Z-RATED94

No expert here, but i think you could run the Impy gaskets with no problem seeing as how it's a stock (deck hieght) short block. That and a set of 1.6 rockers might pick up the HP by 15 or 20. Ever do a compression test? As far as your #s go, I think there half way decent with that many miles on the motor. And as most will tell you, dyno #s are nice but track #s also help tell the true story. Good luck.

BIG SHAFE

Definitly too lean (especially the second run), need to be closer to 12.7 A/F.

Z-RATED94

My tuner likes it at 12.5 to 12.7 also. His reason is that the motor sees more of a load on the street or track than it does on the dyno.

BIG SHAFE

The real reason is 12.7 is called lean best torque and 12.2 is rich best torque. These are typical values (some theory there but seems to be widely used) where you will attain the highest torque, purely by A/F alone, timing adjustments also are needed to achieve safe operation.

For the different loadings, I know with typical tuning programs, changing acceleration enrichment is what helps translates loadings. Basically it is some factor that changes how fast more fuel is added. I'm not familiar with LT1 tuning personally but I would imagine there is an equivalent somewhere.

Denny McLain

I agree the car would pick up with just more compression and 1.6 rockers but dyno's tell no lies unless someone makes them do it. If you know what your looking for there is a lot of data in a dyno pull including about how it would do at the track. You compute average hp within the intended rpm range in each gear and use that instead of peak hp.

You need to pull the head a measure your deck height an do the math for dynamic compression and a tight quench.

Denny McLain

Not true. Another wife's tale. You tune to what the car likes and then look at what the 02 comes out, not visa versa. Depends upon the car but his Air/fuel is within the range a lot of LTx cars like.

Denny McLain

Did you look at the engine?? How many people are running around town with vacuum pumps running race fuel? No question it made the power, but that's not a street engine running 93 octane with the belt hooked up.

BIG SHAFE

What the car likes?????

With your theory O2 readings are pointless, weird why so many tuners use them to tune by not a mystical "what the car likes" theory. In what I have read (somewhat extensive) and in my own tuning experience 12.2 and 12.7 are gold numbers for peak torque numbers. After and before peak torque A/F can be leaner, because of lower VE.

Heatmaker

Heres the reality... the guys cam is falling off way to early. he should find out why.

Denny McLain

What you're reading is flat wrong.

Was sponsored by a dyno shop and have seen literally over a 1000 cars tuned. My personal cars have had over a 1000 tuning pulls tuning, testing mods and even testing prototype devices. People have given me items to dyno test based upon my experience, not because of what I've read. I'm very comfortable with the technology and base my observations from experienced.

In the beginning, we had no wideband 02's and it was all what the car liked. O2's come in real handy getting a car into a "range" but after that to get he most potential you still do trial and error.

Yes....cars respond somewhat differently and there is no magic number, only a "range" I'm sure due to production variables in the both the engine and sensing devices. The same reason you can't buy a mail order tune and expect it to be right on the money unless your flat lucky.

Brian from PCMforless came to Dallas this weekend to tune cars and saw him tune Lloyd Elliotts personal car this last saturday even and no, it didn't end up in the "magical" 12.2 to 12.7 range you refer to.

FYI.....Pro Stock cars tune in the 13.7 to 1 range.

zx1216

What injectors and fuel pump are you using?

ulakovic22

Didn't really read the whole thread but have you scanned the car to see if you have knock. Ion was really aggressive with my tune and I had up to 8* knock retard. Also make sure you adjust your valve lash. Those were the biggest two things on my build.

Denny McLain

Very good point. Many times it’s the little stuff and yes, the valve lash can make a big difference. In looking at his dyno sheet it doesn't appear to be pulling out timing, but agree that you need to scan one to really see what going on.

I'd suspect just going to 1.6 rockers, setting the lash to around 1/8 to 1/16th of a turn and thinner gaskets would put it firmly in the 390 rwhp range and overall typical of the combo. To do it right you need to know the cc's of the combustion chambers and deck height to get the compression and quench to where they should be.

FYI…normally the stock deck is about .025 and running the stock gasket will give a less than ideal quench and compression. My luck as my old 97 SS must have been a Monday morning car and had a deck of .040. Busted my ***** trying to make 400 rwhp with a 306 cam and MTI heads until I learned the real problem was lack of compression. Then the car got stolen before I could correct the issue.

Another FYI…..I’m just under 13 to 1 compression currently and it drives pretty much like stock so don’t be afraid to bump it up some especially with that much duration in a cam.

SS RRR

These threads always make me giggle a little.. and throw up.
Just take it to the track. Your graph looks healthy. As Denny stated, it's the power under the curve that matters.

Doesn't mean there was no wideband present. When are you going to the track with that beast? With the gain you have w/ this new setup I'm looking forward to some 120+mph trap speeds.

mdacton

I just like the dyno to get me in the ball park......
Track tuning is where you see you gains, We do have a dyno that does simulated 1/4 mile passes......most of the time the cars have less peak h.p. after tuning, something to think about


Also do the small mods that were already stated