Best MOD Motor to build 5.0-5.8

[Garrett114]

I have a 04 Cobra with a 3.4 Whip auto 9inch its going this week to put in a 10point and go on a diet. I have reached the 9's with the stock motor but im looking for more now. I want to turn about 7000RPM at the track and make as much power as I can now. The car only runs on MS109 and has a return style fuel system so fuel is not a problem. I heard in the past the big motors could not take the RPMS

What engine setup would net me the most power with the blower maxxed

 

[mustangmanjeff]

well 1st of you really cant go any bigger then 5.4liters for a mod motor..


Now if im not mistaken the biggest stroker kit goes to around 5.5 liters for mod motors. 5.8 liters is a pushrod motor 351 c.i , average stroker kits for the 4.6 cars 2 valve and 4 valve seem to be 5.0 and 5.1 stroker kits


I belive you can get a 5.0/5.1 stroker kit for your cobra that would make serious power along with that blower

 

[BajaBoy]

well 1st of you really cant go any bigger then 5.4liters for a mod motor..


Now if im not mistaken the biggest stroker kit goes to around 5.5 liters for mod motors. 5.8 liters is a pushrod motor 351 c.i , average stroker kits for the 4.6 cars 2 valve and 4 valve seem to be 5.0 and 5.1 stroker kits


I belive you can get a 5.0/5.1 stroker kit for your cobra that would make serious power along with that blower

MMR has the 351R block (ohc) but I dont know anything about it. to the OP, 4.6 or 5.4 base could hold that power but through your specific application (3.4) arnt you up against the crank snout strength? If your going to spin it that high i would stick to stock stroke. Im sure someone else will help you out better then i have.

 

[SlowSVT]

Based on your cars current set-up and the fact your running 9's I am suprised your even asking this questions. You should know more about this stuff then most of us :shrug:

 

[Garrett114]

I have had lots of success with my current setup I ve been 9.8 consistent full weight 3900lbs stock motor I've built lots of LS motors in the past making big power and theirs no replacement for displacement I saw MMR has a 5.8 stroker sleeved Ford GT based mod motor I just want to know what would net me most power I can achieve and I need the RPMs for the track

 

[SlowSVT]

There is a replacement for displacement. It's called: Boost

Displacement and RPM's tend to be mutually exclusive. The stroke on these motors are horrendously long and the bore spacing does not lend itself to very big pistons. If you want both the best your going to do is to get an iron boss 5.0 block and leave it at the stock stroke. If you want to go bigger you can stroke to 3.75" but your going to pull a lot of piston out of the hole and push the wrist pin into the oil ring so your will be starting to compromise reliability. If you go this route you might want to consider a 5.4 engine but now your stroke is up to 4.165". If you want to go faster then 9's I suggest time to retire the 3.4 and go turbo but I hope you don't plan on driving this car on the street because to won't be much fun.

Use the search function. Many of your questions have already been asked and much to be learned. Good luck.

 

[Garrett114]

I have used the search feature but it don't pull anything up I'm staying with a blower instead of turbo because the car will still go on the street at times I know boost is a replacement but in LS engines a 427 at 20# makes a 1000RWHP while a 383 with 20# makes about 800RWHP what about a 3.7 bore block from ford with a small stroke anyone try it r a 5.3

 

[Jimmysidecarr]

I have used the search feature but it don't pull anything up I'm staying with a blower instead of turbo because the car will still go on the street at times I know boost is a replacement but in LS engines a 427 at 20# makes a 1000RWHP while a 383 with 20# makes about 800RWHP what about a 3.7 bore block from ford with a small stroke anyone try it r a 5.3

That BOSS iron block is about the only 3.70 bore block I would want to subject to these cylinder pressures. The MMR 5.8 is a 3.70 DARTON sleeved high deck 5.4 based block, they could tell you how cylinder head gaskets would survive at various power levels and whether it would be a good choice for your goals.The downside of stroking is that even a 4.6 crank has a fairly long stroke, but the real issue is the amount of skirt that comes out of the bottom of the cylinder at bottom dead center even on a stock stroke 4.6 engine.

Add high RPM and collapsed skirts can happen.

Are you running or planning on running a billet crank or the stock forged crank? Twisted off crank snouts are a problem on the big blower high boost stock crank 4.6 engines.

