Artofgio

Okay. 1980 corvette L-48 standard 3 spd auto. Here goes:


So the brand new GM Goodwrench 350 small block is in. I'll get some pics of the motor in the bay next time I'm able to snap some. Last time I saw her I was to excited to see it painted blue just like it came from the factory.
Attached you will find pics of the engine bay sans motor, the old motor, and then the new motor in the stand.


Next, the plan is to put on a pair of those new, cast-iron vortec heads (small port), corresponding vortec intake manifold, demon 670cfm 4-bbl carb (or 750; I haven't decided-help me do so?), and then a COMP cam CL12-256-4 - Comp Cams 'Xtreme Energy' Hydraulic Flat Tappet (CL12-256-4 - Comp Cams 'Xtreme Energy' Hydraulic Flat Tappet )


What think, gentlemen?

toobroketoretire

Only buy a vacuum secondary carburetor because mechanical secondary carburetors aren't intended for street use.

TedH

What are the measurements on your air cleaner, carb, intake (height)? Any concerns with hood clearance with the vortec heads/intake in this setup?

What condition is the OEM (aluminum) intake and Q-jet?

BKbroiler

Heads have no impact on hood clearance. Just about any Vortec intake, with a drop base air cleaner, will fit under a stock hood.

Little Mouse

I would use this UD harold designed lunati Voodo cam and lifter set 10120701LK

256/262, 213/219 at .050, 454/468 lift.

$180.97 cam/ lifters at summit

The 670 carb is big enough for what your doing.

Artofgio

q-jet in excellent condition, just rebuilt by a vette pro. if there are hood clearance issues i'll get a new hood,mbut the vortec intake manifold shouldnt be more than an inchnor two higher than stock. also, the stock dual plenum housing sits low as is

Artofgio

vacuum secondaries were the plan. i didnt even know you could put mechanical secondary carbs on these

Gale Banks 80'

No mention of what Goodwrench Shortblock You have now. I will assume Flat Top Pistons probably about the same thing as the L-48 that came out.
As far as the Intake height its easy to figure out since You have the original engine sitting there on the stand. Take a Straight edge across the Carb Plenum and measure down to the Block where the Manifold seals. ( the China Walls). Then do the same on Your new set up. If its to tall there are a number of things that can be done with the Air Cleaner set up. You can also Machine the Plenum down its easy for a Machine Shop to do.
As far as a Cam Shaft goes I would just give Comp Cams a call and ask them. What You are building is what many have done before You so its nothing they haven't all ready done.
For future upgrades I would be looking at an overdrive Trans with a lower 1st gear.

SteveG75

Quadrajet is a mechanical secondary carb. It just has an air valve that responds to demand and controls the secondary fuel rods.

cv67

ive used that 256 cam before works great in stock/mild 350s
rebuilt Qjet should be fine, 670 vs oughta work ok too but why not stick with what you got

96 lt-4

If the vortec intake is square flange then I would go with a 650/670 vacuum secondary.For cams ask 10 people and get 10 recommendations.Comp/Lunati/Howards (I prefer Lunati or Howards) 256 or 262 grind would work well.If you are keeping manifolds I would go 256 if you are going to use long tube headers go with the 262 and let it breathe.
Don't forget to recurve the distributor.

SteveG75

I would recommend staying away from the Xtreme Energy cams. They are good cams but have very aggressive profiles. If the break-in does not go exactly perfect, they will wipe a lobe in a heartbeat. I had two wipe in a row, second in less that 500 miles. That necessitated a rebuild and I upgraded to hyd roller cam at that time.

427Hotrod

Good lord...even Pintos and Vegas used mechanical secondary Holley/Weber carbs!

I can't tell you how many mild mannered cars I've helped people swap out their vacuum secondary carbs for a double pumper and seen their mouths hit the floor the first time they punched it. Certainly the vacuum carb can do OK IF you tune it...but guess what?...tune the double pumper and it will walk away from it everytime.

Most recently was a buddy with a '69 GT350 Shelby. Auto trans, 3.50 gears. Installed a healthy 351 crate motor and then ported heads, swapped intakes and cam for more power. Was using a 750 vacuum. He played with it for a long time...ran OK....but was a weak performer. Dropped on a 750 DP and instant tire smoke, 2nd gear rubber and hard pulls to redline.

"Just 'cause you can't do it doesn't mean it cant be done!"

JIM

cv67

I had a few of them go bad also including a hyd roller they were larger cams though. The 256 no issues with maybe as its smaller????

These days i wouldnt use much of anything wiht that name. Not bashing just had too many issues. The XEs that went bad were when they first came out too when there was "good" oil. Couldnt believe it, both wiht less than 1000 mi.

Hope that doesnt deter the op

Anyway didnt realize he was using vortec
If he really wants to step it up GM sells a 185cc Bowtie vortec head which is very nice. Their 206 would be too big. Good GM stuff for cheap. They breathe pretty well for what they are if he doesnt mind cast iron

Oldguard 7

Keep the q-jet. I foolishly gave mine away.

96 lt-4

Do NOT feed the troll.

SteveG75

My 496 started with a stock oval port Tripower setup (wanted it to fit under the stock '75 hood). That was fun with the vacuum secondary end carbs but then I found a set of Mopar 4872/4873 mechanical secondary six pack carbs. What a kick in the pants.

Went to EFI last year for a variety of issues (wife did not like the richness at idle, engine would die when I hit the brakes hard due to all the fuel rushing to the front of the bowls). The EFI is much more drive able but the mechanical secondary setup was an absolute blast.

Mechanical tripower (sidehung float carbs with accelerator pumps on all the carbs):


"Tripower" Port EFI (FAST XFI 2.0)



Dyno (rear wheels) for the EFI:

jkippin

personally I would not build anything with a flat tappet cam anymore. before you get to aggressive on the cam selection take a look at your flow numbers for your heads and choose a cam that works with their flow.
I run a performer rpm intake ported and a rough polish to keep the fuel mixture suspended.Also a 1.0 spacer under the carb to help it flow better. Carb is a 750 and it works well for me.with the 3.73 gears and a th 350 i do need an overdrive.
From 1800-5800 I make over 400 ft/lbs of torque and max hp is over 6k
I use an aluminium head with 185 runners which works.
Match all your parts do a lot of research on your own a lot of key board dynos here that will tell you don't use this don't use that.
on a side note I have run double pumpers on the street and they work fine for making a lot of power.
Its always been my school of thought double pumpers work the best with a stick and vacuum secondaries best for an auto....that's not to say that it cant be done though it just requires more patience and tuning which most don't like to do.

if I did it all over again FI is the way to go better tune ability.

Artofgio

okay, folks, sorry for the delay. Got Roxanne back from the shop the other day and the new 350 is running great. Attached are some pics of the new motor along with the great clean-up job the pros at Elco Chevrolet in St.Louis MO did for me.

Now all I need is some feedback from anyone who has ever used a demon carb. It turns out they dont do a 670; that's just holley and I think Edelbrock. So that said, I'm opting to go with the 750 cfm demon, most likely with vacuum secondaries because she's a driver. I could, however, be convinced to go mechanical if the facts are right.

Help me out, fellas.





great clean-up on the air cleaner housing





new lines. gonna probably replace the master here soon





couldnt help this pic





Figured you'd all appreciate one more.

jim-81

this is what I have and it fits fine