3v build questions

[v8venomgt]

my 08 bullitt has a currently running stock block at 10psi on a stock motor. it's running like a champ but earlier this year i bought an update 08 longblock. as for my long term goal i'm considering cleaning the heads up and a NSR set of cams because i really don't want to put undue stress on the phasers. that said i'm thinking an rpm limit of no more than 7500, 93 octane despite e85 being available.

my original thought was cobra crank, take off cobra rods, weisco pistons and overbuild for my goals for a safety margin. realistically my goals aren't extreme, cobra cranks reman'd are pretty expensive, and used ones require an unknown amount of machining/ aren't as plentiful as they once were, cobra rods are becoming more elusive.


now i'm considering boss/15+rods, stock crank, cryotreat them both, weisco 10.1 pistons and build accordingly. i'm thinking with 93 limiting power output to maybe 725-785 horsepower would this engine have long term durability? what sort of power ceiling could the previously mentioned assembly have?

 

[46addict]

Wouldn't it be better to have compression at 9.0-9.5 for a strictly 93 octane setup? I thought lower compression with more boost would make more power in the end than bumped up compression with boost dialed down.

 

[05sonic4.6]

Stock springs won't take more that 6800 rpm I believe, so you may need to upgrade them and limit/lock phasers anyway if 7500 is your desired rev limit. Turbo cars typical don't have much cam timing retard anyway. I completely deleted the vct on my turbo setup.

Like 4.6ddict said your gunna be better off keeping compression around 9:1 if you want to stay on pump with those power numbers. Though some tuners believe 6-650 being the "safe limit" for pump. Not to say some haven't pushed it further. Better cams and ported heads will help push the limit further.

 

[v8venomgt]

Stock springs won't take more that 6800 rpm I believe, so you may need to upgrade them and limit/lock phasers anyway if 7500 is your desired rev limit. Turbo cars typical don't have much cam timing retard anyway. I completely deleted the vct on my turbo setup.

Like 4.6ddict said your gunna be better off keeping compression around 9:1 if you want to stay on pump with those power numbers. Though some tuners believe 6-650 being the "safe limit" for pump. Not to say some haven't pushed it further. Better cams and ported heads will help push the limit further.

i'm open minded to all suggestions. i'm not set on a particular number when it comes to, well anything really. it's just a street car, that i'd like to remain competitive with bolt on hellcats, trinity cars, etc. being the fastest isn't really on my mind. dialing the compression back to oem levels isn't a big deal , i was just keeping tabs on stock power plant boosted 'yote cars and going loosely based on that. that and i don't want it to feel too lazy out of boost. any thoughts about the rotating assembly ?

 

[eighty6gt]

I'd run h beam rods just so you don't use TTY bolts. They had to take a lot of metal off of my boss rods to get them to balance - at the factory, they just match up a set.

Just grab a stroker reciprocating assembly, already balanced, install.

 

[v8venomgt]

I'd run h beam rods just so you don't use TTY bolts. They had to take a lot of metal off of my boss rods to get them to balance - at the factory, they just match up a set.

Just grab a stroker reciprocating assembly, already balanced, install.

thanks for your input, i'd consider aftermarket rods but definitely don't want to go stroker.

 

[Speedboosted]

What's the appeal of takeoff cobra rods? Why not just get a set of new Molnar or Manley H beams? I can't see there being a big price difference. Molnar's are supposedly the new bad boy rods out there for motors, and they're only around $600 with big ARP bolts.

Run the TFS by PAC springs. It's $195 for a set and they use stock retainers and stem caps, coupled along with stock or a turbo cam under .550" lift and you've have a great valve train that can handle high rpm. https://www.summitracing.com/parts/tfs-16213-24

You have a better chance of the stock crank living at 750 whp being that it's a turbo car, but that still seems kinda high for cast. I know there have been few (if any) documented factory crank failures around that power level but I wouldn't want to be the first. Weisco makes a good piston, but they can be noisy even with correct PTB clearance. I like the Manley's with a coated skirt and valve reliefs of course for safety. Compression wise, 10:1 is fine but you'll ultimately have to make a sacrifice somewhere with pump gas. At 10:1, there will be less timing available to run at WOT (possibly less power, but not necessarily), however it will act/drive better when not in boost. Whatever you do, don't go less than 9:1.

