[roxanne68]

I need input for improving this combination. I inherited this engine brand new with a project car, never having been run (until I installed it). I am looking to achieve a couple of goals:

1.Reliability: I am a little concerned at the RPM this engine has to spin to get to the HP, plus the cast core roller cam leaves me a little leery.
2.Drivability: as you can see from the specs, there is not much torque down low. Love the current power up top, but need to fill in the low/mid range. Engine idles decent, and overall is a smooth around town – it is a street car only, so I don’t want to loose this.

Here are the specifics:

SBC 383, 2 bolt w/studs
Pro Action 220cc heads, 10.6:1 CR
Accel EFI for fuel delivery
Accel Pro ram intake with 1200 cfm TB (efi single plane similar to victor type)
XR280R cast core mechanical roller cam (.605 lift @ valve with 1.6 rocker, 242/248 dur @ .050) retarded -4
Comp solid roller lifters
Springs are the Comp Cam recommended 145# seat/430# @ 0.5” 977-16’s
6” Eagle SIR rods, and 4340 forged crank
Forged probe pistons
3100 pound street car w/manual

Below 3K it is pretty listless (even with a 3100# car with gears), and mid range is mediocre. I currently have it shutting down at 6500 RPM, but it is still building really good power at that point. Probably good for another 800+ rpm, but the bottom end and valve train are not up to the task. After getting it tuned, the VE’s don’t hit their stride (into the 90+ % range) until about 5K RPM and are still going up at 6500. Based on VE and RPM the theoretical peak HP is in the approx 450-500hp range at 6500, but have not yet been to a dyno.

Is there any hope with these heads? Or is the 220 runner just too much for the street?

Would a cam change be of much use without a head change? If so, any recommendations? I would like to swap it out for a billet one anyhow. I don’t mind revving an engine, but not really what a 2 bolt 383 is best at.

Any other suggestions for what direction I should consider? Don’t really want to throw and additional $2500 at a decent running, brand new engine, but if that’s what it takes…

Thanks, Derek

[ernkazern]

I think a cylinder head with intake runners in the range of 185 to 200 cc would be more appropriate. Also a cam in the 220 to 240 @ .050 range would help too. I run a 383 in a 67 Camaro conv with a pair of 195 cc Trick Flows and a Comp Cams 268 cam ( 226 and 230 @ .050) and I have way more torque than my tires can handle. My tires are Firestone ZR50's I believe. I can run consistant 1.9, 60 foot times with them and I'm no professional driver by any stretch. So they're pretty sticky for street tires. I can light them up from a rolling start if I want to though. I should add I have a 3:55, 12 bolt posi with a 700R4 trans so that gives me a pretty low first gear combination. Your mileage may vary.

[Big Mouse]

EDIT: * Whoops. Somebody beat me! *

Wow, sounds like one heck of an engine --- except for those 2 bolt mains. It would probably cost less to swap blocks (to a 4 bolt block) rather than heads

You could pull & sell your current top end. I would think you should be able to do pretty well for yourself with that setup. If you want to be shifting at about 6k & want mild street manners, why not consider something in the ball park of 185 to 195 cc intake runners (AFR's, Eddy's, etc...), an RPM style intake, a 270'ish duration cam (less lift as you won't need it), and a 750 cfm carb? That should be pretty safe on a 2 bolt setup.

It will idle nice, the rpm range will drop about 1000 rpm's, and it shouldn't cost you much out of pocket once you sell your current setup.

[53_belair]

As this has already been stated, your heads are killing your low and mid range power. Large runners move the power band up the bigger they get. I would move down to a set of heads with the runners in the 190cc range and make a cam change as well, since you already have a roller stick with it. I would move down to the XR270, and by all means keep your fuel injection set up as you have it all sorted out. Of course you will have to re tune for the smaller heads and cam. good luck

[454C10]

Instead of retarding the cam 4 degrees try advancing the cam 4 degrees.

I hope you are using a 4.11 gear with this engine. I would think you would need an overall 1st gear ratio between 10 and 12:1 to get you moving.

I use a setup like yours except my heads are 200cc iron eagles but my cubes are only 362. 10.5:1, 244/244 cam duration, 2700 car, 3.90 diff with a 2.75 first gear ratio (3.90 x 2.75=10.7:1 overall). Has tons power in all gears starting at 3000 rpm and pulling to 7200. I also have a 2 bolt block with no issues. Even spray a 200 shot of n20 with that.

Could also be the efi tune. Maybe some dyno time will help. How is the ignition timing curve setup?

[Rick WI]

Nope, not the heads (although they are bigger than they need to be), not the cam and it certainly isn't making more power much past 6000 with that cam, let alone 7000. It's all in your tune. Why you have the cam retarded 4 degrees is also unusual to me, which I classify as part of the tune by the way. What is the intake centerline?

Your VE off the EFI screens has no earthly relationship to actual recorded VE's from a dyno. It is simply a function of the injector firing pulsewidth needed to achieve the target air fuel at that cell point. Only in a situation where you actually tuned in the mapping on a dyno, cell by cell, would you be albe to get any true relationship as to actual VE versus EFI imput number.

To get responsiveness out of the engine you need to concentrate on the base spark map and the base air fuel map. You should have decent throttle response with wide open setpoints in the 12.8:1 area which would be the 85 to 100 kPa range on your map. In those areas is where you dial in total timing as well, which I'd suspect to be in the 35 range or so. Lower RPM, below 3000 you'd dial back some on the timing. By 3000 though you want to make sure you have all the timing dialed in those cell ranges.

The two other screens that control throttle response and crispness are the TPS and MAP based enrichment. TPS is the major one and I try to tune up a new engine without the aid of MAP enrichment if possible.

