FRPP King Cobra vs King Cobra Sort of...

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FRPP King Cobra vs King Cobra Sort of...

Post by cgrey8 »

I'm in the parts gathering mode again for when I finally get the 331 done. It's a long ways off, but as I get a few bucks here and there, I'm buying the various pieces of the puzzle that I think will speed up my engine swap when I get the 331 done. One of the pieces I picked up last week was another flywheel. It's the same PN as the one I'm running now...and I got it for the same exact price too. The better news is this one is absolutely brand new so there's no resurfacing required for this one. The seller took it off a crate engine that he's running an automatic on. So he didn't need it.

Being it's brand new, I think it'd be a slight waste to go back together with the same clutch I'm using now on a brand new flywheel. So to compliment a brand new flywheel, I got to looking at King Cobra clutches on eBay and I found something interesting. Astro Performance (same people that sell the 500ft-lb upgrade kits for the T5s) sell their version of a King Cobra clutch. Its supposed to have similar clamping force as the Ford Racing Performance Parts (FRPP) King Cobra Clutch as well as the same stock-like feel the KC offers. However unlike the FRPP KC kit, theirs is a good bit cheaper. Typical FRPP KC kits from Summit Racing are ~$210-220 plus s/h for a pressure plate, clutch, and TOB. I found some places on eBay selling them as low as $170 inc s/h. The Astro Performance clutch kit is $155 inc s/h for pressure plate, clutch, TOB, pilot bearing, and alignment tool.

Obviously Astro sells reputable stuff and has made a decent name for themselves in the aftermarket T5 arena as well as a few others. But that doesn't mean some of their stuff isn't junk. I'm all about getting a bargain, but I'm struggling with experience learned from the old saying You get what you pay for! So before I make a purchase, I thought I'd ask opinions from others that might have used their stuff.
...Always Somethin'

89 Ranger Supercab, 331, ported GT40p heads w/1.6RRs, Crane Powermax 2020 cam, ported Explorer lower, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, A9L w/Moates QuarterHorse, Innovate LC-1, James Duff traction bars, iDelta DC Fan controller

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Re: FRPP King Cobra vs King Cobra Sort of...

Post by Dave »

I've delt with Tony down there when I had my T-5 converted to the S-10 tail-shaft. He does a lot of work also with G-Force (or did). Very knowageable on the T-5 and swaping parts. I would have no problem dealing with him again.
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Re: FRPP King Cobra vs King Cobra Sort of...

Post by MalcolmV8 »

I have not used either but my bit of advice is make sure you check on drive-ability. As in how the pedal engages on the street. I've spent upwards of $500 on clutches that hold 800 rwhp only to find they clamp down like a mofo when engaging and there's no slipping the clutch. Vehicle shakes and shudders and is plain horrible on the street.
92 302 Ranger - sold
94 302 Ranger AWD - sold
07 BMW 335xi - tuned, boost turned up, E85 - sold
04 911 TT - to many mods to list. Over 600 All Wheel HP on pump gas - sold
2015 Coyote - daily driver
03 Cobra - 2.3 TVS on a built 12:1 CR motor with ported heads, cams, long tubes etc.
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Re: FRPP King Cobra vs King Cobra Sort of...

Post by cgrey8 »

I asked about that specifically, and they said that this is not a high stage clutch. It's designed for up to 350hp and to be their version of the King Cobra. And as such, its designed to be a stock like feel. The guy I talked to (an Astro dealer) said its their most popular clutch for Fords. But I also take that with a grain of salt since that's coming from the guy that is trying to sell me something.
...Always Somethin'

89 Ranger Supercab, 331, ported GT40p heads w/1.6RRs, Crane Powermax 2020 cam, ported Explorer lower, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, A9L w/Moates QuarterHorse, Innovate LC-1, James Duff traction bars, iDelta DC Fan controller

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Re: FRPP King Cobra vs King Cobra Sort of...