I would think if this is going to get any serious street usage, that at least a cursory investigation of compound boost turbos should be looked at as an option. A ported Eaton with a turbo would not be a crank killer and would also be capable of close to 30 pounds of boost at the crank of a knob if a large enough turbo is specified. The big motor option still amplifies the power potential just like any other engine, but there would be several durability advantages from going with a stock bore, stock stroke 5.4 with REALLY good rods, plus compound boost.

 

[SlowSVT]

I have used the search feature but it don't pull anything up I'm staying with a blower instead of turbo because the car will still go on the street at times I know boost is a replacement but in LS engines a 427 at 20# makes a 1000RWHP while a 383 with 20# makes about 800RWHP what about a 3.7 bore block from ford with a small stroke anyone try it r a 5.3

That kind of power on a PD blower is going to put a lot of stress on your bottom end. With a 3.4 at high boost levels you could probably add 200+ hp to whatever is measured at the wheels which is used to drive the blower. You might want to give some consideration to Jimmy's suggestion about compound boosting the engine but that will require putting the Eaton back on because twin screws seal between the rotors prevents the turbo form boosting the engine. Perhaps Digital will catch on to this thread and chime in since he has experience here.

Personally, at the power levels you are seeking this car if set-up correctly for the 1/4 will make for an awful street car. Perhaps nursing it over to the local burger joint but I would avoid any road trips in it. Once you put the 10 pt. in there it's pretty much a race car and would be very dangerous if you and any passengers were in an accident and not wearing a helmet. You might want to consider back-half'ing the car as well to take full advantage of the power you want to make. Pretty slippery slope.

 

[Garrett114]

The car is for minimal use on the street I have a daly plus another SY 04 cobra with cams and a whip to cruise on the weekends the race car is only going on the street for races that require a Cruz before the race I'm not going turbo with this car though I'm just trying to get the best motor I can for my setup I 60' 1.31-1.34 right now with MT DR full weight I'm taking some weight out now with the ten point so traction should just get better I am looking just to go 8.90-9.20 with my car

 

[jm@ReischePerf]

I am looking just to go 8.90-9.20 with my car

I take it you're still shifting this car, right? You really start fighting an uphill battle with the power required to shift a car into the 8s. You've got some good advice here about the engine but I'd really think about going auto if you want serious ETs.

 

[SlowSVT]

I take it you're still shifting this car, right? You really start fighting an uphill battle with the power required to shift a car into the 8s. You've got some good advice here about the engine but I'd really think about going auto if you want serious ETs.

Good call!

For driving on the street I loath an automatic transmission :cuss:

Takes the fun out out driving :nonono:

 

[redfr03svtsnake]

says whipple, auto 9"

 

[GodStang]

Just get the 6.1L Stroker kit for the 5.4L and be done with it. That is what all the cool kids are doing.

 

[SlowSVT]

Just get the 6.1L Stroker kit for the 5.4L and be done with it. That is what all the cool kids are doing.

A stroked 5.4 to 6.1

How long is that arm?

 

[webleedorange61]

That kind of power on a PD blower is going to put a lot of stress on your bottom end. With a 3.4 at high boost levels you could probably add 200+ hp to whatever is measured at the wheels which is used to drive the blower. You might want to give some consideration to Jimmy's suggestion about compound boosting the engine but that will require putting the Eaton back on because twin screws seal between the rotors prevents the turbo form boosting the engine. Perhaps Digital will catch on to this thread and chime in since he has experience here.

Personally, at the power levels you are seeking this car if set-up correctly for the 1/4 will make for an awful street car. Perhaps nursing it over to the local burger joint but I would avoid any road trips in it. Once you put the 10 pt. in there it's pretty much a race car and would be very dangerous if you and any passengers were in an accident and not wearing a helmet. You might want to consider back-half'ing the car as well to take full advantage of the power you want to make. Pretty slippery slope.

lol ............


To the OP build the new 5.0 block, I beam rods, diamond pistons, Ported heads, cams. Pulley the 3.4 to 22-25psi and you will go deep in the 9's pending weight/ converter.

 

[Garrett114]

My buddy is runing 9.30 with a 2.3 and imported fr500 heads with a 5.0 hopefully I can go 9.0 with the 3.4 I'm going with a 5.3 from MMR

 

[GodStang]

A stroked 5.4 to 6.1

How long is that arm?

My bad BORED and stroked...