Can heads flow too well on Explorer 5.0?

[rjrobin2002]

I was looking at sbf heads for a potential 302 upgrade and 347 stroker down the road.
I found heads flowing from 180 to 250 on intake, and some of the heads had great intake flow but not very well on exhaust.

Question is..... if I were to buy the better heads and put them on a stock explorer 302 with stock gt-40 Explorer efi intakes, would if cause performance issues.

Is there a reason some high performance heads restrict exhaust flow?

How much flow head can the Explorer intake handle before it's the limiting factor.

 

[bmc69]

Yes, you can always have heads that flow too much for a particular application. High flow heads can hurt, particularly, torque in lower RPM range. As an anecdotal example of that effect, look how many mods have been developed over the years to reduce the size of the ports and runnners on 4v Cleveland heads for many racing applications like circle track racing. Or why I only use 2v Cleveland heads on my 408 builds..

 

[pcf_mark]

bmc69 has more experience than me I'm sure. In my experience a bigger / better flowing head is not bad if you stay within a reasonable range. The cam can keep things working well. A bad cam choice is always a bad cam choice. Too big a cam you can't really live with until you grow into a bigger engine stinks. But a good flowing set of heads with a modest cam can work just fine. Then you can grow into a bigger engine with the bigger cam to take advantage of them. But if you pick a head with big flow numbers and they are soft down low they are going to lose torque for you. The GT40 based head is a rockstar on 5.0 engines looking to make power under 5k. The twisted wedge would be an example fo going too far.

 

[blubuckaroo]

Bigger valves and ports accomplish the same thing as a high lift/duration cam. I've found I get better response on a 302 with 1.94" valves rather than the 2.02" valves.
The biggest restriction on SBF heads is the exhaust ports anyway. That should be your focus on a driver.

 

[rjrobin2002]

What's yalls opinion on the gt 40x heads compared to the gt 40 flow?

 

[WheelHorse]

It's not so much about just CFM flow numbers...velocity on small cubed street engine is what you will need, especially if you want to operate in the idle to 5500 range.

If it were me, I'd run the GT40 stuff on a 347 in a Bronco.

Read up on some Tmoss articles.

 

[sykanr0ng]

It's not so much about just CFM flow numbers...velocity on small cubed street engine is what you will need, especially if you want to operate in the idle to 5500 range.

If it were me, I'd run the GT40 stuff on a 347 in a Bronco.

Read up on some Tmoss articles.

Excellent resource:

http://tmoss.efidynotuning.com/

 

[Broncobowsher]

One of the last YouTube engine masters did bigger and bigger heads. In general big heads and a small cam work great.

 

[rjrobin2002]

Excellent resource:

http://tmoss.efidynotuning.com/

That was some good reading on the gt-40 dyno graphs compared to the others. Much more usable power range.

Does he still do port work?.

 

[blubuckaroo]

One of the last YouTube engine masters did bigger and bigger heads. In general big heads and a small cam work great.

Yes, but the important words there are big head & small cam. Not necessarily both.

 

[sykanr0ng]

That was some good reading on the gt-40 dyno graphs compared to the others. Much more usable power range.

Does he still do port work?.

Last I saw was a few months ago and he was then.

 

[Broncobowsher]

Yes, but the important words there are big cam & small heads. Not necessarily both.

You mean big heads & small cam? I think you typed that backwards.
Because with a big cam and small heads you have a bad idle (well it can sound great) but you still don't have any flow to make any power.

 

[bmc69]

One thing missing from this discussion is a frame of reference regarding what is a big head and high flow. I focus on the Cleveland and 385 series world, where the smallest of small heads absolutely dwarfs the largest head Ford put on the 5.0/5.8w engines. So for the ole wheezers, you have to get a head from the likes of AFR before you are getting in to “too big” territory for stock or mildly built engines.

 

[rjrobin2002]

I was referring to the Twisted Wedge and gt 40 x
Flow numbers above.

 

[bmc69]

I was referring to the Twisted Wedge and gt 40 x
Flow numbers above.

I think you would be giving up some bottom-end performance if you went as far as those Twisted wedge heads. Or..you'll never reap the benefits they might offer at the high end...because you are not building a 6000 RPM race engine; yr building a truck engine.

Those Edelbrock heads look good..but as others have noted, you'd be fine with the gt 40 x heads too.

I still have a couple sets of the 351w heads I built for our EB race truck. The 302s delivered 487HP peak at 7300 RPM (solid lifter engine). Those heads have 1.94/1.60 valves and a ton of port and bowl work. Those Edelbrock Performer heads would be the closest analog. I wouldn't go for anything larger for the application and state of build you are talking about. HP numbers are one thing...but bottom end matters too. The 487HP race engine I referred to had spit for low-end torque. Edit: I went and dug up the old dyno report for that 302 487HP race engine. Uncorrected HP and Torque at 3000 RPM: 156 HP and 273 ft-lbs. LOL... A build has to be carefully designed to suit the need.

 

[rjrobin2002]

Gt 40x it is then, and for what its worth, this is for a f100 street truck build I am doing another Explorer efi swap.


Or you can ship me a set of your 351 heads.

 

[Boss Hugg]

It's not so much about just CFM flow numbers...velocity on small cubed street engine is what you will need, especially if you want to operate in the idle to 5500 range.

Does velocity really matter on port EFI like the OP seems to be going with? My understanding is the velocity keeps the fuel atomized as it comes from the carb, which is over a somewhat lengthy distance. With port EFI, the fuel is already nearly in the CC when sprayed, so....???

 

[duffymahoney]

I was thinking about the ford racing aluminum heads and my 5.0 HO cam. Would that be good? I want around town fun power. Not anything super high rpms.

 

[bmc69]

Or you can ship me a set of your 351 heads.

Sorry...They's already attached to something...;D

 

[blubuckaroo]

You mean big heads & small cam? I think you typed that backwards.
Because with a big cam and small heads you have a bad idle (well it can sound great) but you still don't have any flow to make any power.

OOPSIE!
Thanks! Fixed.
But my point is that both cam and port/valve size will effect the power curve independent of each other. If you're heads have large valves and runners, a smooth idling cam can become lopey, just as if it had a bigger cam.