NastyBuzzard

Probably Bc I was rocking 21 psi fuel pressure!

Fast355

iTrader: (2)

Running rich usually does not cause detonation unless it runs so rich so long that it causes carbon buildup.

With the return line clear, what is the current fuel pressure?

The smaller cam is just going to make it knock worse, FWIW.

NastyBuzzard

11.5 psi. Spark plugs were so drenched in fuel it was missing. =s knock I think.

Fast355

iTrader: (2)

Have you done a warm compression test with the spark plugs all removed, the injectors disabled and the throttle held wide open???

jokerZ71

When you 1st start the engine,it is running under a preset tune.Once it gets up to running temp,the ECM takes over & makes adjustments to timing fuel,etc.This would explain that problem.

NastyBuzzard

Never had a reason to. I checked compression at all plugs and were fine. This is just more of a reason to trash this setup and put a 5.3 in. I just really need it to last until next year.

NastyBuzzard

Seems legit. But shouldn't it compensate some? I mean the "problem" is constant. It never tries to correct itself.

Fast355

iTrader: (2)

I suppose anything is possible. Just never have seen that myself.

11.5 psi is way too low for your setup. Its too low for a STOCK engine, much less one that has a cam, headers and exhaust. Start with the fuel pressure. Get it up to a solid 14 psi. From there you can play with it in 1/4 psi increments. From there datalog for knock counts. If you find knock counts practically non existant, add 2* of timing and log again. Do this until you either get some knock counts under load or you reach 6-8*.

Fast355

iTrader: (2)

A compression test will tell you a lot about the dynamic compression ratio of the engine. Now I am just shooting some numbers out, but for example if it reads 130 psi on a 9.5:1 engine, we know your cam is very retarded. If it reads 200 psi on a 9.5:1 engine, we know it is very advanced. If it is reading 165-180 psi, it is about right.

NastyBuzzard

From everything I've read stock fuel pressure is 9-13??? My tbi isn't adjustable has stock regulator. How do you suggest turning up fuel pressure? An adjustable regulator is expensive as crap for some reason? Also will stock 1987 fuel pun even support 14psi?

NastyBuzzard

When I did compression test it read between 170-180ish.

Fast355

iTrader: (2)

Most stock pumps can support up to about 15 psi. Didn't you just say your fuel pressure was 21 psi???? It sounds like you may not even have the stock pump in the truck. The stock pump usually will not reach 16 psi.

9-13 is the "factory acceptable range", but I am telling you right now with a wideband hooked up on a stock engine and chip it needs atleast 12 psi to keep from going lean above 3,500. Your engine NEEDS more like 14-15 psi from prior experience with these engines.

jokerZ71

If your running .030 over flat tops,your CR is just over 10:1 & with a thick gasket to boot,this very well could be part of your problem.If knock counts were high especially.Try running some 93 octane in the tank & see if it improves.You really need a custom tune based on your data & specs.You've made quite a few changes there & you're not real sure exactly what all is goin on w/o know what your true CR is along with other vital info.Even w/ shorter flat tops,you're prolly @ 9.3:1 with less quench which could make things even worse,especially with a stock tune.

NastyBuzzard

True.. Lol. But return was completely blocked. How to achieve 14-15psi? Truck doesn't seem starved for fuel at all. Sprays good cone pattern all the way through wot

NastyBuzzard

I am pretty sure it's flat top. It is whatever stock was. Who to tune? Brian is all I know! He suggested that tune is only beneficial with my setup is if I swap heads.

Fast355

iTrader: (2)

My regulator had a Tamper proof torx screw on it. I have also taken and broken the welds on ones that did not.

NastyBuzzard

I'm not fully understanding what you did there

jokerZ71

That's BS on the tune.A tune is beneficial on even a completely stock engine.The factory tuning is very conservative & leaves a lot to be desired.Stock pistons should have been a 12cc dish piston.

NastyBuzzard

If you google image search 350 tbi piston that's what they were

Fast355

iTrader: (2)

There are 3 different factory TBI 350 pistons!

Fast355

iTrader: (2)

Dave....a very good TBI tuner wrote a how to article.

http://www.gearhead-efi.com/Fuel-Inj...sure-Regulator

NastyBuzzard

https://www.thirdgen.org/forums/tech...iston-ccs.html the ones posted by fullsize fun

or here http://www.mabbcomotors.com/catalog/...d_Warranty/142

Fast355

iTrader: (2)

Ok that is flat top with 6cc worth of valve reliefs. Only question would be 1.54 or hopefull 1.56 compression height. You could be over 10:1.

The 2nd link has 12cc dished pistons fwiw!

NastyBuzzard

over 10:1? but it doesnt detonate on regular. i know what that feels like from ownin ls1s n lt1s
does that translate to no power unless over 65mph?

Fast355

iTrader: (2)

It could if the load is causing the knock sensor to pickup detonation that you cannot hear. The TBI ECM can remove up to 10° of timing. Most calibrations start out negative at heavy loading and low rpm.

