Please take a look and let me know what you think for a street car with limited racing. This is not a dailey driver. If you have DD2000 and you see if larger AFR heads gain anything, I seem to lose with files :confused: .



How's this for a flat torque curve :) .

 

That's the file you sent me last week, right? Take a look at the .flw file I just sent you. It umps th HP to well over 600 :eek:

Tim

 

if i only had money :smash:

 

Let me tell you my thoughts. Since I bought my 68 six years ago, I had a good-performing small block and literally drove it everywhere, including cross country once. I wanted more power.

So I built the 427 big block and threw everything at it, squeezing out the most I could get out of that engine. Now, it's a jewel. It's beautiful and powerful....but also will probably get almost single digit gas mileage.
Basically, I have traded in some of the driveability for all out performance.
So I won't be able to take it very far, and it will be very expensive to gas up.

Had I built something better than a 350, but kept it a small block, I could have kept it much more streetable. I'm going to miss hopping in and driving it to work whenever I want, although when I do drive it, it'll be a trip for sure! A short, but intense trip.

If you build an all-out trick small block stroker that you can no longer daily drive, you'll have to trailer it to the Cruise In, instead of cruising it cross country.

If I were you, I'd build a healthy 406 and still shut out 98% of the cars on the streets, then take the money you'll save and spend it on cruising gas.

By the way, the power and torque curves seem kinda low. Especially for an open exhaust. I think you can get power numbers like that out of a 406.

What would I have done differently? I do have a 406 in my garage. I probably would have destroked it to a rev-happy little 377 with a pair of turbos and a big intercooler.
But don't get me wrong...I love the big block so far. I just won't be able to drive it nearly as often as when it was a small block.

Something to think about.

 

I think 421's can run pretty good, and can still get close to 20 mpg.


[Modified by tpi 421 vette, 4:25 AM 10/24/2002]

 

That is not a good cam. You never even get up to 90% Vol E I'll send you some H-roller specs I thought up for another guys 421 ci. I was very surprized when then .050 number I thought up were very close to the Crane 222/228 look at the crane sight under power max cams and then plug in the numbers on DD2000

 

Yes Tim, it's the same one :yesnod: . I didn't realize that I lost some of the numbers on the pic when I tried to make it legible here on the forum to after I posted :rolleyes: . I need to update my winzip, then will be checking out your file. :eek: 600hp :eek: that sounds like it could be fun :D !

Qwickvette :D :cheers:

MoMo as usual you bring up some very good points. The mpg is one of the reasons for me to stay with a small block ;) . I recall talking to you at BG about your 427BB :yesnod: , I can't imagine how that monster must feel :D ! I do hope to make it back to BG for the next cruise-in, but this next engine won't be ready before then :sad: .


TPI421, 20mpg would be incredible :yesnod: ! If I could still get 15mpg afterwards I'd still be very pleased ;) .

George I did noticed that my Vol E wasn't the greatest. I did get some incredible efficenty number when I added a turbo, but I'd like to keep it to all motor for now ;) . I'll try the numbers from Cranes site later when I get home :) .

 

You can get AFR 220 flow numbers from their website, better than the 210 but not a big step (I have a set on order). If it's a street/strip "toy" then I think your cam is a little small, compression too low (especially with aluminum heads) and intake choices pretty restrictive. With the big inch motor you can stand more and still keep bottom end torque up. I'm "expecting" (ala DD2000) something around 550 HP from my 406.

Try the Crane 118751 cam (my choice), 11:1 compression and a single plane manifold with 850 carb. When you build it go with a 850 vacume secondary carb if you want gas milage better than single digits (DP's on the street really suck down the gas).

Use this $0.02 wisely - Greg

 

My concern is that the engine peaks at 6000 RPM, and it can get very expensive to build a 421 for 6500+ RPM redline. You might want to calm the cam down a bit to something like the XR270HR. You can gain 45 lb-ft in torque at 2000 RPM, and average close to 540 lb-ft from 2500 to 4000 rpm. You will sacrifice peak HP (496 at 5500) and RPM, but the engine build should be cheaper, and it will last longer.

If you want lots of Revs, how about a 377 or 386? I've simulated a wild 386 (Speed-O-Motive 3.562" crank) running 11:1 compression with 575 HP at 6500, but the torque is way below yours at only 400 lb-ft at 2000 rpm - and this one is through the mufflers.

Here it is:



[Modified by bcwaller, 12:47 PM 10/24/2002]

 

Greg those are some good tips that I'll take a look at :) .

BC- Looking at your dyno, it doesn't peek until 6500 rpms. Why do you think that 6000 rpms is high :confused: (I ask because I don't know) ?

If I'm going to buy a whole new rotating assembly and go with all forged components will this be safe for those type of rpms? Also destroking is good for rev happy engines from what I've heard, so that's my reasoning for looking for something that peaks around 6-6500 rpms.

Is it recommended to have a lot of torque down low or something that climbs with the rpms for traction/ drivibility purposes?

Lastly, what makes for a quick revving engine since I've heard that 400sbc's were dogs (something I would be VERY unhappy with)? Is it a light weight assembly, short/ long stroke, torque, hp ?

Thanks, I'm asking lots of questions because I have time before I buy any parts and want to be sure I spend wisely :cheers: .

 

I don't have all the answers, so I hope others chime in. Your 421 was a stroked 400, and the 400 already has a longer stroke than the 350, which is even more than teh 327. You talk about destroked engines, but you were listing a stroker in your simulation.

My simulation has a shorter stroke than yours, so I think it can take the revs more than the stroker 421 you showed us. It also sacrifices low end power for high rpm power. The 421 will be the king of torque compared to any small block out there!

