AFR HEAD GURUS Help me figgure out what fuel press to run and estimate my hp level.

[5.0Droptop]

Ok I have around 350 miles on my new motor. I am still playing with fuel press. Timing is at 14 degrees give or take 1 degree.

I am running autolite 3924 gapped at .052
fuel press is at 41-42 psi.
Right now the nitrous is not hooked up so it is set up for NA...

According to the chart that I have, 40 psi is good for 358 base hp. According to DD2K my motor could make 350-375+ base hp, but I dont put alot of faith in that yet.
What do you think my base fwhp power is and how much fuel press do I need to run?

Here is the complete mod list to car.

New Combo:

Fully prepped zero decked 1987 302 block bored .030 over to 306 cid
Rotating Assembly Balanced. compression to 9.8:1
AFR 165 58cc alum heads with smog provision. 3/8 stud rockers
TFS Stage 1 cam 221/225 @.050, .499/.510 lift advanced 2 degrees
1.72 3/8 Stud Mount Roller Rocker Brings lift to .536/.548
Probe forged flat top pistons with fly cut valve relief’s
Forged Sportsman cnc profiled lightweight rods with arp studs
302 Nodular High strength Crank 28 oz imbalance
SFI Billet Hawks Racing Flywheel 28 oz
SFI Professional Products balancer 28 oz
Billet timing chain set
Hastings Street/strip rings and Bearings
StudGirdle with Arp Main studs
FMS Hardened Push Rods
FMS roller lifters
Melling High Vol. Oil Pump.
Arp Head stud kit
Felpro Oringed head gaskets
Milidon hi volume water pump and Milidon hi flow brass 180 t stat
New timing chain cover
New 93 Cobra High Tq Mini Starter
Tmoss Ported Gt40 cobra lower.
Stock cobra upper
½” Phelonic spacer
65 mm accufab TB
24 # FMS injs
Kirban AFPR
Pro M maf 75 mm 24 # calb.
New Chrome Gear head racing full-flanged unequal shorty headers
Off road h pipe
American thunder series 2 chamber cat back
Under drive pullies
160 amp 3g alt
sn95 elec fan
93 cobra coil
Accell billetech dizzy
3924 Auto lite plugs gapped at .052
Taylor wires
Sub connectors and strut tower brace
T-5 swap
3.73 fms gears
alum fms drive shaft
134-ac conversion
Zex dry Kit 125 shot

 

[Michael Yount]

I believe the 24's will support what you've got - I'd run the stock pressure. If you need significantly more than stock pressure, move up in injector size. And get some time on a dyno with wideband to see where you're really at a/f ratio-wise. Any other approach is just guessing.

 

[5.0Droptop]

Yes I belive 24's are fine. I guess I was just wondering if 41-42 is enough. When I ran the code scanner KOER it didnt say it was lean or rich.

 

[Michael Yount]

Stock is 38-40 measured with the car idling, warm, vacuum line off the regulator and plugged. Some wide-band dyno time will give you an idea on HP level and mixture which will tell you what's going on. Just about any approach other than that is guessing.

 

[5.0Droptop]

I plan on some dyno time but it will be after I save up some money. I spent all of it building this motor, LOL

 

[5spd GT]

I run 39psi with 30lb injectors on my car...my Autolite 3924's are gapped at .045...and my timing is at 16* (spout out)...

I would think your car would run pretty good at 43-44psi...

 

[5.0Droptop]

5 spdgt thanks for the info. Did you have FTI work the heads or are they box stock?

 

[5spd GT]

5 spdgt thanks for the info. Did you have FTI work the heads or are they box stock?

Box stock 58cc 165'swith ARP upgraded studs with springs to match the cam and the viton seal upgrade...

 

[5.0Droptop]

same here except for the seal upgrades.

 

[5.0Droptop]

..............

 

[jrichker]

Use the SOP meter...

Get one of your buddies to ride along with you. Find a level stretch of road where you can do some testing. Don't choose a speed range that will make you shift gears, the shift quality & speed will affect your results. Use 2nd or 3rd gear and do a run from 2000 RPM to 5800 RPM. Call out the RPM as it increases and have you buddy record it and the elapsed time. If you have one of those cheap digital watches like I do, a stop watch is built in. Start the fuel pressure at 36 PSI, vacuum off and make a run. Turn it up to 37 and make another. Be sure to reconnect the vacuum every time you set the pressure. Keep turning up the pressure and making runs until you notice a drop off in time. If your bud was careful to record the results, you'll have a nice chart to use to find the optimum pressure.

 

[Michael Yount]

To confirm jrichker's suggestion (which I think is anything but seat of the pants) - for 8 years I did all my tuning on my old SCCA racer with full throttle pulls in third gear from 4000rpm to 7500 rpm - and measured acceleration times. Did several runs in opposite directions on a rural road near my house, and averaged the times. And made timing/carb changes quickly as ambient temps make a big enough difference that if you're looking for subtle performance changes from tune, a 20F temp change can cause you data problems.

But, it will only guide you with wide open throttle performance. If it's a street car you're trying to tune, the bigger issues usually occur at idle, cold start, low rpm/high load conditions - which this technique won't help you with at all. Also, about the only way to get reasonable a/f ratio data is with a wide band sensor - no way around that one.

 

[runningmole]

39psi on my fuel pressure. What's your compression? Isnt' that gap a tad high assuming you have high compression. Before I got my 327, I was going to get a 10.5 comp 347. AFR said to gap the plugs around .035 FWIW

 

[5.0Droptop]

I just gapped the plugs to the stock gap. I am running stock coil and an accel billetech dizzy. Maybe the plugs are to wide gapped. My comp is 9.8-10 :1 the best we could figgure.

What are you guys runing gap wise? I bought new plugs today and I am going to drop them down to .045 and adjust pressure.

Thanks for everyones help!

 

[5.0Droptop]

New plugs are in and press at 40 I also cleaned the maf meter because it looked rather dirty.

I will drive it later when my wife gets home to see how it does.

 

[5.0Droptop]

We went for a cruise and it seems to be running much better. the very slight surge I felt is gone. I cleaned the MAF meter because it was pretty dirty. Maybe it was the cause of the surge I felt when cruising around 2200 rpm,.

Anyhow thanks for everyones input.