You are begging that thing to detonate. Either limit the boost or back the timing waaaaaaay down. Why does it redline at 4500rpm?? Many of us launch at that rpm. You will tear up way less shit turning higher rpm than lugging the engine.

 

It's a syclone 4.3. They are not high revers. Stock is 4300rpm.

 

I know some guys run timing locked at a particular number, 24*-28*ect and the at would be at low rpm too.

 

Carbed? E85? Water meth?

 

That stock 17C is a smaaaaaalll turbo for that motor.

 

E85, no meth. Stock air to water. Temps are around 130-150 degrees

 

Switch your tach to 6 cylinders.

 

Dude it's a stock tach.

 

Stock 4.3 have to rev higher than that

 

I'm not familiar with that turbo but by a post above it may just be choking the engine so bad 4500rpm is all it will go. I would personally make a change to a more appropriate turbo that would rpm like a normal engine.

 

I agree with turboII, there are many well priced turbos that'll make more power more safely than the one you have

 

I can careless about the power, it's a collector and not a race car. Just want to get it pulling clean. Right now is misfires while under boost.

 

Have you checked out syty.net? I'm sure someone there would be better versed answering your question.

 

You can rev them to 5800 or so just fine with a set of comp 980 springs. The indicated factory redline is totally bogus. I ran turbo Buicks for many years. 4.3's and 3.8's. With a cam and good springs 6k is no problem. Can't go much higher than that without spending alot of money. The factory pistons are HEAVY. They have steel inserts behind the ring lands.

The TB head design/CC is lazy. Couple that with the low compression and they need lots of timing. I'd say your right around where you need to be. 20-21* is the norm for 20ish lbs depending on charge temps.


I ran my best ET on a box stock 3.8 (untouched heads/cam/bottom end) at 25* and 25lbs of boost. 91 octane and 30gph of 100% meth injection. Te63 turbo. (I did have a 2700lb chassis though so I'm sure I got away with a more aggressive tune.)

 

The turbo is probably the down fall. Old technology. Too much back pressure.

I was running a stock 4.3 with a N/A cam and a stock 87 Gn turbo. It was done at 4800ish. 986 spring with a bit extra seat pressure with a N/A non factory style roller cam so Im sure the cam was letting in a bunch exhaust gas. Ran on e85 ,carb blowthru, 15 psi , and distributor locked at 31 deg. Ran best there. Changing turbo and cam hoping to make more hp and rev a bit more.

So my setup was a bit different than yours. I would say give it what it wants.

Ive seen a 4.3 make 760hp and still be done by 5800.

 

All stock setup, Id investigate ignition and then valve sealing/seating if its popping up top.