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Serious tourque and radical lope from a 400? need advice!


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I want to build my sb400 for some stump pulling tourque, and still get that super radical idle that soulnds so sweet. Is that a conflict of interests? Also will a T56 work well with a tourqey motor like that? I want to make a serious streetable drag car. I don't mind a high compresion motor, as I will only take it out on the weekends, so CAM2 isn't a problem. What do you guys think?

Laterz,

Tony Rohn

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Guest Anonymous

The T56 will handle it. As far as the super lumpy idle, thats usually caused by a long duration cam which the lumpy'er you go, the less low end torque you get.

A manual transmission though and the car's light weight in a drag/street car will make up for the cam's lack of bottom end torque.

Note, it will be a tad weak unless your taching 2000-2500 rpms so street driving will not exactly be as crisp as a smaller cam. Vacuum will also be lower, if its low enough, you may need a vacuum resevoir canister to keep your power brakes working ok. Just a opinion.

 

Lone

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Guest Anonymous

I a word for sbd and tourque look no further than lingenfelter for the tourque.

seems like nowadays he is only promoting new car stuff though but his book is great place for understanding the tourque planning. His 406 for the silver state challenge had I think 500 ft/lbs 500hp!!! and another vette he did went 12's ,180mph and 25+mpg!!! all with the help of monster tourque!

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I agree with the small lobe sep angle. Helps the low end and adds to the lope. Used to run a 256 @ .050 with 106 lsa. Really nasty!! Heck, call comp cams tech. Tell them exactly what you're looking for. There's an article addressing this in a recent performance magazine. Anyone remember?

JS

 

[This message has been edited by John Scott (edited April 06, 2001).]

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Tony, I like having the torque and the lope as well. How about a cam with like a 106 or 108 lsa (as mentioned), with added compression (since your BMEP will be down with that cam) and make it solid flat tappet to boot. 230-240@0.050 duration.

 

There's something about the hearing a lumpy idling V8 through low restriction exhaust and header tubes that's very visceral and appealing to this old hotrodder.

 

But I do know that all that lope takes away the lower part of the torque band, and more importantly, throttle response.

 

Ahh, the compromises we must make wink.gif.

 

------------------

Pete Paraska - 73 540Z - Marathon Z Project

pparaska@home.com

Pete's V8 Datsun 240Z Pages

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Guest Anonymous

I donno, I'm thinking of putting in a Type R driveline in the rear of the Z and a nice racing seat where the current small block resides. Add a big clear prostock hood scoop to clear my head. I figure this ought to go real fast, have good ventalation and it would have variable cam timing!

 

tongue.gif

Lone

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Hmmm,

From all the stuff I've been reading, and the arm twisting my mechanic gave me, I think I want to go with the type of cams suggestions given, in a 377!!! I think I can get plenty of tourque with that and have a quick revving engine that feels like it belongs in a Z. Plus super tourquey cars are king on the street and 1/8 mile, but seem to lack a little in the 1/4 mile. Only problem is there seems to be two ideas of what a 377 is. The most common seems to be a 400 w/ a 327 crank & .030 pistons. The other is the same only it's a 350 crank. Whats the story here?

Little confused,

Tony Rohn

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Guest dankinzle

There was a nice article on cam specs and such in this months (somehow it's May already) Chevy High Performance Mag. It mainly just talks about theory though.

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quote:

Originally posted by TonyZXT:

...Only problem there seems to be two ideas of a 377, The most common seems to be a 400 w/ a 327 crank & .030 pistons. The other is the same only it's a 350 crank. Whats the story here? Little confused,

Tony Rohn

 

Tony,

 

A 400ci has a bore 4.126 & a 350ci crank has a 3.48 stroke -vs- a 327ci stroke of 3.250. If you put a crank of 3.250 in a 400ci that would give you 348ci & if you used the 3.250 stroke w/400 after a .030 you'ld end up w/a 353ci...so you see-you cant get a 377 by using a 327stroke crank in a 400.

 

To get a 377 you have to use a 350ci crank with the 3.48stroke & put it in a .030 400.

 

One other thing about your idle quality; its usually a rule of thumb that in order to maintain engine quality w/long duration you will need a wider Lobe Separation Angle....so if you want the lope then go w/a cam that has a narrow Lobe Separation Angle w/a long duration & you will get that Lopy'ness your looking for!

 

One more thing about cams; if your not sure about your profile you can derive close proximity of what you need by reading about your engine in other articles & comparing their cam w/your needs by: Lets say their build is too much and peak power comes in at too high of an rpm/you simply deduct 500 rpm's for every 10degrees of Duration removed to determine where your Peak Power will come in; or if the build is too small you can add 500rpm's for every 10degrees of Duration you add! You get the picture/just takes some time & a piece of paper/pen!

 

Kevin,

(Yes,Still an Inliner)

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