1gary

There are times with this thread I do feel I am talking to a empty room.Can anyone answer the questions to this recent post??.

RFmaster

I think what you need to do is to put down a list of 'wants' and 'can be done with $' in two side by side columns in order of importance.

At the end of any discussion what do you want to achieve?? A well mannered, capable 383 for towing or ???? As you have seen do far in this thread there are many opinions - but ultimately it is you that will have to live with it.

The end goal should dictate which parts you should choose for your build. Do this on paper before spending money on parts....


IMHO

1) You do not need TPI - added complexity and costs unless you have a complete TPI system on hand, including injectors.

2) 50mm BBC TBI with 80/90 lb-Hr injectors and VRFPR will support 325 to 350HP 383CID (I run 24 PSI at WOT and about 10PSI at idle).

3) Keep LSA on the cam around 112 and 0.050 duration no greater 220 deg. If you have a roller you can go a bit more. If you are building a street engine and you want to run AC having a smooth idle is must.

4) Keep CR around 9.5:1 - this will allow to burn pump gas without getting too much retard, while still having some punch.

I may rattled a hornets nest, but hey - you ask for it!!

//RF

1gary

Well at last a direct answer.

C/R as stated is set already @ 9.2-DECK CUT-PISTONS BOUGHT!!!.Gezzz

Already stated this is a roller build.

Ya know guys I don't mean to be rude..............BUT.

I get the sense that these systems are a tinker toy guy's delight.I mean post after post of issues and solutions.What is going on??.

I am getting more interested in the Holley Commander 950.So why would I need a EBL??.Just for the sake of a programmable replacement of a chip??.

Why oh why do I want to cut the limits of a system to the peak hp of this set-up??.READ THIS PLEASE!!!.It is 4400 rpm and 350 HP.Repeat,after repeat.I have said this I don't know how many times.AND THIS IS NOT MY FIRST RODEO!!!.Come on jump in and have your say.

Don't please don't bury me in ref links and more info.TIMELINE on this build.Said that too a number of times!!!.


Hello-anyone out there???!!!!.

RFmaster

Well, I'll be direct and brief as possible...

GM 2-BBL TBI has a HP limit - since there are only two injectors (along with airflow ) that is a limiting factor.

Since this is not your first rodeo then I would recommend to go with a 4-bbl setup. It will support your target HP and more. Make sure that you size injectors to hit target level with margin. You have choices - Holley Commander or FAST (and possibly others). Each system has its share of nuances and $$$$ to be spent.

I do not care how glossy the sales brochure is, but both will require some amount of tuning - it is the nature of the beast.

//RF

thomas1976

If using TBI, it is the best and easiest you can find.

1gary

Are you saying if i was inclined to use a O.E.M. TBI??.Holley Commander series is a stand alone.Is it not??.Why do I need to add to that??.

1gary

All most everything I look at worth anything has a price starting at $2,000 and up.I am becoming a Commander fan for the features I looked at so far.You and I are of the same mind.All the magazines are tools for promotional sales.Certainly you have to be able to read threw the lines to find the truth.

So what is the down side of the Commander series??.Remember-direct blunt answers.I think the 900 cfm would cover the engine.

1gary

One other thing as I look more at this:

It seems TBI's are carbs with 2 or 4 injectors and are more likely to to build HP


Also TPI's are more likely to build torque and less likely to build HP because in upper RPM ranges they don't flow well.

So is it a fair statement to say volume is = to torque and pressure is = to hp?.

So if what I have said is a true theory,me wanted to max torque,then which OEM TPI do I need to get to make necessary improvements??.Also is a TPI more accepting of lower lobe centers like 108's??.

dimented24x7

iTrader: (2)

TPI is a resonance based system (hence the name Tuned Port Injection). It will be soggy off the line compared to a TBI system with a dual plane intake. Itll make best torque around 4k or so, and on a 383, the torque will likely drop off rapidly after that due to the airflow limits of TPI. If you port it a bit and add aftermarket runners, you can extend its operating range.

Another option, of course, is to run an aftermarket MPFI system. I have the edel victor-E and with MPFI and a mild cam it makes plenty of off idle torque. Not as much as you would get with a small dual plane, but it gives good top end power and doesnt pose a restriction airflow wise. The TBI PCM can also do MPFI if you bypass the sense resistors and make some changes to the memcal. I have a MAF code for the MPFI as well. So far only one person has it, but they like the way it runs. If you dont like it, you can simply just switch back to the stock SD code, so there are lots of options with the stock PCM. The commander system will be some serious $$$ if you want to go that route. FWIW, I think I did my whole SFI system for less than the cost of the commander. If money is no object, you could go with the FAST XFI system. That looks like its a pretty slick setup, but its pretty damn expensive.

How much money do you have to play with? Thats the real question. MPFI gets expensive fast as you need to buy the whole induction system. The nice thing about the TBI is that you already have most of what you need. The holley units are nice, but a 4 bbl will require staging to work properly. Its hard to meter fuel at idle with all four injectors going at the same time.

If your towing, STAY AWAY FROM THE TIGHT LSA!!! You will regret that when your pulling a load. I ran a cam with a 108 LSA and it sounded great, and made lots of midrange power, but it got terrible fuel economy around town. Im talking like 12 MPG in a car. It allows the cylinder pressure to bleed off at low RPMs. I pulled almost no vacuum when I was cruising with it. Go no lower than maybe 112 for a smaller grind, 114 for a larger grind. With a roller, a 108 LSA will be more drastic then it is with a flat tappet. You really dont want that.

1gary

Without A/C anywhere and the recent heat wave I have laid of anything to do with projects.Sorry I haven't replied to your post.I am in the age group that is at risk with some heart issues.Been spending time to take care of that.

Anyways.Cam/head choices is the same with me as it is with anyone else.I want my cake and eat too with the lowest broadest torque band I can get.I do worry about building a 383 that is sooooooooo like some of the diesels where they would pull a house off the foundations,but beyond 60 MPH are a brick.

I am digesting your post and will look more into it after the heat passes.One term you used which might be a typo or a term I don't understand is:"memcal"

thomas1976

Yes OEM.
I have no experience with the holley system, going by the instruction manual and chevy tech article, it still sounds like some fueling and tuning experience is required.

dimented24x7

iTrader: (2)

The memcal is a blue thing in the TBI PCM that contains the knock sensor module, calibration resistors for the inejctor firing rate, and EEPROM with the computers software code on it. You can change the injector firing stratagy to that used by TPI by making changes to the memcal. This can also be done through the source code running on the PCM, but I havent gotten around to writing a patch for the stock code yet.

Fast355

iTrader: (2)

Having towed all over the place with a tight LSA, I disagree. You want more mid-range torque in the 2,500-3,500 rpm range while towing and the tight LSA gives you this extra torque. While towing you will really never be off the throttle or under the stall speed of the torque converter. We are talking small cams, not 218* @ .050 plus.

My 355 is still running to this day with a Q-Jet on it and its 110* LSA roller cam makes plenty of grunt in that RPM range.

The 4.7 Dakota I run around in cams that spec 218/224* @ .050, .502/.520" lift, 111* LSA and it pulls very well turning 2,600 rpm @ 60 mph.