Mid Output Intake Question

Topic: Mid Output Intake Question (Read 6188 times) previous topic - next topic

Mid Output Intake Question

Reply #15 – November 03, 2018, 12:25:47 PM

Vintage is exactly right.

I have some pink top bosch injectors and a speed density HO computer laying around somewhere I'd be willing to part with if you needed them. Maybe a speed density HO camshaft too just PM me.

Mid Output Intake Question

Reply #16 – November 03, 2018, 12:46:20 PM

My buddy has what he thinks is an early 90's cobra roller cam he says he'll just give to me. I'll hit you up about the computer and injectors, Outsidedog. You guys have convinced me to take the build farther since I already have a lot of the parts. I was also able to get an explorer GT40 upper and lower, along with new fuel rails for $45 yesterday. They are very clean and recently painted as well. I think I got a killer deal. Any suggestions on which rockers and pushrods to buy?

Mid Output Intake Question

Reply #17 – November 03, 2018, 12:50:40 PM

I meant roller lifters, not rockers

Mid Output Intake Question

Reply #18 – November 03, 2018, 01:08:31 PM

As with the HO cam, the factory Ford roller lifters are completely fine to utilize in used condition assuming they came from a clean, non gunked up engine. Ford designed these for a very long service life. I've tore down well maintained HO motors with over a quarter million miles on the factory roller lifters. Looked nearly new and still functioned perfectly fine. Oil changes every 3K miles is the reason.

Like anything else new or used that goes into your engine, they should be clean, closely inspected. I do this with brand new oil pumps, roller rockers, gaskets, everything. I have rejected new, out of the plastic, parts before because of defects.

You did great scoring the explorer intake for under 50. Go out and find some of the regular 3 bar GT40s for under $100 so you can use regular headers and you might even make OutsideDog cry!

Mid Output Intake Question

Reply #19 – November 03, 2018, 01:57:34 PM

I do envy a nice budget build haha and I'll help out however I can. (I sent you a message CowboyKiller) You don't need thousands of dollars to have a solid fast everyday driver just a little patience and a place to take stuff apart.

Mid Output Intake Question

Reply #20 – November 03, 2018, 04:10:18 PM

Used HO cams are usually good to go assuming the engine wasn't oil starved (mine weren't).

I'll look for it in a bit, let me know if you want it, like I said, if it's here, you can have 'er for the stamps

Mid Output Intake Question

Reply #21 – November 03, 2018, 10:13:35 PM

Quote from: TheCowboyKiller;467891

CougarSE, you mentioned that the stock computer couldn't handle these mods. Which mods do you think are taking it over the edge and what do you think could be scaled back to make it work?

Anything you do to increase airflow, basically every performance mod. The old HO speed density systems could make good power and were tunable but had no provisions to adapt like the MAF cars did. The combination of heads and intake are your worst offenders but the most desirable for performance. Adding the Cobra cam is a great Idea, even with stock 1.6 rockers it has a greater profile than a stock HO cam. At this point you need to run a MAF system or HO speed density with the fuel pressure turned up or call an SCT shop and tell them what you have and get an HO computer tuned. When I say fuel pressure turned up I mean running the 19lb injectors too. This is pretty much the setup I had on my car at first and it ran incredible.

Mid Output Intake Question

Reply #22 – November 04, 2018, 01:40:08 AM

Stock computer on sd can compensate up to 10% for general wear and tear. We have e10 which takes up 7% for fuel correction, so you really only have 3% to compensate as far as fuel goes.

I like e10, I bump the timing up to like 14 or 16° and get a bit of the power back.

Mid Output Intake Question

Reply #23 – November 04, 2018, 09:06:13 AM

I'd like to pick your guys brains about this cam I just picked up from my buddy. It's definitely a Mustang cam because it's got ZE engraved between the the distributor gear and the first lobe. The only other marking it has is on the last cam bearing journal (flat side). There is an etching that says "20:52" and underneath it says "02/16/94". I assume these are time and date stamps. Being that I can't find any other markings on this cam, how can I tell if it's a Cobra or HO cam, and does it matter? I was able to find these specs to compare the two but can't tell how different these cams are from one another:

91-95 GT:
Lift: .278 intake, .278 exhaust
Duration: 276 intake, 266 exhaust
Overlap: 39 degrees, 19.51 factor
Lobe Center: 116 intake, 115 exhaust

93-95 Cobra:
Lift: .282 intake, .282 exhaust
Duration: 270 intake, 270 exhaust
Overlap: 33.5 degrees, 15.24 factor
Lobe Center: 115 intake, 121.5 exhaust

Another question: The cam has been sitting for awhile and has acspoogeulated some surface rust. If I were to use this cam would it be recommended to clean in up in my blast cabinet using walnut shell?

Thanks!

Mid Output Intake Question

Reply #24 – November 04, 2018, 01:21:06 PM

Quote from: Haystack;467909

Stock computer on sd can compensate up to 10% for general wear and tear. We have e10 which takes up 7% for fuel correction, so you really only have 3% to compensate as far as fuel goes.

