jgedde
Well-Known Member
- Joined
- May 17, 2016
- Threads
- 38
- Messages
- 297
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- Location
- Middle Island, NY
- First Name
- John
- Vehicle(s)
- 2015 GT Premium PP, M6, Triple Yellow
- Thread starter
- #1
Anyone have their cylinder heads off with engine in car? I may have blown my head gasket.
My Whipple supercharged GT has a bad misfire on cylinder 8. I am Mode fairly sure that's where the misfire is - the engine doesn't throw any codes apart from random misfire. However using ForScan's Mode $06 test mode, I read the misfire counts on cylinder 8 to be vastly higher than the others (Mode $06 in PC version not iOS or Android).
I have also noticed coolant level has been dropping. Compression is more or less OK - hard to measure since I don't have a long reach plug adapter and have to use the rubber tipped thingy. It's not the plug or the coil. Swapping them around makes no difference. One clincher making me think head gasket is that my coolant gas tester shows a slight bit of combustion gas in the degas tank.
The final nail in the coffin is that the engine still sounds like it's missing on deceleration when injector duty cycle is zero! So definitely not fuel related. If no fuel, spark doesn't matter. so I can rule that out
It's gotta be a loss of compression somewhere. Yes? I'm thinking a head gasket leak between cylinders 7 and 8 and slightly into a water passage. Gonna do a leakdown test today to confirm. No signs of coolant in the engine oil.
I'm really hoping it's not a head or a block issue.
I have already changed the timing gear and OPG gears so I know how to take off the manifold, front engine cover, etc. My big concern is accessing the exhaust manifold bolts. Certainly can't do from above. Hopefully I can get at them from underneath. The second concern is that damn brace in near the firewall. Can I get the head off without removing that fiasco?
Wish me luck! Any words of advice are welcomed!!!
John
My Whipple supercharged GT has a bad misfire on cylinder 8. I am Mode fairly sure that's where the misfire is - the engine doesn't throw any codes apart from random misfire. However using ForScan's Mode $06 test mode, I read the misfire counts on cylinder 8 to be vastly higher than the others (Mode $06 in PC version not iOS or Android).
I have also noticed coolant level has been dropping. Compression is more or less OK - hard to measure since I don't have a long reach plug adapter and have to use the rubber tipped thingy. It's not the plug or the coil. Swapping them around makes no difference. One clincher making me think head gasket is that my coolant gas tester shows a slight bit of combustion gas in the degas tank.
The final nail in the coffin is that the engine still sounds like it's missing on deceleration when injector duty cycle is zero! So definitely not fuel related. If no fuel, spark doesn't matter. so I can rule that out
It's gotta be a loss of compression somewhere. Yes? I'm thinking a head gasket leak between cylinders 7 and 8 and slightly into a water passage. Gonna do a leakdown test today to confirm. No signs of coolant in the engine oil.
I'm really hoping it's not a head or a block issue.
I have already changed the timing gear and OPG gears so I know how to take off the manifold, front engine cover, etc. My big concern is accessing the exhaust manifold bolts. Certainly can't do from above. Hopefully I can get at them from underneath. The second concern is that damn brace in near the firewall. Can I get the head off without removing that fiasco?
Wish me luck! Any words of advice are welcomed!!!
John
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