I was contacted in November of 2005 by Chris Napolitano, www.inertiasport.com/home.html, about porting a stock intake for his 88 Speed Density 5 speed Mustang GT that sports 3:55 gears. Chris wanted to use stock Ford parts and work them over to see what he could produce and build a fun speed density GT.
The base car was a VERY stock 88 5 speed GT hatch. Chris did a tune up and put some Flowmaster 2.5” cat-backs on the car and had a dyno run with no other changes. The car made 201RWHP/286RWTQ.
Chris contacted me to buy a ported stock upper and lower intake to be used on ported Thumper Stage III E7 heads that use GT40 1.85/1.55 size valves milled .040" that flow 218I/154E cfm @ .500". A Crower 15511 cam, Scorpion 1.72 roller rockers, a 70mm throttle body were purchased new and stock 24# injectors were used. FRPP 1 5/8” shorty headers were purchased along with an X-pipe and the Flowmaster cat-backs. This is a very common combination of parts that are well matched and use an off-the-shelf cam.
Chris got the car running with the worked and new parts but experienced some drivability issues that he thought was due to the speed density computer. Later, it was determined to be the distributor. Since the car ran great at wide open throttle, Chris decided to have a dyno done with the current speed density combo. Below is the stock and speed density dyno curves, done at the same shop and SAE corrected.
The Car made 261RWHP/297RWTQ in that form. This is very close to what I consider about as high a peak HP number as you will get with worked stock parts and off-the-shelf cam from anyone but a factory stock style full-race effort. I’ve also seen 255RWHP/311RWTQ from a very similar combo with a Steeda #19 cam in a 95 car (Rio5.0 – results in the Photo Galleries on stock intake results on this site). Can you make more? Yes with professional help and expensive parts including a custom cam, but this is about what you can expect from the modified stock parts and off the shelf cam many of us use. One customer of mine recently made 272RWHP/327RWTQ with ported E7 heads (1.90/1.60 valves) that flow 228cfm/182cfm and a Buddy Rawls custom cam with one of my ported upper intakes and a 60mm TB (see 7/20/06 update below)
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The dyno graph for the stock combination and the speed density modified combination on Chris's car is below.
As mentioned, the car was experiencing some drivability problems so Chris had the car converted to MAF and had a 77MM Pro-M air flow sensor installed along with a A9L computer while retaining the 24# injectors. It was during the MAF conversion that the real problem, the distributor, was found and fixed. Chris then had the car dyno tested again with the MAF combo. The car put down 254RWHP/300RWTQ. Here is the dyno graph from that session.
I made grids on the dyno sheets and took off the data to put in a spread sheet comparing the curves. This is the first time I’ve had a customer do the speed density and MAF tests on the same car. Here is the graph and average numbers through 5,500 rpm. You can see that modifying the stock parts made both modded combinations loose low-end torque to the stock intake, but that all ended at about 3,200 rpm where the power of the modded parts really started to make power. What’s very interesting about this comparison is how the MAF made more torque down low but less up top in the rpm band. It averaged 2 more lb-ft and made the same average HP, but the torque curves were significantly different. For this car, that might suggest the speed density tune was lean in the lower half of the rpm band and a little more rich in the upper rpm band when compared to the MAF tune. The cars were tuned for best overall timing and fuel pressure on both dyno runs, so both should be close to optimum within the capabilities of a stock computer and an adjustable fuel pressure regulator.
Don’t make the mistake of generalizing this test – this may not come out the same on another engine run both speed density and MAF.
What the numbers don’t tell is how fun the car was to drive. Chris has driven many high performance cars much more powerful and faster than this little coupe, but he loves to drive this car on the street due to it’s very flat torque curve and snappy throttle response.
Update 7/20/06
I had a customer, Mike Hudson, recently test a ported stock upper and lower HO intake on a engine that included custom ported E7 heads that flowed 228cfm intake/182cfm exhaust along with a custom cam specified by Buddy Rawls who specializes in "restricted intake" combinations like these ported stock parts combinations. Other parts were a stock 60mm TB, 24# injectors, Hooker Super Comp 1 5/8" long tube headers, 76mm C&L MAF, and a Kieth Schuster tune/chip in Arizona with temperatures over 100°F. I thought it would be a good indication of the upper limits that can be reached. This power would undoubtably gained 5-10HP by using a 65mm throttle body in place of the stock 60mm unit, but Mike went from the ported stock upper to a VERY worked over "race" ported stock upper intake that I did for him to test (see 7/22/06 update below), so a test with a 65mm throttle body on the ported stock length upper was not done. The graphs show the first untuned power level and then the second graph is after the tuning was complete.
