Contour Enthusiasts Group Archives Forums Modifications Duratec Performance cougar owner with some questions about high rpm power (long read)

ok, so i'm thinking about how i can get power out of my engine the best and cheapest way. the obvious choice is the 3.0L, but all that BASICALLY does is increase the stroke. bore x stroke of stock 2.5L is 3.33 x 2.92 and in the 3.0L it's 3.39 x 3.39. now our bore and stroke are highly condusive for high revs, which depend alot on rods and stroke (along with cams, valvetrain, etc). the Civic Si, as well all know, is a very high revving car. well the stroke on that engine is 3.05. so all else being equal (which it is of course not), we could theoretically rev higher, yes? even our tranny seems geared for high revs. so what i'm wondering is, what kind of valve springs do we have, what are the capabilities of those springs, etc. i know our rods are sintered forged, but that's all i know. do we have any choices for aftermarket rods?

just in case you're wondering, if we got cams that just bumped the power band up 1000rpms and got 170 torque at 7800rpm, that would come out to 252fwhp. just think about that. the way our tranny is, a shift at 8000 rpms would drop us down to 5000 or higher in each gear, which is just about perfect. you know what my roommate's NSX puts down? approximately 175tq at 8000 and approximately 266hp. sound similar?

also, with all that really high-end flow, the two stage intake would be a hinderance, so we'd prolly need a single stage intake manifold, or possibly just eliminate all the butterflies along with the actuator and all the linkages.

so basically, i need to know what our valve springs can take, what our rods can take, and if rod bearings will still be an issue. and if anything needs changing, what would i look for to replace with?

thanks,
uRiDiAN

A 1,000 RPM bump is non trivial. Traditional weak spots are piston rings and the valve train. The trade-off on piston rings is thick/heavy for long life, thin/light for high RPM's. I suspect the rocker/followers/hydraulic lash adjusters are limiters on these engines, based on the change to direct bucket followers on the heads in the Jags (according to T. Haines).
Spinning an engine faster is a classic way to get bigger HP numbers, but creates problems with normal driving. If you want a car to feel fast: push down on gas, have car lunge forward; you want more torque. High reving, peaky engines are better suited for track use.

the low-torque street driving is not really an issue to me. it'd be no different than driving a civic around. plus... with those kinds of numbers it would be totally liveable.

and i realize it's not trivial, which is why i'm asking what else i would need to take into account...

so besides what you've mentioned what else would i need to address?

uRiDiAN

first off i believe that the stroke of the 3.0 is the same as on the 2.5 the bore is the larger factor. second there are things like rod ration when i comes to seting up a car for high rpm operation. the duratec lower end is probably good till about 8,000 beyond that the rods are too weak and the crank to heavy custom parts would be needed i personally dont know about the valvetrain terry will know best in that department also you have to have the flow potential to spin the motor that fast whats the point of spinning that fast if the air cant get in/out quick enough. also i know shift at around 6800 and my car drops to about 4800 when i shift so with a 8000 rpm shift im thinking 5900 or so would be where are motor would land. so far the intake hasent been the limiting factor on out motors there are many 3.0 floating around producing pleanty of power from just a slightly reworked manifold

Actually; stroke stays the same! Same crank, just bigger bore! (Also same deck height, piston compression depth, & connecting rods)

All 2.5L & 3L engines have a 79.5mm Stroke
Through 99 2.5L's have a 82.3mm Bore
00 and up 2.5L's have a 81.67mm Bore
All 3L's have a 89mm Bore

Raising redline past a certain point (about 7500rpm) would get exponentionally expensive!!!
The amount of engine work and custom parts needed would add up very quickly!

Stock valvetrain is capable of 8k rpm's without failure. Tested for several seasons.

Stock piston rings as well and these same rings were used on the 450+ HP Duttwieller turbo engine.

The weak point IMO is the rods and bearings at high rpms and/or boost... Still with that said several folks with 7500rpm S/C Duratec's that have no problems with reliability. Not including the S/C that is...

well leo capaldi, as far as i can tell has run his (on the dyno at least) up to 8500 with stock rods, and runs it to 7500 on a regular basis on stock rods. all he's changed is valves, valve seats, bearings and cams...

so if the stock valvetrain can handle that many revs, and the rods can, all i'd theoretically REALLY need would be rod bearings and cams to make the power up there?

uRiDiAN

As noted the 3L has same stroke/rods etc but different bore (actually slightly siamezed).

As far as max RPM been trying to get a concensus on max safe RPM on stock block/valvetrain. Can say that Chris Reinke's 260+ HP Duratec Touring car used stock rods and valvetrain (except 3L valves) with an 8000 RPM redline with no problems. Course, he may have rebuilt the engine frequently?? Mirko once said 7800 RPMs safe IIRC. But would longevity suffer?? The crank whip/harmonics issue may well be worstened at high RPM. The dual mode damper would be a wise & cheap precaution for increased redlines. So would an Accusump. With these 2 precautions, I "think" that a 7500 RPM that is visited briefly (as opposed to sustained) may be reasonable, though normal longevity may still suffer somewhat. Just do not think anyone knows for sure..

explain this dual mode damper a little more for me?

uRiDiAN

"explain this dual mode damper a little more for me?"

OK here is the deal (as I understand it - Terry or Judge can correct me if I screw it up). The Duratec is prone to "crank whip" related to harmonic frequencies at certain RPMs). This crank whip is tough on rod bearings which causes premature failure in some cases "spun bearing" = broken rod. This is why some racers have used the SHO trimetal bearings. In fact, this MAY be the major reason for Duratec failures and be falsely blamed on oil starvation (though starvation is probably a problem in some cases /situation). But beyond the SHO bearings, an easier solution exists (though the trimetal bearings may be a better solution - they cost $600 + an engine teardown). The Ford OEM damper supplier found that the stock damper was not dampening the harmonics well enough and developed a "dual mode" damper that works much better at eliminating undesireable harmonics = less crank whip = no more spun bearings(?). Ford has changed (as of about summer 2001 production date) to the new damper on the new 2002 Mondeo and probably 2002 Cougars. It is a direct bolt on and currently a member of CEG has one and is testing it out. So far, I have no part number and not sure when they will be available. Cost about $75 or so.

As harmonics are probably more of an issue with higher RPMs, it seems to me the dual mode would be a must for all with elevated redlines. Actually, I think everbody should consider this damper when readily available. Group buy! Group buy! Hint, hint..