AlkyIROC

Like everyone else who keeps asking this same question but my performance is still a little off and I don't know why. Correcting for the weather, the car is still down around 45 corrected HP. I have no idea why but I'm starting to suspect an internal engine fault causing the decrease in HP. It could be something like valve lash is off or maybe the timing chain is stretching and the valve timing is off. It might even be a wrist pin starting to sieze up. I always tell people who ask, that they need to log all the weather conditions to see if the lack of performance is weather related. I can now say that my car is down on power and it's not weather related. I was suspecting it was a fuel problem but that's now been fixed and I'm chasing ghosts again.

Other than that, the car was running great. Constant 1.59-1.60 60' times. I lowered the ladder bars down one hole last night anticipating a slippery track and it took a lot of shock off the wheels. They don't spin as hard and the 60' times show it. Tires are starting to go away as they're getting to the end of the second season. I just need them to last a few more races. The car ran very consistant 11.5x and I was able to run a 11.504 on a 11.50 dial however the -.137 red light didn't get me the win. That was a second round red light.

The day started off bad with a 5500' density altitude and a long delay while they tried to fix the christmas tree. By late afternoon the density altitude had climbed to just over 5900 feet. Even taking into account the poor air, performance was still off.

No major parts breakage today. The transbrake works again at lower rpms but still slips at high rpms. Fine by me. A 2500 rpm launch doesn't hurt parts as much. There's still a bit of a coolent and oil leaking from the engine. The leaks are slowing down but I'm still trying to track down the oil leak at the right front lower corner of the engine. I'm starting to suspect the pan gasket. There's nothing else down there that I haven't already fixed.

I have new pictures online in the Gallery at my web site.

SLP IROC-Z

iTrader: (1)

im havin the same problem aswell, theres now way im loosin 3-4mph from weather differences. last year i gaind/lost 1.5mph from this time of year to the fall. but its hard to say because the car could have been maxin the injectors out in the cool weather hense not a major pick up of mph in the cooler air. since the cams differnt its hard to compare. all i know is if i go to the track the cars quicker et and mph wise when its warmer out then as the night goes on and gets cooler i actually loose over 1mph. the cars getting cooled down sufficiently it actually sits longer in the stagin lanes as the night goes on due to the higher volume of cars. i think im gonna get an AFPR and a wideband. hell might as well get BFGs and get back into the thirteens

IHI

iTrader: (1)

How many passes are on the valve springs? Our Mod. points leader went from 10.2-.3 to 9.95 just changing the valve springs-first time I ever heard of that. 5500' DA-WOW, let me say that again, WOW!!!! Is there any oxygen all, maybe you could install a flower box under the hood, get some flowers growin in there and help throw oxygen straight into the carb!!!maybe make a forced induction set-up with the plants...that is some cruddy air wow.
But, the good news is that it was consistent!!

AlkyIROC

They're new this year so I'd guess less than 30. I'd have to check my logs to get an exact number. The cam isn't aggressive enough to pound out valve springs for a long time.

We're talking a performance drop after a couple of races. Early July, I was running low 11's. Mid July I had some carb problems and was running high 11's. I fixed the carb problem and at the early August race it was running mid 11's when it should have been close to low 11's again. Another thing I'm going to try is backing the timing down a couple of degrees to see if that helps.

Next race is Aug 15-17. Test and tune all day Friday and points races on Saturday and Sunday

IHI

iTrader: (1)

Have you pulled your oil filter and cut it to see if there's any glitter at all in the element. Friend had a loaner big block short block this weekend since he fragged his, Fri. TT it ran a few passes pretty consistent, then started falling off. Sat. for the race TT, it fell off even worse and actually died onhim-sounded like a dead battery when cranking on it. Pulled the filter and talk about glitter-felt bad for him as he just sent a cam through the back of other big block 2 weeks ago. Like you said, maybe there might be an internal problem that's sneaking out, how's your oil pressure at all stages of life, idle and the big end?
If your cam is'nt crazy and there's only 30 passes, that'd kinda rule them out so long as the seat pressure is correct, but I think by now there would have been other signs of problems if the seat pressure was'nt correct. Carb opening all the way?!!! What about your mph, are they all the same or are you dropping, could it be possible the convertor might have a hand in this?

AlkyIROC

I'm off 2-3 mph from where it used to be and that's consistant with the ET drop. That's why I'm figuring about 45 corrected hp loss.

Monday I had the rocker covers off to check the valve lash. They were all a couple of thou loose so I reset all the rockers. They weren't off enough to say a cam lobe was wiped out or anything. Just a couple of thou. I wanted some drag on the feeler gauge and they had none or very little.

I pulled all the plugs so I could crank the engine over easier going through the firing order. Putting a socket on the crank pulley bolt and just using a 1/2 drive ratchet, the engine cranks over very easy. No indication of anything binding.

