planning my engine, need help

[DukeGnarley]

Ok, so I'm starting to plan and collect parts for a new engine to put in my '65. I'm in the fox section though because you guys know a lot more about fuel injection.

I'm trying to build a 400+ rwhp all street engine, with efi, and room to grow.

my current plan is...

dart shp or boss block
forged internals, 306ci
afr 185s or twisted wedges
'93 cobra upper and lower intake
comp cams blower cam
s trim/novi 1200

I'm still contemplating my computer options, but it's down to EECIV with tweecer or megasquirt

If you have any suggestions about what I've listed so far, I'm willing to listen (although i already have the cobra upper).

My main question right now is what size throttle body, and fuel injectors do you think I need? I've searched but haven't really found an answer as to how many lb/hr I need per hp. Also, will I need aftermarket fuel rails/regulator?

Thanks,
-duke

 

[NIKwoaC]

Why get an aftermarket block and go with stock displacement? If (actually, more like "when") I get an aftermarket block, I wouldn't consider anything less than 347ci. I'd actually probably go 363 or bigger.

The AFR 185s or TWs 170s are "big enough" for your power goals on a supercharged 306, but if you go to a 347, you'd be better off with something bigger, like Twisted Wedge 185 or 205 (yes, TW 185s are actually a "bigger" head than AFR 185s, don't let the numbers fool you).

The Cobra manifold will probably be your weak link in the end. The power goals on a supercharger with that intake are possible, but understand that it will be the bottleneck.

For the TB, again, the Cobra intake will hold you back on what you can do. I believe a 70mm will fit with very little or no port matching. A 75mm or bigger will probably require port matching. On EFI cars, you really almost can't go too big with the TB. It's not like a carburetor, we're not worried about velocity through it or anything like that. All you really want it to do is get out of the air's way at WOT.

For injectors, you'll probably want something around 42s. Take a look at this calculator:

Injector Size Calculator

You probably will not need aftermarket fuel rails for 400rwhp.

 

[2000xp8]

That combo is all over the place.
Make that dart block into a 347 for sure, use race heads like the cnc wedges or similar, good intake and you should be well over 400rwhp without the blower.
The way you are doing it, you are going to have to take the whole thing apart and do it again.

Then when you are ready for more power get a D1 or Ysi and then the hp will jump up to around the 650 range.

 

[_Cheese_]

most people dont need to upgrade the fuel rails when building a new motor -but they certanly look better then the stockers. FWIW stock rails can support 700+hp

 

[DukeGnarley]

Thanks for the input guys. That injector calculator was extremely helpful, and you've given me some things to look into.

I've just been adding everything up (bad idea I know), and it looks like I probably should set my sights a little lower on the hp levels, at least for now. I still have paint, interior work, a new steering box and transmission to go. Adding 4k+ for an aftermarket short block would probably set me back farther time wise than I would like.

I know the stock short blocks tend to give up around 500 hp. Is that at the wheels or crank? and what is the "safe" limit? I'm hoping it will be enough to get me by for a while so I can at least get my car back on the road. It's currently all torn down without an engine or transmission.

 

[2000xp8]

A safe number to expect the stock block to hold to is 450rwhp, some put up with more, but IMO, stretching it for a few more hp isn't worth the risk.
Don't go nuts on a 306 rotating assembly either, it's the block that's the weak link not the internals.
If you like though, consider a good 347 rotating assembly for the stock block, one that can be transferred into a race block in the future. Just remember though, if you crack the stock block, all the internals will be garbage.

TW's have been on sale at summit for $950 so check that out too, to save a few bucks.