How high can a DOHC be made to Rev (reasonably)?

[Corbic]

Well I still have not fixed my '96GT, but the 240 will be out of the garage in two months which means the Mustang can rise again.

I was thinking of picking up a Lin. DOHC engine for around $500 and starting there. I was wondering, are there any right ups on building the engine to Rev higher? Will the heads support it? De-stroker kits?

Thanks

 

[Magic]

You can rev the stock Cobra DOHC engines right upto 7,000 RPM.
Im sure the same can be done with the Mark 8 engines, but your limiting factor there is the stock Mark 8 intake manifold (97 and older) and the camshaft profiles.

What is the concern with MAX RPM? Race?

 

[pmot]

Don"t forget the mark 8 does not have the forged crankshaft like the cobra I think I heard that the cobra crank is only good for 8200 RPM.

 

[duff daddy]

You can rev the stock Cobra DOHC engines right upto 7,000 RPM.
Im sure the same can be done with the Mark 8 engines, but your limiting factor there is the stock Mark 8 intake manifold (97 and older) and the camshaft profiles.
What is the concern with MAX RPM? Race?

This is true, the bottom end will out spin well after the top end has reached efficency. IE the crank pistons and rods will spin well longer then then intake manifold and cams have reached peak hp.

Don"t forget the mark 8 does not have the forged crankshaft like the cobra I think I heard that the cobra crank is only good for 8200 RPM.

Where did you get your info from rpms. Tim Matherly in his NMRA 5.0 Real Street(finished first again this yera) car used a STOCK crank... Jim St Charles NMRA ACT Factory Stock #4 finisher this year also runs a FACTORY STOCK CAST CRANK. Im spinning my engine to 7k this year(yea i know its a 2v) and a few of my friends 03 Mach gets shifted at 7k every race...

 

[pmot]

You can rev the stock Cobra DOHC engines right upto 7,000 RPM.
Im sure the same can be done with the Mark 8 engines, but your limiting factor there is the stock Mark 8 intake manifold (97 and older) and the camshaft profiles.
What is the concern with MAX RPM? Race?

This is true, the bottom end will out spin well after the top end has reached efficency. IE the crank pistons and rods will spin well longer then then intake manifold and cams have reached peak hp.

Don"t forget the mark 8 does not have the forged crankshaft like the cobra I think I heard that the cobra crank is only good for 8200 RPM.

Where did you get your info from rpms. Tim Matherly in his NMRA 5.0 Real Street(finished first again this yera) car used a STOCK crank... Jim St Charles NMRA ACT Factory Stock #4 finisher this year also runs a FACTORY STOCK CAST CRANK. Im spinning my engine to 7k this year(yea i know its a 2v) and a few of my friends 03 Mach gets shifted at 7k every race...

I think I got it from this book: How to Build Max-Performance 4.6-liter Ford Engines but i looked again and couldn't find it. I'm still sure it was in there but I'll have to read it again to find out.

 

[duff daddy]

Dont forget alot of your rpm range is going to be reliant on the weight of your rotating assembly, the lighter you go the faster you can spin it BUT the shorter life your going to have. You can get ultra light weight wrist pins, rods and pistons but alot of those light weight parts (some say) will wear faster. Its hard to tell what way to go with out knowing what your going to do with the motor

 

[95PGTTech]

This will not be cheap.

 

[Shame302]

Well, NA, you can spin that **** to the high 7s but you wont build power doing that. The heads and cams, like duffy said cant supply the A/F to do so. Mark VIII engine. Treat it like a GT engine with say, 500 more RPM. Don't expect to spin it to 7K and build power. Cobra intake and what not, spin her to mid 6k 1-2 and low 6K 2-3 and you will do okay.
Forged or cast crank, don't worry about the RPM under 8K less you build some crazy HP.

A cast crank, rod and h.p. piston assembly will make more HP, than a forged crank, rod, piston, assy. will any day of the week NA all other specs the same.


As for info you are looking for. We don't have enough info. We need to know how far you are looking to go. I will assume you are looking to maybe work your heads over, keep your cams and throw them on a mark viii SB. You won't gain RPM at all really. It will be much like your stock engine, minus some overall weight in the car.

Mark viii engine?
Sucky torque curve, with useful RPM in the low-mid 6K range with a cobra intake. 93-98 mark VIII engine basically= to 99-04 PI 2V engine with more RPM extension.

De-stroker kit? Time to do some research dood. You list NONE of your goals, or what you would like to achieve. Where Did you come from?

 

[shaunk]

We've spun the stock cobra forged cranks to 8800 more than a few times with no problems at all.This was with forged rods and pistons. With a stock rotating assmebly I wouldn't go much past 7,000.