comatose 88 WS6

Im planning out a motor build, but im not sure what size injectors and possibly TB on it. Itll be a 408 with AFR 227 heads, HSR intake, 58mm TB and crane cam with 262/266 duration at .050. im thinking 36#, but im not sure. Also will the TB be big enough to flow the right amount of air, or should i look for one that flows closer to 1000cfm? thanks for the help.

doc

30#/hr SVO injectors will do and the Holley AFPR. If you need 36#/hr, the 30s will flow 36 at 58psi.

Also, you should think about a high flow fuel pump. I installed the fuel pump from the TTA. The stock fuel pump will not keep up with injectors much bigger than 24s.

Roostmeyer

iTrader: (3)

a good set of heads are going to flow more air, so you'll need more fuel as well, but whats going to kill you is the 7000 rpm shifting points. Just think that those injectors will have under 8 micro seconds to stuff enough fuel into the engine for around/over 550hp.

I'm guessing you'd need 40lb minimum. A stock ECM isn't going to be able to control that big of injectors at idle very well, but then again, you won't have that great of an idle with that big of a cam anyway. At that RPM your out of definition in the stock ECM anyway, so you might as well go aftermarket FI with some 45lbers for some breathing room. Not to mention a HSR won't fit a 1206 intake port and as far as I've heard nobody has pushed that much air through a HSR.

My suggestion... your dealing with an almst unstreetable engine at this point, so why even bother with FI? just my .02. If you want EFI, take that cam down about 20 degrees on both sides and live with an honest 500++ hp. Start saving up.

Edit: for content... and why go for a TTA pump when you can use a walbro 340 for around $100 that'll supposedly support 750 hp with 14.5 volts?

CaptPicardsZ28

What do you mean by almost unstreetable? Why bother with FI?Your kidding right? There are many efi applications that are streetable over 400hp. Check around. DIY is the best way to tune efi with that much hp. I am running 500hp and it's plenty streetable.

Comatose:
I use 30# SVO's on my 406 and it's plenty good. You can go 36 if you want. Also, the 58mm TB is 1000cfm. You shouldn't need more than that. Here is a link to use to find out what size inj. you need. http://www.holley.com/HiOctn/TechSer...l/Artcl07.html
An HSR will fit a 1206. Do a search or visit www.stealthram.com and find out for yourself. Also, you may have better luck with the build by switching to Speed Density. Hopefully you are going to do your own tuning and not have someone tune it for you through the mail. Hope I answered your questions.

comatose 88 WS6

thanks capt, and yes, this motor is streetable. the actual build uses a carb and victor manifold to the tune of 620hp, pretty much 10's all day in the 1/4. Before I go looking for a carb'd bird or Z to put it in though i wanted to test the FI waters. yes SD would be the only way id go with FI as well. Im not sure to go 6speed or auto 350 with it, but either way ill be haulin azz

doc

If you really think that you are going to make 620Hp, then 40#/hr injectors will be needed. Injectors dont work well below 0.75msec for idle stuff. If you can get it to idle with a 1.0msec PW, you should be OK overall. But, I think that I would start with a smaller injector just the same.

And as stated above, the 58mm TB flows 1000CFM.

Are your cam specs correct? Is that duration total seat to seat or at 0.50" lift as you state above? Just wanted to check.

And what idle RPM do you think you can run?

MTPFI-MAF

Well here is my . You Might Look into Single Plane EFI like the Holley Pro Ram, Edelbrock Victor EFI, Accel single plane. You can purchase These Witout Electronics and use the GM SD computer, This will is a option and the System will have close to the same charistics as a Carb set up, with better Gas mileage and tuneability.

