Thread:

Big problems with Chev small block

So in true rookie form, my Dad and I went out and tried to destroy our hot little small block during the first race out for the new SE class @ Moses Lake, WA this last weekend. I wanted to get a thread cooking in order to get some feedback from the informed on this site and also to send a warning shot out to those other newbies like us.
So what happened is the boat was running great for approx 2 laps at almost 7000 RPM (3/4 throttle) in the straights. On the 3rd lap, about halfway through, Dad says he started losing power and it continued to go away slowly until he pulled to the infield and shut it down. No smoke, no odd noises, nothing telling at that point. One weird thing that I can't believe is related but went down at the same time is that the tach was bouncing all over the place (not like the normal vibration bouncing, serious movement) and then it went dead. He was towed in after the heat ended, we yanked it out of the water and started the inspection process. First thing we did was start following the wires from the tach back and realized the starting solenoid (the end where the cables connect to the starter) was totally corroded and when we went to loosen the connection to clean the connection points the end actually broke apart. Could this have been the culprit to a major electrical issue that started the bigger problem??


Upon further inspection we started taking out plugs. At that point we realized most of them were relatively loose, and a number of them were totally destroyed (porcelain GONE on the inside to just beyond the bottom of the plug) and looked like this:



Next we drafted some help and performed a compression check. The drivers side of the engine showed over 120#, 125# and two of them were just over 150#. On the passenger side, the front two read around 125#, and heading towards the back then showed 40#, and then down to 25#. This is going off of memory and we didn't spray in any oil before the test...another baddie.
We then inspected the System 1 oil filter and luckily did not find any metal inside. To be safe, we were directed to keep it shut down for the rest of the weekend and took that advice.

I am more concerned of the events that lead up to the meltdown then I am of the unkown damage that I'm waiting to hear about. Heads will come off tomorrow and that will tell us a story........

So I'm going to keep this one going, for informational purposes as well as to get some educated feedback on the root cause of the issue. If anyone who was there can add some additional information or correct some bad information that i have posted in error PLEASE speak up.

Let the games begin............ -Shawn

Originally Posted by Shawn Waters

So in true rookie form, my Dad and I went out and tried to destroy our hot little small block during the first race out for the new SE class @ Moses Lake, WA this last weekend. I wanted to get a thread cooking in order to get some feedback from the informed on this site and also to send a warning shot out to those other newbies like us.
So what happened is the boat was running great for approx 2 laps at almost 7000 RPM (3/4 throttle) in the straights. On the 3rd lap, about halfway through, Dad says he started losing power and it continued to go away slowly until he pulled to the infield and shut it down. No smoke, no odd noises, nothing telling at that point. One weird thing that I can't believe is related but went down at the same time is that the tach was bouncing all over the place (not like the normal vibration bouncing, serious movement) and then it went dead. He was towed in after the heat ended, we yanked it out of the water and started the inspection process. First thing we did was start following the wires from the tach back and realized the starting solenoid (the end where the cables connect to the starter) was totally corroded and when we went to loosen the connection to clean the connection points the end actually broke apart. Could this have been the culprit to a major electrical issue that started the bigger problem??


Upon further inspection we started taking out plugs. At that point we realized most of them were relatively loose, and a number of them were totally destroyed (porcelain GONE on the inside to just beyond the bottom of the plug) and looked like this:



Next we drafted some help and performed a compression check. The drivers side of the engine showed over 120#, 125# and two of them were just over 150#. On the passenger side, the front two read around 125#, and heading towards the back then showed 40#, and then down to 25#. This is going off of memory and we didn't spray in any oil before the test...another baddie.
We then inspected the System 1 oil filter and luckily did not find any metal inside. To be safe, we were directed to keep it shut down for the rest of the weekend and took that advice.

I am more concerned of the events that lead up to the meltdown then I am of the unkown damage that I'm waiting to hear about. Heads will come off tomorrow and that will tell us a story........

So I'm going to keep this one going, for informational purposes as well as to get some educated feedback on the root cause of the issue. If anyone who was there can add some additional information or correct some bad information that i have posted in error PLEASE speak up.