Somewhere I have the math that talks about the stress on the rod at various RPM and strokes. But you can imagine the the stress rises with both stroke and RPM, so an assembly that is ok for 6500 RPM with a 3.25" stroke may no longer hold up at 6500 RPM with a 3.875" stroke! Even forged parts have their limits...

My 386 is just a tad more stroke than a 350, so I would think it would be equivalent from a build standpoint. But now we get into dricing style! Torque is what pushes the car forward, so torque is good. Having lots of torque down low makes a car very streetable, and most street cars do 90% of their time below 4000 RPM. But if this is for some street, and for fun on the track, you will spend more time at higher revs. Think a bit about how you plan to use the car and realisitically guess the RPM range. Build an engine for that range.

I think that the engines rev more quickly when they have lower mass rotating assemblies. In general, the shorter stroke engines have lighter assemblies (or can) because there is less metal in the crank, the rods might be lighter if they are not going to be stressed as much, etc. You can buy lots of lightweight ($) parts to make even a stroker rev quickly. But the lightened crank will be a lot more money than a forged crank. Lighter flywheels and clutches are avaiable in a range of prices.

As my final reference, I have always driven manual transmission 327 C2s, so my latest engine is a 353 - a 400 block with a 327 crank. Now you know why I like peak power at 6500 RPM!

 

BC I have a friend who has a 3.0" (302)forged crank that says I would love in my car because of how snappy the engine would be with such a short stroke. He has shown me the high hp 3's you an make with a destroke and there is no denying(sp?) it, but the thing peaks up near 8-9000 rpms which I just don't ever see myself pushing :crazy: !

Your correct, my example is a stroked 400 to a 421 because I've heard all this talk that theirs no replacement for displacement. I'd like BB power in a smallblock package :D . Realistically I don't see myself going above 6500 rpms on purpose ;) .

A 353, now that's a combo I've never heard of, interesting, I'm going to have to play some more with DD :rolleyes: ....... :)


[Modified by SmokedTires, 5:49 PM 10/24/2002]

 

400's aren't dogs if they're built right.

With 6 inch rods, they have a rod/stroke ratio of 1.60, which is very close to that of a 350. What this means is, a long-rod 400 will rev every bit as well as a 350, except with 50 more cubic inches.

 

How about long rod 353? 6.3" rods and a 3.25" stroke (and a 4.156 bore makes 353 cubes), also a lightweight flywheel. Think I can rev it?

 

On a street/strip car I would run as much cubic inch that's practical, or should I say affordable.Torque is what you use and what makes a street car fun.

 

Thanks for the info MoMo :cheers:

TPI421 your thinking is right inline with my own :yesnod: . You've got some great #'s :D !


[Modified by SmokedTires, 10:50 AM 10/26/2002]

 

If anybody said that one motor revs faster than another:( What are they talking about? Once your hooked through everything including the rear tires. It doesn't really matter unless everything is light weight.

I wanted a 3.875 to make my motor a 396 instead of a wimpy 383. Snappy throttle is the total tune and brut torque. Your going to need 315's like me to keep it moving in first gear:)


[Modified by gkull, 7:43 AM 10/28/2002]

 

Thanks SmokedTires

 

That motor is very similar to the 434 I bought. (http://cemu.org/car/434/434.html) Haven't run it quite yet. Small blocks that big like big cams though. I ran a 224/230 hyd roller (XR276) in my 388 and it was too small. My 434 has a 240/248 hyd roller (.614/.576 lift) and I think that is going to be on the small side. BTW I think a good target max rpm is about 6500 (shift point 6200-6500 ish), which is as high as you'll want to go with a hydraulic roller (if you choose to go with one), and also about as high as you'll want to go to maintain good low rpm manners for a nice drivable car.

Then once you are running larger cam, you'll need to get the compression ratio up closer to 11:1. Skip the dual plane, on an engine that big you can gain power across the board with a single plane. My 434 has a 750 Race Demon (no choke tower, I believe it's a little underrated @ 750 cfm). If I bought another carb it would be at least 825 cfm. And double pumper for sure - but that's just personal preference. As for headers the smallest you'd want to go is 1 3/4, it sounds like 1 7/8 is a better size (Ed Henneman recommended 1 7/8 for my combo, and he prides himself on not erring on the large side). Unfortunately the largest reasonably priced off the shelf headers for us c3 guys are 1 3/4, I just got a set of Hooker Super Comps back from Jet Hot so I'm going to run those.

My motor also has AFR 210s, and with the combo as is I'm hoping for at least an honest 550 hp. With a little port work and a cam upgrade it'd be nice to have 600 hp, I'm just going to play it by ear. At either of those power ranges I'm going to be hoping my rear end stays together, and I'll worry about more power after I get safety loops all around and a few other things.

Rob

 

I totally agree with Rob. When I built my NA SBC 427, I tried 4 different mech roller cams on the dyno, and the largest cam (256/264) made more power and torque all the way across the rpm range than all the smaller cams. Each time I increased the duration, the result was the same - more power and torque everywhere, with no decline in idle quality or throttle response. I think you could probably go as big as something in the mid to high 260's before you reached the point where you started to sacrifice low end torque for more mid range and upper rpm power.

You're basically building a big block in a small block package, and all but the best cylinder heads are a restriction, so you can run more cam than you'd otherwise consider for a street small block. The 4.00" strokes have a lot of pull on the intake, so velocity is not an issue. My heads have 255cc intakes and the engine still produces tremendous torque and response. In NA form, it was making 500 ft lbs by 3000 rpm, and never fell below that until past 7000 rpm. I

There's alot of bias against small blocks by certain groups on this forum, but with the right combination, a small block can be built that will outperform most big blocks you see on the street. Of course, given the same level of mods, the big block will outperform the small block, but I don't think an big block fan would say 500+ ft lbs from 2800-7000 rpm is not impressive.