Vortec Head and Roller conversion: TBI Bore

[Connorpod]

Hey Crew,

I have a 1995 Chevy k2500 with a 5.7 tbi.
So far I have truck headers, Exhaust, CAI and Fuel Pressure bumped to 14psi with Ultimate TBI.

I am starting a build and have picked up some Junkyard Vortec Heads. If the heads come back from the shop crack free, I plan to swap out the heads using the insight from Erictheawful.

The hope is then to install a roller cam using rebuilt junkyard roller lifters and spiders. The cam I was thinking of using was Summit Racing™ Pro SBC Camshafts SUM-8800 and summit’s electronic distributor with Melonized gear.


My question was around the tbi. From what I have read, next to increasing fuel pressure, I need to have my TBI bored?
Is this necessary and how would I go about doing this in Canada. It seems like all the links I have found about it go to
Dead websites. I guess the challenge with modifying mid nineties tech…

Any and all insight is appreciated for this bucket list build of mine.

 

[Drunkcanuk]

Have you been to Harris tunings website?
He has lots of info on TBI builds. Unless you are going full crazy build I don't think you need to get the TB bored out. They flow pretty good up to like 350hp(if I remember correctly). Any competent machine shop should be able to do it if you decide to get it done.
I'll be watching this one as I'm still undecided if I'm going LS or building up my 5.7 the same way you are headed.
And hello from one province over!!!

 

[Erik the Awful]

Camshaft Manufacturers Description:

The Summit Stage 1 Cam is the largest that can be run with a factory tune in 1987-1996 TBI, L98, and LT1 engines. It has a perceptible idle and makes great power through the range. A torque converter isn't required. It pulls strongly from 1500 to 6000 rpm with good valve springs.

I'd try it as-is. I went with a significantly bigger cam, and above half-throttle the engine fell on its face and tried to stall. I tried doing some TBI mods, but in the end I went with a Sniper. That's a fairly expensive solution, but once you start down the TBI modding path you quickly reach the same expense. Especially if you don't have any of the tuning tools.

 

[PlayingWithTBI]

From what I have read, next to increasing fuel pressure, I need to have my TBI bored?

Yep, if you're gonna run it up over 5,000 RPM. I have a 383 stroker with Summit Racing aluminum heads that flow a lttle better than Vortecs. The TB is bored to 46mm and the Edelbrock 3704 manifold is bored to 48mm. With my fuel pressure at 20 PSI, my MAP sensor only reads up to ~95 kPa (instead fo 100) at 5700 RPM. Before, my 5.7 was OK at ~5,000 RPM with that setup.

Here's a calculator you can use for sizing your carb, or TB. Just go to the bottom line and load your data to see.

TCI Auto Racing Calculators - TCI® Auto

TCI Auto offers you an array of Automotive Racing Calculators allowing you to figure out displacement, Horsepower, Quarter Mile Times, and more!

www.tciauto.com

Edit: the 46mm TB is rated 650 CFM.

 

[Connorpod]

Thanks everyone for the quick replies! Yup, I will keep you guys posted on the build once things arrive, and when I of course have time. I feel a story in the works... The ultimate goal of this truck is to build something that is reliable, able to keep up with modern performance and mileage. I am quite torn between cutting my losses with the tbi and moving into an introductory EFI system like the Jegs Bandit or Summit, or continuing to modify my TBI.

 

[GoToGuy]

A big block TBI has higher flow/ cfm, that's another option.

 

[garet]

A big block TBI has higher flow/ cfm

 

[Erik the Awful]

Can't ever find one at Pull-A-Part, though.