383 Vortec/TBI Build Thread

[Derick C.]

I am running a stock vortec cam in my 92 GMC. No complaints

 

[Daveo91Burb]

I am running a stock vortec cam in my 92 GMC. No complaints

Cool, good to hear! What's the rest of the build like on that rig?

 

[Derick C.]

Cool, good to hear! What's the rest of the build like on that rig?

30 over, procomp aluminum heads, 202/160, stock rockers for now, I want to try a set of 1.6's
Don't remember the dish on the pistons but it is 9.5:1 CR

 

[Daveo91Burb]

30 over, procomp aluminum heads, 202/160, stock rockers for now, I want to try a set of 1.6's
Don't remember the dish on the pistons but it is 9.5:1 CR

Great, thanks! And you're still running TBI with that? What'd you do for tuning it? Burn your own chip or have it done?

 

[Daveo91Burb]

Update on the build:

- brought the block to a new machinist (good reputation locally) last week but I'm gathering a bunch of new/different parts that he'll need to balance the rotating assembly.

- bought keith black KB 135 pistons. 18cc dish. Found them on ebay, new but open box so a bit cheaper than brand new. I should be sitting right at 9.5:1 with these.

- bought a Cloyes single roller timing set. (He wants to have the crank gear for balancing) Hasn't shown up yet.
- bought a Pioneer 8" balancer for external balanced. Hasn't shown up yet.
- bought a Pioneer FRA-321 flex plate. Showed up on Saturday and it's the wrong one. I think the 321 is for a big block. Pretty sure I need a FRA-159, which would be 168 tooth, one piece RMS/externally balanced, for small block.

Can anyone verify that I need the FRA-159? '91 3/4 tons are tricky to buy parts for since it was the first and only square to have the 4L80e. Some of the parts databases aren't correct - Amazon's sure wasn't. (I think it thought I had a big block, but we all know that can't be since I have a 4x4)

 

[4WDKC]

Update on the build:

- brought the block to a new machinist (good reputation locally) last week but I'm gathering a bunch of new/different parts that he'll need to balance the rotating assembly.

- bought keith black KB 135 pistons. 18cc dish. Found them on ebay, new but open box so a bit cheaper than brand new. I should be sitting right at 9.5:1 with these.

- bought a Cloyes single roller timing set. (He wants to have the crank gear for balancing) Hasn't shown up yet.
- bought a Pioneer 8" balancer for external balanced. Hasn't shown up yet.
- bought a Pioneer FRA-321 flex plate. Showed up on Saturday and it's the wrong one. I think the 321 is for a big block. Pretty sure I need a FRA-159, which would be 168 tooth, one piece RMS/externally balanced, for small block.

Can anyone verify that I need the FRA-159? '91 3/4 tons are tricky to buy parts for since it was the first and only square to have the 4L80e. Some of the parts databases aren't correct - Amazon's sure wasn't. (I think it thought I had a big block, but we all know that can't be since I have a 4x4)

if you are ordering all these parts why not get it all internally balanced? Then you could reuse your balancer, flexplate, starter.. etc.

 

[Derick C.]

Great, thanks! And you're still running TBI with that? What'd you do for tuning it? Burn your own chip or have it done?

Still using the mostly stock tbi, I change the spring in the fuel pressure regulator to bump up the pressure, put in a wide band gauge and have been running fine. A chip might help but air fuel ratio is fine so I haven't worried about it.

 

[MikeB]

LSA on the L31 is 111, and I have also read that 112 is about as low as you want to go with TBI, but at least some of the articles I read said that was with stock tune. My tuner seems to think no problem with that cam. What do you guys think about my plan to use the 1.6 rockers to get more lift?

Mike B, not sure about quench height - how do you calculate? Compression height is 1.433 (speed pros were 1.425) and my new machinist measured deck height today and I'm at 9.015. I'm coming up with about 9.5:1 in my compression calculator, assuming .04 head gasket compressed.

Thanks!

Yes, use the 1.6 rockers if your heads can handle the lift. Check carefully because on some Vortec heads the spring retainers will hit the guide seals at .450" lift. Really. Also, the pushrods may rub the edge of their guide holes. Maybe neither will be an issue with the very low lift of the stock cam.

Quench height is the sum of gasket thickness and how far down the hole the piston is at TDC. So, piston down hole .015" + .028" gasket = .043" quench height. Just about ideal according to John Lingenfelter.

I wish people would forget the 112 LSA minimum for EFI. Vacuum is a function of overlap. Sure, overlap is a function of LSA but MORE IMPORTANTLY duration. Earlier in this thread I mentioned the GM EFI RamJet cam with 109 LSA. Here's another: I once had a Crane 194/204 cam with 104 LSA in a 350. Yes, 104. It made 21" vacuum at idle, for crying out loud. More than enough for EFI.

In fact, check out Crane's 104201 roller cam for 87-up engines. It is 184/194 with 106 LSA. Here's their description:

For low-end and mid-range performance in 87-92 cars and light trucks. Fine w/auto or manual and stock rear gears, great for 305 requiring extra low-end torque to cruise below 1800 RPM, ideal for TBI engines w/auto trans and stock converter.

Probably a bit on the small side for a 383, but you get the point.

 

[Daveo91Burb]

if you are ordering all these parts why not get it all internally balanced? Then you could reuse your balancer, flexplate, starter.. etc.

