Hot 355 runs awesome but won't idle..?

[Emmettology 101]

Dont understand why you cant get this engine to idle, but I am no EFI expert. I'd turn down that fuel psi. Thinking about my set-up and yours, there is no way you should be having problems.. The only thing that is in your "equation" thats different that mine(fuel system wise) is your pump.

Seems to me that a 355 and a cam is not much to make even a stock tbi(and fuel system) run that terrible.

A little back history on my set-up:

89 Block bored .30 over, Scat 383 crank, Manley rods, KB Hyperu pistons, Comp Cam, Trick Flow Twisted Wedge heads(very high compression), Stock TBI manifold, Holley 670 TB, stock fuel pump from Auto Zone and stock tbi chip..

This is my set-up at the moment. It runs rich but usually idles fine when sitting. When I say usually, I get a bobble now and then at lights and when turning right, its a little gremlin I am chasing.... Anyhow. My compression is so high that even on 94 octane I get pinging. My timing is retarded to help againt it but still get some.

Granted my set-up is not even close to being right(everything working together), but I get a decent idle. My main problem is I am working in the dark.. I dont know the compression or if there are flat tops or what in the engine. My friend had the engine built by a shady guy... Last figure I heard on the compression was around 10.5:1-11:1. Then my friend burnt a valve and they had to machine the heads. The cam is another area where I dont know. It's a Comp Cam that is for a carb'd engine. Supposedly it is about two steps larger than the largest Tbi cam.

Oh and another thing, I am not running a knock sensor because my friend chose to run a PJ Gear drive....

So I am goign to side with the others who say your trying to shove too much fuel down the throat of your 355. 35psi on a TBI is way too much. Look at the other person on here running a TBI 383, they only have 18 psi. So why the need for the other 17psi on yours? Thats enough PSI for another complete TBI engine...

 

[K5er4Life]

I have a 383 TBI and I am pumping quite a bit a fuel through mine, 37 psi. to be axact. You should really look into getting WinALDL, work on burning some proms, through in a adjustable regulator on the pressure line behind the tbi with a gauge and I gurantee you will get that thing running like a champ. I have only tuned 3 different chips for my stroker and it runs awesome. Talk to the guys over at thirdgen they are extremely knowledgeable when it comes to custom prom burning. When I had my stock chip my motor would run real rich when cold and a little better once warmed up but when I hammered it, it would start to lean out. Thats why if your pumpin 35 psi. into it that may not be all that much for that motor. You might have to dumb it down a bit to help it but you biggest thing is the chip. Stock ones dont do good with aftermarket parts.


Heres some specs on my motor, atleast to the best of what I can remember:

383
s/r torquer 2 heads- 2.02/1.60
holley intake w/the 2inch bores
comp cam 220/222 degrees @0.050 and .465"/.470" 114 LDA

The only thing Im not exactly sure of is the cam specs, its been a while, they are pretty close to the one I described though.

 

[dirtwarrior17]

Damn this post is getting so long they don't know what im running.


355(.030 over)
10:1 flat tops
l-79 cam 350hp 272 dur. .447/.447
flowtech headers
camel hump heads 2.02 1.60
3" exhaust
k and n
Holley projection dual plane high rise manifold
Holley 670 cfm tbi
accel high pressure fuel pump

This combo makes 386 hp at 5500 rpm, 382 at 5000, and 358 at 4500.

Most people tell me that tbi is only good for 4500-5000 rpm. the whole reason this thing has so much fuel goin to it is because i don't want to leave any hp on the table. If I can get 5500 with a chip and 35 psi then thats all i want. I can deal with 382 hp at 5000 but i want this thing to hit 5 grand at least.

If you talk to anybody who has put an l-79 cam thell tell you that alone is enough to throw off the idle because its a loping idle. the prom can't deal with all those mods with nothing done to it.

Alll i need is to get a chip burnt after a couple dyno runs and it will be fine. Just need to lean out the idle.

If you read further back in the post theres people having this problem with a stock motor except the tbi.