Under part load conditions, 65 to 80 kPA fueling in the 13.5:1 range should get you somewhat in the ballpark. Lean enough to be responsive but rich enough to not melt anything. Spark lead is easier to dial in on the chassis dyno but on the street can be done via feel. Conservative is best but in the lower RPM ranges it's going to want some timing to give throttle response. make major changes such as dialing in 20 degrees of advance in the 70 kpa range areas and run the engine into these areas, then change to 30 and see the difference. Again, the TPS and MAP enrichement tables have an affect on the initial throttle response.

I am totally guessing on where the engine is sitting in the kpa ranges and going of my gut based on your camshaft. I'm guessing you idle somewhere in the upper 50 kPa range maybe 60ish, based on the specs.

After doing lots and lots and lots of dyno work on combos similar to that there is no reason the engine should not have razor sharp response and be very responsive.

If you can post your spark map, A/F map and VE map I can give you some feedback on it. Also tell me where it idles and cruises at relative to the kPa.

[roxanne68]

Thanks! I know that to get the power shifted lower in teh RPM, a smaller head volume is really the big money winner, just was not wanting to face the inevitable pricetag. I'll probably yank them at the end of the season and send them down the river and go with some 195ish heads. I think that I like the cam profile, and may stick with it for the time being, will probably gravitate to a less agressive lift in the future, possibly switch to hydraulic at the same time.

At least with low torque on the bottom, its a littler easier on the drivetrain and tire bills

Derek

[roxanne68]

in response to Rick, I idle around 60kpa, have AFR set to 12.5 during WOT/min MAP vacuum, at cruise I am at 35 kpa/3000 rpm and have AFT set at 14.0. At idle have backe the AFR down to upper 13's as it really protests if you lean it out much. If am a little puzzled about the VE, as I thought Accel does a direct calc to determine fueling: AFR X VE = fuel mass injected (other compensation not withstanding such as accel, temp, etc) so it should be a direct relationship. I am however a certified novice to tuning with EFI, so I am very interested in your assesment of my fueling strategy. I will post my current maps tonight. BTW, I am using the the Gen VII with the latest firmware/software and have the pro key.

Thanks!!!

[roxanne68]

also, I have not messed much with the tps acceleration enrichment, been relying primarily on the base accel fuel modifer and the Tau/map tables. under full throttle accel, afr's hold right at the comanded values of 12.5, but if I accelerate up to redline say, at 3/4 throttle, the AFR's will plummet to 11ish only recovereing close to redline, so I am way fat in the mid range

[Rick WI]

Here is the safe and easy way to think of VE on these maps. The bigger the VE the bigger the PW of the injector, the smaller the VE the smaller the PW of the injector. The VE number, if not adjusted correctly, will give you a poor tune, as it's the lookup table to the A/F map. If the VE is off the A/F is off, no matter how fancy the EFI companies explain what or how VE is manipulated in the program.

Your idle and cruise kPa's make sense. Your fueling logs though indicate the VE table is WAY off. In a log that you have recorded under wide open trottle overlay the trace line on the VE map and off the dash display lean out those VE values by the percent rich they are. If the TPS and MAP enrichment tables were the problem that overly rich condition would be gone within a few hundred RPM as that's only a trasition table(s) after throttle input. Like a shot from an accel pump. That's assuming the MAP table is not totally fubared up.

On the TPS tables, which you won't really want to mess with until the other tables are tuned in, all you want is to get the car to rev crisp when it's in idle as well as on the initial hit of the throttle. If it does that good enough for right now.

That engine should idle at 14.7:1. I'd say at idle, cells surrounding the 60 kPa range, timing should be around 18ish, maybe 20. It won't need anymore than that based on my experience. Also, cell values around idle in the VE table MUST be smooth. You can't have a cell at idle at 32 and then right next to it at 60. if the idle varies between cells it will invoke rich to lean via the O2 sensor feedback. I window pane VE, A/F and spark at the same time when tuning a vehicle, no matter if it's on the dyno or on the road. Those are the maps which make it run and they all relate to each other.

Will check back tonight to see if you have the tables posted.

[ernkazern]

This may be a dumb question, but what scan tool or PC based software are you using to get this info. I do a lot of driveability on newer cars and I don't recall that info being in the scan tools or software I have now. Or maybe it's there but I don't realize it.

[roxanne68]

in response to ernkazern, this is an aftermarket efi system by accel, specifically the gen VII model. it has similar features to most of teh modern speed density, such as dataloging of all sensor inputs and multiple compensation stretegies. There are a number of decent systems out there. so far I am pretty hapy with it, with better drivability as far as super hot days and hot starts then I have had with carbs in the past.

[roxanne68]

as promised here are some of my fueling tables. if needed, I can email my global cal file if you have/use the accel software

[ernkazern]

Thanks for the reply. I didn't understand that the diagnostic software came with the EFI package and was specific for it. That's some great info to tune with. Can you dial in your EFI using the same software? Is it PC based or a seperate hand held scan tool? It may be sacriligious to say so, but a carb can't hold a candle to a dialed in efi system for overall driveability.

[roxanne68]

I think that my ve is pretty close, I am monitoring AFR with a wideband, and under stady state conditions, the actual AFR's pretty much match the target AFR's, which indicates that my VE is pretty accurate. where I run into some issues is durning transient conditions, more specifically under approx accel with 75% throttle in the mide range. I think that my accleration enrichemnt needs a little polishing here. I posed a shot which shows this happening. the first half is teh 3/4 throttle accel, the second half is a WOT pull. there is no scale, but the values in the boxes are a measurement where teh vertical yellow line is (middle of second accel segment) following the green trace (afr) you can see that I am really rich in moderate accel.