NastyBuzzard

I'll go out n hook up laptop and see what it says. I got a feeling it won't show anything too odd.

NastyBuzzard

from cold start. knock count was 0, jumped to 21 from starter and stayed 21, even when I took it down the road.

BLM a lil high at 133
AC 99
Coolant temp 72.3
Map 1.7
RPM 725
TPS .55 volts
INT 128
02 1.061 volts
batter 13.8
rich/lean cntr 27

Fast355

iTrader: (2)

Yea advance the timing 4° and get it some more fuel to drink.

NastyBuzzard

To advance it to 4* I turn it ccw or cw? I just want to be 100% sure. Also, i don't even have a timing light anymore, it burnt up. How would I know exactly 4* without a digital timing light?

NastyBuzzard

I am now afraid to just do cam swap.

My Truck:
1987 GMC V1500 4x4
700r4 Transgo Shift kit with corvette servos
3.42 front/rear gears w/ 32" tall tires 15" rim
1991 gauge cluster swap w/ drac module w/drac mod
Fuel Pressure 10.5-11PSI


My Engine:
92 350 TBI
Swirl Port Heads
.030 flat top pistons (Speed Pro) (felpro head gaskets)
Flowtech Long Tube Headers
Heated O2
Dual Electric Fans
Y Pipe into Flowmaster 1 in 2 out exhaust (No Cat)
Compression check was good 170-180 range
Timing set a 0* TDC
Spark plugs gapped .035

What everyone else is saying is the stock tbi cam specs are different. They are also saying I need to change timing to 4-6* advanced. Also saying my fuel pressure isn't high enough and that my compression ratio could be 10:1 b/c of flat top pistons and that I need a tune.

FROM THE FORUMS:
"Those 350 TBI cam specs are way, way off, not even the 305 peanut cam is that small.
The 305 peanut cam was 178/194 @ .050, .350/.385, 109* LSA, 106* ICL.
The 305/350 vortec cam has faster ramps and not much more seat to seat duration, but has more area under the curve at 191/196 @ .050, .414/.428", 111* LSA, 106* ICL.
That IS STOCK COMPRESSION RATIO for a light duty 350 TBI and it came with a 195-210 HP depending on application. There were about 4 different exhaust setups and several intake/air cleaner, and 50+ different stock chips for a 350 TBI.
Timing needs to be higher than 0*BTDC....4-6* works out well with some engines liking up to 8*. Watch your WINALDL datalog for knock counts. Also if you can screen shot the BLM table and post so I can see what is happening. You may be running lean and need some additional fuel pressure. Many stock TBI regulators came running as little as 9-10 psi of fuel pressure. Most stock engines need 12 PSI MINIMUM to keep from going lean above 3,500. With airflow mods they often need 13-15 psi.
The stock 350 had a cam with specs as follows 194/203 @ .050, .383/.410, 112* LSA, 108 ICL

100% sure of this and every autoparts house across the nation lists the stock replacement cam as this. It also lists a 204/214 grind as a replacement for more torque. The 204/214 cam, known as the MTC1 or the CS1014R runs GREAT in a stock TBI 350 with the stock chip.

If your running .030 over flat tops,your CR is just over 10:1 & with a thick gasket to boot,this very well could be part of your problem.If knock counts were high especially.Try running some 93 octane in the tank & see if it improves.You really need a custom tune based on your data & specs.You've made quite a few changes there & you're not real sure exactly what all is goin on w/o know what your true CR is along with other vital info.Even w/ shorter flat tops,you're prolly @ 9.3:1 with less quench which could make things even worse,especially with a stock tune."

jokerZ71

Do you know which vehicle this 92 engine came out of?Do you know which casting # heads are on the motor now?

NastyBuzzard

It was a 92 C1500 or silverado, whatever they are called that year. I think they were 188 or 193's I can't exactly remember.

jokerZ71

So,are you using the chip from the 92? Did you just swap the long block & retain all your 87 equip,or swap in all the 92 stuff?

NastyBuzzard

I am using serpentine setup from the 92, everything else is from the 1987 Truck. ECM and chip are all stock to 1987. I don't think hardly anything changed, I am thinking even all the sensors pretty much stayed the same. I am running the 87 tps that isn't adjustable as well.

NastyBuzzard

Anyone ever heard of motorvation? It is a company that burns chips and does tuning. I called and they said they could do a full custom tune for $400 and it will run correctly.

Fast355

iTrader: (2)

Already told you to talk with Dave if you want it to run right.....However NO tune is going to fix a mechanical issue, like you have!

NastyBuzzard

Who is Dave? Where do I find his contact info?

Fast355

iTrader: (2)

http://www.gearhead-efi.com/Fuel-Inj...Old-School-EFi

NastyBuzzard

So my heads are the 14102193's swirl ports. Seems that their is argument whether these heads are 65.33 cc or 76cc. Anyone know for sure? Can measure?

