running problems after head gasket
Discussion
Nick1point9 said:
How much was skimmed? Any evidence the head may have been skimmed before? I guess it's possible that the squish zone has been affected by the skim.
But I await more informed people to say otherwise!
Nooo, no matter how much you skim from that head the squish clearance won't change, that is altered by the block (deck height), piston height and head gasket thickness.But I await more informed people to say otherwise!
An air leak seems to fit, especially with the revs increasing on changing gear and almost stalling.
If the idle valve is disconnected, it'll be able to rev by itself on air getting past the throttle, and at idle, air can come in at that point and the MAF gets not readings for air coming in the normal way.
If the idle valve is disconnected, it'll be able to rev by itself on air getting past the throttle, and at idle, air can come in at that point and the MAF gets not readings for air coming in the normal way.
Nick1point9 said:
Evoluzione said:
Nooo, no matter how much you skim from that head the squish clearance won't change, that is altered by the block (deck height), piston height and head gasket thickness.
Touché! I knew someone would be along to correct me!Evoluzione said:
Nooo, no matter how much you skim from that head the squish clearance won't change, that is altered by the block (deck height), piston height and head gasket thickness.
If you skim the head, the squish/quench clearance will change! It's the same as installing a thinner head gasket.I think the most likely explanation here is a vacuum leak, by the description of the symptoms.
ian_uk1975 said:
If you skim the head, the squish/quench clearance will change! It's the same as installing a thinner head gasket.
Squish clearance is the distance from the flat top surface of the piston (if any, not all pistons have this) to the flat surface of the cylinder head surrounding the combustion chamber. That distance doesn't change when skimming a head - only when skimming the block.The distance from the piston crown to the top of the combustion chamber will reduce but that isn't defined as a squish clearance.
Pumaracing said:
Squish clearance is the distance from the flat top surface of the piston (if any, not all pistons have this) to the flat surface of the cylinder head surrounding the combustion chamber. That distance doesn't change when skimming a head - only when skimming the block.
The distance from the piston crown to the top of the combustion chamber will reduce but that isn't defined as a squish clearance.
Having trouble visualising that, but I don't doubt you are correct The distance from the piston crown to the top of the combustion chamber will reduce but that isn't defined as a squish clearance.
Time to do some revision as my mind has evidently gone a bit hazy on this topic!I know a lot of people seem to get unnecessarily hung-up on quench when they're only building a street motor. I have about .058 quench on my 383,but still make just shy of 500bhp on super unleaded with no knock.
Your squish is 1.5mm in European
We would run .9mm on a street motor running to 8000 rpm for safety .75 in race mode
Your bhp per litre is 80 not to shabby but room for improvment we would expect that from a factory motor
Honda S2000 runs 120 per litre N/A Mitsibishi runs 200 per litre (Turbo) in their FQ400
We would run .9mm on a street motor running to 8000 rpm for safety .75 in race mode
Your bhp per litre is 80 not to shabby but room for improvment we would expect that from a factory motor
Honda S2000 runs 120 per litre N/A Mitsibishi runs 200 per litre (Turbo) in their FQ400
PaulKemp said:
Your squish is 1.5mm in European
We would run .9mm on a street motor running to 8000 rpm for safety .75 in race mode
Your bhp per litre is 80 not to shabby but room for improvment we would expect that from a factory motor
Honda S2000 runs 120 per litre N/A Mitsibishi runs 200 per litre (Turbo) in their FQ400
Except the S2000 uses a high-revving, 4v, MPI lump and a Gen-I SBC is a slow-revving, 2v, carb affair We would run .9mm on a street motor running to 8000 rpm for safety .75 in race mode
Your bhp per litre is 80 not to shabby but room for improvment we would expect that from a factory motor
Honda S2000 runs 120 per litre N/A Mitsibishi runs 200 per litre (Turbo) in their FQ400
An NA 383 running 120/litre would be an insane full-on race motor. In fact, I doubt such a specific output is even possible without FI. Even then, it would be a race engine. If I wanted to improve my output, I'd be porting the heads rather than trying to optimise quench Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff