What's the bottleneck in my engine?

[ItBites]

I'm not up to speed on Ford heads, but I noticed a few things I would do differently in general since an engine is an engine:

2.05/1.60 valve sizes are a little small for 425 ci. (I use 2.30 for intake size on 427 ci BBCs). Your valves would make big low RPM power however.

750CFM, while OK by the usual formulas is a little small for PEAK (dragstrip) power in 425 ci. See other posts I have made regarding the relationship between max power and manifold vacuum and charge density at the valve. I use 1000 CFM throttle body on 427 ci.

.544 and 230 deg (I assume at .050 valve lift) is indicative of a low end power cam (short duration and low lift), but 110 deg lobe center is a little narrow and will produce more overlap similar to a high RPM cam. This cam seems to be a contradiction of itself from the manufacturer?

while .544 and 230 deg will work with 10.5:1 CR, the 110 lobe center wants higher compression and higher RPM. I would use 114 lobe center with 10.5: CR.

I think the Vic Jr is a high RPM manifold, and with 10.5:1 CR and 230 deg you can't effectively use that manifold.

210 cc intake runners in a BBC would be a low RPM power setup with good throttle response. I assume Fords are comparable (?)

In summary, I think you have some mismatched parts. My suggestion is to use the 10.5: CR and heads and go from there (since those are the most expensive components). The 10.5:1, 210 cc runners, 2.05/1.60 valve sizes just scream to me low RPM power with good throttle response. Now how to get the rest to match(BTW 600 HP is likely not where you are going with those heads/valve sizes and CR):

I'd put in a cam with maybe around or less than 230 deg at .050, but I'd up the lift to ~.620 and 114 lobe centers. This cam will have enough lift to fill the cylinders nicely (even with the little valves), a short duration to work with 10.5:1 and along with the wider LC, will tend to make the engine think it has higher compression (dynamic compression).

Then I'd go to a dual plane manifold. Maybe Air Gap or Stealth and if they have a separated plennum, I'd machine the divider out to get a combined plennum below the carb. Id also go to an 850 double pumper style carb.

I saw a suggestion to run to 7000 RPM earlier. I wouldn't with your CR and valve size. 7000 requires more overlap and your low static CR doesn't develop enough dynamic CR to work well with a lot of overlap.

I think you'd be much happier to try to work with the 10.5:1 CR and small valves and build more power on the low RPM end.

My $.02

[blykins]

I'm not shooting for 600hp....But I would like to see the 500 number come up on the hp....

I would really hate to tear the engine down to swap cams....I would much rather do an intake swap.....but I guess I'm open for anything.

[ItBites]

Do the cam.

.620 lift may require you to check valve/piston clearance? Some Ford dude can pipe in here. Get the 114 LC. Keep the duration short. Maybe as much as 235. No more.

On the intake: Levy may have good advice here. If this was a BBC, I'd for sure be right not to use the Vic Jr. They flow way too much for below 6500 RPM. In a Ford, there may be some big restrictions with a dual plane that I am not aware of? If not, the dual plane is a better match for your combo, given you use one with open plennum.

[blykins]

What really chews my butt is that Roush is offering a 402ci crate engine that makes 515hp and 500 lb-ft....with 10:1, and set of heads with 2.02's and 1.60's with a 770cfm carb....It's got a single plane intake and the max rpm is listed as 6250.

See, it's stuff like that, that makes me light-headed....They're making 30 more hp than me with 23 less cubic inches, a half a point less compression, and smaller valves....

It's gotta be the cam....

[Gordon Levy]

You are right about the parts for the BBC. The SBF is a totally different animal and is built totally differently. You can't compare the 2.
Having built many 408 windsers, we have tested everything you can put into one and the parts that are being used by this gentleman works the best with the proper cam profile. We have come up with our own cam profiles that do work great on the street but is a real monster when you get hard into the gas.

[MidOHasp]

blykins...

232 Intake 240 Exhaust duration at .050
.576 Intake Lift
.580 Exhaust Lift
1.72:1 Rockers

Therein may lie the difference. I'm running more than 0.030 additional lift. Also, that may be further compounded by the rockers. Not sure what rockers you have.