Post by MalcolmV8 »

Sounds good. Although with a 331 stroker aren't you going to exceed 350 hp? oh and if you haven't already purchased the stroker kit why not go 347? is it a lot more expensive? If I was going to all that work and expense building a stroker I'd go for broke and make it as strong as I could :)
92 302 Ranger - sold
94 302 Ranger AWD - sold
07 BMW 335xi - tuned, boost turned up, E85 - sold
04 911 TT - to many mods to list. Over 600 All Wheel HP on pump gas - sold
2015 Coyote - daily driver
03 Cobra - 2.3 TVS on a built 12:1 CR motor with ported heads, cams, long tubes etc.
MD Racing Lean Protection Module
E85

Tuned by MD Racing

https://www.youtube.com/c/MalcolmV8
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Re: FRPP King Cobra vs King Cobra Sort of...

Post by cgrey8 »

I've debated that a number of times over the past few years with LOTS of people. And here's why I decided on the 331...

For starters, this isn't a MAX HP build. It's a high torque/high efficiency build. One of my complaints since the swap has been the lack of off-idle torque that the 302 has. While the 302 is capable of very impressive HP numbers, at low RPMs, it's limited in what it can do mostly due to its displacement. The two options to improve low RPM torque production are stroking, boosting (super/turbocharging), or a combination of the two.

The problem with supercharging to me is the supercharger is a parasitic load on the engine that you accept for the added power it provides. You also have to build the compression of the engine lower to make room for the added air that'll be shoved down the engine's throat at WOT. This reduced compression really kills fuel economy at the cruising RPM/Loads unless you have a VVT/VCT engine that can adjust the cam events to recoup some of the lost compression...and 302 blocks don't have that. Thus supercharging is not something you do on a Windsor engine when you care about maximizing fuel economy.

Turbocharging is far better than supercharging. It makes use of left over energy the engine can't make use of at the end of the compression stroke. So in effect, it is recouping energy that otherwise would've been lost into the exhaust pipes. But in an off idle situation where airflow isn't high, the turbo isn't going to be much help. Turbos need flow to build pressure. They also have lag associated with them. When properly sized, the lag is minimal at running RPM/Loads, but at off-idle, even an undersized turbo is going to have a substantial lag. Add to this, the benefit of turbos is generally only seen at high loads. Their benefits are lost at cruising conditions unless you are turbocharging a diesel. Diesels can make use of turbos at any RPM/Load. And just as with superchargers, you still have to downgrade the compression of the engine which again is a cruising fuel economy sacrifice without VVT/VCT.


I've also heard others say slap a bigger cam in the engine to get more out of it. That's a bad idea too. Bigger cams do make more power, but not off-idle. Most upgrade cams actually hurt off-idle performance. The wider the off-the-seat duration and the narrower the Lobe Separation Angle, the worse off-idle torque gets due to lowered Dynamic Compression Ratio. So, even though I will be going with an aftermarket cam, it'll be a mild, but high lift truck-oriented cam. Most all aftermarket cams (except FMS cams) have much faster ramp rates so they get the valves open faster and further than stock cams. At high RPMs, they act bigger than they really are because of this. So when you don't need ultra-radical, this allows you to dial back the duration a bit and run a milder cam without sacrificing everything on the top end. Mild aftermarket (truck/towing/RV/efficiency oriented) cams often have less off-the-seat duration (duration@.006" lift) than stock GT cams so they improve off-idle performance while at the same time improving the top-end as compared to the stock cam. It's an improvement across the RPM range. So, I'll be going with a Comp XE258HR-12 or a Crane Powermax 2020. Both cams absolutely require aftermarket springs and retainers due to their high lift and fast ramp rate.

I've often heard the argument that high lift is a waste on stock heads like what I'll be using. That's not true. While you don't gain more flow as the valve is opened further, you don't generally loose significant flow either. So what the higher lift is doing is getting the valve to max flow lifts earlier, holding the valve at or higher than the max-flow lift, then closing the valve down below the max-lift point much later than a lower lifting cam would. At low RPMs, this means nothing. However this is a huge benefit to extending torque production into the higher RPMs. This is what makes the engine still usable at 5500RPMs vs absolutely falling flat on its face above 5000.

