Thoughts on using this setup on 351 build

[Hoytster]

what are the 302 block splitting hp numbers? 400 ish right?

That's a loaded question, but the general consensus is 500 RWHP is the limit. RPM is what really kills these engines. My 93' is over 500RWHP but doesn't get spun over 5800 RPM and has lived since 2008 at that power level. Others have split the block at 450RWHP.

 

[from6to8]

That's a loaded question, but the general consensus is 500 RWHP is the limit. RPM is what really kills these engines. My 93' is over 500RWHP but doesn't get spun over 5800 RPM and has lived since 2008 at that power level. Others have split the block at 450RWHP.

wow

 

[Labora]

what are the 302 block splitting hp numbers? 400 ish right?

People argue but it depends on tune, power adder, and I'm sure plenty of factors along with some luck. 450-550 IMO.

 

[from6to8]

People argue but it depends on tune, power adder, and I'm sure plenty of factors along with some luck. 450-550 IMO.

is it the same ballpark numbers for max hp on a 351 block?

 

[a91what]

no 351w block can survive much higher numbers.

 

[Hoytster]

750 - 800RWHP is the what I've always heard on the stock 351 block, but I've never tested that.

 

[from6to8]

no 351w block can survive much higher numbers.

I'm trying to find numbers on header primary and collector lengths but can't find anything on google nor does BBK provide that information. I just called them.
I've never thought about those lengths other than understanding the difference in primary diameter. He must be talking about the overall length from the primary down to the collector. Just text him to ask but asking here too. Wondering if you guys have inquired about that when looking for headers lol?

He said 35-36 inches long primaries and not 30-31 inches
Collector length 16-18 inches and not 7-10 inches

 

[from6to8]

Just had another conversation with him about a 347 as well as a 427 and the longevity of those cars as to rod length and stroke will not be really reliable. He said sure he can build a 408 or 410 but using a 4 " stroke is not what he'd recommend vs a 3.750 crank and talked about the advantages of the shorter crank. Ultimately he has always said building via big bore vs stroke is the way to go but understands for what I want to do a stock block is more wise.

He said if he did the 408 or 410 he'd use a brodix 17 degree head and that a 220 in it vs a 220 in a 20 degree head is huge difference. If I stick with the 3.750 crank (385 c.i.) I'd likely just do the AFR 185 or the brodix 17 degree 190.

so still thinking

 

[revhead347]

There is no specific number to where the 302 block splits. It was rumored 500hp. The rumor came from back when I started doing this. Hardly anybody did a computer tune back then. There was no where near as much understanding about tuning, and RPM, and how that stressed the block. There is a guy on sloppy that has put over 800 to the tire on a Turbo Mustang; complete stock bottom end; consistently. His name is not coming to my head. I know he is from South Carolina. I am not trying to say that if you through a ton of power at a 302 block it would be fine; more that the quality of the parts, and the time, effort, and restraint put into the combo/tune will be more rewarding and less likely to fail in the end.

Keep in mind that the primary reason a factory 351 block is regarded as "stronger," is due to the casting design in the main webs that allows it to be drilled for 4 bolt main caps. If you leave the 2 bolt main caps on there, it's not much stronger than a 302 block. So add the cost of three 4 bolt main caps, and the machine work to the 351 block when comparing prices. I still contend that it is usually cheaper to get a 4 bolt main 302 block into a Mustang than a stock 351 block.

FYI, my last 347 put 372hp to the tire with 192cc heads. You had to wind the snot out of it before the power kicked in. I don't think my new 347 will do a whole lot better.

Kurt

 

[jozsefsz]

The failures aren't typically related to the main bearings, the block splits through the lifter valley. I imagine in the old days a cast-iron intake manifold bolted to cast-iron heads would have helped hold things together a bit. High rpm and high-lift cams seem to contribute from what I've gathered over the years. I've likewise been putting 400+ to the rear wheels since 2009 without issues, so it's probably somewhere north of that. I do run the stock cam with the turbo however.

 

[from6to8]

A 75MM TB will support some good power. I know Accufab rates their 75mm throttle body @ 924 CFM @ 28". 924 CFM will support 700-800 HP. I'm not saying you wouldn't pick up some additional power at that level with a larger throttle body due to reduced restriction, but 75mm is more than enough for your power goals and won't be a restriction at that level.

Edit, just did a quick calc and it looks like your engine will need ~600-650 CFM to make the desired power output (Spinning to 6000 RPM).

hey in relations to what you just said, what size cold air pipe would I need 3" or 4" or either? Depending on which I find/have to buy new or used depending on availability , I just want to make sure I'm not doing anything to negatively affect drivability and low end torque which will be the ultimate goal and not high end hp/torque. Don't get me wrong it would be nice to have ALL lol but I realize to have the latter It'll be sacrificing down low.

 

[revhead347]

The failures aren't typically related to the main bearings, the block splits through the lifter valley. I imagine in the old days a cast-iron intake manifold bolted to cast-iron heads would have helped hold things together a bit. High rpm and high-lift cams seem to contribute from what I've gathered over the years. I've likewise been putting 400+ to the rear wheels since 2009 without issues, so it's probably somewhere north of that. I do run the stock cam with the turbo however.

The block splits through the valley because the bearing caps start to walk at high rpm at high load. The cap walk wrenches on the main bolts that go up nearly to the top of the valley fatiguing the metal.

Kurt

 

[from6to8]

so what about the filer in the engine bay?

 

[General karthief]

so what about the filer in the engine bay?

you mean filter? Yeah, that's a no no.

 

[from6to8]

you mean filter? Yeah, that's a no no.

Give me the scenario in on when should I use a 3 3 1/2 inch pipe instead of a 4-inch pipe? I'm thinking for is going to be Overkill and may hurt

 

[General karthief]

The bigger pipe would be needed on an engine that is gulping large amounts of in coming air at higher rpms, larger pipe may induce turbulence, less velocity may screw with the maf readings on stock engine even with mild modifications.
just thinking out loud,

 

[from6to8]

The bigger pipe would be needed on an engine that is gulping large amounts of in coming air at higher rpms, larger pipe may induce turbulence, less velocity may screw with the maf readings on stock engine even with mild modifications.
just thinking out loud,

So are you saying either way it could potentially be a negative LOL?

 

[General karthief]

I'm thinking yes

 

[from6to8]

I'm thinking yes

That's why I'm trying to figure out is there a formula to figure out exactly what size pipe you need? I mean many guys have done it before so do they just go by what people say hey get this get that don't get this don't get that LOL? I wish we can pretty much take your intended combination and match everything up according to cfm's of whatever to get the right thing

 

[General karthief]

Thats going to be scientific mathematical stuff with a bit of velocity/turbulence theory tossed in. WAY above my pay grade.
i can tell you that the air needs to be able to move smoothly but not be lazy about it. In reality if you size the tube to the throttle body just a little bigger and keep the tube size into and out of the maf the same on a mildly modified street engine you'll be good.