Tulip intake valves again
 

:hitfan:Okay I need help, I have twin 350’s in my 28ft Checkmate, and am afraid that it will happen again, some background on my problems, bought the boat early last season, had it in the water early ran great, one day decided to see how it would run wide opened, it ran great for a bit and then started popping through carb on one side, okay not good, I managed to get it home, pull top end off motors and messed up the valves, okay so I have the heads all redone, slap it all back together run it for about a month and bam, bad valves again, now I’m thinking it has to be reversion, set out on a mission to get performance exhaust, nothing would fit, turns out motor placement is to tight, EMI no good Stainless could not help, got burned by Trick on the hole thing nightmare, anyway I got a hold of the cam card and part number for the cam’s only 220 duration, so it looks like it’s not Reversion, so I think I need help on timing, or has anyone had this problem before, any ideas would be great, could it be pre-ignition? I have the timing set to 34 deg total advanced, I just can’t figure it out.

------Im no expert but it sounds like your engines are running lean. Fix it and fatten up the secondaries some, and also get more input than just me (LOL). I still have a valve out of my old Mistress (twin 540s) thats at least a quarter of an inch longer than when it was new. Did just what yours did and the miracle is that it didnt break off and destroy the whole motor.......Bill S

Timing will certainly do it. Depends on what heads and compression you are running. If they have fast burn heads, such as a Vortec engine that's way too much timing. About 30 degrees maximum. Lean A/F mixture will also do it.

Don't have fast burn heads, So I will see if I can ajust the carb, maybe bigger jets, don't know much about carbs only that they are 750's holley, I do however have a box of Jets that came with to boat, I'll have to see what is in it now and maybe step up, I think you go two up or two down? but a good place to start. Thanks, Fast Frank

Read the plugs!!

spend the money to set it up on dyno, then you will know exactly where you are at and what needs to be done.

Or spend the money rebuilding your motors.

What do you have for ignition boxes on this boat? Do you set total or do you set initual and add the boxes to it? Also how did you adjustt the valves? All food for thought. And do you have vacuum secondarys or Mechanical?

:stupid:

The plugs will tell you if it's lean and I agree with that diagnosis so far...

reversion usually shows up at idle

+1.

I have a buddy that it did the same us you, Stock 350 he was running the cheapest gas he could find, 87oct,It would tulip the valves , they put in a good grade stainless valve in it and told him to run 89, i think he;s still running the 87 but he hasnt had anymore probs, Just throwing a idear out there.Goodluck:D

I checked the ignition boxes the other day, and what a suprise I got, one is a V-8- 24, the other is a V-6-14, so I know that I will need to get at least one new box, like I said I got the boat last year and it ran fine for a while, and then problems, I was setting the total time to 34 deg, however maybe I'll back that down to 30 deg. the plugs all looked good, untill I statred having problems, then I would check them they would be wet, not fuel wet, water wet, what I think might have happened was the first time I ran it hard, I blew it up, it was a head gasket, and the second time maybe timing, or pre-ignition

Anybody know if water from leaking exhaust tulip a valve?

Yes that could happen. But... It's more likely that it's tuliped from heat because of a lean condition... then, once it's tuliped the valve never seated right (obviously, LOL) combine that with an aggressive cam and it will suck water back while idling back to the dock.

Okay, I think I got the right answer, it seems to me I am experiencing a brain fart, you are all right and I’m wrong (along with a bunch of my friends) I think it’s pre ignition and not reversion, when it was running good I was told that I needed to be turning more RPM’s, I was running about 4800, I was told that I should be about 5800 RPM’s, seems like too much, but I said okay let me re-adjust the timing, I did and the was on the trailer again, Oh and by the way just got out of the hot tub with the wife and a few beers later, so I hope that I make sense, if not have a d ink, anyway I will let my timing to 30 deg, and see how it runs in the spring, I just love my boat, I also hope that all of you at OSO have a great, fun and fast season in 08:cool-smiley-027:

4800 is a bit low, probably need to be in the low 5000 range... but, low RPM's could come from a million things (props, engine alignment, etc). good luck regardless

At what RPM are you checking the timing?

Timing checked @3000RPM

I'm going back 20 years but I thought full advance was well above 3K. Hopefully someone who knows for sure can chime in.

Katz

I'm not a mechanic or anything, but if there was reversion...wouldn't that effect the exhaust valves from the cold water hitting the hot valves??????

I think that he said that it's just the intake valves that are getting tulipped.

Without using a book (hazy memory) I think the range is 2500-3000 RPM so that should be ok:)

Reversion is an idle-only thing. Exhaust gas velocity overcomes it off-idle.

