First, I posted this message on the FormulaSource, but thought I'd look for input here, plus I've got some additional questions....

Well, I've gone and done it. Bought a new motor to replace my sorta tired 5 speed 305. Its a high nickel 4 bolt block, .040 over, cylinders torque plate honed, polished oil passages and lifter valley, cast steel crank, PM rods, coated flat top Speed Pro hypereutic pistons, Speed Pro chrome molly rings, 10.56 compression, aluminum roller rockers (1.6 intake, 1.5 exhaust), Comp Cam custom specs .(525 intake .492 exhaust, duration 218 degrees intake 228 exhaust, 109 lobe seperation), Dart Sportsman 2 heads (2.02 I, 1.60 E, 200 cc runners). Those are the LT1/LT4/LS1 GM "Hot Cam" specs, which is what this custom grind was derived from. I'm no cam expert, but the engine builder says the "custom" part is strictly in the 109 lobe seperation(versus the "normal" GM LSA of 112). According to Desktop Dyno with a 750 CFM carb and a dual plane manifold it will crank out 440HP @ 5500RPM and 500 ft-lb @ 3500. I plan on using a TPI on this motor, which D2K shows should go about 512 ft-lb @ 3500 and 436HP @ 5000RPM using a 750CFM TPI setup.

This car will seldom if ever go to the strip. It's gonna be my daily driver and play toy. Performance above 4500-5000 RPM is not too great of a concern as a result

What would you suggest for runners? Slightly ported factory runners, a set of Accel/Lingenfelter runners, or ???

As for the plenum, will a ported/gasket matched plenum flow enough to support this motor? Will that provide the 750CFM I used in the D2K? Or do I need to do something like a SuperRam? And if I do, how much would that hurt me on the lower end where 95% (or more) of the use of this motor will be?

Now for the touchy questions... How about the throttle body? 52mm or 58mm? The 58 seems a bit excessive to me since you can't hardly even port the plenum openings that big. I've seen lots of "discussions" about how the 58 is a waste on a TPI motor, but would a 52 be sufficient for the 383?

And finally, what about the lower intake manifold? Will the factory manifold flow enough for this motor? Even if I use the Accell runners and a 52 or 58 TB? Will it need to be ported too, or is that a waste of time and money?

Here's your chance, folks. A free solicitation call for advice! I'd just like to hear what everyone here recommends. And before y'all put a bunch of caveats on your comments, I realize full well advice is frequently worth exactly what you pay for it! And please, I'm looking for honest "expert" advice, not flames.

Have a Great Day!!!


- Vern

 

Good luck getting any TPI type computer setup to run with the 109 lobe seperation angle...
Use the carburetor, or ditch the cam...

My $0.02

PS
Nobody will be too high on recommending aluminum rockers, either.

 

I agree on the LSA of the camshaft, 109 is too tight. You need to be at 112 for a TPI setup.

I gave this advice to a buddy, who immediately ignored it, and now he hates the way the engine runs.

Has taken it to another shop and was told him the same thing, ditch the cam.

A LOT harder to change it later than to change it now.

Just my thoughts.

Jake

 

Your stock computer is not up to the task on handling that cam for 1. 2. what size injectors are you using? 3. as far as intake goes, here are your options.

1. Stock LTR setup, which will kill the breathing capacity on that motor, even if its ported to the max.
2. The ever so popular Holley Stealth ram, not EPA legal, but can provide the breathing capabilities, stock TB, or a conservative 52mm, since its a street car.
3. Miniram, similiar to an LT1 intake and like the stealth ram, not EPA legal
4. Accell/Lingenfelter Superram, provides decent low end on all the way up. this one is street legal.
5. Aftermarket base, TPIS, Accell, Edelbrock, all are ok, port them for better performance, with a set of aftermarket (preferably siameased) runners, ported to the max.

either way you go, you should look into DFI for management issues, dont use injectors less than 24LB/HR with high impedence, but with DFI you can use a low imedence and have infinate tuning possibilities.

Also you may want to invest in a vaccuum canister, you may not have enough for your brakes, maybe!