I don't see any mention of timing components, and sadly I see people over look that all the time. On any built motor at minimum I would do a 13/14 pump assembly with TSS billet gears. And then optional extras depending on mileage, usage, budget, etc would be billet chain guides, billet crank gear, and iron tensioners. I never checked when I had my 3v apart but I know the aluminum 5.4's have a 6mm guide pin which can and has failed. The popular upgrade is to drill out and tap the hole to accept an 8mm guide pin. Iron 5.4 already have the 8mm pin, but like I said I'm not sure what Ford did on the 4.6's.

 

[raredesign]

thanks for your input, i'd consider aftermarket rods but definitely don't want to go stroker.

I’m doing the same research. I’m still torn about the stroker, because I too was looking at the cobra crank, but it looks high risk due to it having been balanced prior or even multiple times, having worn journals, etc.
Also, it looks like serious builds (I’m shooting for 1000hp) require heat treating the crank.
Instead of taking the risk, and extra cost, im considering a Manley crank, whether stock 3.5” or stroked.

Is stroked really that bad for turbo?

 

[702GT]

I don't know why so many feel the need to rev the piss out of the 3v. The heads just don't support it. There's plenty of ways to make huge power without reving to the moon. Your motor and wallet will thank you for it in the long run. Unless you've got sponsorship money to burn, it's just not a cost effective method to making power.

 

[mrt2you]

i make 650rwhp
i run a cobra crank with 10.5:1 compression, 20lbs boost with pump 93 octane gas. it's not a stroker motor. i am not sure what the timing is but i am sure it's not much.
i also run USED MMR H beam rods, i bought the crank and rods from someone i knew.

the extra compression is worth the extra tuning problems. when not it boost you more power making a better driving car.

 

[v8venomgt]

What's the appeal of takeoff cobra rods? Why not just get a set of new Molnar or Manley H beams? I can't see there being a big price difference. Molnar's are supposedly the new bad boy rods out there for motors, and they're only around $600 with big ARP bolts.

Run the TFS by PAC springs. It's $195 for a set and they use stock retainers and stem caps, coupled along with stock or a turbo cam under .550" lift and you've have a great valve train that can handle high rpm. https://www.summitracing.com/parts/tfs-16213-24


You have a better chance of the stock crank living at 750 whp being that it's a turbo car, but that still seems kinda high for cast. I know there have been few (if any) documented factory crank failures around that power level but I wouldn't want to be the first. Weisco makes a good piston, but they can be noisy even with correct PTB clearance. I like the Manley's with a coated skirt and valve reliefs of course for safety. Compression wise, 10:1 is fine but you'll ultimately have to make a sacrifice somewhere with pump gas. At 10:1, there will be less timing available to run at WOT (possibly less power, but not necessarily), however it will act/drive better when not in boost. Whatever you do, don't go less than 9:1.

I don't see any mention of timing components, and sadly I see people over look that all the time. On any built motor at minimum I would do a 13/14 pump assembly with TSS billet gears. And then optional extras depending on mileage, usage, budget, etc would be billet chain guides, billet crank gear, and iron tensioners. I never checked when I had my 3v apart but I know the aluminum 5.4's have a 6mm guide pin which can and has failed. The popular upgrade is to drill out and tap the hole to accept an 8mm guide pin. Iron 5.4 already have the 8mm pin, but like I said I'm not sure what Ford did on the 4.6's.

sorry for the delay! my interest in the cobra rods mainly are/were is theyre in OEM component. after going down the road i have, i've grown to have an appreciation for oem/oem like parts. my heart isnt set on them though. im strongly considering a K1 rods /weisco piston combo from modular headshop. that in mind, you mentioned that the weiscos can be a bit noisy? is that upon cold start? or as a generalization? any videos offhand to give me an idea? im also curious what it is about them that creates more noise? that would make me reconsider those too. ive read about the TSS oil pump for years, and now the gt500 billet backing plate with tss gears? is is a lateral move in terms of longevity/reliability?

as for the guides, i thought the oem plastic ones were best? from my research the metal based ones have a tendency to stick creating all sort of issues? whereas the plastic guides dont need oil pressure to function?
thanks for your insight thus far!

