meadmarc

I have a 1997 Vortec 350 (truck engine) that I would like to rebuild and put in my 89 Firebird (in place of my 305 TBI). Should be a pretty stock rebuild, for the most part, I was going to replace the existing spider fuel injection with an Edelbrock Performer intake, with a 1405 Carb. New vacuum distributor, of course. And I have a set of Summit shorty headers, the cat has already been removed and I have no plans to replace it.

1. What kind of FWHP do you think this will put out? I'd like to hit 300, the stock motor was supposed to be good for 255.

2. What kind of HW MPG can I expect?

3. Are there any other modifications I should consider while rebuilding? I had looked at cams briefly, but I kept hitting the "and then you get bigger valves, and machine this, and replace the springs, and oh-yeah-now-between-the-cam-and-all-this it's another $800" wall. Anything that DOESN'T invlove dramatically re-working the stock heads, which I understand are quite good already?

THANKS!

gwarren007

iTrader: (1)

When you have the heads rebuilt they can/will cut them for larger lift cam if you ask them to.

meadmarc

I'm don't think I'll get much further than pressure-checking the heads. They should be okay, the problem with the engine was a spun bearing, and I need to keep the rebuild as inexpensive as possible or it will never happen.

If they need to be torn down, then I could possibly look at that, but adding a new cam, valves, and springs (and possibly lifters), it gets expensive quick.

A friend of mine who has been building/racing cars for decades told me the cam in the stock Vortec was actually pretty good, and based on what I was shooting for, not to worry about replacing it.

Guest

I think I'd just install a stock LT1 cam. No machining required. Bolts right in.
How are we to guess your MPG potential without knowing your transmission, your axle ratio, and your rear tire size?

TNT_Z28

If the motors gonna be rebuilt, that's the best time to do a cam. I spent under 200 bucks for my flat tapper cam, lifters, pushrods. I did however have the machine shop install better valve springs that I had.

Those heads are worth improving though, and now would be the time to do it.

MPGs and carbs don't really go together, but I can get 13 maybe on the highway. You won't need anything bigger than a 650 on a 350.

Guest

I've done repeated 27 MPG trips with the carb'd 350 in my '86 IROC-Z that I used to have, so don't accept 13 mpg.

jchaussee

If you can tell me the secrets of a 22 mpg trip I would be happy

Guest

I sent you a PM so as to avoid hijacking the thread.

meadmarc

My bad, try to keep the posts short. 700R4. 3.42. Stock 16".

As far as the LT1 cam, I had thought that, but the aforementioned mechanic told me that the Vortec heads are very close to the LT1 heads, and that the Vortec truck cam was effectively the same as the LT1 cam. He then called his speed-shop connections and they confirmed.

Is that not correct? Time to go pick up a used LT1 cam?

meadmarc

That was what I was hoping. Mid 20's would be very satisfactory. With headers and the Edelbrock intake, that sound reasonable?

Guest

The L31 cam is 191 intake duration, while the LT1 cams are in the 203 range. Not a huge difference. Similar situation with the lift. The LT1 has a couple of hundredths more lift. But the difference in useable rpm range is at least another 500 for the LT1 cam.
Price it, then decide for yourself. I've driven an L31 FS 1/2-ton pickup, and I've driven an LT1 Impala SS. I'd definitely swap cams.

Your combo isn't so far from what I had success with, mid 20s for MPG should be possible, if you can dial in your fuel and spark.

Fast355

iTrader: (2)

Nope that is intake/exhaust/compression ratio/tuning differences between those engines.

The iron head LT1 has the very same camshaft as the L30/L31 truck/van engines do. Its the F/Y- car LT1s that have the larger camshaft. The B-car engine has 260 HP and 330 TQ compared to the 285-305 and 340 of the hotter engines. The timing maps are vastly different as well. Vortec trucks only run about 22* BTDC, B-car LT1 about 29*BTDC and F/Y cars run 33* BTDC. The advance curves are also vastly different.

InfernalVortex

iTrader: (4)

Your mechanic is actually about right... the Vortec heads are very close to the LT1 heads. They're actually an improvement on the LT1 heads in a lot of ways, but they are related. The cams arent what I would consider that close to each other, but I can see how that would be a subjective judgment in some people's eyes. I'd suggest getting a decent mild aftermarket roller cam... or an LT4 hotcam. That would require a little work on your heads, but I think it would be more than worth it. A nice roller cam in a vortec headed engine is the difference between 250hp to the wheels and a 350hp to the wheels.

meadmarc

I know cam brands can become a religious debate rather quickly, but any specific recommendations that would hopefully allow me to re-use the rollers and lifters?

3rdgenmaro

iTrader: (9)

lt4 hotcam

simple swap. Have the heads worked correctly for the extra lift. Any machine shop that is even half decent knows what needs to be done.

I drove my car with the stock vortec motor for awhile. Then went to the lt4 hotcam. Night and day difference. Went from running a 9.28 to an 8.50 with a cam swap and tuning.

It will require a stall converter to get full potential.

Guest

No, the Camaro was 275 HP, while the Impala was 260 HP, because of the intake and exhaust systems. The iron LT1 heads had slightly better intake ports, but used the same cam as the Camaro.
The pickups actually had the best exhaust flow, because of the extra space underneath for freedom of routing.