Where should I build power?

[Guest Anonymous]

I'm wondering, with the light weight of a 240Z, would it be better to build a motor for mid-range or high-end power? This car is going to be 95%-97% street driven, and more in a auto-cross or rally-cross style than shooting for 1/4-mi. times. I'm posting on this board because it looks like most are shooting for 289 or 302ci engines, which don't seem to make as much lazy-torque as a 350cid SBC.

 

I'm actually looking at either a 4L or 4.6L Rover V8, which is why I'm asking the question. The former likes to spin up to about 6K, while the latter develops its peak power around 4500rpm or so.

 

Finally, I know the typical reaction to Buick 215/Rover V8 questions -- I actually have leads on both of these engines at reasonable prices. If I didn't, I probably would do a SBF or SBC swap instead.

[Guest ScaryFast]

I am going for high-end power because I figured it would be less prone to breaking things like u-joints. Also, the engine I got already has a pretty high end cam so that is what I am trying first. With a car as light as a Z, I wont need the low end grunt to get it moving either.

 

That is my theory, but I am new to this whole thing.

[Guest jens]

Running a wild cam on the street would be irretating no mather if the car is light or heavy. The only way i can see it possible is to use a set of hotrockers www.hotrocker.com but they limit total lift to 577 and are rather expensive.

[Guest Tom Scala]

If you want variable valve timing and don't want to go broke doing it for around $70 you can use Rhoades lifters. They work as advertized and will make a barely streetable cam liveable in stop and go driving. I've used them for years with good results.

[Kevin Shasteen]

Originally posted by op1.., I'm wondering.., mid-range or high-end power? This car is going to be 95%-97% street driven, and more in a auto-cross or rally-cross style than shooting for 1/4-mi. times.., QB]

Keep in mind my comments are not relative to Class Rules; as I have no knowledge of what is allowed in any particular given Auto-X/Rally-X Class. Now, after giving my Disclaimer: I would have to ask, Is your car going to be street driven car or is it going to be an Auto-X/Rally-X Car; as the two are not one in the same.

 

The 96-97% Street Driven car will want low end power & Expect, "NEED", low rpm idle quality as it will rarely see above 4000rpm's and be expected NOT TO OVERHEAT in Stop-n-Go rush hour traffic. Whereas the Auto-X/Rally-X engine will need its power at High Rpm and will not come on to the cam until well after the 4500rpm range....these two engine needs are diametrically opposed; providing you truly wish to be competative on the Auto-X/Rally-X.

 

For if you wish to build an engine that performs competitively on the Auto-X/Rally-X, then it will not perform well on the street. Yes, you can build an engine that runs both on the street and the Auto-X/Rally-X; but it will be a huge COMPROMISE in both Streetability and the performance at the Auto-x/Rally-X.

 

I think (IMHO) that most people who want a "Streetable Engine" dont really know what they mean when they use the word "Streetable" and then combine that term in the same breath as a race car of some kind. You cant have both; without a turbo/supercharging.

 

If you are running A/C and Vacuum assisted brakes (for the street) then you will need a cam that offers that ability at low rpm; or a vacuum assist of some kind.

 

Still; you cant have "Streetability" and Auto-X/Rally-X Performance unless you are only wanting to do the Auto-X/Rally-X just for fun...and are not deadset on Winning...then and only then can you get away with an engine that is also "Streetabile" within the Auto-X/Rally-X arena.

 

Yes, of course this is "Just My Opinion" and still based on the fact I dont know about any Class Rules pertaining to Stock -vs- Non-Stock performance.

 

Kevin,

(Yes,Still an Inliner)

[Guest Anonymous]

A car with that much percentage of street use would need some low end IMHO. As far as breaking things, IMHO it won't matter, the torque curve is just going to get shifted up in RPM and when it hits its still hard on parts.

 

Low/midrange power is a street cars friend, running around with a lumpy cam that doesn't come on unless you have the engine singing IMHO removes what is so wonderful about street V8's in the first place IMHO.

 

If you need to wind it up real high, heck why not get a SR20DET or something and skip the V8 altogether.

 

If you need first hand experience on what a lumpy cam on the street is like ask 'Zya' he changed cams to get a better street experience I believe. (I think it was him, someone had to recently because the cam was just to lumpy and down on torque for the street).

 

General rule of thumb for non stroker motors (which can tolerate more because of the added torque) is about 225 degs @ .050 lift of duration, larger than that by a bit is probably ok but getting marginal, way more than that and you'll have no vacuum signal which makes it idle lousy and gives poor response until the motor can catch up and start making power at a higher RPM.

