Also, I'd have them check the SEAT WIDTHS. In marine applications, you want a nice wide seat margin to aid in cooling the valves.

Theres a reason Teague marine machines their AFR heads before they sell them. You pay a little extra for it, but they aren't out of the box car heads, mass assembled, with inconel valves thrown in and called "marine" heads.

Although, I will say, in AFR"s defense, they specifically told me in an email regarding a marine application, that for marine and boosted applications, that it is the engine builders responsibility to size the guides accordingly. Here is the email from them

Joe,
Based on the engine combination, power range and Marine application, you should look at our 305 Magnum heads. Our 305 head is designed to generate optimal airflow translating to stout horsepower, torque and throttle response specific to your application.

You will need to special order your heads with our #8002 “spring exchange” to suit your hydraulic/roller camshaft.

Note: We do not size our valve guides specific to Marine/boost usage. It is the engine builders’ responsibility to check for correct guide clearance per their Marine/boost application. We recommend that you special order your heads with an “Inconel” exhaust valve upgrade, better suited to marine exhaust temperatures and the possibility of exhaust reversion.

Hope this helps. Please call if you have questions or require further assistance with your order.

Rob Wood
Air Flow Research
661-257-8124 ext.123
[email protected]

Tim , how did the oil look ? An excessively tight guide and even a little moisture in the oil will gall and weld the valve to the guide . Dont ask me how I know........ Good luck , you'll get to the bottom of it !

You never answered my question - one wideband per motor or two? And if one was it on the side of the motor that let go? I keep going back to the previously milled intakes. Are you sure they were flat milled and not angle milled? I'm not trying to point the finger at you at all, but you still have one motor that hasn't lynched, so getting to the root cause of why this one let go is imperative. As far as I know the only thing reused on these motors were the intakes. I still think the fact you dropped an intake valve instead of an exhaust valve points away from tight guides short of a quality control issue. 10 seconds at close to peak cylinder pressure before it let go really sounds an awful lot like detonation.

I cannot afford to have 2000.00 in work done to new heads right now, if I find out that all this is wrong and not marine spec, there are gonna be some serious issues, fuk me for trusting..... I am so close to selling stuff and buying 420's drop in garbage and run the boat

wideband on one side each engine, same side that broke, the intakes are same both engine gaskets were 100% sealed, this is NOT detonation related, I would have signs of melting on plugs, eyebrows of pistons.... I do not... I didnt drop a valve I broke a valve, I can't get heads to machinist tonight or I would....

Full Force, I would recommend starting a new thread pertaining to your issues. Others might be better able to offer help, and hopefully your post-mortem on your engine will reveal the issue and help others avoid the same thing. I'm very sorry to hear about your bad luck! Hopefully you will be able to find the cause and get this motor back in action soon to salvage the season. I sure hope it's an isolated problem and the other engine does not have a similar issue. Good luck with it!

Tim, did you have 4-7 swap cams?

tim,i feel bad for you.i really can,t tell from the pictures but do i see tuliping on some of the valves?on a side note about 10 years ago i bought an edelbrock kit for one of my harleys,it consisted of pistons pins&clips rings cams and cnc heads.it ran for 2 minutes and stuck a valve.when i called edelbrock to tell them about the failure i mentioned that i suspected a tight stem to guide clearance,the guy told me that it was not possible and they had me send the head to them for checking.long story short,they sent me a new head with gaskets but never called me back to tell me their findings.it just so happens that the guy who owns the business i purchased the kit from is a personal friend of vic edelbrock so he made a call and got vic involved.the failure was caused from the person who assembled the head forgot to lube the stem prior to instalation.i am in no way saying that is your issue but it is a posibility.do you see any signs of galling in the guide or on the stem?

Valves not tulips that's how they were new..

I am texting you a video tell me thought...

Yes

I am not blaming any one person at this time, when I have guides checked and see why lifter is stuck from coming out of the bore I will see what happened...

There are a few things that can cause this so more research needs done, I certainly expected no issues

Man I`m feeling your pain Tim, sorry to hear about your troubles that really sucks buddy.:(

Wow. Heartbreaker. My condolences.

What about galling on valve and guide whether cause by heat, tolerance or lack of oil.

How about the cylinder wall and piston........any galling there?

I bet the circulating pump impeller failed....causing a hot spot around number 7 cylinder.

Why does it always have to be number 7 cylinder when number 8 is farther away from the coolant sourse ?

It was #2. On a big block Chevy, the fuel pump is located on the even bank side, in the front of the block. Like in the picture shows. #7 is in the rear, on the opposite side.

Then 4-2 fire next to each other...

Honestly I give, I don't care, I don't wanna care, I don't think I am gonna move forward, might sell the good engine, sell parts off the bad one, take a loss and move on.... stock 420's will have to work, buy 500 hour ones that will run another few hundred hours.... this tapped me, hurt me and is turning me off to having cool boat... f this crap. this should not have hapened no matter what, yes I get that it does, and will but happens to me too often, f this