Is your engine the 351 or a 302?

The Explorer upper intake flows the same as the Lightning upper does. All of the GT40 variants should flow within say 10cfm of each other. They have been tested many times over recent decades, by magazines etc. There is no notable difference in power between any of those, from the 93 Cobra upper,the Lightning upper, the 94/95 Cobra upper, or the six years of Explorer 302(96-01) uppers.

Some of the Explorer uppers have a mounting ear that is prone to breaking off, I forget which version it is. The 96 and early 97's have internal EGR passages like the older intakes, while the late 97 to 2001's all have external EGR, so no passages in those uppers.

The lowers also all flow the same except for the Lightning lower(I don't recall any comparison of that longer passage intake).

If you find them in local JYd's, the intake should cost maybe $50 per part, I'd look for those.

 

The lowers also all flow the same except for the Lightning lower(I don't recall any comparison of that longer passage intake).

We flow tested the stock Lightning lower all by itself at 273 cfm average, it is larger in area. Without a lot of work you can get it to 300 cfm average. Higher if you enlarge the cross section.......

 

its not really for anything of mine, i would just use aftermarket. its just more info id like to know for other peoples builds especially on the truck forums. i heard the different 302 GT40 flow pretty similar. wasnt sure how the 351 GT40 flowed if it was better/same/worse. and im not actually sure how well the 302-to-351 intake adapters actually work, i only heard of them used on making 302 blowers work on 351.

in the truck world people want to use the Lightinng intake because they hear it makes more low end torque than larger aftermarekt intakes. and the only truck direct swap performance intake is the Edelbrock 3881 which is about 900$ anwyays.

my thought was why spend $1000 on a Lightning intake if you can get a 302 GT40 intake cheap and a set of intake spacers to use them on a 351 for 300$. would cost half as much. but i wasnt sure if there would be any unforseen consequences of using the 302 intake with spacers instead of using the true 351 intake

what does a stock 302 GT40 lower flow at if the Lightning lower is about 273cfm? how bad would you think of intake spacers like these dampen flow?

AP-01 and AP-04

im jsut trying to find a 'poormans' 5.8 GT40 intake

 

5.0 GT40 style lowers flow ~205 cfm stock. Porting gets them up to 250-275 cfm depending on how much work is done. The upper + lower length then becomes the main restriction but it's also what builds that low-mid range torque. Not sure what size that adapter is, could be a 1250 or 1262 size.

 

Now we see the deal, I'd forgotten about how many of those adapters there are now. I have a pair of plates made 30+ years ago, to install a 4V Cleveland intake onto a 400.

The plates are aluminum, you can match those perfectly to the heads and intake. So those would not be a restriction at all. The port length would likely be about the same as a Lightning 351 intake. The 302 lower is the weak link, but some people like Tom here do a wonderful job improving them.

I would also go to an aftermarket intake. The 351 needs more air than a 302, and they both have similar stroker potentials. For a mild 351, the GT40 intakes might be a good alternative for less money.

 

The Explorer uppers, Tubular uppers, Factory Cobra uppers, Chinese Cobra uppers and each ones original lowers DO NOT flow the same. We have flowed and tested each of them many times and currently have all of them in our shop right now.
We have found that in stock form the Tubular upper and Chinese Cobra uppers runners flow the most. As far as imported lowers, the Chinese Cobras and factory Cobras flow the most but are also the thinnest so maximum flow cannot be achieved without welding. They tend to top out on a max effort port and welding at 360cfm average runner flow. The uppers once max ported with welding and material adding tops out around 335cfm.

 

They tend to top out on a max effort port and welding at 360cfm average runner flow. The uppers once max ported with welding and material adding tops out around 335cfm.

Lowers alone may max out at 360, uppers don't flow 335 without being significantly shortened (then you loose torque) or welded majorly, beyond a stock look - and then when you bolt them together they flow less than the lower flowing piece, it's just Physics.......... let's be honest and forthright here. Flow testing at 28" depression, the industry STANDARD is also best for accuracy, attested to by your own flow bench manufacturer..........

