bubbleguinea Posted June 3, 2007 Share Posted June 3, 2007 Sooo..a few of you know i used to have some headgasket problems back in the days...untill i figured out my head was warped in the rear two cylinders.... well....recently right before SEZ, my felpro gasket blew again by the waterjacket on the rear cylinder...i defaulted that to being a crappy felpro gasket.... well- i was supposed to leave for basic training in the Marines Corps on may 14th, but my recruiter didnt get my paperwork finished in time, so now im leaving in september....and i never told anyone this, but right before i was supposed to leave, something very bad happened to my engine... it started to smoke like hell through the PCV, and idel real rought....well, i kept driving it for the past month, cause i needed to have a car to get to work with Paul (Majick) at Main auto parts....well ive been driving on what i thought was 5 cylinders till today... i finally did a compression test, and ive got 225psi in the first 4 cylinders, and 125 in the rear two...then it got me to thinking... the only time ive ever had a problem blowing gaskets, it has been in the rear... when we went to the dyno, my AF ratio was spot on....so i know my car is somewhat tuned right via SDS......but the only thing i can think of is detanation!!! how could this happen? i guess it blew the rings this time, cause i torqued my head down to 70ft/lbs instead of 65, so the gaket couldnt have blown real easily... for the pro engine builders, and thoughts on whats up? could my rear fuel injectors just not be squirting that well, but still maintain a good af ratio? Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted June 3, 2007 Share Posted June 3, 2007 i'm not a pro, but could it be because the rear cylinders run hotter because of poor oil circulation? i know that the rear cylinders suffer from this and a good swap is the turbo oil pump, but my #6 cylinder blew the headgasket as well, and i was attributing it to oil circulation.... Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted June 3, 2007 Share Posted June 3, 2007 #6 is the furthest cylinder from the waterpump and cool fresh antifreeze.. Cylinders #5 and #6 run the hottest.. you probably blew the headgasket on cylinder six which blew cylinder fives seal. Increase heat = increased chance of detonation or pre-ignition. Best way to tune is individual EGT sensors on each cylinder much like aircraft do... but clearly this is hard to achieve. Tuning on the other hand for each indivdual cylinder and timing is expensive and difficult to do Quote Link to comment Share on other sites More sharing options...
bubbleguinea Posted June 4, 2007 Author Share Posted June 4, 2007 prox, thats what i thought... its just i dont understand what to do... ive got turbo oil pump, and temp never goes above 190degrees..... theres got to be something else up with it...maybe i just need to recheck timing and all that...and get some hotter plugs... Quote Link to comment Share on other sites More sharing options...
MatMan Posted June 4, 2007 Share Posted June 4, 2007 have you had the head and block boiled? There may be some corrosion or other blockage in the water jacket and/or oil gallies in back...? Quote Link to comment Share on other sites More sharing options...
bubbleguinea Posted June 4, 2007 Author Share Posted June 4, 2007 yeah...it was acid dipped when it came back from the machine shop...(block) Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 4, 2007 Share Posted June 4, 2007 Deadhead fuel rail, with swarf logging the back two injectors, causing them to run lean? Quote Link to comment Share on other sites More sharing options...
bubbleguinea Posted June 4, 2007 Author Share Posted June 4, 2007 tonyD, thats what i kinda thought...perhaps my back injector (s) are not quite running to full capacity...but i dont understand why my AF ratio would be good if this was so....unless i just richened it up to compensate for it, and i didnt realize it... ill test the injectors when i start the head swap.... im in the process of paininting the new spare engine and getting it ready with a new timing kit and gaskets...then in one long day im going to pull my short block, install my head on the "backup" junkyard engine, and figure out whats wrong with mine.... Quote Link to comment Share on other sites More sharing options...
fear_me Posted June 5, 2007 Share Posted June 5, 2007 with #5 and #6 being the furthest cylinder from the waterpump and cool fresh antifreeze..... what about using an electric water pump to solve this problem? that way the antifreeze is always moving at a constant presure not like driven off of a pully were the flow will slow down in the lower rpms. ~Andrew Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 5, 2007 Share Posted June 5, 2007 tonyD, ...but i dont understand why my AF ratio would be good if this was so....unless i just richened it up to compensate for it, and i didnt realize it....... Two injectors down 20% on flow because something like a fuel filter's cellulose fibers got clogged in the inlet injector screens will easily be compensated for by a manifolded O2 sensor where you made the other 4 injectors pig rich... JeffP's engine lost four or five pistons from detonation from the very same thing. Watched on the wideband at is instantaneously went from 12.5, 18.0, 22.0 as quick as the display would accomodate it. Never heard a ping, never heard a rattle... Just Jeff calling one day saying "there's a lot of smoke coming from my valve cover, it's overwelming my breather box already"... Flow testing is the only way to verify them. RC here you come. As for an electric water pump...who needs water flow at lower engine speeds. This didn't happen at lower engine speeds, it happened above 3500rpm, best guess. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted July 6, 2007 Share Posted July 6, 2007 Sorry to bring an old topic up but there is another thing I'd like to explain about individual cylinder abnormalities and what you won't find on a wideband. If a single cylinder isn't flowing the same amount of air or fuel or running the same timing, etc. it will be almost impossible to catch it. Here is a somewhat dramatized example of what can happen; I've seen it multiple times in real life: Actual Individual Air/Fuel Ratios at WOT on Boost: Cyl 1: 11.3:1 Cyl 2: 11.3:1 Cyl 3: 11.2:1 Cyl 4: 11.3:1 Cyl 5: 11.2:1 Cyl 6: 13.5:1 Reading From Wideband during this period will be ~11.8:1. You would be tuning for 11.8 and that's what you show on the wideband but an individual cylinder is not running right. The easiest way to catch this is with individual EGT probes. Obviously very few cars run this other than OEM test engines and tune shop test cars. The next best thing is to run an EGT gauge in the one cylinder you know the particular engine runs the hottest; ie., the sixth cylinder in the L28, evidently. From past experience, I had 4G63's and they liked to suck the fuel rails dry so you always used the EGT probe in the cylinder farthest from the fuel pump. Mark Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.