427 Low Riser - 500hp Goal

[Autoholic]

If the OP, or anyone else for that matter, wants help selecting gears I'm happy to help out by creating a gear spreadsheet for you. I can show you approximately the speed the car will reach in each gear at the shift point and what the RPM's will be after the shift. It can be a helpful tool when looking at various ratios and how they will impact the car. I take your shift point RPM, tire size, and trans gear ratios and look at the various final drive ratios available for your given rear end. Also helpful if you are looking at various transmission options. The math is sound and accurate to a few MPH and RPMs, unless you start nearing 200 MPH and then wind resistance becomes a PITA and all hell breaks loose. Aero becomes an issue and you start dealing with is the car gear limited or power limited. For street / freeway driving, it's a reliable way to look at the problem.

[SRS_Chris]

Thanks for the information everyone.  I will be sure to post updated information as this motor comes together.  It likely won't see the dyno until spring.

[turbohunter]

I'm happy to help out by creating a gear spreadsheet for you.

That might make a good sticky or some other way for quick reference.

[cjshaker]

The math is sound and accurate to a few MPH and RPMs, unless you start nearing 200 MPH and then wind resistance becomes a PITA and all hell breaks loose. Aero becomes an issue and you start dealing with is the car gear limited or power limited.

Gearing math shouldn't change with MPH or wind resistance...unless you have tire slippage, or maybe a converter is slipping in an automatic transmission. Do people still use those things?

[cammerfe]

Some years ago I built a 390 with 'good parts'. I used a C4 PI block. I also used 'F5' Dove so-called Canadian CJ heads in aluminum with 2.100 and 1.65 valves. I used a Dove single 4 intake and had both heads and manifold massaged and matched by Wayne Kuchtyn at Headwinds.

Comp did up a solid roller for me after I spec'd it as giving the 'most possible while having the street manners of a factory AA cam'. They gave me 242-248 at .050, 110, and .658-.666. It idled at 800 or so, pulled hard to 7500, and made more than your target 500.

Since a custom cam grind from Comp only costs a little bit more than an 'off-the-shelf' I'd certainly look into it.

KS

[Autoholic]

Gearing math shouldn't change with MPH or wind resistance...unless you have tire slippage, or maybe a converter is slipping in an automatic transmission. Do people still use those things?

True, that it shouldn't change but the problem you'll face is that the MPH is unobtainable without more power. That's what I was trying to say. I've spec'd a real-life trans and diff combo that could hit roughly 300 MPH, using a TKO 600 and 2.73. The problem is the power required to go that fast is in quadruple digits in any car. You can use the same math though to show if your problem will be gearing instead of power to hit a desired speed. And rolling resistance comes into play and you can't look at this in a simple linear way because tires don't have a linear performance but this only has a small impact on actual speed vs theoretical.

In the end, I also don't want someone to take a spreadsheet I created and say I built it using these precise numbers, why can't I hit 100 MPH in 4th when your math says it can hit 101?!?!? I trust my numbers but I don't feel like being on the hook LOL.

[gdaddy01]

would you mind doing the math for us common folks ?  I have ' 61 390 hi po in a '62 ranchero with straight axle , four speed , 3:00 gear , 26 inch tires . I drive it a lot , about 7000 miles , cheap tack reads 3000 rpm at about 70 mph . I do not think it is right , but have not taken the time to change the tack . auto gauge tack .

[Autoholic]

I have created a thread for the calculator and any discussion about gear ratios should probably move over there so as to not hijack this thread.

[Autoholic]

would you mind doing the math for us common folks ?  I have ' 61 390 hi po in a '62 ranchero with straight axle , four speed , 3:00 gear , 26 inch tires . I drive it a lot , about 7000 miles , cheap tack reads 3000 rpm at about 70 mph . I do not think it is right , but have not taken the time to change the tack . auto gauge tack .

Check the other thread for my comments and questions on your setup.

[SRS_Chris]

An update on this project...

The C3AE-H heads flowed really well out of the gate.  A basic three angle valve job and some minor blending in the bowl has yielded 271cfm@.500", 277cfm@.600", and 280cfm@.700" with a 2.19" valve.  These are much better numbers than I expected from these vintage iron heads.  I have a few more minor things that I want to try in the throat and at the SSR in an attempt to get solid 280's at .500 - .600 lift. 

The exhaust is flowing equally well with minor clean up.  Peak flow is around 220 cfm @ .700 lift. 

Does anyone have any tried and true Low Riser porting tips they wish to share? 

[westcoastgalaxie]

Hey Joe,

Do you mind posting a link? Not finding your posting in the search. Only going to get harder as the months pass.

Thanks

[Tommy-T]

To the original poster:
I realize that you're selling 500 horsepower to a customer so this post might not be relevant. I know little of building an engine to a dyno number.

The engine you describe in the opening post could easily run 11's in a 3300 lb. car with 4.56's, a flat tappet cam 245@.050 with .600 lift, and 10" slicks. I've seen Low Riser 427's in Mustangs do it time and again. There are few on the street that can run harder. I can't really tell you if that takes 500 hp or not.

As far as the center oiler 427's and solid rollers go, for me at least, it's kind'a moot. Your springs will go away WAY before your lifters will. From my experience, springs every year as normal maintenance, lifters every third. This I learned the hard way running the old Comp 308R...with which I "tickled" the 10's in my Mustang.

[SRS_Chris]

Thanks for the feedback Tommy.  I appreciate the experienced input.  There are dozens of formulas out there that people (myself included) use to calculate horsepower, airflow, required intake valve size, etc, etc, but relevant experience trumps all in my opinion. 

[Mack]

Where would I find the link to the calcutator for gear ratios

[SRS_Chris]

Unrelated to this thread, but try this link...

http://www.wallaceracing.com/Calculators.htm