And of coarse, dont over look the exhaust, the stock t-5 WILL brake, the rear me need a lil beefing up, and chassis reinforcement is a must.

 

Thanks for all the input, folks!

Please excuse my ignorance here, but why is 109 lobe separation "too tight"? From looking at the DD2000 specs file on this setup using the DART Sportsman II heads flow numbers, I noticed he input the cam with a -2 Timing advance, which I believe means its retarded 2 degrees, which if I read CompCams web page right gives it an equivalent LSA of 111 degrees. Does that sound right or have I got it all turned around? What is magical about the 112 LSA on a TPI? I'm not trying to be sarcastic, I'm just trying to learn and make sure I've got it "right".

As far as the injectors go, I've got a NIB set of Holley 24 #/hr from an earlier project I planned to use. Sound okay?

As for the computer, I figure on having to have or make a new PROM. Only question is what to use as a starting point if I try to make my own.

As for the intake manifold, again, DD2000 shows a 750CFM TPI setup to work pretty well, but I admit I'm skeptical of it. I've got a ported factory plenum and ported factory intake as well as some LPE runners, will that be enough with a 52mm or 58mm TB? Or would I be better off with a total Accel/LPE SuperRam? I hate to spend the extra money if I don't have to, ya know? I'm also curious about which size TB I should use if I go to the SuperRam.

I was also hoping to avoid all the hassles I ran into with a Holley Commander 950 setup on a 454HO I've used in the past and was hoping to get a fairly reliable setup initially for this daily driver.

As far as the exhaust goes, this is a dual cat setup with 3" throughout, but I've also got some SLP Tri-Y headers I was thinking about using. I just figured the factory manifold, even if I Jet Hot coated them, would be too much restriction.

As for the T-5, yeah, I've been worried about that one too. Is there any way to beef it up? Or is a 6 speed the only alternative?

Finally, what beefing up should I be looking into for the factory 3.42 rear end?

Sure hope someone replies back on this stuff. I'm a 51 year old phat phart who likes to play, but still prefers EFI over carb setups. Especially since it has to pass emissions testing here in the Dallas, TX area. I have to at least match the original 91 Formula 305 emissions levels. I know there are cam differences between the carbs and EFI, and that's why I'm asking some of these questions to begin with. I just don't know what changes have to be made, if any.

Have a Great Day, Y'all!


- Vern

 

Too much overlap with a 109.

Jake

 

I went with all Accel/Lingenfelter parts. Cam, intake, and LTRs.
They get along well and it sorta looks stock (for visual emission check reasons). Makes for tons of midrange torque, which IMHO, makes for a really fun street car.

Lingenfelter has done a lot of R&D with TPI.
Hard to fail using a known-good combo.

The Super Ram is a nice piece, but it's too much of a pain for my application.

 

Your have parts for carburetor instead of fuel injection. Port velocity and low-lift flow is what TPI needs. Consider AFR 180, Vortec, or some other similar Edelbrock aluminum head. MAtch it up with something like the LPE74211 cam, or something recommended by Comp Cams or Crane Cams.

Check out www.lingenfelter.com. Contact them and see what they recommend. They developed the parts you have, and the SuperRam.

TPI parts you have would be fine with 48mm throttle body.

109 LSA is set by distance b/w lobe centerlines. The "tighter" the LSA, the more overlap you have...which tends to promote higher rpm power. Wider lobe seperation will help emissions requirements as well. A good computer tune will also slove the emissions issue.

Those tri-y headers are no good...sale them to me!!!
They will work fine. are good headers. Are not made anymore, though.

24# should work fine on the injectors.

Typical 10-bolt mods should suffice the rearend.

Don't trust DD2000 when it comes to analyzing TPI injection systems.

https://www.thirdgen.org/techbb2/sho...fuel+injection

Tremek TKO is 5-speed swap option

http://www.g-forcetransmissions.com/tran_gt-5.asp

Liberty Gear
6390 Pelham Rd
Taylor,MI 48180
(313)278-4040

https://www.thirdgen.org/techbb2/sho...hreadid=104792

https://www.thirdgen.org/techbb2/for...php?forumid=16


Hope this helps...