Tuned Port Injection

I'm want to ream my stock 48mm TPI throttle body for 54mm throttle blades. Blades are 2.125 from Bo Laws Performance here in Orlando. I'll go ahead and machine the shaft bore for bushings while I have the shaft out, but the bushings are not what I'm posting about. I've fabricated a fixture for the H16 adjustable reamer. That part is not going to be a problem either I do envision a couple of issues however, and wonder if anybody has found a solution. Number one is retaining the coiled return spring. I could build a retaining clamp to keep it coiled, but surely someone has already solved that problem. I see the two "nubs" (which appear to line up) on each plastic spring retainer, and wonder if these nubs are there for clamping/alignment during removal and reinstallation. Second is which end of the throttle shaft to grind off: the throttle bracket end, or the throttle position sensor end. Either way that end of the shaft will have to be machined for a retaining screw for re-assembly, as the peened end will be gone. I appreciate any experience anybody would like to share. Thanks. Paul
 





gains from a larger throttle body size are minimal, they used the same 48mm throttle body on the marine 454 bbc engines as they did on the tpi 350 engines vettes, what they don't point out is that as the vacuum increases the flow also increases, yes there are a few hp gained with a 58mm throttle body, but its the stock intake manifold, cam and heads that are the major power restrictions

related and useful calculators
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
 
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gains from a larger throttle body size are minimal, they used the same 48mm throttle body on the marine 454 bbc engines as they did on the tpi 350 engines vettes, what they don't point out is that as the vacuum increases the flow also increases, yes there are a few hp gained with a 58mm throttle body, but its the stock intake manifold, cam and heads that are the major power restrictions
related and useful calculators
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
 
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Hi Grumpy - Thanks for your reply. Here's a little bit of background. I'm 78, a retired aerospace mechanical engineer. My Master's thesis was the design & development of the world's first and only working variable venturi carburetor. It was completed and patented in 1978, perfect timing for the advent of computerized fuel injection. Ten years earlier and I'd have been world renowned and filthy rich. As it is it's a novel topic of conversation at cocktail parties and little more. I've written a book titled, "The Little Black Book of Carburetor Modification & Tuning", covering classic Holley 4150 & 4160, and even more interesting spread bore 4165. How to convert to cathedral bowl, how to tune metering blocks and air bleeds using a wide-band O2 sensor, machining for annular boosters, etc. In 1967 I set the AHRA F1/DS 1/8th mile ET national record, which due to the subsequent disbandment of the AHRA, still stands. If we only knew about tuning then what we know now! I've built a flow bench, with which I port and develop heads and intakes for myself and others. I've built a fixture for cleaning, testing and calibrating injectors to determine flow transfer functions To make a long story short (but I guess it's already too late for that) I'm an engine builder with almost 60 years of experience. I experiment because I can, and because it's fun. My current projects are 413 cu. in. SBC's, using long tube chevy TPI. Lower manifolds are max ported, runners are enlarged and siamesed, and plenums matched to the siamesed runners. Peak torque is increased from 4500 to 5500. Calculations indicate 54mm throttle body is required. Heads, cam and compression are clearly not the flow limitation. 58mm throttle body is not required. I don't feel like the 54mm experiment warrants a $400 cash outlay. Therefore I'm doing it myself. Like I say, because I can, and it's fun. But being fairly new to TPI, what I would like to know from someone who has clearly been there, is how best to remove and reinstall the throttle shaft, and how best to modify the shaft such that the throttle lever or throttle position sensor might be reattached. Thanks for letting me ramble. Look forward to your reply. Paul
 
your back ground sounds very similar to mine in many areas, I've custom built, milled and modified and extensively welded a good many carb and custom designed and built many a mechanical and EFI fuel injection intake manifold, just because I had the skills, curiosity, tools and knew instinctively, after close inspection of most commercial castings that ease of manufacturing and low cost obviously took precedence over producing the best possible results.



btw I had a couple KENDIG/ PREDATOR carbs in the 1970s

 
your back ground sounds very similar to mine in many areas, I've custom built, milled and modified and extensively welded a good many carb and custom designed and built many a mechanical and EFI fuel injection intake manifold, just because I had the skills, curiosity, tools and knew instinctively, after close inspection of most commercial castings that ease of manufacturing and low cost obviously took precedence over producing the best possible results.



btw I had a couple KENDIG/ PREDATOR carbs in the 1970s

Ah yes - the famous Kendigrator. I've studied them, but never actually had my hands on one.
 
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