Oil pressure is always fine. With 20w50 oil it never falls below 30 psi even when hot at an idle.

I may pull the oil filter off to check inside. I want to pick up a reusable one first.

It's possible the converter has a problem but not high on the list. It's a full race 8" converter. All the internals are designed for NOS or transbrake use and I'm not abusing it anywhere near what it's designed for but that doesn't mean something didn't happen to it when I've blown engines but then it would have shown up a long time ago.

I checked the carb open position before the last race. I thought of that too. Fuel pressure is good through then entire run also. The -10 line feeds a lot of fuel to the carb.

IHI

iTrader: (1)

Okay, another recent experience for what it's worth. Brother in laws 11.0-high 10's Regal was "falling on it's face" on the big end. Can't remeber the pump he was running, but he too had the -10AN lines. Anyways, called BG and explained the situation. They told him to pull the main line to the carb from the pump, place it in a bucket and run the pump for 25 seconds-they then told him for his motor and times 20 seconds and it should have about a gallon of fuel in the bucket. He did this and all he got was around a qt. So calls BG back and they told him with that kinda of hp he was literally sucking his system dry if that's all the fuel he got. Ordered an all new fuel sytem with a monster pump that was way bigger than needed-took it to the track and fraggedit first pass-busted the nuber 2 & 3 main caps, so we never got to see if the new fuel sytem worked or not. I understand with the alcohol your using twice the fuel as gas, but could that be a problem? I can't imagine a few less than perfect valve settings causing that big of a drop, but maybe it does.

AlkyIROC

That is another possibility. I use a BG 280 pump mounted in the rear. It's not alcohol compatible but neither is a Holley blue pump and I've see people use 2 blue pumps to feed an alcohol system.

When you see this pump beside a Holley blue pump you just think "Wow, is the Holley pump ever tiny".

All these suggestions are good but it's not like there was a gradual decrease in performance. One weekend it was great. The next weekend something was wrong.

The BG site suggests a gallon in less than 20 seconds. They don't specify the type of fuel. Since you need almost twice as much alcohol as gasoline I would assume the pump should be able to push a gallon in 10 seconds. They also specify that you check it at the carb inlet so the fuel requirement is the regulated pressure reaching the carb. The pump should have no problem pushing unregulated fuel in that amount of time. That means even the regulator could be causing a fuel restriction. I run mine at 9 psi.. Alcohol at WOT should be 9-12. I may have had the pressure a little lower on those early quicker passes.

I use float bowl extensions to prevent a fuel starvation. A fuel log would help even more.

AlkyIROC

Out of curiousity I had to go and try the flow test tonight. I can easily fill a 4L jug (more than a US gallon) in 15 seconds from a regulated fuel line. That's just to one float bowl since I use 2 seperate lines from the regulator to each of the float bowls so it looks like I don't have a fuel flow problem.

IHI

iTrader: (1)

LOL, yeah, I think your pumpin plenty of fuel!!

darbleinad

why do you use 20w50? i am assuming this is amsoil series 2000 racing oil. i just switched over to the stuff from regular valvoline 10w30, and i went with the 0w30, cause i thought the 20w50 was a little thick and 0w30 was the only other choice.

AlkyIROC

Don't forget this is a full race engine. It's also running on alcohol so contamination for moisture is very high. The thicker oil doesn't look or flow like water after a run.

darbleinad

sorry about quoting your entire original post. i should have cut it down. thanks for editing it for me.

hmmm...i didnt realize that alcohol caused more moisture contamination. good to know. definetly better to use a thicker oil. thanks for answering my question. good luck with the car and racing.

AlkyIROC

Oil contamination in an alcohol engine comes from 2 sources. First of all you need to use almost twice as much fuel as gasoline. This can create a very rich mixture inside the cylinders and can be washed down the cylinder walls. The second is that an alcohol engine runs cold. If the oil temperature doesn't get hot enough, the condensation in the oil can't burn off. Ever pull a valve cover to discover the inside looks like mayonaise? That's water contaminated oil from an engine that runs too cold.

I did an oil change, installed a remote filter onto the front motor plate and did some tinkering on the car today. A reusable oil filter is too expensive for me at this time. I cut open the old filter to have a look inside. Lots of small paint chips, some dirt and a few flecs of metal which could have come from the last rebuild. I'll cut open this new filter at the end of the season and recheck to determine if the engine comes apart again over the winter.

It runs much better now and I think I may have found another possible fault. I never checked before but both float levels in the carb were way too high. I won't know if the performance is back up until Aug 15 but it sure sounds good in the garage. Big 3 day race weekend coming up and I took Friday off to get some more track time for tuning. I should just go pay for some dyno time.

383backinblack

methanol contaminated oil looks like a milkshake anyhow.....and it doesnt take long to get like that......one day of racing with the truck and the oil will be totally white