HawkHunter

I have a 383 stroker in my 86 iroc - i'm not happy with the performance of it yet, I have had a few suggestions about things that i need to fix but i would like to hear what a few people here have to say...

*Problems
now - with my current setup (below) - im making 12-13" vaccum at an idle of around 1075-1100 rpm - if i try to lower the idle to say 875-900 or so, it will not go there. It will drop off (even if i move the screw just a tiny bit 1/2 turn say) to around 500 rpm the vaccum signal will drop to 3", and will continue to slow down rpm until it stalls within 15-20 seconds.

with the 1000 rpm idle, when i shift into drive, and it idles for a few seconds at around 575-600 rpm (say at a traffic light) - but the engine will eventually stall if it idles too long in gear - i have to rev it a few times and get it into neutral at the traffic light to recover the RPM and stay in neutral until the lights go green

When i try to take off from the start line at the track, it will hesitate and have no acceleration until it reaches about 2500rpm and has CRAWLED about 10-25 feet from the start line. To try and compensate for this - i tried to pre-load the engine (brake stand) and hold about 2000-2500 rpm right after we're both staged - but it doesnt always work, and my front tires arnt always able to hold the car back to stop it from red lighting when i do this... (probably due to lack of brake booster signal from the carb)

Someone told me that until i put in 3" springs into the carb, it will always do this crawling out of the hole thing? someone else told me until i get the proper stall converter (as recommended by comp cams), it will always behave like this. someone else said that i need my posi working in order to get out of the hole properly... but i think i need to get the motor working properly before i worry about traction at this point...

*Here's the list of suggestions:
1) get 3" (yellow??) springs for the edelbrock carb (metering rods)
2) get a 2800 stall converter
3) get a posi - or get the posi that's there fixed

*Here's my setup
1986 Iroc with L48 block and Cast Iron heads ~9.6:1 compression
scat 383 stroker crank, speed pro flattop pistons with 2 valve reliefs, comp cams "big ***** thumpr" part# 12-602-4 (243/257 @ .050)

*what i figure i should spend on with my just less than $1000 budget
I think i should get a 2800 bargain basement summit stall converter for my 700r4 and that i should not expect my new cam to be able to idle at anything less than 1100 rpm. changing the metering rod spring is useless as the engine wont idle at 600-800 rpm even with the proper 3" spring. last but not least - i could always resort to the final option of "sell it and buy beer!"

Suggestions please what order, and what items exactly would people recommend for the next step? would changing the metering rod springs allow it to idle at 600 rpm?

you can see it running pretty good here, but i never really idle'd it - i put my foot on the throttle right away to keep it from loosing rpm/vaccum

xpndbl3

iTrader: (5)

here's my suggestions:

3500 stall minimum
ditch the edelbrock and get a 750double pumper holley
get a posi.

what is your timing curve? you will want 24 degrees initial and 36 total for a quick ballpark range. That converter is lugging the engine at a light because it is too tight and causing a lot of the stalling issues. It will never idle at 600rpm, you're looking for 850 in gear with the motor hot.

HawkHunter

Timing "all in" is about 30 degrees (6000 rpm)- any higher and i start to get pinging under a load - i disconnected the vaccum advance to try and get less spread between the idle and all in... that was as suggested by a friend. It loves way more advance to idle, but it'll ping like a b@stard as the timing advances - so for now, ill make do with what i got i guess... although i heard that's an easy change (the springs and weights inside to lower the advance curve to 6 or so) - as far as i know - it's a stock HEI timing curve

so you also think it's the converter causing all my motor issues - that's comforting - ill just have to decide what stall converter to get - some people say 2800 is plenty - others say 3500 - what's the benifit of a higher converter? i have 255/40R17 sumitomo HRZ-II (i think that's the right model# very soft/directionals...) tires with 373 gears... will these hook up with 3500+ stall? or am i going to need sticky boots? i think i could do sticky boots and a stall converter on my budget as i have wheels already...

xpndbl3

iTrader: (5)

That cam with that much duration would want 3500 minimum to keep it from chugging and in its powerband. I doubt those tires will hook up if you just stab it and go, but that's why you built a stroker right? to make power.

Shagwell

x2.

There are people that have had great luck with those edlebrock carbs, I'm not one of them. Have you adjusted the idle bleed screws in relation to the vaccum gauge as you dial the idle screw down?

That is way to much duration for a stock converter, and it is never going to like idling in gear against it. I agree that something around 3500 is going to be a lot better, however DO NOT buy a cheapy for a 700r4, you definitely get what you pay for. - If you can't afford to do it right the first time, can you afford to do it again?

It's definitely not going to hook w/o a posi, it's probably still not going to hook on those tires.

Pushing through the brakes when trying to brake stall the converter is a sign of a tight converter and too weak of rear brakes.

brandoz28

iTrader: (1)

from my PERSONAL experience with edelbrock carbs, they're good for STOCK motors or ones with a baby cam, i had a heck of a time with my friend's 750 with an XR288 cam... of course i was rebuilding it last night and it was missing a gasket under one of the venturi's....... put a holley 750 double pumper with mechanical secondaries on and picked up .2 in the eighth.

edit: guess i should add i've never had a problem with the 600 on my car with a bone stock vortec 350 out of a suburban and an edelbrock performer intake

HawkHunter

No - i didnt think to adjust the idle bleed screws while i was adjusting the idle screw. So if i try to lower the idle, i should probably turn the bleed screws out to allow more air to mix? or should i turn them in to help generate a better vaccuum signal to help fight the metering rod springs?

HawkHunter

okay so - im just a bit concerned about what i read about 3500 stall converters - well converters in general...

they say that converters although they say "3500" will actually engage at closer to 3000- or so rpm - so does this mean i want a 4000 stall so im closer to this 3500 or i want a 3500 stall so im closer to the comp cams recommended power band of 2800-6000 rpm?

KWIK84

iTrader: (5)

Actual "engagement" of a convertor is tough to figure out exactly unless you know ALL of the specs of your car, and can really only be done precisely with either using a TB (not gonna happen with a 700R4) or using a convertor dyno that can accurately measure fluid movement.

The 3500 is where you want to be at, it will work good for you on the street and allow you to "load" on the line. Be sure to have a good working cooler, and using a secondary wouldn't be a bad idea with a 700R4.

And lastly if you want to see what it can do on the strip, give the car a chance and put some stickies under it.

HawkHunter

thanks everyone for your suggestions - i know it takes a fair bit of thought to reply to tech questions like this, and it's cool we can get free advice here - I talked to another friend after work yesterday, and he also suggested a 3500 stall with lockup and anti-ballooning.. He said to run a toggle switch for the lockup, and that the 3500 also would be a good compromise between street and track use.

So I'll get a 3500 stall first, and go from there thanks to all the great advice again

Fast 383

iTrader: (2)

I sell some nice converters for your application. If you want to, PM me I can give you some details. Or check out my store at
WWW.Transmission-Specialties.com.

joeblue83

iTrader: (8)

I went from a art carr 2500 lockup converter to a 3500 vigilante converter and watched my 60 foot times go from 1.75 to 1.59 with only the converter swap. X2 for a 3500 stall converter for your combo