If they are 65.33 w/ my flat top pistons, what would my compression ratio end up as? Why does it seem like its drinking the 87 w/ up to 10% ethanol blend just fine? I don't have high knock counts.

jokerZ71

The 193's are in the 64cc area.With factory 12cc dish pistons & stock deck hgt,your CR is rite @ 9.4:1.Your engine & tune is set up to run on 87 octane gas.If the flat tops you installed are 1.56 pin hgt,your CR is in the 10;1 area.If your ecm is sensing detonation due to this,it can pull timing,which in turn kills your power.If your flat tops were 1.54,your CR is somewhere in 9.3:1 area.Your deck hgt is approx .045 + the approx thick gasket you used.Again,this will kill your CR & power.You would be better off with a 10:1 CR & a tight quench than the lower CR w/ excessive quench.

NastyBuzzard

I've never really had to look too deep into cr before. However with stock deck height, 4.040 bore, stock head gasket thickness of .041 and flat tops with approximately 4cc worth of valve relief (typical) and head volume of 65cc wouldn't I have CR of 9.7:1 which is better than stock and should make more power but will run on regular fuel.

?? Is that right or am I nuts?

jokerZ71

It depends on the pin hgt of your pistons.If you have pistons w/ a 1.54 pin hgt,that put your pistons .020 deeper in the hole,then the added .041 gasket on top of that,puts your quench @ approx .086.That's not a good thing.Depending on which piston you have,with the short piston,you have 9.2:1 with a quench of .086".With a 1.56 piston,you have 9.6:1 with a .066" quench.That's assuming your block wasn't decked.Either way the excessive quench robs you of power & does very little in the way of fighting detonation.I used 6cc on the piston.If they are actually 4cc,CR will be very slightly higher.

NastyBuzzard

I am pretty sure the block was decked when it went for machine work. Or atleast checked to see if it needed to be decked. I wish I would have kept all that info. I've had too many blocks done.

So is it possible to give it some more air/fuel to help the issue? I'm almost done making a adjustable fuel regulator for the tbi , I am looking into ultimate tbi mods as well, such as grinding down edges on top of tbi and doing salad bowl. I also have an injector pod spacer as well.

jokerZ71

Without knowing your actual deck hgt,it's hard to say..A thinner gasket would help some w/ power as well as the TBI mods & tuning.I would completely diagnose everything 1st becuz you may have other issues as well,but,I'm pretty certain your cam is not the problem.

NastyBuzzard

What mods do you suggest?

As far as tuning goes, I have contacted Dave at old school EFI. He needs a .bin file datalogg from tunerpro RT, I am trying now to get tunerpor RT to recognize my aldl cable so I can datalogg it and get him that .bin file. I am really starting to feel like a tune will help it a lot.

Over the weekend I installed the piece w/ a spot for quick access for fuel pressure gauge. That went well. I also have a tbi injector spacer to put on at some point.

Running 10.5 psi (4* advanced). When I first crank it up and drive it shifts at higher rpm and feels great, after it gets fully warm, it has the low rpm shift and it is having trouble idling. Idling at 550 rpm in park and will sometimes die on take off.

jokerZ71

The 1st thing you need to do is get your fuel psi up some.Then I would say go thru the complete setup with a good tune up.Plugs,wires,cap,rotor,everything.Ck all your sensors,etc.Make sure you don't have vacum leaks @ the intake,EGR,TBI,etc.ECM tuning will not benefit you if you have other things amiss in the engine mgmt system.I'm not so sure that all of the swapped parts from the year models you are using are the same as well.

NastyBuzzard

Plugs, wires, distributor, cap, rotor, o2 sensor, egr solenoid, egr valve, have all less than 500 miles. Tbi was rebuilt at the same time. No vacuum leaks I can find.

I just replaced all head gaskets and everything up top about 2k miles ago.

Sensors are all matching 87, tps, iac, map, knock, oil pressure, coolant temp(less than 5k), egr solenoid, etc. It has a heated 02 sensor b/c of headers, I just did that.

Any other mods you suggest before I get the tune done? I am actually rebuilding another tbi this week with a injector pod spacer and adjustable fuel regulator. That is if I can ever get tunerpo to recognize my aldl cable!

NastyBuzzard

So here is what I've been contemplating... That was a used "melonized" gear that I took off a vortec distributor an put on my new billet distributor.

I have recently read that vortec dist diameter is an odd .491 and regular is .5". I seem to remember it not being real tight. I can't remember if I put it on as is or used a bronze one.

Anyways, I am thinking about ordering a new distributor gear that fit a my application. What material should it be? Iron, steel or bronze? I know it needs to be melonized for the roller cam setup and .5" diameter.

NastyBuzzard

Just to see what I had on the distributor. I pulled it. What do yall see?

I have also included pics of the vortec gear that was in it when I orginally built the truck, it was used. About 6 months ago I dropped in a new distributor but old vortec gear wouldn't fit the shaft so I put this gear on it that I had.









Looks like I need a new dist cap/rotor. Any idea what kind of gear that is on the distributor? Bronze, steel, iron?