Slightly dissappointed

[tkleinia]

86 K10 Originally V6 700r4 3.43  NOW 383 TH350 3.43

Sorry for the long post...

Long story short: I swapped out a tired 350 for a home built (I built it) 383 stroker... I took it for a spin... and am slightly dissappointed. While its better than the old engine, a Metro will beat it off the line. I now am deciding what to do next.

I have some ideas of what I can do to the engine... It has an extreme 4x4 cam now, could swap that...
I purchased all the parts to end up with a compression ratio of 9.5, to do so, I had to install dished pistons, but may have gotton carried away cleaning the casting of the cumbustion chamber, lowering the ratio(thought I was helping, I now realize I may have hurt performace since I did not compensate for the loss of squeeze), ... could install flat tops and should be safe.

But my other thought, and my reason for posting... is my trans, gearing, and tire size killing me?
I have a 350 trans, 3.43 rear gears, and 33 in tires.

I am considering swapping in a 700r4. Which is what the rear end was set up for from the factory. I would imagine I will benefit from the 700's shorter first gear. I may swap out front and rear gears in the future.

Any thoughts? Is my drivetrain combo killing me?

[VileZambonie]

What exactly did you do to the heads? What heads are you running? Why did you get rid of the 700R4 in the first place?

[tkleinia]

64cc  Iron Vortec heads

I smoothed the casting "profile" from the chambers and intake runners, and polished the exhaust runners. No reshaping. Stock valves and springs.

Previous owner installed the first V8 and th350. The glove box tag reads v6 with overdrive trans and 3.43 gears (gears verified)

[Gregzz4]

You did not mention fuel delivery
That stroker will want some airflow from a decent carb
What carb and fuel are you using?
I have a stock Q-jet with something like 750-795 CFM and my ZZ4 loves it.
I ran it for years on 92 Octane, but with the new 'up to 10% Ethanol @ Chevron', I now run it on 94 Octane and am really surprised that the stock coil will light the extra Octane. I have a noticable difference in throttle responce.

[tkleinia]

600 Edelbrock (is that too small?)

89 octane.

I use it for towing a boat during the summer. The idea was to not go broke on paying for high octane fuel with the power benifits of a stroker...

[VileZambonie]

IT should have some pep based on what you've told us. HEI Ignition? Is it timed correctly? Cam timing is correct?

[Gregzz4]

Besides the fact that my truck was labeled '91 Octane' from the factory ( Towing/Hauling ? ),
I have always run 92 Octane.
Then when I put in my Crate ZZ4 it needed 92.

So, when I installed the motor, I was talked into a Holley Avenger 670CFM as GM claimed they got their ratings for this motor with a 600CFM, like you have.
I drove it over half an hour from the city, on the highway, to a tuner buddy. I went there because I was Very disappointed with the HP change. He had to Under Jet the Holley so much that he told me either the Carb is junk, or it needs to be bigger.
I raced back home in a hurry because he was closing soon, put on the stock Q-jet, burned rubber all over my neighbourhood, beat the Devil on the highway, and then he changed the rods and jets to Bigger/more fuel ones to make it even better.

When GM says 600CFM, I say BS.

And I only have 58cc Heads.

I'd be willing to guarantee you that you need a Much bigger carb and burn a little better than 89. But you could experiment with that.
Your Spark system will need to handle the higher Octane, as will your Compression Ratio. Mine is 10:1 or so.

Other thing you could do is supercharge it as your Compression is almost low enough  

[tkleinia]

New HEI distributor with MSD internals. adjustable vacuum advance

(everything, i mean everything is new with the engine minus the bored 4bolt block)

The short block was put together by a reputable shop and the cam was degreed. (supposedly, starting to wonder)

The timing is set correctly with input from the cam card (don't remember exact figures, engine was built last summer, and have only driven it 500 miles since. (sat over the winter)

[eventhorizon66]

A few thoughts:

What is your ignition timing?  Get that wrong and you could turn a 572 into a turd.

Did you use a carbide cutter or an emery roll to clean the combustion chamber?  Are you sure you didn't knick a few valve seats?  Did you do a quick check lap with some fine lapping paste?  Have you performed a compression test?

Is your mixture too lean?  Wideband A/F monitors are getting cheaper all the time.  WOT should be 12.8:1-13:1.  Does it do anything in particular or are we talking a general lack of power?  Are you getting adequate fuel volume to the carb (good fuel pump, no kinks in the fuel line, etc.)

[tkleinia]

Other thing you could do is supercharge it as your Compression is almost low enough  

lol Thats not the first time ive heard that!

[Gregzz4]

So what's your initial and WOT timing?

[tkleinia]

A few thoughts:

What is your ignition timing?  Get that wrong and you could turn a 572 into a turd.

Did you use a carbide cutter or an emery roll to clean the combustion chamber?  Are you sure you didn't knick a few valve seats?  Did you do a quick check lap with some fine lapping paste?  Have you performed a compression test?

Is your mixture too lean?  Wideband A/F monitors are getting cheaper all the time.  WOT should be 12.8:1-13:1.  Does it do anything in particular or are we talking a general lack of power?  Are you getting adequate fuel volume to the carb (good fuel pump, no kinks in the fuel line, etc.)

I will definatly check the timing again. If I rembember right I quit trying with it timed at 30 degrees...

I used emery rolls, no carbides. Yes I did a quick lap as the Vortecs already had a three angle.

No idea on a mixture...

[tkleinia]

I am not a mechnic, just a wrench.

I dont beleive I have the cam info any more... Does anyone have a suggestion of what kind of timing may work for me?

[Gregzz4]

As to your first question, no, your gears, tranny and tires are not holding you back from burning rubber
Although you might break some stuff if you push it enough
The TH350 can handle all this IF it was built well enough.....mine survived 20+K with a 12Bolt one tire fire and stock rubber...that's with 355HP and 405FT pounds...then I blew it up 'cause I didn't service it. Blew some U-joints though.
The tires you have will put some stress on the drivetrain, but your Stroker should give you enough power to break them loose, even with Posi.

[eventhorizon66]

Does anyone have a suggestion of what kind of timing may work for me?

If it were me, I'd probably start with around 8 degrees initial and 28 total, then add timing until the engine response doesn't improve anymore.  I'd think you should end up with around 10-12 initial and 32-34 total.