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Discussion Starter #1
Ok, so I don't know a whole lot about this subject. I have done my research but I need definite answers before dropping more coin. I have a '93 Cobra with the stock block. Kenne Bell 2.1 blowzilla at 14psi and meth injection. 240lph fuel pump, 42lb injectors, 90mm maf and 75mm tb. It's running just a little over 400rwhp and same torque. Here is my delima... I need more power lol.
I want to add heads and cam, but I've read that too much flowing heads will have a negative effect on boost. Can anyone who has been there, done that, or is knowledgable help with a few questions? What heads should I use..and 58cc or 64cc combustion chamber size? 1.7 roller rockers? Is an E cam the best with boost? Thank you to anyone who responds.
 

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I haven't read your text but I imagine it's about this. lol The "negative" effect isn't actually negative though. Anytime you make a certain boost number, then let the engine breathe easier by doing heads, cam, intake, throttle body, headers, exhaust, etc., you'll effectively decrease the amount of boost the engine will see BUT you'll make more power.

Imagine taking a straw and blowing into it. you'll build up some amount of pressure in your mouth while forcing the air out. Increase the size of the straw and you can move just as much (or more) air without as much pressure in your mouth.

On supercharged engines, you'll see a decrease in boost pressure but an increase in power.

With turbo engines (since there is a wastegate that keeps the boost at a certain number), you just make a lot more power at the same boost level (but a higher mass flow rate).

The basic ideology is: anytime you make changes that would give you more power in an N/A engine, you'll get more power in a forced induction engine as well. Engines are Air Pumps. more air flow = more power.
 

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Indo-Canuck-Yankee
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Just try to keep your compression ratio below 9:1. Don't need to cam it up either, although an Anderson B-cam would be at the top of my list if I were going to run something other than the stock cam or the Crane 2031 I'm using. When you change heads, you'll need to completely revise your spark tables to take advantage of the new heads' combustion chamber efficiency, so plan on that.
 

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I would suggest this combo:

AFR165s "Renegade" - Valves clear stock pistons, where AFR185 may not...TW heads are an option too, but not well versed with them. The AFR165s are strong little heads...had a buddy make 322whp/340wtq with a TMoss port-matched lower, Ed Curtis cam and GT40 tubular upper on a stock 302 short block...imagine 14psi on top of that!

Comp Cams XE274HR
-274/[email protected]"
-224/[email protected]"
-.555/.565" w/ 1.6
-.590/.601" w/ 1.7
-112 LSA
-108 CL

Roller Rockers - Your choice here as you see the different lift values above between the two.

Send your lower intake out to Matt @ TMoss for a max effort w/o welding extra material to the runner(s)...ie #1 He'll get you close to 300cfm avg across all the runners.

Swap your 75mm TB out for a 90mm Accufab.

You'll drop boost with the ported lower and higher flowing heads, but pick up some with the larger TB...but overall my guess is you'll settle in around 12psi by just being more efficient down stream from the blower. I would estimate 475-490whp and of course similar tq. You may need some fuel system upgrades at this point too...namely the fuel pump(look into an Aeromotive 340).
 

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Discussion Starter #5
Thanks for the advice and suggestions guys. 92vert, I was leaning toward the AFR 165's after doing a lot of research. I wanted to kinda stay with the GT40 theme, but I would lament not having the performance the AFR's would provide. I'm just going to keep all the stock cobra parts in the event I want to restore the car back to factory. I don't want a crazy cam and still want a mild mannered street car. Would a 90mm TB really make a noticeable difference and not affect driveability you think?
 

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I ran an AFM B-21 cam with my KB/stock 302 combo as well as a custom cam from Freezy with my max effort KB/R-337 combo and both had excellent street manners(although Freezy's had a nicer hit to it!). You said you were looking for more power and so I took an earlier combo of mine that made 450hp and suggested some hindsight upgrades that I think would get you closer to 500hp or almost a 90 horse bump over your current set up. It can be a slippery slope to increase hp while maintaining "mild street manners", but up to 500whp on a pushrod KB combo is definitely doable.

PD blowers need all restrictions removed across all components of the inlet. The largest conical filter you can fit in the inner fender, mated to a LMAF or Pro-M 80 meter, attached to an an AFM Power Pipe, then to a 90mm TB is about as good as it gets for OTS components. The Flowzilla has a 90mm opening at the TB so anything smaller is a restriction and HP that's being left on the table. IIRC going from a 75mm to a 90mm is worth about 1-1.5psi...which can be worth about 15-25whp at your boost level. The 90mm TB is more touchy to drive because it lets so much more air as the blade begins to open, but I drove my '92 for years with one and it really wasn't a problem at all.
 

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Discussion Starter #7
ok, one more thing..... Should I go ahead and get a stronger block when I do all this or hang tough with the stock one? I'd like to be somewhat conservative with money, but I love my car more than my woman, so I'm willing to spend more money on it if I have to.
 

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ok, one more thing..... Should I go ahead and get a stronger block when I do all this or hang tough with the stock one? I'd like to be somewhat conservative with money, but I love my car more than my woman, so I'm willing to spend more money on it if I have to.
Lol if you're talking about aftermarket block being an option, the whole heads/cam/intake deal is sort of a moot point.

That block will need machining and if you're wanting to keep your stock bottom end together for resale, you'll need a new crank, pistons, and rods. At that point you'll justify doing a stroker kit since the block needs machining anyway and the added cost over stock stroke isn't much. This means you're probably going to want a Dart 331 stroker where 165 heads will be too small so you can look at the 11R trickflow heads (205cc) and use your Tmoss ported lower manifold on that. The cam can be a hard hitter, like an XE282HR or a custom grind since your new pistons and heads will allow for large lift.

