All kinds of questions...

[Matt]

First & foremost, if any of this has been covered somewhere I missed (inconceivable, I know), please let me know. No need to re-hash anything.

The quick & dirty on the engine- it's a SVO Sportsman 351W block, 408 CI stroke forged rotating assembly (internally balanced & blueprinted), Trick Flow Twisted Wedge 185 CNC'ed heads, ERA bundle o' snakes, & 48mm TWM 8 stack EFI sitting on what I've been told is an original 351W GT40 Weber intake manifold. Pretty much everything else is up for grabs. I spoke to the engine builder & he was confident 550hp should be obtainable with the right cam & remaining valve train components.

Any way to tell if that "original" 351W GT40 Weber intake manifold is real? I wasn't able to find any easily identifiable markings.

The bundle of snakes from ERA have 1 7/8 primaries into a 2" collector (ID, OD is 2 1/8". Coming from mainly modifying Vettes & Turbo applications previously, this seems awfully small given that 550 hp mark. My initial thought was perhaps it was necessary to carry a smaller diameter for the scavenging effect? The only thing I really came across on here regarding the collector size was this post http://www.gt40s.com/forum/gt40-tech-engines-induction-exhaust/15776-reclaiming-lost-horsepower.html and of interest

On secondary pipes (collectors), the diameter was just as critical as the primaries and that given a 4 into 1 collector should have a diameter of 1.75 times the primaries.

Using this method on 1 7/8 primaries the collector should be 3 9/32, that's a LONG way off from 2", do I need a bigger collector & if so how big for a roughly 550hp 408?

Also, since I'm still going to have to get a cam & the rest of the valve train, are there any special considerations to take into account with the bundle o' snakes or 8 stack injection for cam selection?

Thanks all! :chug:

 

I think an original GT40 351W intake manifold would be a rare beast indeed as, if my memory serves me well, only a couple of cars ran 351s (in South Africa maybe???) and didn't one of the mirages have a 351 at some stage? Someone with a better memory than me may be able to supply more details.

 

[Matt]

Ya, the story was that there were insanely few cars with a 351W, I think the # given was 4, but I have no idea how accurate that is. But if it's true...

 

[Seymour Snerd]

Ya, the story was that there were insanely few cars with a 351W, I think the # given was 4, but I have no idea how accurate that is. But if it's true...

Below some pictures and history releative to the Mirage 351s. These people would no doubt know how to verify your manifold.

Ford GT40 Restoration - The Motivation

 

[Matt]

Thanks Alan, I'll see what they have to say!

 

[Matt]

I could have sworn I left that edit button somewhere around here...


Looks like the primaries are actually only 1 3/4" OD primary tubes, I got the 1 7/8" off of the collector's OD not ID.

That changes the primary dia x 1.75 calculation for the "recommended" collector size to = 3 1/16".

 

[Bob Putnam]

The collector size shouldn't be much larger than an individual pipe in a 180-degree system. Each exhaust valve is only open slightly longer than 1/4 of the time (and there's 4 pipes feeding into the collector), so you want the collector volume to maintain an individual pipe's velocity for the best scavenging.

 

[Matt]

Thanks for confirming that for me Bob!

Anyone have any pointers for cam selection with the crossover headers & stack injection, or is it safe to just plunge ahead as normal?

Thanks all! :chug: