You guys on this site have a great rep for builds and EFI systems.I hope to find common ground for my "peanut tow" 383 build for torque with you.Here it is:

1995 L31 roller block

.030 over

5.7 rods Scat rods profiled for stroker with 7/16 ARP bolts

3.75 Howards track smart crank

Icon 18 dished pistons

decked 10 down

World S/R heads 67 cc heads with 170 intake runners.

Static compression ratio 9.2

Hyro roller cams being considered:

GM part number 14097395

288/308 duration @.050

196/206 with rocker ratio 1.5.1

431/451

Lobe centerline 109

OR

Erson cams

Part number E11980

Rpm range 2200-5200

Duration 272/280

Duration @.050 218/226

480/480 rocker ratio 1.5.1

lobe center 108

OR

Part number E119847

Rpm range 2500-5500

Duration 286/294

Duration @.050 226/234

548/540 with 1.5.1 rocker ratio

Lobe center 112

It is going into a custom conversion high top 1989 cargo Astro van who's wt is in the neighborhood of 4,000lbs with a 700R4 tranny and a Ford 9" with a 3.70 rear end gear and 29" tires.Primary use is to tow my small vendor trailer over the road with a trailer wt max of 3500lbs.Then with out the trailer to occasionally put a smile on this old time drag racer on the street lights only.No drag racing race track use.Want to get max gas mileage and max torque.

Ran the build on a computer dyno with using a 600cfm carb application and got about 470 to 480 ft lbs of torque@ 3500RPM and 350HP@ 4400RPM.

 

We played with a custom cam and came out with these numbers on a dyno sym:

Still playin' around with this tow motor....
Custom cam 206/214, 106/113/109.5, 0.420"/0.420, (-3)(29)(40)(-6) installed straight up.
Streetmaster intake manifold (1st design).
http://cgi.ebay.com/ebaymotors/Edelb...Q5fAccessories
RPM HP TQ
1000 88 461
1500 149 521
2000 204 535
2500 247 520
3000 289 506
3500 319 478
4000 346 455
4500 357 417
5000 348 366
5500 319 305
Peak BMEP 210.8 @2000. This is some serious cylinder pressure, so a very tight squish (I would be thinkin' 0.035" to 0.040" with a D-cup piston) would be mandatory to prevent detonation on pump gas.

I'm liking the 535 @ 2000.

 

So you guys see the parts:

The icon forged pistons:



Chart how to set the rings given what use of the engine:



The Howards Track Smart forged crank:




This is home base on a rental medal pole barn shop that isn't at the same place where I live:





I have the left side of it and wired in better lighting and plugs:






Guess what I am trying to do here is a getting to know me better.

 

I got the block back today all machined and the rings gaped.Getting the rods next.

 

e11980 would be my choice from those listed.

 

I worry about a tune port mating up with a 108 lobe center.What do you guys think??.

 

It is a Howards crank internal balance 2pc seal going into a 1pc seal with a adapter.What do you guys use in cases like this for a street driven car's harmonic balancer??.Brand name etc...........

 

id use a factory 400 balancer for street use

 

With those small durations and 383 cubes, i'd go tight on the LSA. EFI will be fine with that.

that high cylinder pressure may become alittle problematic. Need to play with timing and spark plug heat range for that on premium gas perhaps.

Erson cams
Part number E11980

I like that one the best. The duration fits a 383 better. The other cams i think are too small.
You can look into the comp XE roller cams for 4x4's. 111 lsa and lower durations should work well with that setup too.

If your using TPI, its gonna make a LOT of torque either way, but I think the duration in the mid 21x range is where that motor needs to be.

 

I don't own a TPI currently,but I like what I have read about those with mods and would buy a used OEM to do the mods.Thanks for the help.

 

As far as the harmonic balancer-I am considering this:

http://www.precisionparts.com.au/pb_street.html

What you guys think??.

 

I think mine was a Precision, but I could be wrong. I just had the machine shop that did the balancing give me a SFI rated one. They do a lot of there work with circle track racers, so I figured if it can handle the RPMs those guys turn it'd be good enough for me with my limited weekend crusing on the street.

 

Sorry,I missed this post.The Howards crank is a internal balance crank and the stock 400 balancer is external balancer which is the reason I can't use that.

 

Ok-my leakiest knowledge link is the EFI's.I was bummed out because from other sources I was told I needed to run a lobe center of 112 or better to make this tune correctly on Any EFI.Horror stories of a very rich idle conditions washing down my prized build ruining the engine etc.Certainly that 108 lobe center is in part of the concept of this torquer low RPM build.So with the use of a TPI-please help me out with a better understanding of that given the build I have described.I don't have the cash for a complete aftermarket system,but I am interested in buying a used OEM and mod'ing that.

 

I've run a big cam in my 383 with 109 LSA, just fine Closed loop it would run, but I just ran it open loop. Open loop mode does not rely on o2 sensors, its basically like an electronic carb. You give it the fuel input and it will inject that fuel amount, no changes. Makes life easier when using big overlap cams.

Its not the LSA that makes the difference, its generally ovelap area. More overlap you have, the more fresh air gets mixed in with the exhaust gases escaping the cylinder. O2 sensor reads this fresh air and thinks motor is lean, so it starts pumping in fuel. This rich condition will screw up your idle quality. Thats why open loop is preferred for applications like that.

Overlap is more of a function of duration with LSA than LSA alone. That 218/226 cam on a 108 has overlap of 6 degrees. my 383 cam had 19.5 at .050. Total overlap was 78. Thats a pretty healthy amount of overlap. That also gives a choppy idle

My friends car that I helped tune runs in closed loop just fine, and he uses a 230/236 cam on a 113 lsa in a 360" motor. While it has a wide 113 LSA, its got a choppy aggressive idle, as it has 7 deg of overlap at .050, 57 total. Thats a good bit for an overbored 350 motor. Thats a healthy cam for any 350 motor, a mid 6000 rpm puller.

That Erson cam may have 6 deg of overlap but its going in a longer stroke, bigger cube motor. The long stroke big cube motor will "eat up" that cam, meaning it wont act as big in that 383 as it would in a 350 motor.

The tight LSA and overlap will help fill cylinders better at lower/mid range rpms, which is important with a head thats small for the application, with those 170cc runners. I think its a good combination and will make alot of torque.

 

Thank you for your help

As I get closer to the EFI,I will need more support on which parts.

 

I am at the decision bridge for the rods.At first I was going to just buy the Scat 5.7 7/16 ARP floaters because it was simple to mate that up with the Icon dished pistons which are floaters.The thing is that unless your going to swap pistons often,there isn't a performance advantage to floaters and the real chance to have to replace the bushings with some mileage on a street vehicle.Tons of press fit OEM's out there trouble free service some with over 200,000 miles on them.Also,the 7/16's ARP bolts would be over kill that adds wt and really doesn't add to the clamping force.The newest approach is to consider using a 3/8's ARP which is less wt and would give a speed of RPM advantage.Think about some of the Honda rod set-ups used in some of the high performance GM engines.So I decided to use the Scat 3/8 ARP bolt press fit rods.It should give plenty of service for anything I would want to throw at it.Should send out the order for them this week.