The Roush 402 most likely has bigger cam. That's how they do it with 23 fewer cubes.

I think it would be kind of fun to build up a non-stroked 351 (357), bulletproof forged parts, solid (and big) cam, big intake and heads, and just flow the hell out of it up to 8K RPM.

But what we have are some really exciting street motors. I knew I'd lose 30-50 HP with the RPM manifold. It certainly wasn't a cost issue, they cost the same. I just wanted to match a 1500-6500 Cam to 1500-6500 heads to a 1500-6500 intake to a 400 cubic inch 6000 RPM carb, etc... That combo is a TORQUE motor. That's why I did a stroker in the first place. I'd never trade my motor in, but wouldn't mind a high revving monster sitting in the garage next to it, either.

The BBC comparison makes little sense. 2.02(or 2.05)/1.6 valves ARE the big valves on a SB Ford or Chevy. Totally different animals.

Gordon,

400CFM?? wow..... Don't have clearance for the 2" element with that air cleaner assembly, but do if I get a smaller assembly. Any suggestions??

JP

[Gordon Levy]

I like to use a 14"x3" air cleaner with a 1.5" drop base. It clears most all the hoods on most of the cars out there.

[MidOHasp]

Who makes that cleaner?

[blykins]

K&N makes one like that JP.....look in Jegs.....

599-60-1280 is the part # $81.99 with element and everything

[ItBites]

Who let that darn Chevy guy in here anyway?

I'll put in my last two cents and then I'll go away.

1. I didn't say to go to larger valves. I know SB stuff is limited, I just pointed out that for 425 ci a 2.05/1.6 combo is small. Reality - deal with it... To work a combo like that, more lift than .544 is required to make bigger numbers. Ford, Chevy, whatever. I think .620 would work really well if you can fit the springs for it.

2. Lobe centers/duration: for engines (Ford or Chevy), more overlap is used for higher RPM and requires more static compression to maintain dynamic compression. 10.5:1 is low compression and you need to keep overlap reasonable. Do not try to run 7000 RPM with 10.5:1CR. This is better suited to 6000 RPM. I still recommend a 114 LC and somewhere around or less than 235 duration. This will keep dynamic compression high. Intake/Exhaust biasing on lift/duration is head dependent and I've already stipulated to not knowing Ford heads and made no biasing recommendations due to my lack of knowledge. Levy would likely be able to guide you in this area. He has test data.

3. It is known that Fords do not flow like a BBC (what does?) so, as I stated before, the Vic Jr may well be required in your large ci application due to limitations in the design that are exascerbated with dual plane manifolds. Additionally, low RPM torque can be a killer in these cars due to excessive wheel spin. It may be advantageous to lose some very low RPM torque in the interest of more power at higher RPM and if the flow is limited by design, the Vic Jr may be required due to the increase in ci. I passed on putting a 540 in my Cobra in favor of the 427 for this very reason and it is built to run high RPM. By the time I am over 500 rwhp (~6000 RPM), I can be hooked up and better able to utilize it.

Like I said in the last reply, Do the cam.


Now I will vanish into the ether...

[Mr.Fixit]

Your vic jrintake is the one you should be running. The dual plane edelbrocks run out of mustard on stroker SB's at too low an RPM. The vic jr heads don't have enough velocity, found more torque and HP with ported RPM heads. Everybody says "bigger cam" not me. You have heads that flow decent with good velocity, and a tiny cam can make great HP. .544 lift is not insufficient.

You have come pretty good for your first attempt at a parts combo in a stroker SB. The next 100 HP take a lot of R&D in specific parts combos, unless you have a small fortune to waste, you need to go with somebody else's combo, which they don't give away like a free recipe. It's the accumulation of a lot of tiny little things from this point on, no one thing will bump your numbers up to what you want. +3 +5 +10 keep making tiny gains and that how you get to the big numbers. You do have: really light pistons, long con rods, knife edged ultralight crank, well fitted crank scraper and windage screen, stud girdles so you get all the numbers your cam card says you should instead of deflection, a well worked on carb not just out of the box with different jets and power valve, fresh performance valve job on the heads right as they came out of the box, headers made for your engine not just generic fitsd SB fords in this chassis headers, etc, etc, right? You can find some more power with a different cam, I can't tell you which, slight differences in what your bottom end has and what we used to use do make a big difference.