Here is the flow test of Mike's heads:
Update 7/22/06
As a final step in this article (I think), I wanted to post up some results from the efforts of shortening a stock upper intake about two inches to see what affect it would have on power. I was contacted by James Lawrence of Promedia about supplying a ported stock intake for a budget Fox car they were putting together to have some fun with at the track. James found a cut/welded stock upper intake on ebay (if I remeber correctly) for cheap, bought it and had it sent to me for evaluation. Once I had it and took some pictures, James decided that it didn't really look "stock" and may not fit with the true spirit of their efforts. He decided not to use it and I supplied him a ported stock upper and a ported M3 lower for the project. The results are to be published in the October 2006 edition of Race Pages.
So, I had this intake that had very visible welds and a funky "custom" cover for the upper bolts. In about the same time period, I was also contacted by Mike Hudson (cleanLX on the major Mustang boards) about an M3 lower and ported stock upper, so I decided to ask Mike if he would be interested in experimenting with this intake. Mike was putting together a "stock" combo that included Power Heads that flowed 228cfm/182cfm along with a Buddy Rawls custom cam. Buddy has a particular interest and history in supplying "intake restricted" combinations. Once Mike got some valve spring height issues taken care of on the newly purchased Power Heads, he was ready to put the car back together.
Here is a picture of the intake as I received it from James next to a stock intake.
Since Mike wanted some measure of "stealth" for his car, I put WAY too much time into this intake to make it look more stock and to open it for a 65mm throttle body, ported the throttle body runner bolt "pinch" area and did some porting/matching to the lower. The runners in the upper and lower were NOT "hogged out" and retain pretty close to the stock cross section. The advantage of this intake, if any, was to come from the shorter runners. Here is what the upper looked like when I shipped it to Mike and then what it looks like on his car:
In the 7/20/06 update you saw what Mike's combination made with the M3 lower and a ported stock upper intake with a 60mm throttle body. Once he had that baseline down, he swapped on the shortie to see what would happen. Rear-wheel horsepower jumped 8HP right off the bat. Once tuning was done and he switched over to a 65mm Ford throttle body, the little intake had bested the stock length intake by about 15 horsepower and lost no real torque. If the 65mm throttle body had been used on the stock length upper intake, I think it could have hit around 280RWHP. Below is a graph of the final totals, 292RWHP/325RWTQ in 113.38 degrees of heat, 5% humidity and a 28.98 baro in Phoenix where Mike lives. This graph actually has the progression of this effort with both intakes so you can see how the power reacted to the intake/throttle body changes and tuning.
1-21-08. I finally got around to graphing the HP/TQ differences between the long runner ported upper and the short runner ported upper at each 100 rpm increment. Below is the graph. As expected, we lost low end (not too much on average) and gained top end.
Mike's goal was 290-300 RWHP so he was happy, but he's going to wait for the heat to pass to take the little coupe ("mouse") to the tuner for some final tweaks and then to the track in September/October to see what it will do. Mike got his stock engine coupe into the 12s with some exhaust work and good driving. Personally, I hope he gets a 11 second slip from this combo. I wish him luck!
This shorty intake probably has about ~30 hours of work in it by everybody who worked on it. I have since developed a method to shorten them that is less time consuming and takes about 15 hours to do. You can see one I did in the tech article on porting/shortening stock upper intakes.
Update 12/16/06
I had a customer take one of my ported stock intakes send it to Extrude Hone to get the runners polished up before he put it on his ported GT40 head combination. Here is his combination and the results of his first dyno tune running speed density:
Later converted to MAF and here is the dyno after the conversion
Update 3/23/07
I don't know if this is the final chapter in srad2drag's quest with stock Ford parts, but he switched from a ported stock intake to a mildly ported Explorer intake and got the car re-dyno tested. Below is a compilation of all three test curves (speed density, MAF with ported stock intake and then with the Explorer). The result is exactly what one would expect. Below 4,500 rpm, the Explorer gave up significant torque and power to the ported stocker and made more power above 5,000 rpm. Over all, AVERAGE power from the start to 6,000 rpm is very close to the same.
Update: 10/29/07
Dan Drummond contacted me in March of 2007 to port an M3 stock lower intake for him. He wanted 300RWHP and 11s from a stock intake. He opened up a stock upper for a 70mm throttle body, gasket matched the upper to the lower and used the ported M3 that flowed right at 250cfm. Below is the first email I got from Dan explaining his combo and the dyno results.
Dan recently sent me an email with his track results - hes running 12 teens with some more tricks to go..........
