Ok so heres the deal as far as what I know; I wasnt logging because I havent setup my new laptop yet (yeah I know, stupidity). The engine is a recent budget buildup with fairly good parts. Quick rundown, cnc'd heads with roughly 54cc chambers, KB prem. 2618 18.6 dish pistons with scat 7/16" 4340 I-beams and a stock crank with felpro 1074 gaskets, an s-trim putting out about 12-14 psi @ 6500 w/ cc305 cam, and a single meth kit, no I.C.

So I was trying to track down a rear end vibration thats been driving me nutz lately and I reset my pinion angle to -2* and went for a ride and it seemed much better so,......I took it where I could get it above 100. Car usually runs around 10:1 AFR when the meth kicks in. Ive had the car this quick once b4 this with this setup and it started idling kinda funny at times, and rough cold starting, with a high idle, but drove perfectly normal otherwise, no overheating. So I take it WOT all the way to around 100 and the vibes were drastically less, and as I was watching my AFR it drifted north to 12:1 momentarily as I hit 110 so I let out of it. Dont know what happened, did fuel slosh momentarily push air through the rails, did the meth kit shut-off momentarily, or was that just a innaccurate reading wideband as the engine started consuming water? As I coasted down to around 50mph I immediately knew something wasn't right as the eng. started missing and I had to throttle it some to keep her from fouling out but it still ran "well" under load and then I noticed smoke pouring out the pipes and it didnt smell like oil. I babied it back to the shop as quick as I could smoking everybody out, lol. I made it back to the shop and unfortunately I pegged the temp. in less than 2 miles as I pulled in (I know, should have shut it down but honestly I didnt notice it was getting hot as I was just trying to get her back to the shop, thought it might be a piston/ring failure at 1st).

So on the to question and answer part. Was this momentary 12:1 AFR that bad to cause the blown head gasket, or do you think maybe it was just a bad seal? undertorqued? I don't remember but I think I may have torqued them to 65 ft/lb with oil when I now see ARP bolts are supposed to be torqued to 85 with oil and 70 with arp lube. Should I be looking into cometic gaskets or will I need to get the block cut for proper sealing of these? Am I pushing too much boost for 1074's? I have a smaller pulley I was going to use as well until this. The car normally hits 10 psi quite easily but more than 12 psi if I really stay in it past 6500 rpm with the current pulley. Im personally chalking this one up to error on my part in assembly, but I'd like to get your thoughts on this? I hope I didnt hurt anything else, Ill check the heads for straightness when I get it apart. Maybe Ill get some chamber work done to lower the compression a little more while theyre off. Should I change both gaskets if only one is blown, or tighten the other one down more? Its a good thing I have patience for this car.

 

Well it's hard to say just what got you but looking at the gaskets will probably tell you something - maybe it was the head torque or maybe you detonated.

You can make pretty high boost on the S-trim but it isn't efficient at high boost/high rpms and it's making a lot of heat so even assuming your tune is OK, any hiccups from your meth injection and you are screwed.

You don't say what your timing is but I'm guessing your static compression at 9.7:1 or so and I figure you somehow detonated and pushed the gasket out.

So, better gaskets, better safer tune, lower compression, more efficient blower, all these things may help you out.

 

On boosted applications you should go back and retorque the heads after a few heat cycles. Could be detonation. Sounds like you have a pretty high compression ratio.

 

Yeah, ill get it apart this week/end hopefully and we'll know.

True, and Ive never pushed it that far b4 to see that kind of boost, so I might have ran lean in the tune. Im thinking of doing a DIY aftercooler setup or bite the bullet and fab an intercooler(which I really dont want to do since the lack of room with a T/A and no airflow) along with a higher psi meth pump.

Sorry, I knew I'd leave something out. I believe I have it set at around 26* above 4k rpm. I believe the comp. ratio calculator says 9.5:1 with stock deck height and 1074's.

Im kind of stuck with this blower for now as funds are limited and I just upgraded to this one from a lowly powerdyne and trying to buy a house. Ive got a 4340 3.75 crank and 4 bolt block so far for a future buildup and plan on getting a D1SC then, but for now I want to just get this boat anchor back on the road reliably as it was quite a rocket til now.
I guess I need to either work these heads over a little more to lower compression or get another set and sell these for starters. Maybe pull a little timing up top and get a 250psi meth pump and get my laptop loaded up so I can log. I see a lot of guys here are running the 1074's though? Without o-ringing the block or getting the block cut for surface finish, what choices do i have? Ive read cometics wont seal without block prep, is this 100% true? Or do I just get the chambers worked and find a thicker gasket to bring her down to 9:1 or less?

