Well my neighbor went back up to the dyno today to finish up the tune. Numbers still seem low to me though. 203 hp and 310 torque. AF ratio is dead on from idle to 5800. We ended up kicking up the pressure on the holley tbi, the max we could get was 16 psi, which was enough to get the tune down but holley said we could go up to 21. Just to recount the buildup, its a 355 with crane cam 212/218, GM performance tbi intake, gibson headers with true duals, holley 670 throttle body, K&N filter with the aftermarket air tube feeding the filter housing. The truck is a 92 with a 5 speed. Any suggestions on why the numbers might be so low or improvements to be made. The only thing I could think of was valve float or timing retard, but Im sure Jeff would have noticed the timing on the dyno while he was tuning.
Thanks

 

dude rip off that holley and put a 454 tb on it with some 60 pounders.Get an adjustable FPR and a Walbro 255,that should be plenty enough to feed the need. Maybe Fast or Shifty can tell you better.That's just my opinion.

 

sounds as if you could use more pressure from the buildups i remember recalling.

Your tb is fine, just as good as a 454 tb i beleive (little better if i remember right).

the other guy is right though, you will p[robably need a bigger pump it sounds, a walbro 255 would be nice i'd think.

 

The air fuel ratio was dead on between 12.8 and 13.0 for the entire run so I dont think it is a fuel problem, just dont know why I could only get 16 psi out of the regulator?

 

It's probably because your fuel pump won't generate anymore pressure. It seems most stock tbi pumps tend to max out around 15psi at the throttle body (mine did).

 

yah what bones said. The higher hp buildup seems to require more fuel pressure is all i know, i remember reading 28 psi on a 300hp 305 so i'll bet you should see pressure somewhere closer to that i'd expect.... could be wrong though.

I'm sure the timing curve could use altered though being that you have a cam swap and other mods which should yeild you a slight gain.

Bigger injecters are a pretty big must too. Although 13 to 1 afr is about the perfect powermaking formula you may not being getting it's full potential with how it's being delivered.

 

The pressure either pegged because your pump can't go any higher or because the spring in your regulator bottomed out. But if your A/F ration is dead on all the way up based on a wideband O2 I'm assuming right? then it doesn't matter if your pressure is maxed out.

How much timing are you running in it? What's full advance at open throttle and when does it all come in?

 

there has to be something seriously wrong there. 203 rwhp; figure 10% parasitic loss with a manual trans give 223 crankshaft hp. I'm pretty sure a stock 350 tbi truck made that.

There's no way that combination should make less than 250 rwhp. It sounds like the heads and intake weren't swapped; all you have is a mild cam, exhaust and throttle body, but, tuned properly, those mods should be worth 30-40hp over stock.

It can't befuel pressure. If it was lean, the a/f ratio would be off. You didn't say anything about timing .... have you done anything with the chip? Too little timing could account for the low hp. If the cam was installed a couple of degrees advanced or retarded, you'd never see it until you did some datalogging.

 

A/F ratio is dead on, truck has been on the dyno 4 times now and the timing curve seems to be almost perfect. Around here we consider Jeff at Carolina Auto Masters to know his stuff so I dont think its in the tune.

 

What does your timing look like @ WOT? Vortecs are fastburn heads. Too much timing and you will be killing power. Have you tried going to a higher octane fuel and then running it. Knock retard will kill power.

This is a 4th gear pull right?

Have you tried experimenting from 12.8-13.0:1? If this ratio is from after the cat, you will be off. Have a bung installed in the exhaust immediately after the header and install the wideband there, if it is not already there.

Something is still wrong though, I had a stock L03 305 that made 181 RWHP/268 ft/lbs after headers, exhaust, ultimate TBI mods, and a custom chip rework.

 

Played with timing and he tuned for max power on 93 octane. Im still thinking valve float or a fuel pressure issue, although as I stated before the A/F ratio was dead on across the board. Truck runs great, still have some driveability issues to work out with timing down low (surging) but other than that definitely pleased with the results. Still looking for ideas though. Also remember not all dynos will read the same so maybe this one is low (dynojet).

 

I am sure you have checked for the simple things as well. Such as a throttle that is not fully opening. Perhaps the air cleaners thermac valve is not opening fully when the engine is warm causing a restriction and introducingh hot air. What is the MAP and IAT reading @ WOT?

 

Well I thought I had checked for all the simple stuff, your reply reminded me that there was not a heat source for the thermactor with the headers now. Pulled the air cleaner to find that it was froze (rusted) closed. He drove the truck after I removed it and said it drove like a totally different truck. Now to install the rockers and get it back on the dyno, since Im sure the A/F will be off now that it is actually getting air. Do you guys recommend the open air element?
Thanks

 

YIKES, 203 RWHP through the Auto-thermac opening!!! For those unfamiliar, it is the 1 1/2" diamater opening where the hot air tube attaches to the air cleaner. Yes, it makes a huge difference when closed vs. open.

An Open Element air cleaner will look better, sound better, allow for alot more airflow.

 

That's a good sign then that it made that much power through that thermac, man. My guess now, is that you're going to run real lean and probably run out of fuel up top. Now you may need that new fuel pump and upped fuel pressure. You'll see though at the next dyno trip for sure what's going on now with the fuel. Glad it was something easy like that though!

 

sorry but what did you ever get out of this?

 

What is the auto thermac? Is that like a thing that draws warm air off the exhaust untill it heats up?

I too am interested in an update.

 

yes it is, its like breathing out of a straw

 

Well I know its been several years... but man, I read the whole discussion and you left us all hanging...? LOL.. I think we are all dying to know what the Dyno read?

 

reviving from the dead eh? haha.