Just thinking out loud

Roostmeyer

iTrader: (3)

We aren't talking about over 400hp on DIY EFI, were talking over 550hp @ 6500+ rpm, and yes I think 620hp is feasible with everything working right in that setup. The big problem is getting the injectors needed to feed that engine to idle on any stock ECM. When you couple that together with the resolution you lose at that RPM, its seems to me its time for a different computer. I haven't messed with SD much but for MAF the last ignition cell is 4800 rpm and the last PE adder cell is 6400rpm. I know you wouldn't really need more cells above that, but it might come in handy. About it being "streetable" this is very much a matter of opinion not fact. IMO with that big of a cam you kinda lose some of the reasons that people go with FI, such as better gas mileage, driveability, cold start, etc. Its all the same for a much more radical build, its just you've got a lot worse driveability and gas mileage to start out. IMO might as well just go carb and have less headaches, but if you want to be different and want a challenge I'd say go for it. I'd really like to see this combo running at the thunder shootout .

I'd check out the victor E series intake from edelbrock, you can buy them with fuel rails and bosses for FI. I posted part numbers a little while back and I can look them up for you again if you want. You'd still need to use either a 4 barrel TB or build a plenum box to attach the 58mm to and of course custom fuel lines and regulator feeding the fuel rails, but it's easier than going completely custom.

I think that would be your best bet to stay as close to the original build as possible, you really don't know how much hp you might gain or lose on that combo if you use a stealthram compared to the original carbed victor. I doubt it would be much, but these damn builds seem to work out that way

oh almost forgot is this the 407 that hot rod mag build for some lucky reader who designed it?

Picard can you PM me your cam specs and dyno info/et's if you have any, I'm just curous what RPM your turning with the 30lb SVO's. I'm kinda undecided on the cam I want to use on my 407 that i'm slowly collecting parts for. If your wondering the future 407 is the reason for my current oversized injectors.

Grim Reaper

This is my concern on both points. I would chat with "DF" of Holley and get his opinion if the ports can be built up and then ported to fit.

As for using the 7730 ECM, I have been amazed on some of the engines that have been made to work with it (as well as MAF). You also may be surprised how far you can push smaller injectors. Don't rush to quickly to buy 40#s.

gta324

Go to www.chevytalk.com EFI board there is a thread about 1206 and HSR that D.F answered....

MTPFI-MAF

and here is the link http://www.chevytalk.org/threads/sho...5&o=93&fpart=1

CaptPicardsZ28

[QUOTE]When you couple that together with the resolution you lose at that RPM, its seems to me its time for a different computer. I haven't messed with SD much but for MAF the last ignition cell is 4800 rpm and the last PE adder cell is 6400rpm. I know you wouldn't really need more cells above that, but it might come in handy. About it being "streetable" this is very much a matter of opinion not fact. IMO with that big of a cam you kinda lose some of the reasons that people go with FI, such as better gas mileage, driveability, cold start, etc. Its all the same for a much more radical build, its just you've got a lot worse driveability and gas mileage to start out. IMO might as well just go carb and have less headaches, but if you want to be different and want a challenge I'd say go for it. I'd really like to see this combo running at the thunder shootout .[QUOTE]

I believe I mentioned switching comps. As for "streetable" I guess we have to define what it is. My definition is probably different from yours. Most people who swap to FI don't just do it for driveability and mpg. They do it because with efi tuning your options for better performance are greater. You can tune much more precisely with EFI than you can with carb. There is nothing like being able to fine tune your car with your own tuning equipment. I had the option of scrapping the FI for carb (and still can), but I have done a lot of research and there are just more benefits to staying with FI.

I believe the fuel cells top out at 6400 for SD as well. You can also get a hack to extend them if necessary. For the moment my 30#'s are fine. I have not seen otherwise. If so, then I will upgrade. Not a big deal.

CaptPicardsZ28

Ditto.....

Grumpy

I run 60 PPH saturated injectors on my 1227749 ecm'd GN. Batch fire mode, idles at 800 RPM in gear. BTW, that's a 3.8L v6.

comatose 88 WS6

just a thought, can a LT1/LT4 manifold be matched up to AFRs?

doc

I'm going to say Yes, there are several people on this board who have converted to the LT1 intake system from the L98 TPI setup, depending on the EGR issue (if there is an issue).

Also, because you are taking big HP, a custom prom will be required to get the engine running good.

Go onto the General Engine board and the Custom Prom board and do a search concerning the LT1 conversion and the related Eprom.