I never throught of that...it doesnt sound like any exhaust leak ive heard before. I guess i could change the gasket out and see. Thanks for the suggestion.
X2 and the leaking header gasket would throw the O2 readings way off. Usually when I hear it I think it sounds like a rocker has a large amount of lash to the pushrod, very loud tap, tap, tap, but engine noises vary. If you want pop your valve covers off and run it for a minute and watch each valve/rocker as it goes throught the motions. If somethings off you can usually pick up the difference in motion after you watch all of them going through the correct motions. If you burn a valve compression in that cylinder will usually be close to zero. If you check your engine vacuum and it is reasonably smooth then you should be fine.
I did that yesterday and the rocker assemblies looked great while running. I also checked the pushrods and they were good and tight and no bends. i guess I'll order some new gaskets and give them a change out and see if that takes care of the issue.
Looks like you guys were right. Went to detach the header amd foumd that both both for number 7 cylinder were missimg. Hmmn. Guess i need to check the bolts more regularly. New copper gasket will arrive Wednesday. thank you all for your quick replies, saved me a lot of work.
Glad to hear it may be an easy fix. That's happened to most of us who run headers at one time or another! Devon
Got the new gaskets in tonight. Replaced the drivers side...btw NEVER again will i buy headers on a stage one type engine, these freaking bolts are such a pain in the ass. Anyway, fired her up really quick and wouldn't ya know it...noise crazy noise and engine runs like a top! Thanks again guys.
They are a pain, but at least you got it licked. Be sure to retorque after a few hot/cold cycles. Devon
LOL, oh yeah. I'll be re-torquing them every month from now on and after every night at the strip...now its time to get the carb tuned and THEN maybe some nitrous!
So after driving the car around the last couple days with the wide band hooked up I've made note of trends and would like to start my carb tuning. Here are the specs for the carb: Holley 850dp baseplate with stock metering blocks Proform 750 main body with annual boosters (with the smaller bores but taller venturis this effectively has turned the carb into a 950cfm based on what ive read) Pri/Sec jets 80's Secondary float it nitryl with indents for the jet extensions 3.5" high flow power valves front and back stock PVCR's secondary .078 PVCR's primary Stock IAB and FAB in the Proform main body Proform Fuel bowls (not installed yet) Driving impressions: -Car idles at 1000rpm in gear and roughly 2000rpm in park -Both primary and secondary throttle blades are cracked open probably .060 which is a lot but not enough to uncover the transfer slots just yet -At idle im seeing AFr in 18-19 range -While coasting to a stop AFR reads around 15 -As steady cruising speed in 4th gear as soon as i touch the gas even, so lightly as to not increase the rpm, the AFR drops to 11.5. If I mash the peddle it'll go to 10. -Haven't done any WOT test to see where AFR is but i would imagine it'll be rich. -The car responds well but doesn't seem very snappy if that makes sense. There's no bog or surge to speak of...it just doesn't seem to jump the way I think it should. -When cruising in 4th gear at 65mph AFR is 13.5. -Part throttle acceleration gives me anywhere from 10.5-12 AFRs. Not really sure why idle is so lean. The only thing i can guess is that the excessive overlap is confusing the O2 sensor, but honestly the car runs fine at idle so I'm not really sure if its worth messing with. I WOULD like to get the throttle blades closed to only have a .020 gap but I'm not sure how to go about that other than drilling holes in the throttle blades. My first step will be to jet the primaries back down to 72's since that's where they were when i was making my runs at the track. I also plan to change the secondaries down to 78's to see how that effects cruising AFR's. If i start to go lean at WOT due to the jet change on the sec, I'll open up the PVCR's appropriately. From there I'll start in on the Air bleeds and restrictions and see how finely tuned i can get this thing.
Do you really have a 1,000rpm drop going from park to in gear or is that a typo? I don't even know what to make of that if it's not a typo. At the 1,000-1,500rpm range if you have enough overlap it will screw with the O2 sensor and read lean. I'm not a master tuner, let alone on holley's so take ANYTHING I say in regards to that with adequate skepticism. I'd say the 13.5 cruising AFR is decent, especially considering the overdrive load. It won't get you huge mpg's but it should do decent. The AFR's should dip when ever you hit the throttle for the accelerator pump shot enrichment. It should be just that, a dip and clear out in a three or four count and settle where ever the actual jetting/PV is tuned too. Other than possibly loading up the plugs when at lower rpm, dipping into the 10's on the pump shot isn't too bad, but leaner wouldn't hurt. It might get snappier leaned out a bit too. That's all I got, I don't know crap about air bleeds, power valves or restrictors.
Yeah, your engine will not run with an A/F of 19:1... Cam overlap, and possible exhaust leak will show this "lean" reading. Remember that your sensors are designed to read O2, and our atmosphere has 21% O2...
Yeah, the idle drop has always baffled me. The problem is, I've always had to crack the tb's open more than they probably should be to get the car to idle when in drive so then when i shift into park the idle of course goes up. My initial timing is set to 24* so i dont think its a matter of not enough...although with only 5" of vacuum my vac advance doesnt work so maybe i should just dial in all 34* and lock the distributor. I don't know, I'm sure I'll figure it out eventually.
Gotmy new fuel bowls on today and I wish i had gotten them sooner; so much easier to set the level when you can SEE the fuel in the bowl. Anyway, while i had the bowls off i decided to do some jet changes. I went from 80s all around to 74 pri and 78 sec and i also swapped the 50cc primary accelrator pump to a 30cc pump. Went for a quick drive and here are my results: WOT - 10 Cruising@65 - 13ish Light Acceleration - 10.5-11.5 Came home and jetted down again, this time 70pri and 74 sec WOT - 11.5 Cruising@65 - 14.2-15 Light Acceleration - 11.5-12.5 I think I'm getting closer, the throttle response is MUCH better and I can definitely feel a seat of the pants difference at speed. I think I'll keep the primaries where they are for now and keep going down on the secondaries. I have no lean stumble while cruising or during acceleration. I think once I get the WOT AFR in the 12s I'll start messing with the squirter size as I think i can get the snappier throttle response if i go down a little on the primary side.
Went to the track again tonight and made some good runs with a best of 13.45@98mph. however, the last race of the night i got stuck on the line waiting for the track crew to clean up some parts. Well, i turned everything off while waiitng and when i started back up i forgot to turn on the e-fans. ou: so yeah, by the time i got back to the pits the oil light came on and the car wanted to die. I realized my mistake and turned the car off. I didn't realize the extent until i capped the cutouts and heard the carnage. ****! Easily a few rod bearings. It still ran so I started home. I knew it was only a matter of time and i made it about 30 miles before BOOM. Sigh, looks like its time to build one of the 455s i have sitting in the garage. All in all though, a 13.45 is pretty good for a heavy ass boat with an iron head motor. There was probably a little more in it with some more tuning as my AFR's were in the low 11's at the end of the track. Oh well, stay on the lookout for my 455 build. LOL.
So, this is the end of a pretty well built motor. Self built with a Mutha Thumpr cam and self ported heads that got a 4600lb Riviera down the track at 13.45@98mph. The cam bearings were still in good condition and the heads look fine too. I'll probably re-use the heads and build the 455 with a cam that will give me enough vacuum to use my power brakes. Oh well, onward and upward.
Damn, that's a heck of a blow out. Any chance it over revved? It sounds like you think it over heated and thinned out the oil, is that likely in one pass?
