Mid Output Intake Question

Topic: Mid Output Intake Question (Read 6186 times) previous topic - next topic

Mid Output Intake Question

Reply #30 – November 04, 2018, 07:56:19 PM

Yep, thats true. The thing to keep in mind however is that if you look at the flow numbers for unmodified Gt40 heads is that they pretty much level off at a little over .400" valve lift. It hardly improves from .400 to .500 and lifting the valve even past that becomes really pointless. So with the stock cam having roughly .444 valve lift using the stock 1.6 rocker ratio, its right where the flow starts leveling off.

Honestly, I've always ported my own heads and intakes including more Ho and Gt40 heads then I care to recall way before I even considered swapping from an Ho cam to aftermarket. The low hanging fruit on the 5.0 are the cylinder heads and intake. Per dollar or per hour of labor, that is where the most impressive improvements to the entire powerband are to be had. The other benefit not often talked about is the reduced pumping losses and better fuel mileage that is attained with the improved efficiency.

Ironically, this also allows more of the fuel to be redirected towards increased engine power instead of being wasted overcoming engine pumping losses, with the increase being better the higher the engine speed is.

The stacking effect of gathering all these improvements together can result in an engine with the stock Ho cam that quite easily outpowers the engine with unported heads but with a performance cam. Not just at one rpm point but everywhere on the curve and by an embarrassingly noticeable amount when on the street or track.

Mid Output Intake Question

Reply #31 – November 05, 2018, 09:39:09 AM

Wouldn't let me add pictures in the PM so here's what I'll be sending you these are the injectors and computer I ran before I switched over to MAF. Also I had a Jet chip for this computer I'll send with it not sure it did anything performance wise but I have no use for it.

Mid Output Intake Question

Reply #32 – November 05, 2018, 09:39:50 AM

Mid Output Intake Question

Reply #33 – November 06, 2018, 08:06:49 PM

Thanks again for the hookup, Outsidedog!

Another questions for you guys regarding this swap. Do you guys generally leave the EGR system stock when doing this swap? If not, what do you need to change to keep things running smooth? I don't believe emissions will be an issue since I've had this car registered and inspected before and they gave me an emissions exempt sticker. If it helps to keep the system stock I will do that though.

Mid Output Intake Question

Reply #34 – November 07, 2018, 08:42:18 AM

When I did the swap from S.O. to H.O. I used a 70 mm bbk throttle body with egr spacer and left the egr on it and plugged in, actually passed emissions pretty easily too. Just retarded the timing and aired up the rear tires to 60 lbs.

Mid Output Intake Question

Reply #35 – November 08, 2018, 12:29:38 PM

Speaking of throttle bodies, I've been thinking a lot about which units to use here and I'd like to get ya'lls thoughts.

A) Since I'm upgrading to a GT40 intake I'm imagining I have around a 70mm opening to work with. That said, if I take advantage of the opening size is it worth spending the money on an aftermarket throttle body/EGR spacer? I'm sure that acquire a stock explorer combo would be cheap but it looks like getting the linkage right and having to re-route the air intake tube due to the different orientation of this setup might be a pain in the ass.

B) I could stick with a stock 87'-93' HO throttle body and EGR spacer for cost and simplicity sake. I've read that they bolt right up to the GT40 upper. Is this true and will I be sacrificing anything by using a stock 60mm size.

I guess the general theme of my question is, for my build what throttle opening size is ideal? 60mm, 65, or 70mm?

Mid Output Intake Question

Reply #36 – November 08, 2018, 03:16:35 PM

There is no appreciable power gains to be had by anything larger than a 87-93 Mustang 60mm throttle body and Egr spacer at your engine's level of airflow.

There is a place for larger throttle bodies but it simply isnt on near stock engines. Multiple independent dyno and track tests over the years have borne that out. Save your money for better, more effective mods and improvements.

Just as an FYI, the explorer upper intakes that I have measured have a stock throttle body opening of 67-68mm. Ditto for the Cobra uppers that I have measured. The additional size is fine for use with a stock HO 60mm throttle body and Egr spacer.

Vendors sell lots of throttle bodys for the same reason they sell a lot of cold air kits, its easy to bolt on and the customer convinces himself during the subsequent test drive that he realized a sizable power gain because he paid a couple hundred for it. Wouldve been better off throwin the $200 in a jar and putting some more with it each week or month to buy some good heads/intake and/or port work to same.

Mid Output Intake Question

Reply #37 – November 08, 2018, 07:27:12 PM

Sounds good to me! That's less money I have to spend, so I like it. I'll start searching around for a good deal on a stock HO throttle body and spacer now!

Mid Output Intake Question

Reply #38 – November 08, 2018, 08:43:18 PM

After you get it running what are your plans with it? Daily driver ? Any power adders or racing in it's future? Sorry if you already answered I didn't read back through the posts

Mid Output Intake Question

Reply #39 – November 09, 2018, 01:12:40 PM

If you're adding GT40 heads and a HO cam to a stock 86-88 short block be sure to check piston to valve clearance. Better to know if you need to cut some piston valve reliefs than finding out when you bend all the valves the first time you rotate the engine over :hick:.

Mid Output Intake Question

Reply #40 – November 09, 2018, 02:49:55 PM

I'll def check PTV clearance once I start tearing into this thing. My intentions for this car are for it to be a fair weather driver. I like how comfortable it is for long trips so I'll probably try to get some of that in too.

Mid Output Intake Question

Reply #41 – November 09, 2018, 09:23:46 PM

Right on man looks like you're well on your way, a stock 60mm mustang throttle body will be perfect. and let us know about the piston to valve clearance with that setup just so I know because I'm curious. I assume it will be fine but never done it.

Mid Output Intake Question

Reply #42 – November 11, 2018, 04:20:50 PM

It should def always be checked but I've done it years ago with an 86 GT. It had the flat top piston with no valve reliefs or dish. Using the stock 86 GT cam and Gt40 heads off a 93-5 Cobra. It ran surprisingly strong for a fairly basic bolt-on car using a ported HO lower and extrude honed upper intake. I still have that upper intake, come to think of it, haha.

Cowboy, you might want to shop around the cost of having a quick cleanup port job on the lower intake. Someone local and experienced should be able to pickup some torque and horsepower from the midrange rpm's to wherever your shiftpoint is at. Money well spent for a budget build. The intake is already off the car, there is no better to time to get it done then now.

Mid Output Intake Question

Reply #43 – November 12, 2018, 08:29:17 AM

What does this porting job typically cost?

Mid Output Intake Question

Reply #44 – November 12, 2018, 04:46:40 PM

You need to get ahold of Tom Moss and have him port it. He ported my lower Cobra intake and it was like night and day on the dyno. I believe his email is mosstpsa"at"sbcglobal.net (put the "at" in there in lieu of the symbol) and this should direct you to their website (took a minute to load up).

http://tmossporting.0catch.com/