Im leaving the regulator where its at because when i stab the throttle on this thing is torques over like the roudy mouse motor it is. It doesn't seem to have any problems being lean up top but its too rich for idle.

What rpm does your 383 stop spinning?

 

[Emmettology 101]

I read every post fromt he beginning... I am honestly not trying to be an ass or anything.. But what you're listing is just a 355 with a larger cam and flat tops yet you seem to think you need to fuel it like a top fuel dragster....


I dont know much about cams specs, but I looked on Comp Cams website.. Your cam is not that big in relation to their computer cams.. Their computer cams have about the same lift, if not more, with similar durations.

If you talk to anybody who has put an l-79 cam thell tell you that alone is enough to throw off the idle because its a loping idle. the prom can't deal with all those mods with nothing done to it.

I have all my mods listed in my post and am running the stock prom.. And my truck idles good.

 

[K5er4Life]

Im assuming you were talking to me, the 383 seems to quite at just under 5000 or so. Which is screamin for that thing. I can hear goin AWWWWWWWW!!!!!!!!! I find that I never really take the thing to WOT, it just doesnt take that much throttle. I think thats pretty decent for a stroker though. You should have no prblem getting yours up there and past that. It sure is nice to be able to romp on it and spin 38's without much trouble at all. I believe in my fuel injection, F.I. seems to have so much lower end grunt, the throttle feels right at your toes and just wants to wind out. Although after this engine build I already want something else in there. Not because Im unhappy with it at all but becuase I really like the sound of 496. Hmmmmm......496 kinda rolls of the toung nicley. 496. Hey a 540 merlin would be nice but a MMMMMMMMM 496 is already way pushin on my budget.

 

[K5er4Life]

I read every post fromt he beginning... I am honestly not trying to be an ass or anything.. But what you're listing is just a 355 with a larger cam and flat tops yet you seem to think you need to fuel it like a top fuel dragster....


I dont know much about cams specs, but I looked on Comp Cams website.. Your cam is not that big in relation to their computer cams.. Their computer cams have about the same lift, if not more, with similar durations.



I have all my mods listed in my post and am running the stock prom.. And my truck idles good.

Im not sure if he does need more fuel or not but I do know that if you compare those specs to stock TBI cam there is quite a bit of difference. I cant remember the stock cam specs (Im sure someone here does) but that damn thing isnt even worthy of being called a peanut cam.

 

[Emmettology 101]

They do need more fuel whether or not he needs more or less I am unsure of but I do know that if you compare those specs to stock TBI cam there is quite a bit of difference.

I didn't compare his specs to a stock cam. The comp Cams I looked at were aftermarket cams for more power.

I still dont see the need for that much PSI on a TBI system. I am not running anywhere near that and neither was the other 383 person(wasn't it you)... And I would think they would require more fuel that a 355...

 

[dirtwarrior17]

posted by K5er4life:I have a 383 TBI and I am pumping quite a bit a fuel through mine, 37 psi. to be axact.

It has a 284 dur. and a 480 lift cam (not the l-79) with 1.94 1.50 heads runin speedpro flat tops. that puts the compression at 11:1. the builder told me it was 10:1 before i bought it and he also said it had the l-79 cam with 2.02 1.60 camel humps. He might have been right the first time and thougth i was someone else when i asked him for the specs but either way the prom can't handle that setup.

Any cam especially the one i have will throw the computer way off as said in one of the earlier posts. The older the computer the worse they are at relearning curves. 88 has 2 years of technology in the computer since they started the efi in 87. add the higher comp, bigger heads, bigger lift, longer dur, headers, kandn, intake manifold, high flow tbi, and fuel pump is a lot for a stock prom to handle at any year.

I am runnin this much psi so the motor can get up over 5 grand with no problems. If i ran 12 psi it would stop spinning at 4500-5000. the extra psi is for the top, not the entire powerband.

 

[CFM]

Great site: Was referred here earlier today. Figured I'd chime in and say thanks for your support and throw some info out.