So with a mild cam, I'm left with displacement/stroker options to attain my goals of improved off-idle torque while improving fuel economy/efficiency. As it turns out, stroking is beneficial in a number of ways. As pointed out, the mainstream choices are 331 or 347. Both cost about the same amount for the kit so its no surprise that the 347 is the more popular stroker kit for people that ARE only interested in max HP. The 331 and 347 pistons are lighter than stock 302 pistons, but they need that improvement since the pistons are traveling faster and further in the bores for any given RPM as compared to the 302. At lower RPMs, the lighter weight pistons are an efficiency benefit in either kit. Both kits increase compression due to the higher displacement and longer stroke. However the amount they increase compression is different...and relevant to me. And so this is where a discussion of what makes the 331 better for me than the 347.

The benefits of the 331 are hidden, but there. The 331, when using the 5.4" connecting rod has nearly the same Rod-to-Stroke Ratio (RtSR) as a stock 302. Most people that are performance focused pooh-pooh the whole focus on RtSR since the benefits and losses at WOT are negligible and are dwarfed by the added power the extra cubes gives the 347. But back to looking at it from a longevity and fuel economy standpoint, the RtSR is still relevant. And since I'm not looking for max HP, but rather max efficiency with improved off-idle torque, the 331 wins here. That's not to say the 347 wouldn't produce more off-idle torque. It is a higher displacement. I believe the benefits of the better RtSR are significant enough that I prefer the 331.

The 331 also has never had any complaints or issues with oiling. Most of these issues in the 347 kits have been improved and worked out. There's plenty of people getting 50-100kmiles from their 347 stroker. I think 87ranger is one of them. So this is less of an issue than it was before. But the fact that the 331 stroker kit has never had this problem and didn't require special engineering to overcome it is a benefit to me. Also most of the kits that no longer have the wrist-pin encroachment issue (the fixed oiling issue) use a shorter rod (5.315" vs 5.4") which worsens the 347's RtSR even further. To me, that's another check mark going for the 331.

As mentioned above, both kits increase compression. Well, after doing some analysis of Dynamic Compression Ratio (DCR) using the components I plan to use and efforting towards tight quench, it turns out, I'll be on the bleeding edge of what pump gas can do...and that assumes a 331. Using a 347, I'd be in trouble. Most people don't hit this limit because most people are installing a bigger cam which lowers DCR and allows you to run higher compression without issue. But as discussed above, my cam selection caters to my intention. So upping the cam duration just to overcome this issue is pissing on my intentions and overall goals for the build. So this 1 technical detail completely throws out the possibility of me using a 347 stroker kit with pump gas. If I had convenient access to E85 so I could run that on a regular basis, the 347 would be back in the running. But being I can't rely on E85 to ever make it to 1/2 the availability of diesel, I can't hinge my build on being married to E85.

So with the high compression 331, mild cam, mildly ported GT40p heads, ported GT40 lower, and some tuning, I expect I'll be in the 300-325hp range. With a bigger cam, I'd be higher than that, but the truck cam does have the trade-off being the torque curve begins falling off in the 4000-4500 RPM range and somewhat nose-dives after 5500RPMs. That RPM range perfectly coincides with my Explorer intake's RPM range of idle-5500. But in the typical street RPM range of idle-4500 where I use the truck 99% of the time, the torque should be absolutely phenomenal. In fact, I'm a little worried about how well my T5 is going to hold up to it if I'm not careful. Hopefully the weak link will be my tires ability to hold the ground and not the transmission & clutch.

Anyway, there's my reasoning for what I'm doing. I recognize this approach is not for everybody. But it's what I'm trying to do. When/if I get done with this project, I'll see if my diligence to NOT focus on max HP has the benefit of maintaining the fuel economy I'm currently enjoying. I'd really like to think that I'll be increasing Mile/$ fuel economy. I'm just not sure how possible that is to do. I don't know how inefficient the Explorer engine is. Based on my calculations of a Stock Explorer's DCR, I should have a significant efficiency improvement from the higher compression alone. Even if I do increase efficiency, will it be enough to pay for the additional $.30/gal for premium? That's yet to be seen.
...Always Somethin'

89 Ranger Supercab, 331, ported GT40p heads w/1.6RRs, Crane Powermax 2020 cam, ported Explorer lower, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, A9L w/Moates QuarterHorse, Innovate LC-1, James Duff traction bars, iDelta DC Fan controller

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Re: FRPP King Cobra vs King Cobra Sort of...