This is going to make you a LOT more power than you're bargaining for, so fuel system upgrade is a must, trans upgrade will be a good idea, 31 spline rear diff and axles, and any suspension you don't already have.
 

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Indo-Canuck-Yankee
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I ran at the 500 hp level for a long time with the stock block. My thinking is that as long as the engine is not subjected to violent loads it should be alright. You could try running a main girdle, but not entirely sure how useful they are.

In total agreement about the transmission and rear axle upgrades as well. I was twisting the axle tubes in the housing and crushing the carrier bearings in the stock axle before upgrading to 31-spline, carrier bearing girdle, welded and gusseted tubes. The transmission will let go rather suddenly, so I'd just run that until it died.
 

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Your stock shorty should be fine up to 500rwhp/tq...assuming your tuner keeps it safe and puts safe guards in place with the methanol.

The rear end in your Cobra is basically a 4-lug SVO set up. I ended up putting that R-337 with an Si Trim in my '89 Saleen making 690h/680t and twisted the SVO 5-lugs axles "some"! lol I had custom 31-spline SVO length axles made shortly before I sold the car. So I'm really unsure as to how much yours can handle?? Probably depends on how you drive too?

An aftermarket block is a bit of a waste with a KB 2.1 as that blower only moves about 950-1,000 cfm and the manner with which it does on a pushrod makes 550whp about max without some extra assistance(like a 50h shot). So that's a lot of coin for 50-60whp more than what I'm suggesting.

I would try the path I suggested and enjoy it...otherwise it's a snowball of supporting hardware beyond that! #trustme


Sent from my iPhone using Tapatalk
 

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Twin Screw
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Afr 165s, Steeda blower cam, small roller rockers to fit under the factory vc. After market ones dont play nice with the kb. Accufab 90mm ,80mm ProM shorty and methanol if you dont have it.TMoss ported cobra lower. People will say stock block is good to 500. But if your making 400+ to the wheel your at 500 at the crank. You dont want to go down that road to a dart block. At that point the 2.1 will work, but a 2.8 is ideal, and the 165s go out the window.I dont understand your comment on negative affect on boost. Boost is a restriction reading. You could have 14psi now, do the upgrades, same pulleys on motor and see 10psi, but have 80-100 more hp. Dont worry about boost numbers, worry about end result numbers at the wheel.
 

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Discussion Starter #14
Ok so I'm gonna go with AFR 165's and either an Anderson B cam or steeda and have the intake ported. I'll let you know if the block holds....and for how long. Thanks guys for the input.
 

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Afr 165s, Steeda blower cam, small roller rockers to fit under the factory vc. After market ones dont play nice with the kb..
Can you expand on this? I not sure I get what you are saying.

Picture below is of AFR 220 Renegade heads with 1.7 Jesel roller rockers, and it all fits under the stock valve covers...



You can see the polished stock valve covers on the work bench in the background.

Valve covers on the engine,

 

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Twin Screw
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Some rockers are bigger than others. A taller cover wont fit under a 2.1 kb. With a gt40 lower. Your motor looks to have neither. Im speaking of the stock type stuff which is what the op was asking about.I had to use ss comp cams units to fit under my stock covers. Op has stock type setup ,AFR 165s, GT40 cobra lower etc. You have 220s and a Trick flow lower. Different dimensions than stock type stuff. Totally different.
 

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I could take the trick flow lower off and install a GT40 lower and then install a 2.1 KB and it would all fit due to the stock valve covers. I don't want to do that and lose the power though, Lol I guess the point I was making was that even with big heads and a 1.7 ratio roller rocker, you can still get stock valve covers to fit if you source the right parts. And these covers work even with over .700 lift at the valve, so the rocker arm is articulating quite a bit.
 

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Some rockers are bigger than others. A taller cover wont fit under a 2.1 kb. With a gt40 lower. Your motor looks to have neither. Im speaking of the stock type stuff which is what the op was asking about.I had to use ss comp cams units to fit under my stock covers. Op has stock type setup ,AFR 165s, GT40 cobra lower etc. You have 220s and a Trick flow lower. Different dimensions than stock type stuff. Totally different.
I could take the trick flow lower off and install a GT40 lower and then install a 2.1 KB and it would all fit due to the stock valve covers. I don't want to do that and lose the power though, Lol I guess the point I was making was that even with big heads and a 1.7 ratio roller rocker, you can still get stock valve covers to fit if you source the right parts. And these covers work even with over .700 lift at the valve, so the rocker arm is articulating quite a bit.
Not that I know this for sure about Renegade 220's, but I know trickflows and other aftermarket heads have a valve cover rail that is raised compared to stock, so it forces the valve covers away from the rockers (providing room obviously). This could be why Saleen's stock covers work on his combo with the 220's. idk what the 165 rails look like in comparison to the stockers.
 

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And then there was this build, AFR 205 heads with a 2.8L KB with stock valve covers.

 

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Twin Screw
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I could take the trick flow lower off and install a GT40 lower and then install a 2.1 KB and it would all fit due to the stock valve covers. I don't want to do that and lose the power though, Lol I guess the point I was making was that even with big heads and a 1.7 ratio roller rocker, you can still get stock valve covers to fit if you source the right parts. And these covers work even with over .700 lift at the valve, so the rocker arm is articulating quite a bit.
Thats not what I was saying. I was saying some aftermarket rockers dont fit under the factory covers. Hence you would need differnet covers. The 220s have a different height in terms of where the the cover rail is, if Im not mistaken vs factory style or a 165 afr.I tried Harland Sharp on mine, they didnt fit under the factory VC. Mine is a 94. On the 363 I bought the drivers side cover rail is machined down vs the pass to clear the KB. That picture you posted, I bought that motor it sits in my garage and the vc is machined down on one side. Shawn told me when I asked.
 
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