 

e85!

 

Your combo will work with a good tune unless something goes wrong. You can always add a second meth nozzle, too. For gaskets, deck prep is important with Cometics. Maybe you could look into Titans or something similar. I would think the best thing for you to do if you can't use fancy gaskets just yet cause the block is in the car is to clean it up the best you can without scratching or gouging the surface, use your 1074s and make sure you torque your bolts down with the proper moly lube, then limit your boost to 10 or 12 and it will still be a gas to drive. Also check your heads for flatness so you don't have a repeat.

 

Well, I pulled the plugs and found coolant in about half the cylinders. Strange I thought. Drained all my coolant out so it wouldnt suck anymore back in the cylinders and had no coolant in the oil so I put some fresh plugs in just to fire it back up and see if it knocked. At first start it kinda sounded like a wrist pin knock but quickly went away. These KB pistons are kinda loud when cold, they had the proper clearance when I put it together, not excessive. So other than the normal cold piston slap, I dont think I hurt it but Ill roll it over and check piston hieght when I get the heads off. So how the hell did I get coolant in 4 out of 8 cylinders? Only thing I can think is it lifted the heads and pushed out the gaskets, but on 15 psi? I must not have torqued them enough is all I can figure. They're ARP bolts by the way.
So I was trolling ebay the other day and came across something that seemed to good to be true. If they are what he says they are, then these will not only help lower my compression ratio, but they flow better than what ive got now.

http://cgi.ebay.com/ebaymotors/ws/eB...=STRK:MEWAX:IT

I thought about it overnight and figured I cant pass them up so I snatched them up. Gonna get 'em checked out and flowbenched and hope the decks haven't been cut yet. What do you guys think? Ive found a little info on them, but not much out there.

 

Just arp bolts and 1074s? I can easily see how it happened I did the same thing. People keep saying the 1074 should be fine for boost - maybe in an ideal world but they won't survive if things are not perfect.

I think I lifted the heads at first. Go with studs next time around.

I went back with arp bolts and a copper gasket - leaked again - I think this is the point when I broke the pistons. Boost + water = bad things.

3rd time I just pulled the heads - slapped on commetics and arp studs - sealed great and no water issues. 3 broken pistons and lots of burnt oil though.

 

If I had to choose, I would rather have to replace gaskets than have to replace some pistons...

 

Agreed,.....which is why I think these heads might be the answer to my prayers. Although im going to need offset rockers for these, the larger chambers should drop my compression to a pump gas friendly >9:1. With a little added insurance like a larger meth pump (mine is only 150 psi, so 2 nozzles is out of the question as it might drop 2 much press. to properly spray) and another walbro pump in the tank SHOULD do the trick, I think, lol. Im pondering a front mount intercooler or an aftercooler, but I think ill try the extra walbro and larger meth pump first and pull a little timing. I think Ill give the 1074's another shot, and make sure I properly torque them down this time around.

 

Never had a problem with 1074's @ 24+ lbs of boost. The tune is the most important part . Running them on the new TT setup looking for 7 second 1/4 miles.

 

And what head/bolt combination?

I'm willing to bet its not a stock casting with just arp bolts.

I might consider going back with 1074s next time just because of the cost.

 

How much are you willing to bet? Stock castings! bolts at first and then studded but never hurt a head gasket .
The new set up is not stock castings and is studded.

 

Very cool then. Mine held perfectly fine until nearly 5k miles. Could have been bad gas who knows. The pistons did not show signs of detonation.

 

Well, finally got the heads off today. Ill try to get some pics up this week. One piston looked like it had slight detonation but im not sure what im looking for. Anyone got some pics? The heads were still str8, so I cleaned them up and made sure all the pistons came up the same height. Both head gaskets were blown on the middle cylinders near the intake side like some others ive seen. It pushed the firing rings right into the bolts and actually broke one of the firing rings and split the gasket layers and almost spit it into the lifter valley. Could be any number of things to blame. I made sure I used the arp lube this time and torqued them to 80 ft/lbs but used an adapter and extension, which I know will cause some torque loss. Made sure the surfaces were spotlessly clean this time as well. Plan on pulling some timing, higher press. meth pump, and possibly a 2nd walbro in the tank. Im wondering if running them w/o the bucket is a bad idea or not due to cavitation under hard pulls? Can you fit 2 in the bucket?