 

Regards,

 

Lone

[Guest Anonymous]

Hmm...maybe I can follow this up. I used to be a Mopar guy, and in the Mopar small-block realm, there is a large contingent who argue that a 340ci is better than a 360ci because it has a more square bore-stroke ratio. The 360 is a long stroke motor, and many Mopar nuts would argue it won't be as quick to rev. According to these folks (and I'm not saying I agree with them), the extra 20 cubes aren't worth it.

 

As far as the Rover motors go, it is much the same argument, that the 4.0L will spin up better than the 4.6L (one guy explained that the 4.0L is a large bore, short stroke engine, and the 4.6L is a large bore, long stroke engine). Now, is there really such an instance in street engines where you'll trade off displacement for a shorter stroke? It's entirely possible the guy wanted to sell me a 4.0L -- the 4.6L is fairly rare in the US and I am only considering it because I have a solid lead on one at a good rate.

 

When I mentioned the auto-X/rally-X, I do these kind of track events occasionally. It's really for my personal fun, I'm not competitive and frankly, I don't care to be. Well, not with this build, anyhow. I merely wanted to convey I am more concerned with handling & balance, and therefore power & responsiveness over a broad rev-range rather than 1/4 mile times.

 

My confusion is simply that most everything I've built has been in the 3100 - 3400lb range. With a 240, I'm talking close to a 1,000lbs lighter. I've no doubt that these cars can be just as quick as some 3000+ lb musclecars, but have a torque curve shifted much further to the right.

 

I apologize for getting so far off the Ford issue, maybe the moderators should move this thread. I only posted here because it seemed to me that the 350ci Chevy is inherently torquey, and even the mildest builds put out over 300ft/lbs. I'm figuring the Ford engines, especially the 289ci, will be about as close a relation as I can get to dealing with a smaller displacement V8.

[blueovalz]

I ran a 302 for many years, and recently went back to a 289. Formerly, I used the old Ford "LeMans" camshaft which had a great broad torque curve (never did find a cam I liked better until only very recently with my solid roller), which made it a great road cam. What I looked for, and ultimately have been very satisfied with was matching torque with the chassis limitations. With the properly set up SBF (289 or 302, of which I like the 289 better), you can stretch the torque out into a wide range that will allow a "proper" acceleration without excessive tire spin all the way up to 7500 RPM. Only a lightweight car can allow this, and the Z fits nicely into this window of light weight, and strong drivetrain. Brute force is great, but I enjoy the finesse of the smaller stroke motors.

[Guest jens]

If you buy one of the rover engines buy the 4.6. All the new engines has a better bottom end with stronger maincaps. 4.0 and 4.6 use the same small valve heads thats why the 4.6 dont rev as much. the heads needs to be seriusly ported. With the 4.0 you wont be much faster than a bmw it only has 190-200 hp the 4.6 has 225. You can compare performance with a tvr v8. But all the aftermarket ford spareparts makes the decision easy.

[Guest Anonymous]

Since the Rover V8 is a decendant of the Olds/Buick 215, you might consider looking up info on the turbocharged version of the early 60's and see if a modern duplicate can be built. The Buick 3.8L turbocharger used from '78-'83 can bolt on to any single carb intake via a simple homemade adapter plate and has an integral intake plenum/carb mount.

[Guest bobs302z]

thought I would throw my 2cents in. Iwent with the 268extreme energy cam and am farly happy with it .I am able to lanch hard and pulls all the way through rpm.(have beat my brothers 69 firebird and my friends 83 mustang with a 400hp 302 he cant get power to the ground have him contimplanting z car).At the same time the car has been used as a daily driver and to much fun all around .My dad (cobra with 429) and I are going to Silverwood theme part (Just north of Spokane Washington) for a little 18 mile fun on the long weekend in sept. My best run with gteck was a 13.98 at 105. All said and done go with mid range cam . ( http://members.shaw.ca/rguido/

[74_5.0L_Z]

I am using the Crower 15511 hydraulic roller cam in my 1989 powered 260Z. The car has the stock 5.0L bottom end, Edelbrock Performer Aluminum Heads 1.72 Roller rocker arms, Cobra intake, 24# injectors, 73mm MAF. The cam has the following specs with 1.6 rocker arms:

 

Part # Description LC Adv Duration Duration @ 050 Gross Lift w/1.6 RPM Range Kit #

15511 Excellent 5 speed cam, shifts @ 5800 114 278 / 282 218 / 224 .468 / .486 1800 to 6500 redline 84562

 

The lift for 1.72 rockers increases to .503/.525

 

I am quite happy with this setup. I have run 12.60s at 113 with autocross tires on the car (autocross tires suck at the 1/4 mile). The car pulls very well from just off idle to the rev limiter.