406sbc and TBI

[scrambld8]

Hi all. Been lurking for a while and joined up the other day. I have a planned project and wondered if I had any fatal flaws in my plan. Any and all suggestions welcome as I am new to building TBI equipped vehicles (somewhat as I have a Howell GM inj 383 in my CJ8 << but that was prepped for me by Howell). This motor will be placed in my 1994 FS Blazer/4L60E 4x4. Trying to keep the budget on the lesser is better side......projects almost never go that way.... :)

My Plan: a 400 sbc and my usage is a TQ'y truck/tow motor. RPM range most used idle to 3500rpm's...wouldn't mind a blast to 4500-5000 occasionally but that is not a requirement and maybe not likely given my desire to stick with the 193's and low rpm goals.

I have been sitting on a 400sbc (would consider just doing similar things to a 383) as I love the TQ potential of 400's
It'll be built with 5.7" rods, I would make it easy and go with 5.565" rods (lets not get into long vs. short rod thing, in this application I don't believe it'll make any difference) but I find it near impossible to find (5.565") pistons that'll give a reasonable comp ratio with 65cc 193's. So......

400 .030, 5.7" rods, and looking at KB126 pistons 30cc D dish hypers (9:1 w/64cc). Still need to measure deck height as they vary (can be quite a bit) and deck as needed. I will shoot for a good quench and try for mid 9:1 comp ratio if possible. I want to stay with 193's for their good low rpm TQ potential and minimal headaches and EGR compatibility and intake coolant heating. Correct me if I am wrong that EGR can be a good thing? I don't need it for emissions testing.

Heads: As stated trying to stay with 193's (considered Dart 165's and Vortecs) because I think the 193's fit this application best. Any suggestions for mods to these heads that will help them out. Chambers I would clean up and smooth out any sharp blocky edges and may unshroud the valves a little....I do realize that a 400's bore unshrouds the intake valve by it's 4.125 bore (stock)

For the cam, I have a RamJet350/HT383 roller setup with all the required components. The block will be modified to retain use of the lifter OEM retainer. As far as that mod, all I know it has been done to non-roller blocks w/good success...lifter valley tapped and top of the lifter bore machined flat for the retainer.

Fueling. 87-89 octane...hoping. Here is where I would need some help/suggestions. For the TB, I would look at "the ultimate TB mods" bored throttle body (R.V. Morse for example) for increased airflow (keep in mind low RPM goal), OEM intake machined to match TB as needed. Injectors open to suggestions and/or fuel press mods if original 5.7L will flow enough (they will visit Mr. Injector for a rebuild) with using a EP381 fuel pump (?) and adjustable FPR.

Exhaust: Shorty headers or factory manifolds into a Gibson 3" cat back (presently on the truck).

Then will come tuning. I am not up on doing actual tuning myself, willing to learn, but in the interest of time and equipment needed I was wondering is it feasible to have tune done off site (heard bad mojo with TBIChips...so will not go there)? Is this plan to out of reach for a tuner to get pretty close with a tune? Displacement is approx. 16% more, planned rpm range is not high, and camshaft is fairly tame....?

I am sure I am leaving out some important details and can provide info if needed. And again, I any and all suggestions are 100% welcome. I am just in the planning stage as of now. Only parts I have are the block, 193's, and camshaft and roller setup, and shorties. Thanks a lot in advance!

[PJG1173]

which TB are you going to use? I had my 5.7 tb bored and it only flowed a hair over 630 CFM. if you are using a 454 TB you should be good. I'm also not sure you want to use the oem intake with that much displacement. I have had good luck with the 193 heads on a 327 I had. they flowed fairly decent with the 1.94/1.5 valves and the "swirl ramp" in the intake bowl ground down a bit.

[scrambld8]

^^^ I was just going to run the 5.7L TB. If it gets to 630CFM, I would think that'd be OK with my proposed RPM use. Again, NOT looking for high RPM performance. I am looking to build low RPM Tq "monster", airflow velocity/throttle response, and drivability.

As far as 454 TB's I recall there being differences in the years. I would consider a bolt on and the years I forget...especially with the sensor plugs and I don't recall if that was IAC or which plug exactly...without cutting and splicing. I just recall it not being a 1:1 swap....years may have been the differing factor though?

Edit: It is my understanding the TBI was more limited by GM with it's cam choice and ECM programming....not to say the TB, intake, heads were stellar pieces of equipment but not bad for the intended purpose...which I am trying to replicate, but by sneaking a mild 406 where the 350 cubes would reside.......again, approx a 16% increase in C.I.....if that is even important to remember..?

[PJG1173]

the difference in the years is for the pressure regulator which are interchangeable with 4.3/5.0/5.7 TB's. yes the plug on the IAC and in some cases the TPS is different. I run the 454TB on my 355 with a roller cam and vortec heads. I can spin that motor over 6k before it starts pulling vac. my ported 5.7 TB is on a 4.3 v6 to get it to 630 we had to fill some of the vacuum ports and passages as we had to bore into them to get to 48mm.

[scrambld8]

I can spin that motor over 6k before it starts pulling vac.

OK, but that is way above my interests....the 193's taper off at around 3500-4000rpm anyway. IIRC I was looking at 46mm (bored) TB's.

Just for reference, I don't know the reliability of these outfits...just that they've been around quite some time (then again, so hasn't a "certain" tbichip ...uh-uhm tuner).

