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Mercruiser detonation chevy 350 with 4bbl carb

"I am not sure about the answe

"I am not sure about the answer to my question about the EGR. If the engine was designed with an EGR(as I think a 87 truck engine was)...if everything else remained the same, running without that EGR will cause definite engine pinging. Can you temporarily disconnect the secondarys and run the engine at full throttle on the primaries alone to see if this makes a difference???"
 
"i'm not sure what the que

"i'm not sure what the question here is anymore. if we assume for the sake of this discussion that the motor really does have detonation over 3500 then the diagnostics are obvious.

detonation is combustion chamber temp too high. that is :

a) too much air = air leak somewhere

b) too little fuel. = either put another carb on it or some massively bigger jets to see what happens

c) too much/too little ignition timing. you say you have checked this and it was fine.

you are not going to get some precise answer here. you are standing next to your hardware and only you can make the changes necessary.

so if the ignituion is correct, throw some big jets at it and keep going bigger until the plugs change color or the pinging stops or change the carb but either way, eliminate the lean issue once and for all one way or another... just like you did with the timing.

and if that doesn't work then take the intake off and find out whats going on. and if you can't id something THERE then all thats left is the cylinder heads and gaskets.

you have tried the shotgun approach. now its time to do everyting over again, one thing at a time until you eliminate all the possibilities.

what's left will be what was wrong."
 
"going from EGR to no EGR wont

"going from EGR to no EGR wont affect pinging its to help with emissions.

Can disconnect the secondaries but with the small primary's of the 4bbl Quadrajet he wont obtain full power and the engine will be lean and cause more damage.

The secondaries can be made to run more lean or rich by changing the height of the hanger ever so slightly.

The pinging is caused by a second flame front hitting the front from the spark,

I think he needs to retard the timing a bit, can also try a colder plug.

The high compression with the low octane is going to be a problem but only has 87 oct available where they dock.

There are thicker head gaskets available, can also swap the heads for ones with a larger volume.

That and check the cam timing. If he used a crank gear with 3 timing slots he may have put it in the 4 degree advance which would cause the pinging."
 
""Going from EGR to no EGR

""Going from EGR to no EGR won't affect pinging"
The EGR introduces exhaust gases into the cylinders and results in lower combustion temperatures which result in lower Nox emissions. The engine timing and fuel mixture are calibrated to compensate for the introduction of exhaust gases. If it is removed or sticks in the closed position, the higher combustion temperatures will cause the engine to ping. The carburetor and timing can be recalibrated if the device is removed. The suggestion to Disconnect the secondaries was not meant to be a permanent fix but only a diagnostic technique to find the actual cause of the problem.
Follow this link for one of the many explanations of this subject.
http://www.hotrodder.com/kwkride/tech.html"
 
"with all due respect you are

"with all due respect you are flat wrong. egr raises the combustion chamber temps. eliminating the egr is a perfectly good thing to do and will lower the combustion chamber temps and will make any motor run better simply by keeping the charge density better and the the charge itself less contaminated. and if he got the cam advanced too far the cranking compression would be lower, not higher so if anything the cam is way retarded but he insists its correct so thats that.

and the egr isn't his problem anyway. and if you read the previous posts, all your suggestions have been offered at least twice before by others.

there is no new advice to offer here. this problem will be resolved when who ever is doing the work starts working the variables one at a time instead of looking for the one size fits all magic bean."
 
The thing is i never had pingi

The thing is i never had pinging with the old engine but then again the the old engine was really low on power.We ran the boat tonight with a seperate gas tank of 93 octane still pings.A friend had a quadrajet carb that was setup for a big block it had 76 primary jets compared ti my 68 jets still pings.So what i know at this point in time is it's not fuel octane causing it to ping and it's not running lean.The camshaft is installed correctly.But we did take notice that at around 2500 rpms the engine shakes a little almost like a spark miss. I'm going to try new sparkplugs and c if that helps.
 
Crossed sp plug wires????????

Crossed sp plug wires????????

Also check with a timing light to make sure you are getting full advance by 2500-2700 rpms

Base should be 8 btdc and total should be 30 -32 btdc. If your timing module is not giving full advance then you may see a ping. I believe the module adds 22 to 24 degrees I forget specifically.