Let the games begin............ -Shawn

jetting in carb..and or.Timing . You leaned it out, no the electrical problem did not cause this. Spend the money and put it on a Dyno and get it setup right.? why would you run it 3/4 throttle in the straightaway???? when a engine starts to lay over shut it down. you'll save yourself alot a agravation. Sounds like a easy fix. a couple of valves and you'll be ready to go.

big time detonation. Most likely blew the head gasket on the one side.

Pull the rockers, blow air into the cylinder and see where it leaks to. Neighbor cylinder, water jackets? Just listen, you'll hear it.
If it is a head gasket, plan on replace both sides.

Like Jim said, either it was stupid lean, or the timing was to far advanced. I know the compression on the SEs is low, but you weren't trying to run 87 or 89 were you?

What are you using for a fuel pump?

Originally Posted by jimclauss

why would you run it 3/4 throttle in .

Jim, Jim, Jim. This is one of the classes were winning is arriving on schedule, not necessarily first.

We watched (and listened) to the video of your initial test runs and noticed a lean pop. I could've sworn that Paul said he was going to contact you to make sure you fattened up that carburetor. It was dyno tested here at 1200 feet and now runs at sea level with rich oxygen content. Without tuning to that new elevation, the problem seems to have been running lean. I'm really glad that bottom end wasn't hurt! Just like Jim says, go through the heads and tune it to your conditions. Seeing you've burnt the electrodes off the spark plugs (which is part of what was going away in the power) tells most of the story.

Originally Posted by jimclauss

Excuse me, I thought it was a race.

In all honesty, it is, but they don't want to see anybody exceeding 85. Not sure whats inside the enigine, but at 7000, that could be enough to consider backing off the throttle.
It may want some gear. The Millers would be in a better position to determine that. For right now, it needs the heads removed and see where the compression is going.

Originally Posted by Shawn Waters

Yeah yeah, very funny GN7.
The reason for 3/4 throttle was because Dad had a whopping 15 minutes of time in the boat before that initial race. We were trying to go out easy with the hopes of finding some bugs. Turning 7000 RPM @ 3/4 throttle with a small block in a "big" for the class Biesemeyer has got to get some credit though right????
-Shawn

See above post Shaun. It CAN be very impressive. But with the right gear, the same small block in my 3000lb 20ft V bottom could spin 8500...for a short time.

Originally Posted by Shawn Waters

So one thing I read last night while doing some research was that if a plug (or plugs like in our case) is not tightened correctly you could draw air in past the threads from the outside and create a lean situation for yourself. I wonder if this could be a partial reason.........
Something else big-time I did not mention before that I should have is that the cylinder that had the lowest compression reading appeared to have an exhaust valve that was stuck open as we went through that side bumping the engine over carefully with the valve cover off checking valve clearances. Possibility that we have some pieces of porcelain from the plug on that one stuck in between the seat and the valve?
My dad went to work tonight taking things apart in his shop and will have those heads off tomorrow for inspection. At that point I'll post some pictures of the findings and drop the pair of heads off for inspection and probably a valve re-do.
Do you guys think we really need to go as far as taking the whole engine out and tearin it down to inspect everything if we didn't find anything in the filter? There is a reason we started in the SE class..... a limited budget.
-Shawn

Depends on what you find when you pull the heads. I would cut open the filter. It never hurts. If it was detonation, it can take out the rod bearings.
I doubt the loose plugs were the cause. If it was lean, it was probably even leaner at 3/4 throttle at that RPM.
If your running an HEI, severe miss firing will cause the tach to act erratic, as could a intermittent short at the start solenoid.

Originally Posted by gn7

Depends on what you find when you pull the heads. I would cut open the filter. It never hurts. If it was detonation, it can take out the rod bearings.
I doubt the loose plugs were the cause. If it was lean, it was probably even leaner at 3/4 throttle at that RPM.
If your running an HEI, severe miss firing will cause the tach to act erratic, as could a intermittent short at the start solenoid.

We have a System 1 (I think that's what it's called) filter that comes completely apart for inspection and cleaning. We broke it down and went through it very closely. We MAY have seen some shimmers, but that MAY have been our minds creating something that really wasn't there. Very hard to tell and I feel pretty confident that it passed that inspection.
And yes we are running an HEI. Is that something we can bench test or something? I didn't think about that one....
-Shawn