 

BTW, what should the desired ratio of flow be, for the intake versus the heads? Isn't is a larger amount by say 15-20% if you can get it?

 

oof. so then it would be a pretty significant loss of flow using a the 302 GT40 then. never realized the 5.8 GT40 lower was actually that much better. if even with porting it still is only par to the stock 5.8 GT40 but more complicated, i guess it kinda wouldn't really be worth it unless someone ported it themselves or wasn't that concerned about power but wanted the look.

do you have flow numbers on the stock truck 5.8 lower? i imagine it must be pretty terrible

this also makes me question my plan on using the GT40 on my future 347 build with AFR185 heads.

 

The lower Lightning intake is tough to find also, but is it that expensive alone?

 

ebay they're starting at 700$ for the lower alone. can buy a decent aftermarket complete intake for that much. never really understood why the cost

Gt40 Lightning in Intake Manifolds for sale | eBay

www.ebay.com

 

I'm sorry, ouch! I've seen the upper for sale on occasion, and rarely both, but I had no idea the lower would be that high.

 

that is why i had the idea of an Explorer intake from junkyard cheap and 300$ adapters might make a 'poormans' Lightning intake

 

Here's one that's been heavily modified, flows 318cfm bolted together and shortened that looks stock but on this 302 combo put down 360whp/355wtrq on a Dynojet.

 

Here is why we don't race dynos or flow tests, this customer dyno tested at 305hp/351tq on a Dynojet with just a ported lower and a GT40 tube upper but ran 11.85 @ 116mph with a LONG runner setup. Flow is not the end all, be all of how a combination will run......... He weighed 3,300# race weight so that calculates to 392/398 ET/Speed based numbers.

 

305/351 from a 325 stroker running a TFS cam and AFR 185 heads running 11.85 at 116mhp is actually low in my opinion and just goes to show that porting the lowers only on gt40 manifolds leaves a lot of power on the table and this is why we never recommend just porting the lowers. Here's a Dyno of a stock bottom end 302 with a simple B cam, used out the box TFS 170s and one of our stage 2 ported gt40 manifolds with a rpm reducing 1" spacer. 310whp/347wtrq even though the dyno was stopped early and the car was pig rich at 11.85 to 1 air fuel ratio. Car runs 11.60s and still has factory ac. Like I said before, we have plenty of track results to prove more flow equals more go.
Make sure both the uppers and lowers are ported and flow tested on the gt40 manifolds and you will be ahead in the game.

 

We work on uppers as well as many have seen over the years, but we take a hard look at that point at better intake options. We just didn't see the results we wanted shortening the uppers compared to other intake options. I don't see a time slip or feedback there, just a dyno with no engine data. It's not easy getting good feedback along with data, and we try to capture it in forum and email screen shots.

 

That dyno test shows why at some point you look to go Holley, Victor EFI or other intake that will make more power and why we stopped doing shortening uppers. They just didn't do what we expected. You get o that point where it just makes sense to step up.

 

We have TESTED our way of doing the uppers and lowers vs out the box Holleys, RPMs, RPM2s, TFS R and Victor's on real world applications and in every situation the customer picked up power over the out the box aftermarkets. Not to say you can't make more power with a well ported aftermarket, just saying our way and results of porting these parts are not like typical porting. The amount of work we put into these things are not what you typically see others doing. That's what I'm saying. We have boosted guys running high 8s with heavily modified gt40 Cobras. We've already done what many say couldn't be done with these manifolds. Ad ti.e goes on we post more and more data showing what these many can do.
I've seen too many underachieving combos using aftermarket manifolds to not believe they too left a lot of power on the table.

 

Well, I think anybody running high 8s and using a modified GT40 intake is running slower than he could. Just my opinion........

And I guess a heavily modified GT40 intake should have been used for this race car ..........

 

Not at all. He picked up over the previous aftermarket manifold he had on it before. Don't worry as more data comes in more pro will be available and more people will see the true potential of what a properly ported gt40 style manifold can do and more people will save money while still make just as much power as they want too. All porting isn't the same. 👍