Not sure you can do that with this crank? Eagle sells both internal and external for 383 SBC applications. My first machinist actually started out with internal balance, but late in the game he told me I'd need a 400 balancer. Machinist I just hired didn't offer that as an option when I talked to him and agreed that I would need a 400 balancer. Balancer is really the only thing new I need for the external balance. AFAIK, ALL one-piece RMS 350s ('86 and later) have external balance in the rear. Only reason I'm getting a new flex plate is the one from my parts rig (90 3/4 ton burb, TH400) is cracked and I suspect that the one now running in my '91 (4L80e) has a damaged ring gear. And as long as I get a 168 tooth, I won't need a new starter.

Got approval from Amazon to return the Pioneer FRA-321 flex plate today. Will do that and just purchased an ATP Z-167. That one specifically mentions the 4L80e tranny and 11.5" bolt circle in the description. I'm glad I researched further - I think if I had bought the Pioneer FRA-159 like I mention above it would have still been wrong for the 4L80e. I think I could have only used three of six bolts as it has two different bolt circles to make it more universal.

 

[Daveo91Burb]

Still using the mostly stock tbi, I change the spring in the fuel pressure regulator to bump up the pressure, put in a wide band gauge and have been running fine. A chip might help but air fuel ratio is fine so I haven't worried about it.

Cool, this is awesome news, I read so many TBI horror stories of guys trying to get the tune right it's nice to hear someone say they're running great after some significant mods.

 

[Daveo91Burb]

Yes, use the 1.6 rockers if your heads can handle the lift. Check carefully because on some Vortec heads the spring retainers will hit the guide seals at .450" lift. Really. Also, the pushrods may rub the edge of their guide holes. Maybe neither will be an issue with the very low lift of the stock cam.

Quench height is the sum of gasket thickness and how far down the hole the piston is at TDC. So, piston down hole .015" + .028" gasket = .043" quench height. Just about ideal according to John Lingenfelter.

I wish people would forget the 112 LSA minimum for EFI. Vacuum is a function of overlap. Sure, overlap is a function of LSA but MORE IMPORTANTLY duration. Earlier in this thread I mentioned the GM EFI RamJet cam with 109 LSA. Here's another: I once had a Crane 194/204 cam with 104 LSA in a 350. Yes, 104. It made 21" vacuum at idle, for crying out loud. More than enough for EFI.

In fact, check out Crane's 104201 roller cam for 87-up engines. It is 184/194 with 106 LSA. Here's their description:

For low-end and mid-range performance in 87-92 cars and light trucks. Fine w/auto or manual and stock rear gears, great for 305 requiring extra low-end torque to cruise below 1800 RPM, ideal for TBI engines w/auto trans and stock converter.

Probably a bit on the small side for a 383, but you get the point.

Thanks for the info, Mike B. So with the 1.6 rockers I'm at .44 for intake and .46 for exhaust. Sounds like I'll be very close - I'll be sure to check closely. I've also got a call into the rebuilder I bought the heads from to see what he says.

Yeah, I've looked a lot at the HT383 cam, along with other options, but I've got a stock L31 vortec, and that's what the tuner recommends so I'm going with that. HT I'm sure would be a strong runner, but the $$ have been flowing out like crazy lately (this project along with a lot of other things) and I need to slow that flow!

 

[4WDKC]

Not sure you can do that with this crank? Eagle sells both internal and external for 383 SBC applications. My first machinist actually started out with internal balance, but late in the game he told me I'd need a 400 balancer. Machinist I just hired didn't offer that as an option when I talked to him and agreed that I would need a 400 balancer. Balancer is really the only thing new I need for the external balance. AFAIK, ALL one-piece RMS 350s ('86 and later) have external balance in the rear. Only reason I'm getting a new flex plate is the one from my parts rig (90 3/4 ton burb, TH400) is cracked and I suspect that the one now running in my '91 (4L80e) has a damaged ring gear. And as long as I get a 168 tooth, I won't need a new starter.

Got approval from Amazon to return the Pioneer FRA-321 flex plate today. Will do that and just purchased an ATP Z-167. That one specifically mentions the 4L80e tranny and 11.5" bolt circle in the description. I'm glad I researched further - I think if I had bought the Pioneer FRA-159 like I mention above it would have still been wrong for the 4L80e. I think I could have only used three of six bolts as it has two different bolt circles to make it more universal.

Sounds to me like the first machinist ordered the wrong crank and was covering his ass. IIRC only the 400 SBC and all BBC were externally balanced and use weighted flex plates/fly wheels as part of the balancing. You should be able to order a ext. balance flex plate for and 88-95 350/4l80e combo. Think the 96-99 use different tooth # flex plates

 

[4WDKC]

Still using the mostly stock tbi, I change the spring in the fuel pressure regulator to bump up the pressure, put in a wide band gauge and have been running fine. A chip might help but air fuel ratio is fine so I haven't worried about it.

What cam are you using?

 

[88burbboy]

http://www.gearhead-efi.com/Fuel-Injection/forum.php Check out the TBI section. These guys have forgotten more about TBI tuning and specs then I could ever learn. The guys on there are a great resource for tuning. There are aftermarket computers available. The Dynamic EFI and moates.net are both great providers of tuning products. I have been torn between modding a TBI motor or swap in a LQ4 6.0 i have sitting around. Im well versed in TBI and TPI systems.

 

[4WDKC]

http://www.gearhead-efi.com/Fuel-Injection/forum.php Check out the TBI section. These guys have forgotten more about TBI tuning and specs then I could ever learn. The guys on there are a great resource for tuning. There are aftermarket computers available. The Dynamic EFI and moates.net are both great providers of tuning products. I have been torn between modding a TBI motor or swap in a LQ4 6.0 i have sitting around. Im well versed in TBI and TPI systems.

Already on that site, have modded my ecm with the flash chip socket, trying to decide if I want to buy my own cable or borrow one locally... May end up with a Holley commander 950 EFI setup on my truck.