I’m doing the same research. I’m still torn about the stroker, because I too was looking at the cobra crank, but it looks high risk due to it having been balanced prior or even multiple times, having worn journals, etc.
Also, it looks like serious builds (I’m shooting for 1000hp) require heat treating the crank.
Instead of taking the risk, and extra cost, im considering a Manley crank, whether stock 3.5” or stroked.

Is stroked really that bad for turbo?

from my research, my perspective is these motors are built with more than enough stroke to begin with. does adding more increase power? yes, but it has a counterpoint to it. bruceh has gone into it a few times, and to be frank i cant remember what the discussion revealed off the top of my head. however, at the time i was turned off to the idea of a stroker. where are you sourcing a (bew) forged manley cranks from? ive seem a few vendors selling refurbished cobra cranks, but thats all ive found when ive looked.

I don't know why so many feel the need to rev the piss out of the 3v. The heads just don't support it. There's plenty of ways to make huge power without reving to the moon. Your motor and wallet will thank you for it in the long run. Unless you've got sponsorship money to burn, it's just not a cost effective method to making power.

not this guy. i currently shift at 6k to keep the block intact, but down the line 6500 sounds nice. possibly 7k rpm, but in all honesty i dont really want to mess with the heads, vct, high lift cams, etc.

i make 650rwhp
i run a cobra crank with 10.5:1 compression, 20lbs boost with pump 93 octane gas. it's not a stroker motor. i am not sure what the timing is but i am sure it's not much.
i also run USED MMR H beam rods, i bought the crank and rods from someone i knew.

the extra compression is worth the extra tuning problems. when not it boost you more power making a better driving car.

that much compression, 20 psi, and 93?! who is your tuner?! haha, sounds like a fun combo.

 

[raredesign]

where are you sourcing a (bew) forged manley cranks from? ive seem a few vendors selling refurbished cobra cranks, but thats all ive found when ive looked.

I think ModMax Racing may have been, but they do have refurbed Cobra cranks there, but want $900. MMR has Manley and offers a 4.75 kit so shouldn’t be far off from stock. Since my turbo’s power band won’t be in high rpm anyway, I’ll have to do a bit more research on strokers, because at 7000rpm or under, it doesn’t seem like it will hurt.


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[drive_55_not]

I think ModMax Racing may have been, but they do have refurbed Cobra cranks there, but want $900.
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$900 for a used Cobra crank is crazy, I don't care if they don't make them anymore,, They were only $600 new and Ford built 70-some thousand "SVT Cobra's" .

I would'nt pay more than $400 shipped for one.

I bought a mix of used parts, used Cobra crank, Manley SVT rods, new Diamond pistons/Total Seal rings from John Tymensky when he closed his Modular Performance shop ... Wow, that's been 6yrs ago.

The crankshaft/rods came out of a big turbo setup .. The crankshaft was good, the rods not so much, the big ends were serviceable, but the bushing ends were worn and needed honed 2thousands so I would've needed 8 new .869" wrist pins and honed the pistons to fit them, I decided to buy new Manley rods instead ...

I'm still running the crank and those rods .. they're on their 3rd build.

Run the TFS by PAC springs. It's $195 for a set and they use stock retainers and stem caps, coupled along with stock or a turbo cam under .550" lift and you've have a great valve train that can handle high rpm. https://www.summitracing.com/parts/tfs-16213-24

Those springs are going to be too light for high boost/high rpm , you want the TFS-16125-24..

as for the guides, i thought the oem plastic ones were best? from my research the metal based ones have a tendency to stick creating all sort of issues? whereas the plastic guides dont need oil pressure to function?

On the sticking issue, it's the ratchet type iron tensioners that can stick open causing broken guides.

The tensioners do need oil pressure to keep the guides tight tight ..

