Thread: Too much crankcase pressure, novice engine builder

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The goal was to run on pump gas. Do you think that is still feasible? Race gas isn't the easiest thing to get a hold of in my area, though a few stations in the city sell 93. I'm familiar with the function of octane and timing. From my understanding, if some timing gets pulled out, lower octane gas will work ok at the expense of some horsepower. Does that sound right?

I'm running a 1411 Edelbrock. I have an AFR gauge and it's set to run a little bit rich right now just because I don't completely know what I'm doing when it comes to power tuning and I know it's better to be rich than lean. I currently have it idling around 13.5 AFR and WOT gets to about 12.0 AFR. I don't know what my timing curve is. I'm using an HEI distributor. Not sure what the exact model is however. It was a piece I was running on the old engine before the rebuild that I bought from Autozone 8 years ago. I have a basic timing light though.

Originally Posted by NegativeZero

I'm familiar with the function of octane and timing. From my understanding, if some timing gets pulled out, lower octane gas will work ok at the expense of some horsepower. Does that sound right?

Yes, once you've got the AFR dialed in. Curious, are you running aluminum heads or iron? Also, is the 91 octane fuel you run an ethanol blend or ethanol free?

Aluminum heads by Trick Flow. The gas is 100% gas, no ethanol.

Originally Posted by NegativeZero

Aluminum heads by Trick Flow. The gas is 100% gas, no ethanol.

With 10:1 compression and Trick Flow heads I believe you'll be just fine with 91 octane, and I prefer non-ethanol fuel personally, for non-computer controlled vehicles or for anything that doesn't get driven a lot (everything I own!). Like Dave & Jerry said, doing the leak down test is a good idea, and if everything is OK there back some timing out and see if it makes a difference. Just my $0.02. There're a lot of smarter guys on here, and decades upon decades of experience!

Originally Posted by NegativeZero

I'm running a 1411 Edelbrock. I have an AFR gauge and it's set to run a little bit rich right now just because I don't completely know what I'm doing when it comes to power tuning and I know it's better to be rich than lean. I currently have it idling around 13.5 AFR and WOT gets to about 12.0 AFR..

JMHO, your AFR numbers above are not rich enough to wash the rings. And, the compression dropping severely is a good indication of there may be more trouble ahead.
Glad you're tearing it down, hope you get it solved.

Originally Posted by 36 sedan

JMHO, your AFR numbers above are not rich enough to wash the rings. And, the compression dropping severely is a good indication of there may be more trouble ahead.
Glad you're tearing it down, hope you get it solved.

Yea once I saw that big a drop in compression, I knew it was time to crack it open. Rings are fairly cheep, so I'm honestly not too bothered by it. Planning on reducing the gap to 24 on the top and 25 on the bottom. I still think that leaves plenty of room for low boost applications and will hopefully reduce blow-by. Also adding a windage tray so hopefully keep crankcase pressure down a little bit more.

Originally Posted by NegativeZero

Yea once I saw that big a drop in compression, I knew it was time to crack it open. Rings are fairly cheep, so I'm honestly not too bothered by it. Planning on reducing the gap to 24 on the top and 25 on the bottom. I still think that leaves plenty of room for low boost applications and will hopefully reduce blow-by. Also adding a windage tray so hopefully keep crankcase pressure down a little bit more.

JMHO, I really don't think your ring gaps were causing your trouble, unless they were significantly larger than you posted. In my youth (a long, long time ago) I ran some pretty worn out motors, a few had enough blow by to lay out a smoke screen and oil slick out the tail pipes, yet not enough crankcase pressure to blow out gaskets.

When you tear it down look it over closely, I believe there's more to this story than what meets the eye.

Also, I think you are a little confused on what a windage tray does, it does NOT reduce blow by or crankcase pressure, generally they are good at minimizing aeration of the oil at high RPM, which helps with a speedy return of the oil to the sump. There are lots of pro's and con's (and opinions) on windage trays.

I was told when I was young (many years ago) there are two phrases that apply to motor building and troubleshooting;
MOTOR BUILDING - Check, check, check, MAKE MISTAKES less, less, less
TROUBLESHOOTING - Test, test, test, SPEND less, less, less

Originally Posted by 36 sedan

JMHO, I really don't think your ring gaps were causing your trouble, unless they were significantly larger than you posted. In my youth (a long, long time ago) I ran some pretty worn out motors, a few had enough blow by to lay out a smoke screen and oil slick out the tail pipes, yet not enough crankcase pressure to blow out gaskets.

When you tear it down look it over closely, I believe there's more to this story than what meets the eye.

Also, I think you are a little confused on what a windage tray does, it does NOT reduce blow by or crankcase pressure, generally they are good at minimizing aeration of the oil at high RPM, which helps with a speedy return of the oil to the sump. There are lots of pro's and con's (and opinions) on windage trays.

I was told when I was young (many years ago) there are two phrases that apply to motor building and troubleshooting;
MOTOR BUILDING - Check, check, check, MAKE MISTAKES less, less, less
TROUBLESHOOTING - Test, test, test, SPEND less, less, less

I'll be looking everything over to the best of my ability, trust me. I don't think the extra gap was necessarily the cause either. But I'm sure reducing that gap a tad won't hurt. I want to t minimize the smoking.

Since I'm not incredibly knowledgeable of this stuff, I'm debating sending the crank, rods, and bearing, to a machine shop so that can measure them with the proper tools.

I know a windage tray doesn't reduce blow by, but like you said, it does reduce aeration of the oil, which from my understanding would keep pressure down. Maybe not, but still. I'm planning on revving this engine out to 7k so it seemed like a good idea.