So,

http://marine-performance-parts.com/...tbi435057.aspx

http://www.ebay.com/itm/46mm-Ultimat...item3cdceecdd0

[PJG1173]

My original point (not well explained) was I have a motor 50 cubes smaller and it starts to choke on a stock 454 TB. I agree the 193's taper off around 4k and completely fall on their face at 4750. a 406 with a stock to mild cam at 4000 rpm will need 500 is cfm, my question is why spend over $200 to bottle neck the motor for future enhancements? remember tb's are not like carbs so going a bigger on CFM does not affect them.

[scrambld8]

My a 406 with a stock to mild cam at 4000 rpm will need 500 is cfm, my question is why spend over $200 to bottle neck the motor for future enhancements? remember tb's are not like carbs so going a bigger on CFM does not affect them.

Why are TB's not like carbs...they are electronically fuel metered carbs in essence...No? Isn't CFM....just CFM.

4000rpm is most likely my max upper limit. I've owned this truck since new and I can count on 1..maybe 2 hands when I took it above 4000 (mostly because nothing happens) and that is fin with me.......oh, and there won't be any future enhancements. this is a truck motor build to do truck motor things.....ie: diesel like grunt. I know.....just swap in a 6BT I am just going for the factory install look.

Learning about TBI/EFI as I go......bare with me....

[scrambld8]

Using Wallace Racing Carb/TBI CFM calc...they don't differentiate.....and using 406ci/85%VE/4000rpm I get a CFM which falls pretty close to the rated OEM 5.7L TB rating...of which I've seen some variation.

I used 85% VE because I think 90% VE is optimistic considering the mild GM roller, 193 heads, and intake slated for use. Even 85% VE might be optimistic....LOL

[PJG1173]

this is how I understand the differnence: a carb relies on air velocity rushing across the venturi's to draw fuel out of the carb. if the carb is too big CFM for the motors requirements you will loose velocity across the venturi's creating fuel metering problems. EFI does not rely on air moving through the TB to meter fuel. oh and a 6BT just wouldn't be as fun to tune...

[scrambld8]

OK.....be patient with me...LOL

Fuel is injected/sprayed into the entry of the TB. So, if CFM was too great would it cause a lazy situation, air/fuel distribution issues (poor atomization), or pooling? Maybe that would occur if CFM was far to great I don't know....

[PJG1173]

I haven't experienced any of that yet. think about it though when the throttle blades are closed on a TBI fuel pools slightly on the butterflies then runs off the edge presumably being atomized again. I am not by any means an expert on the subject, but I have seen enough over carb's engines come in our 4x4 shop with issues vs someone with issues attributed to an oversized TB (zero to date). Trust me I wasn't suggesting you go with something huge like 830cfm or anything. I was thinking along the lines of a stock 454 50mm TB.

[scrambld8]

OK, so if a stock 454TB cfm's at ~650....and a smoothed/bored 5.7L TB at a claimed 630ish what harm might I do with using a bored 5.7L TB? Wallace Racing calc's show about 650cfm at 5000rpm in my app. It can really go either way. I can do a stock rebuilt 454 TB or a bored 5.7L TB....because that is a piece of the puzzle I don't have (except for the one on the truck now).....but I am trying to keep my 5.7L as complete as I can for a quick and easy R&R....cept for a few sensors here and there. So, if going 454 are any years that would be easiest for swapping...I do see adapter harness's so it may not be that big of a deal.
Am I being picky? Should I not worry about it?

EDIT: I need to do some reading.........

[brian617]

It was explained once on here that with too much throttle bore that the problem was with throttle angle vs map readings and the affect it had on transmission line pressure and shift points.

With the larger bore less throttle angle is required to achieve higher map values.

With a standard transmission or th350/400 it wouldn't have an affect.

[rsicard]

OK, so if a stock 454TB cfm's at ~650....and a smoothed/bored 5.7L TB at a claimed 630ish what harm might I do with using a bored 5.7L TB? Wallace Racing calc's show about 650cfm at 5000rpm in my app. It can really go either way. I can do a stock rebuilt 454 TB or a bored 5.7L TB....because that is a piece of the puzzle I don't have (except for the one on the truck now).....but I am trying to keep my 5.7L as complete as I can for a quick and easy R&R....cept for a few sensors here and there. So, if going 454 are any years that would be easiest for swapping...I do see adapter harness's so it may not be that big of a deal.
Am I being picky? Should I not worry about it?

EDIT: I need to do some reading.........

Before going any further, have that 400 small block sonic tested for cylinder wall thickness. No sense in going through all the engine rebuild to find out the block is WEAK. As for modified throttle bodies, avoid them. Purchased one (454) and found the throttle plates would not close all the way such that it would always have a high idle RPM. Lesson learned. Stock 454TB should be fine with 2" throttle plates.

[scrambld8]

Before going any further, have that 400 small block sonic tested for cylinder wall thickness. .

That will be a given......one factoid I left out. Have to verify the foundation before building the structure on top of it.

So stock rebuilt 454 TB with xxlbs/hr injectors/at xxpsi F.P. seems to be the consensus...?

Maybe it makes some sense as the Howell TBI on my Jeeps 383/Vortec heads/ and mild hyd. tappet cam uses a 670CFM Holley....newer style I am hoping! Not sure on the injector rate though...

Honestly...trying to learn the in/outs...and why's?