The issue with the OE plastic tensioners is they have a tendency to blowout the seals, really not an issue, stick with the OE plastic ones.

my interest in the cobra rods mainly are/were is theyre in OEM component.

Honestly, the reason Ford used Manley for the SVT rods was they needed something stronger than the SVT team could make on fairly short notice, they are good rods but do have their limits ... They can fail when pushed too hard. This was caused by hydroloc from a leaky head gasket.

Weiscos can be a bit noisy? is that upon cold start? or as a generalization? any videos offhand to give me an idea? im also curious what it is about them that creates more noise?

The noise they're talking about is 'piston slap' ,, with a 2618 piston materal you have to run .002-.004" PTW [depending on how much boost you're running] to allow for piston growth as it warms up.

I've never heard any noise on my builds using a 2618 piston and PTW set at .0035".

Stock PTW hypereutectic piston is around .001".

the gt500 billet backing plate with tss gears? is is a lateral move in terms of longevity/reliability?

The purpose of the billet backing plate is to eliminate the back plate flex that Ford found out was letting oil pass out of the cast oil pump back plate on the GT500,

Jasper Engine has video showing how much oil leaks past the cast back plate ..

https://www.youtube.com/watch?v=6QPahVJJqFw

The billet OPG's are to prevent shattered gears, I ran a billet GT500 pump with cast gears for three years, I did install Boundary OPG's in that pump and using it in my current build.

Word of warning, If you take the plate off the oil pump .. Do Not Over Torque the bolts on the back plate when you reinstall em' ..

It's chintzy metal and you'll strip the threads realllllly easy, I used a drop of blue Loctite and torqued to 80in-lbs.


.

 

[Wes06]

pointing out a flaw in a rod by using one that was hydrolocked?

even some of the beefiest rods can hydrolock and completely blow out

 

[raredesign]

$900 for a used Cobra crank is crazy, I don't care if they don't make them anymore,, They were only $600 new and Ford built 70-some thousand "SVT Cobra's" .

I would'nt pay more than $400 shipped for one.

I bought a mix of used parts, used Cobra crank, Manley SVT rods, new Diamond pistons/Total Seal rings from John Tymensky when he closed his Modular Performance shop ... Wow, that's been 6yrs ago.

The crankshaft/rods came out of a big turbo setup .. The crankshaft was good, the rods not so much, the big ends were serviceable, but the bushing ends were worn and needed honed 2thousands so I would've needed 8 new .869" wrist pins and honed the pistons to fit them, I decided to buy new Manley rods instead ...

I'm still running the crank and those rods .. they're on their 3rd build.
.

You are a wealth of information. Thank you.

So sorry I deviated from the ops post on that. I was trying to comment within topic, but as I don’t feel comfortable purchasing a used crank off eBay, I’m looking at getting a Manley crank and billet i-Beam rods.

Your other info about the Pistons is great. Would .0035 PTW apply to an aluminum block or was that for cast iron?


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[JeremyH]

I bought the cobra crank I had in 2004 iirc, got it off ebay for $40 shipped had 20k miles on it. I was gonna use it on my 01 GT 2v, but traded it in when I got my 07, so the crank just sat. When I decided not to use it in 2010ish I sold for it $200. Should have held on to it longer lol.

 

[aboody roush]

What about heads gasket for turbo application?
I use in my car oem gasket but in 15psi it's blown HG passenger side

 

[Sactown]

I will have a set of rods from my 4.6 aluminator, along with a set of ID 1000 injectors and possibly a 76mm Precision ball bearing turbo up for sale in February.

 

[drive_55_not]

What about heads gasket for turbo application?
I use in my car oem gasket but in 15psi it's blown HG passenger side

The OE MLS head gaskets are basically the same as all the other MLS gaskets ...

They don't just go bad,, Detonation is what kills them ...

You need to investigate what caused the failure to ensure you don't take out the replacement.

.

 

[46addict]

I will have a set of rods from my 4.6 aluminator, along with a set of ID 1000 injectors and possibly a 76mm Precision ball bearing turbo up for sale in February.

New or used rods?