IAC isn't working properly.

Before I installed new valve:
When at idle park, my IAC read zero. At idle drive, it read zero. At 2000 rpm cruising, it read 22.

With new valve:
Idle park: 24
Idle drive: 40
2000 rpm cruising: 68

I'm getting a chip burned at Street and Performance and I was told by a technician that these readings are still too low.

Symptoms include stall/hesitation at acceleration from a stop and rough idle. Will increasing the idle speed fix this? As I mentioned, a chip is being burned because there's a stock 305 tbi prom in it now and trying to support a 383. Would this current mismatch cuase this to happen? Note: TPS reads .55 (where it should be) and idle park rpm is 650. Thanks.

[This message has been edited by speedlvr (edited March 03, 2001).]

[This message has been edited by speedlvr (edited March 03, 2001).]

 

adjust it with the info from the tech article.

but your engine needs that prom bad.

 

Yeah, you should be able to smooth it out with the idle and minimum air adjustment. Sounds like it is going to be a real gun ride!!! Let us know what other problems and fixes you find, I'm sure it will come in handy for someone sometime.

------------------
Jerry

-------------------------
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Pst Front Hotchkis Rear
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Most of the bolt-ons
-------------------------

 

You can count on it. Thanks.

 

i may be following this swap soon. If you would please keep track of all problems you run into and keep us posted. If you want email me with info like parts you used to swap, how much came off the 305 when you did it, etc...

 

First off, I would like to share what Dean at Street and Performance in Little Rock told me concerning getting a bigger throttle body (they are the ones burning the chip for me). I told him I was going to get a 454TB and he asked why and I told him so it would get more fuel. He told me I don't need a bigger one. He said that the 350 injectors in the 305 unit would do just fine and that the 1 11/16 bore of the stock 305 unit would make for a crisper takeoff. S & P has an excellent reputation for being damn good at what they do. I was happy to hear that because those 454 Rochesters new are well over $500 at the least (the local chevy "stealer" wanted over $900.00). *%$*#! If needed, later I'll just get mine bored out at the machine shop.

Anyway, I should have the chip and the headers on by the end of next week. I'll post parts, cost and effect when it's done. I hope my info when all is said and done will be of use to you and anyone else out there who is or will do the same thing.

 

yes, ive been researching this, obviously. the little tbi allows the air to move at a much higher velocity than the larger, so gains in flow for high rpm, are lost in lowend torque from loss of velocity. thats my own personal experience of running the 454 on my l03 thats stock. However, i think that if someone were to "redesign" it, they could keep velocity and improve flow. o wait, i am.

here is my findings. 2.25 inch bores, would support almost 1000cfm. as per formulas takin from comparisons in flow with the holley 2". i think a better 2" or even somewhere inbetween a 2" and 1 11/16 would be best. im still working on final design aspects. like bore size. but, 90pph injectors with 454 tbi should go up to ~370hp. thats the top. before having to need bigger tbi, and bigger injectors. BUT, who makes bigger than 90pph. nobody. so, you would then need to either become more efficient or get a 4bbl with 4 x 50pph injectors. ~408hp. would need750cfm by my calculations.

by common calculations for injectors sizes and cfm ratings and finding max potential hp
the little tbi flows 400cfm. that only (in common theory) would support 230hp. now, we know this isnt true, becuase when you increase velocity, the fuel atomizes better and you get a more efficient engine = more hp with less fuel and air.

in my opinion. we all know how cheap gm was. if the 350/305 tbi was meant to support hp over 250. they would have put it on the 454 trucks, but why didnt they???? Because its not supposed to be used with that much hp.

but, this is all assumption based, i intent to test all angles of my theories this summer

------------------
Dale Earnhardt, #3 has crossed the finish line with a victory.

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Open Element Tech Article

ENGINE SPECS:
Stock Rating: 170bhp & 255ft-lbs
305 TBI,Open Element,K&N 14x3,Hypertech Stage I,454 GM TBI
Now Rating: A Little More

STEREO SPECS:
JVC Kalmeleon kdlx3,Infinity Kappa 2way 6x9's,PPI 4x6 Coaxials,PPI PC2400 AMP @ 2ohm
DEI Studio 12" 4ohm DVC,Custom Box:Exactly 1 Cubic Foot

 

I wish you the best of luck.

 

What about raising the fuel pressure on those injectors? Raising the pressure to 20psi increases the flow rate to approx 127lbs/hr each. This is enough fuel for over 425hp.

Check out this doc for more info:
http://www.diy-efi.org/gmecm/faq/tbi_fp.html

 

ooooo, I completely forgot that those were tested at 13psi.
Yes! you are correct, they would support that much. However, I was told by Dan W that Injectors of that size have fuel metering problems at low rpms/fuel needs.

What are your thoughts on that issue with the 90pph's?

 

You don't need the big TBI for a mellow 305... Or a mellow (less than 300-350hp, with FPR changes and PROM changes) 350/383cid, for that matter... IMO and from my own dyno experience, of course.

I'd also consider buying a used OEM PROM from someone/somewhere/boneyard just for ha-ha's. Should be about $25 or less. Not for the final PROM but just for a backup/learning curve piece.


[This message has been edited by FastBroker (edited March 05, 2001).]

 

i know i know i know. Ive said it, this is not for an l03, or a stock 350. Even the 2" unit is too big for an l03, (i still have one on my car) 2" on a 350 is ok. 2.25 is massive, and i probably wont even build more than 1.

But the guys over at 454ss.com wouldnt mind having a 2.25 inch tbi on their trucks.

 

If idle fueling is a problem at higher pressures then you could alway use the vacuum referenced regulator that is mentioned in the link above.