30 degrees is a little too conservative on timing. If you have excessive compression for your fuel, less timing won't realy compensate for it. If you have too much cam for your compression or your exhaust's ability to outflow, it will also be a dog. You really need to find out exactly where you are on these issues before you can get a true understanding on what's going on inside your engine. Those RPM's are way low for a small block. It should be able to run 5800 forever. If it has steel cranks, good rods & 4-bolt blocks, add another thousand.

6800?? I don't know many people running near 7 grand. Actually, I've never met anyone running those RPM's in a small block powered boat.

Merc specs are in the 4800-5200 RPM range. add a few performance related parts and you might be in the mid 5000 range but any higher than that usually requires to much cam for stock marine exhaust.

Like said, you will only get water at idle unless you have MAJOR problems. Being you are having intake valve problems is definitely heat related.. could be caused by bad fuel, wrong timing, wrong plugs, propped wrong, etc... All these things will cause cylinder temps to go up. Do you have any internal or external flaps? If not this will also be a water on the plugs problem if the idle is set to low or the water is able to back up the exhaust at idle or sitting with the motors off in choppy water. Also, how much exhaust fall do you have? Do you have any spacers to get the riser higher? From what I remember of the 28 Checkmates they set low in the water. It sounds like you have multiple problems here. Start with one and fix it then to the next. Once you know you have the problems fixed correctly, leave it alone and enjoy boating!:D

6800 with 4-bolt, forged crank & good rods. I had a set on my 30 Velocity raceboat and ran the 2 full seasons at those speeds. Not occasionally either.

5800 on the light-duty components.

On a race boat I agree. You have a Bravo behind it? Standard SBC/Alpha 1 combo at those RPM's won't last long.

It's unusual to have the intakes tulip. Intakes are cooled by the incoming fuel air mixture. Must be a lot of heat or low quality valves. Make sure you use good valves like Ferrea or Manly severe duty. Exhausts tulip and then if there is a lot of reversion they shatter usually taking your whole engine with it. If you like to run hard, use inconel exhaust valves. I agree with the guys that say richen the fuel mixture. You might also want to put a fuel pressure guage on it to make sure it isn't starving for fuel at high rpm's. Getting the rpm's up into the low to mid 5000's will reduce the chance of detonation also.

TRS. You're right- an Alpha isn't anywhere near a performance drive.

I have had the valves replaced twice, and I'm now looing into spacers to get my riser fall higher, the 28 checkmate dose sit very low in the water, also I have external flaps on the 4 inch tips. thanks for the info

My boat has Brovo 1's it's and 1989 checkmate maxxum, I belive that the motors were 330 EFI, and then changed over to carbs, bored 30 over, mild cam's just a valve eater.....I'll get it, you guy's gave me alot to look at.

So you have no internal flappers? :confused::confused:

No and you know that, I'm working on that now.....:cool-smiley-011:

The old Crusader manifolds are a consideration for the SBC motor. They're taller, have the water dumps all the way back, angled out and will also give you a performance gain. Should be the same width as the merc manifold- maybe slightly narrower. if you have the room, you can use spacers from 3/4" plate to allow you valve cover access. If not, you'll need 2-piece units. Someone used to make jacketed stainless tails for them that blocked the water exits at the rear flange. These were a class-legal upgrade for P class way back when.

I wouldn't do anything until I knew for certain what was in the motors.

I had 350s in a boat once that did the same thing.I spent months trying to figure it out.The last time around I installed manley stainless valves.I also found that one side of my carb was stuck closed.The float was up with no gas.This was my problem,id hit a wave and the float would bounce up and stick causing a lean condition and tulipping the valves.The carbs were edlebrocks and the floats would slide up and down 2 rods if I remember correctly.The flaost were getting stuck on the rods and staying closed.I put demons on and never had a problem again!

Get another v-6 module, you'll be much happier with the timing curve.

Is that true?????

Biggest problem you might have is the motor has to be perfect so you dont have any starting issues with 20 degrees initial timing. Some motors after they are warm dont like to start up very easy with that much initial. Do you have any MSD ignition or Crane ignition boxes?

I think Strip Poker 388 in closer to the problem than you might think. The gas out there today has a lot of alcohol in it and not the best for playing on the water or at the track. You should definately try to use 89 to 93 if you can. It is a mind set that it cost too much. If you bought 20 gallons and spent an extra $. 1.00 a gallon it is only 20 bucks. How much was the engine work? Take a little from all the suggestions and I think you just might be ok. That is my suggestions anyway. Good Luck.

He probably fixed this issue from 2.5 years ago:lolhit: