Hey guys, Its been awhile. Hope everyone is having a great summer and going fast! So I have been running my blown 489 chevy bb all summer every weekend and its been running like a champ. 83 mph at 5400 with a 27 3 blade. I had changed the top pulley and now up to 8.5 to 9 lbs of boost for the past 2 months. Was running 77 to 78 mph @ 5000 with 6.5 lbs of boost with the other pulley and same prop. Saturday noticed a miss and idled in for about 15min or so. Pulled some plug wires and found 3 dead holes 1,5,7. Had water in all three.
Pulled the head this afternoon and the top right of the head gasket of # 7 was burned through to the water jacket but the spark plug showed NO sign of detonation? It looked great. Pistons all looked good. I pulled the plugs on the right bank and the #8 plug had lost 1/4 of the tip and splatter was obvious . All the others looked perfect. Not sure why the rear 2 cylinders got beat up and how the plugs can be in such good shape on the bad side?

I think I mentioned to you, a couple times this year, that you were pushing your luck spinning a 174 B&M blower, to make 6-7lbs of boost on that engine. So you went and turned it up to 9lbs of boost, and hurt the engine now.

Not only do those little blowers superheat the intake air temps, they also have poor fuel distribution with a single carb. Your rear cylinders were more than likely, starving for fuel.

When you have lean mixture, lots of ignition timing, smoking head gaskets or beating the piston, is pretty common when the engine is at its peak torque range. Also you had mentioned in your thread back in may, that you did a compression check and you had 150 psi in the cylinders. That is a bit high for your normal supercharged marine pump gas roots blower setup. It can work, as that is what my cranking psi is, but for it to work, you need a proper setup. Like right size blower, cool water temps, limit the boost amount ( I run 6psi with no intercooler), and a good amount of fuel to keep things cool.

Copy that MT. What make head gasket are you using? I know I have reached the end of the line with my set up.

I have MLS gaskets. Problem with mls is that they are so tough, many times you will melt a piston before burning the gasket thru.

If your going to keep that blower, use fel pro gaskets and cheap bolts so you have a relief valve before it melts a piston

Sorry to high jack the thread but have a question about the 174 on a 454. With that blower on a 454 can you run it for extended periods of time like 30 or so miles on a leg of a poker run or is that to long and would build up to much heat?

You can run it, I just wouldn't do it at WFO.

Are you talking wide open the whole time? That is a complicated question that needs a lot more detail. Even the 174 can be ran for extended periods, but at low boost and chilled for ultimate safety. Bigger blowers make less heat and carry more CFM at lower PSI. Compressing air causes heat, plus that little blower spinning at 20k rpms causes heat. Heat causes detonation, excessive compression without the proper octane causes detonation.

Honestly, the OP at 9 lbs with no chiller I am surprised it was just the HG

To funny lil red. 4bus, I have a chiller ! I'm crazy but not nuts!

Got everything back together and fired her up. Second lesson learned. Should have had the head checked. Low compression on 1 ,5 and 7. 1 and 5 being the worst. Did a leak down test and looks like the intake valve's got beat up a bit. Did a quick tear down and off to the machine shop with the head this morning.