MikeMeyerhoff Posted October 30, 2005 Report Share Posted October 30, 2005 I'm also runing a sch284h cam with raised compression... I noticed that my car seemed to idle better/smoother with higher base timing. I understood that octane affected timing, but never really considered the cam specs could have a noticable affect. I really need to do some tuning on my car! mm Link to comment Share on other sites More sharing options...
Shelby Posted October 30, 2005 Report Share Posted October 30, 2005 a lot of guys don't know or understand ,,this,,when you change the cam duration and nothing else you will increase the amount of fuel in the intake charge,,why cause the valve is open longer so more fuel/air has time to enter the chamber ,this makes the combustion mixture richer then it was with no other changes being made it's also the reason guys with programable ecus have to change their fuel map after a cam swap,, this also works back wards,, going from say a 284 to a stock cam will lean the mix Link to comment Share on other sites More sharing options...
Shelby Posted October 30, 2005 Report Share Posted October 30, 2005 The only other time I saw a head gasket like that was on a blower small block Chevy where he ran gasoline in an alcohol setup. Real dumba$$ because alcohol blower engines can run 11.5:1 compression before the boost of the blower but when you put the gasoline in there look out. On that small block engine it not only took out the copper head gasket but it blow torched through the head and block too. I would say that your engine problems resulted from more than just one cause and more than likey it was multiple things all put together that did it like too high of boost not enough octane fuel and most likely the ignition timing was way too high. I'm going to ask a friend who has seen more carnage than I have too see what he thinks. It doesn't appear to be detonation though, just a leanout and I would say the head lifted to let the combustion gasses start going through then the blowtorch affect came into play. Max boost was 16 psi on that piston. Final timing 20* on an SDS4E. 30* total timing @3000 rpms. The headgasket was running the stock timing curve on the stock TBI. The headgasket I know as much was from the unmetered air. There was a huge tear in the air inlet boot, must have weakened from the long ride up to the track. The headgasket and the piston are 2 totally different timeframes... the gasket I had in with that piston was the TEP metal shim. I am very conservative on both timing and boost. you know Mike i have beat my stock engine much harder then you did your engine and so far i have had not a single problem after i went to the arp studs , and durring that time a saw almost 30 lbs boost more times then i want'd to hehe , and run 18 lbs every day now i will say a ONE time boost spike kill'd new head with the stock bolts , crack 'd the head and blew the head gasket ,but it still ran for another 300 miles untill i had the time to swap the head out Link to comment Share on other sites More sharing options...
brianpaul98 Posted October 30, 2005 Author Report Share Posted October 30, 2005 You just need to get one of these and be done with it. http://www.2.6liter.com/userfiles/brianpaul98/T4%20draw%20through/2.6%20Liter%20Draw%20Through1.jpg No more ripped boots to worry about. Link to comment Share on other sites More sharing options...
Boosted_One Posted October 30, 2005 Report Share Posted October 30, 2005 Brian - this is where I am at - http://a7.cpimg.com/image/CD/48/51300557-4ca0-02000180-.jpg http://a0.cpimg.com/image/6A/B0/52168810-b64c-02000180-.jpg That ripped boot was on my TBI setup 4 years ago..Karman Vortex MAS...I'm now on a MAP sensor and SDS... I'm much past that... Link to comment Share on other sites More sharing options...
Boosted_One Posted October 30, 2005 Report Share Posted October 30, 2005 you know Mike i have beat my stock engine much harder then you did your engine and so far i have had not a single problem after i went to the arp studs , and durring that time a saw almost 30 lbs boost more times then i want'd to hehe , and run 18 lbs every day now i will say a ONE time boost spike kill'd new head with the stock bolts , crack 'd the head and blew the head gasket ,but it still ran for another 300 miles untill i had the time to swap the head out I got studs too...that's mandatory. Truthfully I don't think my combinations were all that great either on that last setup. All I know is I changed everything I thought was an issue and this new motor is night and day difference. I went for reducing backpressure, did mods to the block and other things like an agressive head port, header, larger hot side A/R. I've never had a setup that pulled decent past 7K and this one does now. Live and learn... when I was modding the last setup in '98 there wasn't a nice platform to go by like we do now.... Link to comment Share on other sites More sharing options...
TurboRaider Posted October 30, 2005 Report Share Posted October 30, 2005 Just dont confuse cold clearnaces with hot clearances. The forged pistons may start out looser but since they expand faster once they are hot they should have a similar running clearance to grannies pistons. Isn't this statement a bit contradictory? If the pistons start out looser and expand faster a tight piston to wall clearance like .002" will leave not much clearance. What I'm talking about is machine shop engine honing clearances. I will need to find the paperwork on the piston to wall clearances where it shows NA engines all the way up to Blown / Supercharged and as you go more radical the P to W clearances increase. More power, more heat, faster expansion rates = more clearance. I found the ring gap paperwork from Wiseco but the piston paperwork is MIA somewhere. All I'm going to say from experience is that if you put a brand new set of pistons in your engine with a stock P to W clearance of .0015" - .002" and you run the engine any other way than normal driving they will be scuffing the skirts and the cylinder walls after a few good hard runs. What I was commenting on is that your inital clearance depends on a number of factors. On a cast, higher silicon alloy piston the initial clearance is smaller because the pistons expand a lot less. That is not saying that if you run them harder they dont need a bit of extra clearance, but not to the order that a forged piston made of a low silicon alloy. When hot both pistons will have / should have a similar running clearance that are a lot tighter than many would beleive. Kevin Link to comment Share on other sites More sharing options...
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