[petek]

(A small voice from someone who hasn't ever built his own engine...) man, do I have a lot to learn!

[CJ428CJ]

Blykins,

Have you played around with any of the dyno software simulators like Dyno2000? You can try all kinds of different cam, compression ratio, valve, header combinations, etc. to see what might work best. Some people say Dyno2000 is just a "toy" but I have yet to see anyone post any Dyno2000 numbers vs an actual dyno run that varied significantly. Besides, you've already run your engine on a dyno so you can plug your current specs into Dyno2000 and see how close it is to your actual measured values. That should give you some sense of confidence (or not) that the specs you plug in give reasonably accurate numbers.

Chris

[petek]

A bit of thread drift, but I'm curious... is it possible to build up a 351 (or perhaps a 302) to withstand an occasional 9000 rpm? Not a peaky engine, but one with a fairly flat torque curve from 900 rpm to 9000 rpm. Streetable even.

[blykins]

Hey CJ,

Yeah, I've tried it on Desktop Dyno.....And it was only like 4 hp off....I forgot all about that....guess I should try plugging in some different things, shouldn't I? Duh.

[Gordon Levy]

Pete, Yes it is possible. We have built a couple like that. They are $30K+ engines.

[Mike Simard]

I just plugged in your motor in DYNOSIM ('cept I used my own AFR head flow data). I wish I could post screenshots, oh well. I still think you have a pretty good setup with realistic numbers but here are some individual changes and their simulator effect.
My base number is 493 hp.
850 carb +4hp
retarding cam 4 degrees +13hp
11:1 compression +9hp
240/244 @ .050cam (custom I had made for mine) +22hp

[MidOHasp]

Gordon... so if $30K buys you 9K RPM, how much does it cost for 8K? Are RPMs beyond 7K kind of like HP beyond 600...exponentially more expensive?

What about 7500RPM?

I really want a non-stroked SBF turning well over 7K RPM some day. The difference my 408 made in terms of sound from 6K to 6300 was actually enormous. I will never ever take it past 6500, but may put in that chip soon just to see if there is ANY gain past 6300. All the guts are forged, but I don't have an extra 10K laying around to build a new engine tomorrow.

But maybe in a few years, 7500+ RPM. I just think that the Gods would smile on that. How much would that cost?

[Gordon Levy]

I have what I call my super street 351. It is over 500hp with 9.5-1 compression and can be shifted at 7500 all day. I can do a couple of upgrades to this engine to get 600hp. I sell the engine complete with dyno sheet for $12995.

[BevanWright]

I agree with some of the posts earlier in this thread regarding over exaggerated horse power claims. I have ridden in plenty of modified v8s, and seen lots of different claims, but most engines are pretty tame.

It was only when I got my Cobra that I appreciated what a really big horsepower car was like, and how different my cobra is compared to all the others that I have been in (427, 428, 302, 351, 429 etc).

My car was apparently dynoed at around about 630 hp years ago, and since then has a bigger cam and better flowed heads.

I would be interested in any Chev experts (sorry ford guys) to give me what they would estimate for this setup:

Basically a 454 LS7 Crate BBC with 13:1 compression, LS7 oval port heads-ported (iron heads) running av-gas, Harland Sharp roller rockers, full race cam (sorry dont have the specs at work but power range is between 3 and 7k), dry sump, Hillborn injection, big headers, and side pipes.

I am always surprised by the number of guys on this forum who say that they have 700 hp etc that they use as road cars. My car is a monster to drive on the road, lumpy cam, far too fast for driving in traffic, and really unless you are at over 60 mph is pretty hard work. I have been over 190mph in this car, so it must be making big power, but how much?

Are there such huge variations in dynos?