Carb or DFI? Im sick of my carberator.

[montessgtp]

Well im annoyed frustrated bored and tired of tuning the carberator on my Monte Carlo SS...For the last 3 months ive battled starting driveablity problems and cant get it to idle or rev correctly...The car will not start when cold...usally requires starter fluid. This weekend i took it up to atco raceway and spent 3/4 of night playing with igntion timing a/f ratio settings..best e.t was a 13.7 at 95 mph.Which is HORRIBLE!!!! But still was running funny... The car idle VERY ruffly at 900 rpms but that could be due to the cam specs. But im thinkin its the carberator too...

When normal driving and shifting into second...the car will bog unless your on the gas hard...ligth acceleration sucks....Its not gettin enough fuel above 6000 rpms and to much under 2500...so im wondering if there somthing i can do to correct the carb...or maybe someone can give me some info on a DFI to see if that would make the car more streetable.

The engine has been built for HIGHER reving capablitys. I shift the engine at 7200 rpms. Seem to be the carb i have it for WOT not every day driving. I rarelly race the car it was just a fun street car that i wanted for the average Honda ass kicking. But its gotten so bad i stall more than i race.

Will a Accel DFI system work on this car...any info at all or help on this would be very useful im carberator retarded =(

a lil info on the car.

1986 Monte SS

1974 350 4 bolt main APR main studs Line decked and rehoned deck plates. Pin caps added and complete balenced rotating assembly
understroked 327 scat crank
roller cam lift 539/588 duration 292/300
Vortec ported heads crane roller rockers
TRW 10:1 forged compression pistons
Eagle esp H beam rods
Complete MSD igntion and Edelbrock 750 carb electric choke

World class t-5 (MANUAL TRANS)and zoom dual friction clutch
rear 8.5 housing with Auburn posi and 3:42 richmond gears.

[Juglenaut]

Vortec ported heads crane roller rockers

Their is your problem right there....

I need casting numbers!!!

Square Bore, or Spread bore???

[geoffinbc]

How so?

I would say it is time for a Carb rebuild. Carbs are not for everyone. They take skill to tune and keep operating properly. I am ok with carbs but perfer fuel injection. My dad is a geneious with carbs. He was a GM Mechanic in the 70's and 80's during the emission nightmare vehicles with a million vacuum lines. He really knows his shit.

[Juglenaut]

I Would use a Single Plane Manifold on that engine.

Try to find a GM (3991)492 Cylinder head casting. (340292)< High perf head

[montessgtp]

I'm using a AIR GAP manifold i believe its spread. My Casting # on the heads are 12558060. The heads had inlarged valves put in 2.02 and 1.60 also 4 angle valve job and 400$ worth of porting.

How could the vortec heads be my problem?

[Juglenaut]

You could have gotten a High perf GM head for less than 400 and got the same aspects.

[Juglenaut]

understroked 327 scat crank
roller cam lift 539/588 duration 292/300
Vortec ported heads crane roller rockers
TRW 10:1 forged compression pistons
Eagle esp H beam rods

I am not dogging your combination, but I am just saying to rethink your set-up..It appears to be not well thought out. By many well alot of people refered to the 340292 casting as the best GM head out there Known as the "Turbo Head"

[Juglenaut]

Build: Streetable for your car.

383ci, 4.030 x 3.75
475hp at 5400rpm
1.23hp/ci
486lb torque at 4600 rpm
Commpression:
10:1 on 91 oct
Ignition timing: 35 degrees
Block: production 350
Rods: Scat Steel 5.7 inch I beam
Pistions/rings: Federal Mogul, 1/16 inchrings
Oil pan/pump: Melling standard pump, milodon 5 qt.
Camshaft: Comp Cams 280 High energy hydraulic roller 236/243 duration at 0.050, 0.543/0.561 110 degree lobe separation.
Rocker arms: Roller 1.5:1
Cylinder heads: AFR 210cc heads
Valve Size 2.08/1.60
Intake Manifold: Edlebrock Pro-Flo EFI single plane.
Carburator: Throttle body, 36 Lbs injectors
Ignition: MSD-6a
Headers: 1 3/4 inch.


I think your duration is over kill.

[montessgtp]

I use parts i had avalible to me.... like the heads + crank n rods from a previous engine... i plan on buying a better set of cylinder heads...later on... the cam was choosen by the guy at jegs..he told me that would of been best for what i was doin...i had cam close to the specs u listed before the one i had now n my car had a shit load more low end tq...but fell out of range at around 5600 rpms my power band now is like raised to well over 7000..but i think my valve float after 7000...the light weight rotating assembly is good for reving..but i guess only with right heads =(

[Juglenaut]

but i guess only with right heads =(

yes and the right cam spec.

[montessgtp]

12558060#

This production Vortec iron cylinder head was first used on the 1996 pickup truck RPO L31 with fuel injection. The intake and exhaust port are very similar to the Corvette 350 LT1 heads. This head includes 1.94" intake valves and 1.50" exhaust valves, with pressed-in 3 /8 " studs. This head with compatible valves flows more air than bow tie head P/N 10134392, but the casting may not be as durable. The water passages are the same as the original 1955 small block design. The eight-bolt intake bolt pattern is totally different than the early model V8 12-bolt design. Use new manifold P/N 12366573, 12496820, 12496822.

Technical Notes: The valves seats in these heads can be machined to 2.02" intake and 1.60" exhaust. The rocker arm studs can be pinned or drilled and tapped 3 /8 ". (Casting P/N 10239906 or 12558062.)

[xxrollin]

Those were the old Vortec heads made by Pro Topline and they had durability issues with cracking. GM's got there own now and are about 15lbs heavier, I have these, Casting # 12558062. These arent in the GM catalog yet but thats the # on them. Made in Mexico... I dunno why I bought them but I had to back cut the valves and re-lapped them in to be sure they are good. I got as follows

350 production block, (2-bolt)
scat cast steel 3.75 crank
gm's 5.7 PM rods, ARP bolts
Vortec heads as listed above
Edelbrock performer manifold
Edelbrock 600CFM Marine carb
Crane cam's 450/460 lift with 228/228 at .050 with 112 lobe sep.
DUI's HEI distributor
all this by 2 for 2 engines and they run great, idle down to 800RPM's but only run to 5000rpm's

I'd say get a new carb. I didnt even have to touch mine at all. Had to prime them but turned the key and ran up to 1300, then down to 800-900rpm's....
Probably in the 340-350HP range on whatever the marina has......

[geoffinbc]

Getting a new carb is not the answer. You need to have it properly tuned or it will fail early and need rebuilds more frequentally. 80% of the people who own carbs do not have them running correctly. Rebuild it and adjust it properly. If you cant do it have someone do it for you.

[patgizz]

junglenut - WTF?

get some research done before you tell someone that their vortec heads are the weak link. they are out of the box the BEST production gen1 small block GM head you can buy. easy to get 400hp/400tq out of unported box stock heads.

monte - i suggest you register at a forum with good V8 people - nastyz28.com has a bunch of excellent people that dont care if you have a camaro or not with years and years of small block esperience and excellent knowledge. this forum is great for 60* v6 but i think you need some professional help. basically do not listen to anything that jungleboy wrote and you are on the right track.

[geoffinbc]

No shit Vortec heads are praised by everyone who uses them