Do you get any fuel smell after running it from the back of the boat?
 
just because the old motor did

just because the old motor didnt ping doesnt mean the new one wont. forget comparing the two. get yourself a good set of marine wires and plugs and go from there
 
should i replace the plugs wit

should i replace the plugs with ac delco r43ts's or are there better plugs for a thunderbolt ignition?
 
could using extended tips plug

could using extended tips plugs cause a pinging?
I ask cause this engine was using non-extended tip spark plugs?
 
"That is a possibility. Having

"That is a possibility. Having the extended electrode could cause a hot spot!!
I thought you said you were using R43T's
And by the way with todays gasolines a white ish color is normal as long as all the plugs look the same color.

Plug reading is very difficult, not like it used to be before oxiginated fuels.........."
 
i also noticed before the engi

i also noticed before the engine was replaced the temp was always around 140 to 145 now with the new engine it runs around 170 to 175. I have a 140 deg thermostat installed. I assume it's running a little warmer due to having higher compression
 
"John:

I've re-read you

"John:

I've re-read your posted problem and solutions a few times; very interesting at the least. I was surprised the 93 octane did not help stop the detonation.

Concerning the higher operating temps. of 170-175 F., would bringing that temp. down to under 150 F. cure the detonation? Is the engine RWC? Do you know the condition of the impeller? Is the circulating pump belt slipping? If the engine is FWC, is the heat exchanger working @ 100%?"
 
raw water cooled.New thermosta

raw water cooled.New thermostat and impeller and circulating pump this year. Belt is tight
 
"OK

Are you 100 % sure it i

"OK

Are you 100 % sure it is pinging????

Are you sure it is not the exhaust flappers "flapping" they will make a pinging sound for sure.

If you were to retard the timing to 0 or 4 degrees after TDC you should remove all ingition related detonation,

After rereading a earlier post

""I forgot the camshaft was from the old engine. It was checked out before installing it into the other engine. The head gaskets were bought from my local marina and they were composite head gaskets.

What sparks my interest is this part ""before installing it into the other engine.""

1. why use a old camshaft?
2. should have bought a new one with a slightly higher lift for a bit more power.
3. Where did the timing chain come from?

4. I bet/am pretty confident at this point you installed the timing chain off one tooth and the cam is either advanced or retarded and is causing the higher than expected ccp and therefore causing the pinging!!!!

You have to at this point start to backtrack so I would remove the hamonic balancer and pull the timing cover off! Turn the engine over by hand and make sure the timing marks on the timing gears line up correctly. You have no choice!

Oh and next time you ever do a engine swap NEVER use any of the old internal parts from a worn out engiine. Just my opinion"
 
"I had the same problem with a

"I had the same problem with a 5.7 in a GM truck Tryed richening the fuel mixture ,changing timing and advance curve ,changed egr valve ,installed cooler t-stat ,ran 93 octane fuel .These changes resovled the problem i found the back two lobes of the cam had alot of wear , changed cam and pinging stoped"
 
I've always reused parts t

I've always reused parts that were still good yet. The camshaft is installed correctly. I lines up both dots.Then adjusted the valves and verified that the dots still lined up.Plus at an idle i have good steady vacum.
 
I still think it is a cam timi

I still think it is a cam timimg issue.

Other than that I do not know what to suggest??

You could run a 10:1 compression with 89 octane with no ping as long as the fuel delivery was rich enough and the timing was set to handle it.

One thing that was done in the 80's was water injection to eleimnate detonation on high compression motors.

Next time you lake test it try spraying some water down the carb throat ( spray bottle like a windex type sprayer) and see if that helps with the ping.

If it does than your static compression is the issue but why is something I can answer from here!!
 
"Just had a thought,

1. Wha

"Just had a thought,

1. What year was the original motor?

2. Was it a roller cam?

3. Was the truck motor a roller cam?

If you answered no to 2 and yes to 3 then that could be a issue because the cam profile of a non roller cam would be way different to that of a roller cam.

Probably should have left the truck motor cam in there.