Post by MalcolmV8 »

Interesting project for sure. Just something odd about reading someones plans for an "efficient" stroker. You usually don't see those two combined.

As you know I'm a huge fan of superchargers but like you say the lower compression will hurt gas mileage while cruising out of boost. I wish I had E85 as a local easy access option myself as I'd switch to that in a heartbeat. Guys are making huge power on E85 and running insane amounts of boost on higher compression too.
I'm running around 8.3:1 CR and most guys rebuild their motors with 9.1:1 on pump gas and have fantastic results. The E85 guys are going with 10.1:1 CR and running even more boost. It's quite amazing.

Although if you ran high compression and low boost you could go that way. The 2011 GT Mustang now has a 5.0 as I'm sure you know. It has a very high compression motor from the factory and guys are putting blowers on there making only 5 to 6 lbs of boost and running high 10s in the quarter on the stock automatic transmission which I thought was just amazing.

I can see why you'd pick the 331 over 347 if you're on the edge of pump gas limits with the higher compression and choice of cam which keeps dynamic CR high still. There's just no choice at that point. However I don't fully understand the argument for choosing it based on rod to stroke ratio. As you said the oiling issues are worked out and high mileage is expected out of both builds. So what would the advantage be to the RtSR of the 331? Anything realistically practical?

Also I'm surprised you don't think the 302 has plenty of torque off idle with the stock Explorer cam. It seems like my blue truck used to pull pretty darn hard off idle and have a ton of torque. Maybe because I was automatic and had the torque multiplication of the converter too.

Malcolm
92 302 Ranger - sold
94 302 Ranger AWD - sold
07 BMW 335xi - tuned, boost turned up, E85 - sold
04 911 TT - to many mods to list. Over 600 All Wheel HP on pump gas - sold
2015 Coyote - daily driver
03 Cobra - 2.3 TVS on a built 12:1 CR motor with ported heads, cams, long tubes etc.
MD Racing Lean Protection Module
E85

Tuned by MD Racing

https://www.youtube.com/c/MalcolmV8
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Re: FRPP King Cobra vs King Cobra Sort of...

Post by cgrey8 »

If I burn a little clutch, it has really good pull from a stand-still. But if I let out the clutch easy, start rolling with an RPM of say 600-800RPMs, then with the clutch fully engaged slam the gas, it has a fair amount of hesitation that sticks around until the RPMs get to about 1500. Once I get above that, it pulls pretty good. I'm just not wanting to burn clutch to get it off-idle. So yeah your torque converter is what was giving you the off-idle torque.

As for the newer engines, they have the benefit of being able to change cam timing on the fly, which is changing the Dynamic Compression Ratio to keep the engine where it needs to be. In fact, the old methods of knock control were to retard timing. With these newer setups, there's no longer a reason to retard the timing and waste gas, just close the separation on the intake and exhaust events and you lower the DCR which kills the knock while still using the fuel to its max. Variable Valve/Cam Timing was a huge game-changer for engines. It's what allows companies to build these tiny little 11:1 CR 4-bangers that can put out insane HP for their size all while burning 87 octane pump gas.
...Always Somethin'

89 Ranger Supercab, 331, ported GT40p heads w/1.6RRs, Crane Powermax 2020 cam, ported Explorer lower, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, A9L w/Moates QuarterHorse, Innovate LC-1, James Duff traction bars, iDelta DC Fan controller

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Re: FRPP King Cobra vs King Cobra Sort of...

Post by cgrey8 »

BTW, you asked about what the details of RtSR were. There are 3 different aspects of RtSR that are usually discussed.

