Anyone using this eng? What do you think about it? Any mods you have made to it. TIA

 

I've got one in my truck I made into a 383...

 

I have used the 906 heads in the past on other SBC builds, never put them on a Corvette. Those heads flow great and with the proper cam and valve train setup would be a great upgrade to any stock L83 or L98 engine.

 

High torque engine. Limited intake availability with stock L31 vortec heads, due to unique bolt pattern. GMPP released 2 versions of Vortec heads with standard sbc intake bolt patterns.

 

The nice thing about them is depending on what it came out of it can be a 4 bolt block. Also you're set up for a roller cam if you're not already.

 

I pulled one from a wreck a friend owned. It was stock except someone had done mild port/bowl work on it. From what I'd been told the factory injection is supposed to be a bottleneck and it was pretty weak over about 4500 rpm.

I added 1.6 rockers (had to open up the pushrod holes), LT4 springs (I've read that sometimes they fit and sometimes they don't) shim head gaskets and switched to a carb and distributor.

I had to drill/tap the forward clutch pivot hole to run it in a C3. I also redid the temperature sending hole to use match a '70s sending unit.

It's still weak when the rpm gets up the but those who've driven it think it a lot bigger than a 350 below 3000 rpm.

 

What are your goals...or what are you looking for? I owned/drove one until it had 296,000 miles (and it still ran like new), so I can tell you a few things:
First, they last for freakin EVER, if you do a little maintenance
Second, the fuel economy is great; over 20 mpg in a 4x4, 1/2 ton truck
Third, the power was fantastic, for what it was/was in.


It's not more a "high torque engine" than any other EFI SBC; it makes about 340 tq...just like an LT1, L05 or L98 does.


While the "L31" injection system IS limiting, that is not why it fades above 4500 RPM; that characteristic lies almost exclusively in the cam shaft. The duration is tiny on the L31 engine; something like 191/196 @.050? With duration like that, no 350 sized engine is going to make power over 4500 regardless of heads, intake, injection or whatever. Swap the cam and you'll get more RPM.

L31 heads are fantastic for the money, and the L31 long block is a great, affordable way to get into a roller, 1 pc rear main seal, 4 bolt block.

If running typical TPI or other typical Gen I SBC intakes, some intake bolt hole modifications will need to be made and likely stacking intake gaskets too, since the L31 intake ports are higher/taller than typical Gen I heads.









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I know the cam is a baby but with the low compression I decided not to spend money on a cam. I did a 350 with similar compression and tried it with an L-46 cam (IIRC about 224 @ .050 intake). It would shift nicely it at 6000 and it pulled a 99.9 mph trap speed but it was pretty soft where this L-31 now feels great. Flatops and around 235 intake durration seems to put these engines over 400 fwhp with great low end but these dished pistons

 

I hear you. I feel that a typical stock cam -one in the 205˚ would give you a nice, usable RPM range, w/o hurting low end too much. But I hear you about your combo right now....I bet it feels great and pulls really nice on the street. My truck gave that perception of a nice, strong pull (and it even ran 16's at the track, once!) and it weighed 2000 lbs more than your car. I bet that car is a hoot.

 

I put the 906 heads on a 355CID with a 230/230 .480/.480 flat tappet cam and put it in a 1984 2 Door S-10 Blazer. It weighed around 3500 with me in it and ran 14.0s at 100mph w/ 2.2 60' times. It had an open 3.73 diff, a th350 w/ 2400 stall and TPI log exhaust manifolds w/ 2.25" true duals. It was a fun little truck. Roll racing on the streets it kept up with all sorts of quick cars till around 90mph when it really started pushing the wind. I suspect it was in 280 rwhp range. I would like to put a very similar setup in a C3 or early C4 and build a really cheap driver one of these days.

 

When we built the 383 from it I was planning on using the stock vortecs... but the engine died because it dropped a valve and kissed a piston... So I ended up going with summit vortecs. Again though, they're not true vortecs but they are close. For a 6000 lb truck it hauls ***.

if you want to see it...

 

When people ask about putting a new 280hp target master 350 into their car, I always tell them to find a good used 350 vortec instead. Late 70s tech or mid 90s tech, which is better?

 

Totally. And the Target Master is more like 200 hp, once it's in the car.