Nostang

iTrader: (4)

I ran my car last 2 wed nights at my local track on the 150, 200 and 250 hit to try to get some new bests despite the nasty heat and humidity. Just a little info on my setup. I have a dedicated fuel system with C16 race gas in it and I was running 7 gallons of C10 unleaded in the main tank (200 and 250 shots) (150 shot pump gas). I am running a 355 LT1 with ported heads/intake and all of the bolt ons. I have been running the car for the last 2 years on the bottle with this setup on the 150 hit and I decided to start spraying the 200 hit to get into the single digits.

Well the heat and humidity sucked at Cecil but I was able to manage a new best. I was on the 200 shot and I had some C10 in the tank and pulled 4 degrees of timing. The A/F ratio was 10-1 the whole way down so I have a little bit of leaning out to do with the car. The timeslip read

1.463
4.177
6.495
105.87
8.503
10.203
132.63

All in all I was pretty happy. The car dead hooked but because I am running so rich it did not leave as hard as it should have on a 200 hit. Any ideas on why it isn't hitting hard?

I tried the 250 shot on the next pass but I am having problems melting #7 and #8 plugs in mine on the 250 shot. I tried the 250 hit that night but the car felt sluggish off the the line and surged a little in the top of second about 500ft out so I let out and hit the brakes and went a 11.1@90mph with a 1.53 60 ft....lol. The car felt slow off the line but it was actually faster from 60-330 and 330 to 660 (6.506@103mph 1/8th letting out) by a tenth. I am clueless as to why it only melted 7 and 8 (wasn't totally melted because I let out ASAP) I was pulling 7 degrees on the 250 hit.

I also ran the car last week in less than optimal weather on the 150 hit and pump gas with the M/T drag radials. The car was at 10.3-1 the whole way down and I was pulling 6 degrees of timing. Again the car dead hooked but did not leave as hard as it should have. The timeslip read:

1.546
4.358
6.749
102.56
8.818
10.570
128.70
My best ET ever was a 10.354@129 with a 1.437 60ft on the 150.

Any ideas on why I still melted #7 and #8 plugs on the 250 shot even though I was running 10-1 a/F ratio? All of the other plugs looked fine. I am thinking I am having a distribution problem but I am not sure. Any suggestions on how to fix it?

Thanks in advance,

Matt

Race Car Driver

Those two cylinders tend to run leaner than the others, but your situation seems extreme.

Noyzee

iTrader: (37)

sounds like those cylenders need more fuel. maybe a single nozzle isnt good for your setup

DynotuneN2O

iTrader: (13)

I agree with Brad, typically a fuel issue/distribution.

Noyzee

iTrader: (37)

Dean, he may need you to price him out a DP system!!

NXJeremy

On 250hp and higher I would suggest going to a direct port on the LT1 motor. I've seen the same problem on some other LT1's, although I agree with BickelFirebird that your situation does seem a little on the extreme end of things. About the issue of the car not leaving as hard as it should, 10:1 is too rich IMO. That's why the car leaves lazily, we usually tune cars to be about 12:1. However, the #7 & #8 plug issue would need to be taken care of before leaning it out to 12:1.

SDB

iTrader: (7)

what intake are you runing?
where is nozzle at?
lean out fuel jet a little to get AF ratio 11.5-1
May have too much timing taken out for 250 shot (7 degrees is a lot, especially with sch good gas)

SDB

NXJeremy

SDB- I am curious about your thought/reasoning for suggesting him to lean the motor out and add timing when he is already melting plugs.

NXJeremy

Nosstang- Nitro Dave had the same problem with #7, and he was even running a direct port. He said his problem was entirely the nitrous system though. I've talked to several people and most say it is the intake design, and a direct port should solve the problem. Nitro Dave also said he could install spray bars in the intake, which should solve the problem. Otherwise, I would suggest backing it down to 200hp and leaning it out to 11.8-12:1 and let it rip.

Nitro Dave's Nitrous Outlet

iTrader: (25)

I have seen this problem before.
For some reason the LT1 intake desighn is poor and those two runners run lean.It looks like you are at the point of needing a directport.If you were good at the 200 back the system back down and get the air fuel to about 11.8 to 12.1.This will take the bog out from being to rich.If I can help in any way let me know.Sorry I seen this post so late.
Dave

white2001s10

iTrader: (4)

The intake was not designed for wet flow. This is why you run into problems with the wet systems.
The plugs melt due to a lean condition in those cylinders. You have a few options. I'd also get some stouter plugs in there too. A plug failure can take out your entire engine. I'd suggest trying one of these autolite plugs... whichever one fits into your heads: AR51, AR12, AR472

As a quick fix, try running at a lower engine coolant temp next time. The chambers won't overheat as quick and you'll get more fuel delivered via the injectors.

SDB

iTrader: (7)

I meant on the 150 kit...try getting it better with AF ratio, and double check to make sure your not taking out too much timing....not meaning to put a smaller fuel jet in on a 250 shot right off the bat! I have never burned out plugs but have hurt them with too much fuel.

Like another said, try better plugs, maybe one step colder. Probably just the limit of the LT1/LT4 intake design, 150 is ok, 200 is marginal, 250 is aparently too much.

SDB

Nostang

iTrader: (4)

Thanks for the replies and suggestions. I will stick to a 200 and under shot until I am able to get a direct port. I am almost scared to try and lean it out to 12-1 though as the whole bank could be at 9.6, 10.3, 8.0, and 14-1 A/R but still read rich on my wideband if you know what I mean.

BTW, I was running AC delco R42LTS plugs and my engine temp was ~160-170....it never goes above 170. I am going to try some autolite 103's to see how they work next time at the track. I also bought a sprak plug reading kit so I should be able to analyze my plugs better. Ultimately, a direct port would be a wise investment.

Thanks again!

Matt

NXJeremy

SDB- I gotcha, sorry about that. I get confused sometimes when I read these posts, lol.

White2001s10- No intake was designed for "wet flow".

slow trap

iTrader: (22)

what would be wrong with keeping it at 150 wet and hitting it with a 100 dry shot if injectors is up to the task?

NXJeremy

It would be nice to have a FJO engine management system. That way you could tune the car sequintially and fatten up the two cylinders you're having problems with.

white2001s10

iTrader: (4)

That wasn't a question, but you are incorrect just the same.
Several manifolds incorporated many hours of research to reduce fuel distribution problems in wet-flow systems.

None of the dry-flow intake designs today would fly by even 70's standards for use as wet-flow.

V8_DSM_V8again

I would consider converting the fuel rail to a parallel feed and using a hq hv pump and regulator.

You could be starving those two injectors.

NXJeremy

Exactly what production EFI intake was designed to have fuel flowing through it?

I think one of the nitrous companies on the market needs to hire you as soon as possible, you seem to be the be-all, end-all of nitrous knowledge, haha. I guess to each their own.

NXJeremy

Kinda off topic, but.....V8_DSM_V8, saw your sig and I would definately say put the LS1 in the RX7. It is a beautiful car and looks even better with an LS1 in them, haha