I like e10, I bump the timing up to like 14 or 16° and get a bit of the power back.

While I would like to see something to confirm any kind of adaptive strategy for speed density the combo he is describing is way beyond 10% a stock HO EEC e7 headed 302.

Mid Output Intake Question

Reply #25 – November 04, 2018, 01:21:08 PM

93-95 Cobra cam and 86-95 HO cam are so close that a SD HO computer won't care which one you use.

Mid Output Intake Question

Reply #26 – November 04, 2018, 02:02:36 PM

As the story goes, during the devlopment phase of the Cobra engine program, the Ford engineers were looking to restore some of the torque lost compartively to the regular HO engine due to the higher flow capacity Gt40 heads and manifold being used.

If you compare the numbers, it bears this out. The lift at the lobe is pretty much the same, although the Cobra is multiplying this lobe lift by 1.7 rockers instead of the standard HO 1.6 rocker. This gives it an effective valve lift around .479" as compared to the HO's 444". The additional valve lift helps flow only as much as the valve/port/chamber allows for. Since the Gt40 has a slightly larger as-cast intake port and a 1.84" intake valve vs the 1.78" intake valve, it is better suited to benefit from the additional airflow across the valve, from the added lift.

The 1.7 rocker ratio has the added benefit of speeding up the movement of the valve. Effectively, it is a way of adding a more aggressive ramp on the lobe of the cam without actually putting the aggressiveness where the roller lifters feel it. Overly cautious concerns about valvetrain noise if you ask me, but noone from Ford asked me, so there you are. The valvespring do feel some additional strain from the added rate and lift of the 1.7 rocker ratio but it is easily handled by aftermarket springs. If you look at the factory Cobra heads, they employ a different valvespring with an inner damper spring that the HO heads do not.

Next, duration. Duration on the Cobra cam has been shortened on the intake side and extended on the exhaust side. Why? Again, to better suit the flow characteristics of the cross sectionally larger Cobra intake and heads. The Ford engineers were aware that adding the larger Gt40 parts was changing the negative pressure wave in the intake tract. The cam revision is their attempt to retune a wave that worked with the larger ports and plenum and maintain velocity across the valve. On the exhaust side, since additonal airflow and fuel would create more power and more exhaust gasses, the duration of the exhaust was lengthened keeping the exhaust valve open slightly longer to ensure sufficient time for the piston to push enough exhaust past the valve that it wouldnt remain in the cylinder and spoil the next incoming intake charge on the subsequent combustion event.

The cam overlap was shortened also. This is the brief time where both the intake and exhaust valves are open, or overlapping. The intake on its way to opening, the exhaust on its way to closing. This crossflow effect helps draw some of the intake charge into the cylinder due to the vacuum effect of exhaust scavenging. Basically, working in concert with the pressure drop of the piston, on its way down, creating a pressure drop in the cylinder that ordinary atmospheric pressure immediately attempts to fill or equalize, which brings the air and fuel in past the open intake valve. There is a downside to excessive overlap, and it can cost power due to some lost intake charge, compression, etc. Shortening duration on either intake or exhaust lobes also shortens overlap.

Mid Output Intake Question

Reply #27 – November 04, 2018, 02:23:38 PM

Not sure if this will be of any help..

Edit, apparently I'm missing the chart that would be "page 1"....
I saved this from somebody here, maybe Paul posted it many many moons ago?

Mid Output Intake Question

Reply #28 – November 04, 2018, 02:31:05 PM

Fellas, speed density uses fixed lookup tables for its timing and fuel strategy for a given set of conditions including load,rpm,manifold pressure, etc. Its stuck on picking a strategy from the lookup tables, based on comparing the info it is seeing from the various engine sensors, it then selects its strategy. Operating under either closed loop or open loop, it cannot "adapt" or choose something outside of what is contained within the preprogrammed lookup tables it has to work with. Thats it.

That said, the speed density system is plenty capable of running the engine in a very wide range of conditions and climates which is a testament to the strength of its programming and design. It was state of the art in the eighties and still an effective means of engine management today. Yes, it has limitations and once reached, a change to the mass air system is absolutely the right move.

But for what the OP has repeatedly given for expectations and intended use of the vehicle, speed density will cover his needs and budget. Handily.

Mid Output Intake Question

Reply #29 – November 04, 2018, 06:08:06 PM

All that's moot anyway if he wants a cam that's above an HO or '94/'95 Cobra. The cam itself won't give a rat's ass whether it's speed density or mass air, long as it's HO or Cobra. BUT...if he wants to run higher flow injectors (over 19#) he WILL need to go mass air or else have a chip burnt for his EEC, and that means an SD1. I don't think the Mark 7 EECs had provisions for a tuner chip, unless they open them up and directly solder them to the board (i don't know).

And you're right, there's a hell of a lot of fast-assed cars running SD setups. For a country boy hundreds of miles from a tuner shop, I simply got what I needed and made mine mass air, probably came out money ahead, but the logistics was the deciding factor. When I did the build, money and time wasn't an issue.