The first and probably the most meaningful has to do with side-loading of the piston on the cylinder wall. Shorter connecting rods will create a sharper angle when the crankshaft moves the rod side-to-side. When the piston is being pushed down on by the combusting fuel, the rod is being pushed up on by the crankshaft. But because the rod is at an angle to the piston, the rod is literally pushing the piston into the cylinder wall. The sharper the angle of the rod, the more the piston is pushed into the side wall. You, Malcolm, saw that with your Cobra pistons, how the teflon pads were worn off the pistons due to side-loading. The more side-loading there is, the more friction/heat is produced...hence less of the fuel you are burning that gets converted to mechanical energy because it is going towards friction/heat production. When you reduce the RtSR, you reduce the angle of the rod, reduce the side-loading of the piston, thus reduce friction/heat production. Less friction is more efficiency. This is probably the #1 reason to discuss RtSR.

The next pseudo-compelling discussion of RtSR relates to how the engine dynamics change to require less spark advance to produce max torque due to piston movement differences. Longer rods will dwell the piston at the top of the bore longer which means the piston must travel faster through the bore when it does drop. Some claim the dwell reduces the amount of spark advance the engine needs to produce max torque because it keeps the combustion gasses compacted tighter for longer. Tighter compaction will make the fuel burn faster...like holding a fire cracker in your hand vs holding it tightly with your fist. One burns your hand, the other requires your wife open your ketchup bottles for the rest of your life. The reason reduced spark advance to produce max torque is relevant is the less spark advance required, the less power the engine has to put into fighting the combusting fuel before the crank is on the other side of TDC. Literally, the fuel is burning and starting to expand and the engine is still pushing the piston up further. Reducing the required advance reduces that inefficiency inherent to the engine. This is an argument for a longer rod if this is true.

And the final RtSR discussion, the faster drop of the piston through the bore due to dwell creates vacuum spikes at high RPMs. Some say this is preferable because it produces a greater inrush of airflow which helps get the air moving faster and maintain airflow velocity through the intake and ports. The faster the air can get moving, the more "ram" effect is produced at higher RPMs thus this is an argument FOR longer rods. Others argue just the opposite that this added vacuum produces pumping losses that are greater than the benefits of faster air inrush. And of course the amount of ram effect and pumping loss is based on how well the heads flow and the cam.

If you were racing in high-stakes competitions and needed every possible bit of HP possible, I could see experimenting with different rod lengths to find which worked best in your engine. But for the average person, I don't know that RtSR really makes a hill-of-beans worth of difference at typical daily-driver street driving. Side-loading is the most compelling reason to think that longer rods might improve fuel economy at any running condition. Analysis of airflow and gains from different rods isn't easily provable. At least reduction of required spark advance to produce max torque is something you can test for and "see" on a dyno. But if any of the theory is to be believed, higher RtSR seems to carter to efficiency so that means a 331 is better than a 347 from that standpoint.
...Always Somethin'

89 Ranger Supercab, 331, ported GT40p heads w/1.6RRs, Crane Powermax 2020 cam, ported Explorer lower, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, A9L w/Moates QuarterHorse, Innovate LC-1, James Duff traction bars, iDelta DC Fan controller

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Re: FRPP King Cobra vs King Cobra Sort of...

Post by MalcolmV8 »

Interesting read. However I just don't see that slight extra angle on the rod causing any measurable amount of extra friction that will amount to anything. Will you really loose MPG due to that angle? I would argue no but like you say it's something that's very hard to measure and prove or disprove.

I would think if anything the 331 will get better MPG than a 347 due to lack of cubes. Not reduced friction or heat internally. Which also makes me wonder why you don't just build a high compression efficient 302? The extra cubes on a 331 are bound to use more gas than the 302.

Oh yeah and I got to thinking. You have 3:27 gears in your truck don't you? I had 3:73 in my blue truck and combined with the auto/torque converter is probably why I felt plenty strong off the line compare to yours.
92 302 Ranger - sold
94 302 Ranger AWD - sold
07 BMW 335xi - tuned, boost turned up, E85 - sold
04 911 TT - to many mods to list. Over 600 All Wheel HP on pump gas - sold
2015 Coyote - daily driver
03 Cobra - 2.3 TVS on a built 12:1 CR motor with ported heads, cams, long tubes etc.
MD Racing Lean Protection Module
E85

Tuned by MD Racing

https://www.youtube.com/c/MalcolmV8
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