I really like the broad range of "power" that the Miata 1.8 has insofar as rpm is concerned. For example, the power is tractable enough off idle to get moving, but really starts coming on at 4K and lasts until about 7K (with the revs possibly going higher). Obvioulsy, a V8 is going to have (a lot) more power. My question is, which engine is better to mimic this type of free-revving power curve, i.e., 1K to 7K rpm range, and can do so reliably?

I would think either the Ford 5.0 (302) or the LSx engines from GM would need some work to rev this high, but that is what I really want . . . a high revving, powerful motor that screams "sports car" not necessarily "muscle car."

Does that make sense?

Any ideas, opinions, etc.

Thanks!

 

I lose all traction above 4000rpm.

 

I plan on a similar build goal for winter 2011/12, relatively mild low end torque with higher rpm capability, 8500 seems like a nice rpm target. For no good reason I have 500rwhp as the hp target, I'll use a turbo to get me there if I can't get to it via RPM (unlikely with a 'mild' 3" stroke 302) or if whatever NA power isn't enough.

I fortunately have an alum. 302 SVO block at my disposal so that's what I'm most likely going to use instead of an LS based powerplant.

 

You can spin the newer LS's to 7k fairly reliably. Try that with the 302

 

All else being equal, the 3" stroke of the 302 would lend itself to revs better than even the shortest OEM supplied LS stroke.

But of course, OEM ford 5.0 isnt' equal to OEM GM LS. Put similar spec components into the 302 and there's no reason it wouldn't rev as well as an LS.

 

RPMs cost money, how fast do you want to go?? Any of the SBF or LSX variants can be built to reliably turn 8,000RPM with the right rotating and valvetrain parts. The biggest RPM limiting factor on the stock 5.0 are the stock hydraulic roller lifters which give up around 6,400RPM. NMRA Real Street racers use a variety of tricks with the stock 5.0L lifters to get 7,500RPM but these are not really street friendly combinations. A solid roller cam, stiff push rods, and stiff roller rockers (shaft mounted are better than stud mounted) are all needed to spin high RPM and stay reliable. Current thinking on OHV engines is that strength and stiffness are more important than lightweight components on lifters, pushrods and rockers. Beehive valve springs and lightweight valves and retainers (undersized valve stems and titanium retainers) also help the engine spin high RPM reliably.

 

I can't agree more.

 

I have a solid roller and the right associated parts, and it runs very well to 6500. How often do you want to rev it that high though when you have bucket loads of torque at 3000?

 

make a 5.1L LS engine out of oem parts. Put rod bolts in it, a good timing chain, pushrods, rockers and 243 heads. With a nice cam, proper sized headers and an ITB setup you'll be at 450hp @ 7000rpm. Plenty of power.

 

Probably not that often. This car would be for the street only, so runs to redline would not be often, nor would sustained RPMs.

How many hours does a 5.0 Ford usually go before a valve adjustment on a Solid lifter motor?

 

Is this the iron block or aluminum?

 

I was told 5000+ miles, which is more than I drive mine in a year. I do the valves in the spring, so I am good each year.

 

Vic,

If you don't mind saying, what cam/intake/head combination are you running? What valve-train set up did you use on your solid cam?

I'll have a GT40 Explorer engine, but I only plan to swap out the cam. The engine itself, I hope I can just refresh and not have to go to an entire rebuild.

Gary

 

Heads are AFR 185's, cc'd to 60 cc's for a 10.7:1 compression ratio

Springs put 180 lbs pressure on the seats when closed

Cam is a Schneider racing cam, custom ground:

Grind Number: 278-84R
Intake Duration (gross): 278
Exhaust Duration (gross): 284
Intake Duration (.050”): 238
Exhaust Duration (.050”): 244
Intake Valve Lift*: .572"
Exhaust Valve Lift*: .582"
Lobe Separation: 114
Intake Valve Lash: .020"
Exhaust Valve Lash: .022"
RPM Range: 2200-6400

Intake is an Edelbrock Pro-Flo EFI, carb style intake that has been flowed. It most closely resembles a Performer RPM, except that it has a single plenum like the Victor Jr.

Throttle body is a Weber 1000cfm unit.

 

Thanks Vic.

Pretty warm cam Looks like it would be much more aggressive than the F303 that I'm considering. Of course, you have a much better setup with the AFRs and the Edlebrock. My GT40 setup will not hold a candle to it.

No matter, I'm trying to get my car built with good parts, but on a limited budget. I'm sure it'll move right along if I ever get it built!

 

Why would you do this? That is completely asinine! You can buy a LS1/6 simple cam, valve spring, pushrod swap and your making mid 400's and reving to 7k all day reliably. The LSX platform ***** all over the old Ford 5.0 there is no comparison. It isn't even worth your time to try and justify it.

Don't come to this website to talk about LSX engines. Go over to LS1tech and get some real info. This sight is good for info on swapping not on what to swap.