Almost all 350 marine engines are a truck block anyway..........just different gear for the marine enviroment, oil pan, oil pump, gaskets. The base long block I believe is the same."
 
had time today to take boat to

had time today to take boat to lake. When of the joys of only livng 3 miles from the lake..lol. Water injection does nothing still pings real bad. I'm sure it's not a fuel issue my flow scan is showing 16.5 gallons per hour at 4000 rpm's and when looking at the carb while running at that rpms u can c alot of fuel flowing down the carb.The original engine was replaced with a jasper marine engine. It was a newer style thou cause it has the one peice reman seal. The camshaft is a regular flat tappet style.I finished taking about the old engine to c if it was worth rebuilding. The block was bored 30 over had flat top pistons and 76 cc chamber heads. What i installed was a just a basic 350 from a truck just marinazied. Worst cause i'll pull the engine back out and replace the camshaft.
 
What were the pistons in the t

What were the pistons in the truck block you put in? Flat or domed or undercut?

Did you use the heads from the Jasper motor?

This may be were the issue is comming from.

The 76 cc heads are a bit tight/loose for a run of the mill 350 I think?? I would think they should be more like 79 - 82 cc's. I could be wrong or eversed and maybe they need to be closer to 72 cc's. This is not my area of expertise!

I stll say you have a missed matched set of heads and cam. I feel this is the issue!
 
current pistons are dished wit

current pistons are dished with 4 valve reliefs in them. Heads are 64 cc chamber heads. This is a stock chevy 350 engine
 
"Ok let me see if I have this

"Ok let me see if I have this straight

You took a used camshaft from the worn out 350 Jasper refurbed motor with 76 cc heads and put it into a 350 motor with 64 cc heads. Is this correct?

Well that is a MAJOR increase in ccp's. 12 cc's less combustion chamber size!
No idea what the lift or lsa or any other data on the used cam??

I would just swap out jasper cam for the one from the truck block.

Again I am only guessing but I just think you have a miss matched cam with those heads/pistons in the new truck block.

On Harleydavisons when you miss match head cc's, pistons and cam profiles you get absolutley terrible pinging. It is very easy to hear with only 2 cyclinders.

Also remeber back when the auto makes had this problem? they were making motors with the wrong part combos ( old school ) with crappy gas and no knock retard electronics yet.

I remeber hearing cars going up hills sounding like diesles!!!

So I think a proper camshaft for the new heads and pistons is in order.

I would suggest calling a local engine biulder and chatting with him and relay some of the specs we have discussed and what you have and see if he can suggest a good cam for your motor that may bump your power level up to close to 300 HP.

I think and I pepeat I think, the 64 cc heads are the root cause here. Not a problem in themselves but just a missmatch of parts...

I am out of suggestions at this point..........

Good luck and let us know of any changes good or bad!!"
 
that kinda of makes sense. I t

that kinda of makes sense. I took notice that after i installed this engine i hear my exhaust flappers making noise at idle to 1800 rpm's. I didn't know how the jasper engine was built till just the other day. I left the truck cam outside so that is now shot. engine builders in my area don't work on marine engines so there no help. The local auto parts store has a stock camshaft in stock for a 1987 chevy 350 truck for 43 bucks.
So i'll go that route first just to c if that takes care of the pinging. Is this a single 350 engine connected to an alpha drive and the boat weighs almost 8300 lbs loaded. But i did notice that with the current engine even running at 2 deg timing it has alot more power then the old engine did.
 
Well that is a very important

Well that is a very important piece of the puzzle you left out!!!!!!!!!!!!!!!!!!

A 350 260 hp trying to move a 8300 pound loaded boat is equivilant to a FORD FOCUS trying to tow that boat up a hill............WTF!!

WOW you should have gone with a 454 or a 502.
you need at least 400 to 500 hp to have any fun in that thing!
 
dont take this wrong but that

dont take this wrong but that motor trying to move 4.3 tons across water is gonna labor knock its brains out. that would have been a valuble piece of info like ghost said. that is a no brainer. i wouldnt dump another cent in that motor unless it was for high high performance parts. and make sure they will work well with the rest
 
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