A stock computer chip is told and thus assumes the following:
Stock motor !
Meaning:
stock cid
stock intake
stock heads
stock cam
stock compression
stock injector size
Special Altitude condiserations (Colorado guys know this!)
stock gearing
stock tire size
etc, etc, etc. yeh, that 'Stock' word bugs me too.

Anyway to put this into very simple basics - your computer is programmed / told that at a certain rpm vs certain throttle position vs certain manifold vacuum (ie:load) that this much air is going into the combustion chambers neading this much fuel and this should be the timing.

Example:
Stock 350 at 4000rpm at WOT
300HP 350 at 4000rpm at WOT

Which has more air coming thru engine into the combustion chambers?
Which has more vacuum at idle?
Which has more vacuum at 1000-1500rpm? So and and so forth.

The computer has to be 'told' what going on or it is going to guess and probably trip all over itself.

Big jumps in fuel pressure will band aid some of the operating range but not all of it, if much at all.

Programming maps ar3e dimensiol - fuel pressure/injector change/etc is 1D.

Fuel psi is for fine tuning - not making a 210hp system with all of it's characteristics understand a 300hp system.

Hope this helps.

 

[dirtwarrior17]

welcome to ck5 brother....

this site is the best on the web except for the occasional bickering.

I don't know how old this post is but i thought i'd never see it again...

in the earlier posts on this forum i decided to burn my own chip using a prominator and a labtop...

i don't expect a fuel pump to make up for all those mods. I know there is no way my stock prom will handle 340-350 hp.

thanks anyway.

 

[Emmettology 101]

welcome to ck5 brother....

this site is the best on the web except for the occasional bickering.

I don't know how old this post is but i thought i'd never see it again...

in the earlier posts on this forum i decided to burn my own chip using a prominator and a labtop...

i don't expect a fuel pump to make up for all those mods. I know there is no way my stock prom will handle 340-350 hp.

thanks anyway.

So what was the outcome? Get it to idle? I still think there is something wrong going on or too much fuel... My 383 has the stock comp and idles fine(with a little bump to it) once warm..

 

[dyeager535]

Yeah, did you get your stuff yet??

Friend sent me a pocket programmer II, I bought an adapter/ZIF/chips from Moates.net, now I just need to get the 14SF pinion angle right, (cut/weld perches) get a rear driveshaft, wire up the DRAC and Electric speedometer, and I can start burning and testing.

I really like tunerproRT, been making small changes in my .bin in anticipation of the swap, small things like fan on/off temp, RPM/Speed limiter mods, fixing the cold start issue, etc. Going to be nice to actually have the vehicle running and SEE the difference though. Eventually I'll pay for tunerproRT, really a nice program.

I like the eye candy too...I mean I guess we don't need "live" graphs with a spreadsheet, just fun to look at.

 

[Fierospeeder]

I read every post fromt he beginning... I am honestly not trying to be an ass or anything.. But what you're listing is just a 355 with a larger cam and flat tops yet you seem to think you need to fuel it like a top fuel dragster....

yup, some people should stick with carbs if they have no clue how EFI works.


4X bigger then the stock injectors

 

[dirtwarrior17]

yup, some people should stick with carbs if they have no clue how EFI works.


4X bigger then the stock injectors

Is that why you run a carb?

more like 3x bigger and that will barely be enough to support my motor.

right now its pushing 340-350 hp and when i get the afr heads it will be more around 400hp.

Dyeager: I still have to order the prominator from speedtronics for 275 and get the labtop off ebay.... my dad is getting 17 grand from his disability and hes gonna kick me 1000 to throw at my truck. I about pissed my pants when i heard that... $$$ for my fenders, 14 sf, gears, and the efi stuff. I'm still waiting for him to tell me he got it tho. Like you i still have to put in some labor before im completly ready: cut and weld exhaust secure fuel pump wires and gas lines, get a pressure reading, and hook up my power brakes.

IS there good prominators for cheaper somewhere?

Emmetology101: The idle problems was mostly related to timing and vacuum... i never disconnected the advance when i timed it(first motor i timed) and some of the lines weren't hooked up right not to mention the one i attempted to block off. I ended up getting a T fitting for it.