SBC 421 combo advice

[raynman1969]

I can tell you from the current setup on my car with a well built 415, you will not like a 5000 rpm converter on the street. At the track it is a serious yahoo.

Hard to drive on the street? Does the tranny get hot.

[KnightEngines]

I know plenty of guys running 5000+ converters & 4.11-4.44 gears on the street, not highway use (well, a couple do, but they're 'special'), most guys love big converters & short gears on the street.
Personal preference really.

[steve cowan]

I don't understand why people cry about 5000rpm converter on the street
My hunk of junk Hq Holden Ute Runs pump swill friendly 383 sbc
Turbo 400, 8inch. 5600 rpm converter
4:1.1 rear gear 255 drag radial tyre
11.10 @ 121 consistent
Yes the engine only makes 510 -520 hp
But it is nearly 2 hr drive for me highway driving to my local track sitting on 60 mph @3200-3300 rpm
Yeah I probably should put a gearvendor overdrive on but at $3000 plus $ Australia
Forget it
I would rather spend the money on a new dart block so I can make 600 hp
Drive it, drive it, who cares

Steve C

[cjperformance]

What are you trying to achieve with the combo? Bit of street, often raced.

Are you seriously trying to chase numbers/HP or will you be happy to go with whatever it does and just perfect the tune and car set-up from there?
How much more cash do you want to spend?

You could just get the 220 heads, run the cam and convertor you have and save $$. It will go great and work fine with the convertor you have, yes better with more stall but it depends on how seriously you want numbers. It will drive fine with what you have, but will be faster at the track with 4500++

Id happily run 150 n2o on that cam, if youre happy at that dont change it. Your cam will be snappy as heck with no n2o, wider LSA will dull it off a little and affect the convertor stall so not great if you keep your current convertor.

The wider LSA for an n2o cam has real advantages for higher n2o use, the wider lsa effectively retards the intake events and advances the exhaust events ( decreases overlap figure) and the real advantages here for more n2o are, the retarded intake giving a lower cylinder pressure at the beginning of the n2o pull making the engine less detonation prone, the advanced exhaust events open the exhaust valve earlier in the exh cycle to start getting the much increased volime of exhaust gas out early to reduce pumping loss later in the exhaust cycle, and the resultant reduction in overlap leaves less in/ex valve open time and flow area to reduce overscavenging (unless your exhaust is extremely restrictive) caused by the higher gas velocity thru the header pipes due to the increased gas volume created from using n2o.

So, either leave it as specced and run a small shot and be happy! Or swap cam AND convertor, use more n2o and be really happy!

If you run a 4500+ 5000 etc stall then yes it will still drive fine on the street if the convertor is good. Wether it is 'nice' to drive on the street is subjective to the driver !! Some love 5000 stall and low gears and are happy, i have customers cars that they love but i dont even really enjoy doing a test drive, personally after a lap of the block im over it! So if it were my personal build i would be going max ci, less stall , higher gears but more n2o like 250hp but in 2 stages. Its all subjective to the drivers thought on whats nice and whats not, so decide what you expect/want and run with it.

[cjperformance]

I don't understand why people cry about 5000rpm converter on the street
My hunk of junk Hq Holden Ute Runs pump swill friendly 383 sbc
Turbo 400, 8inch. 5600 rpm converter
4:1.1 rear gear 255 drag radial tyre
11.10 @ 121 consistent
Yes the engine only makes 510 -520 hp
But it is

nearly 2 hr drive for me highway driving to my local track sitting on 60 mph @3200-3300 rpm

Yeah I probably should put a gearvendor overdrive on but at $3000 plus $ Australia
Forget it
I would rather spend the money on a new dart block so I can make 600 hp
Drive it, drive it, who cares

Steve C

Sh!t Steve, i would have slashed my wrists about 20 mins into that drive! Lol

[raynman1969]

Thanks for the advice , I think I will run the cam as is and use 150 shot and see what happens. Only want to build this once and drive/race the snot out of it.

[englertracing]

What are you trying to achieve with the combo? Bit of street, often raced.

Are you seriously trying to chase numbers/HP or will you be happy to go with whatever it does and just perfect the tune and car set-up from there?
How much more cash do you want to spend?

You could just get the 220 heads, run the cam and convertor you have and save $$. It will go great and work fine with the convertor you have, yes better with more stall but it depends on how seriously you want numbers. It will drive fine with what you have, but will be faster at the track with 4500++

Id happily run 150 n2o on that cam, if youre happy at that dont change it. Your cam will be snappy as heck with no n2o, wider LSA will dull it off a little and affect the convertor stall so not great if you keep your current convertor.

The wider LSA for an n2o cam has real advantages for higher n2o use, the wider lsa effectively retards the intake events and advances the exhaust events ( decreases overlap figure) and the real advantages here for more n2o are, the retarded intake giving a lower cylinder pressure at the beginning of the n2o pull making the engine less detonation prone, the advanced exhaust events open the exhaust valve earlier in the exh cycle to start getting the much increased volime of exhaust gas out early to reduce pumping loss later in the exhaust cycle, and the resultant reduction in overlap leaves less in/ex valve open time and flow area to reduce overscavenging (unless your exhaust is extremely restrictive) caused by the higher gas velocity thru the header pipes due to the increased gas volume created from using n2o.

So, either leave it as specced and run a small shot and be happy! Or swap cam AND convertor, use more n2o and be really happy!

If you run a 4500+ 5000 etc stall then yes it will still drive fine on the street if the convertor is good. Wether it is 'nice' to drive on the street is subjective to the driver !! Some love 5000 stall and low gears and are happy, i have customers cars that they love but i dont even really enjoy doing a test drive, personally after a lap of the block im over it! So if it were my personal build i would be going max ci, less stall , higher gears but more n2o like 250hp but in 2 stages. Its all subjective to the drivers thought on whats nice and whats not, so decide what you expect/want and run with it.

Get a used quick change rear end,
Set it up so you can flip the gears when you get to the track

[steve cowan]

I don't understand why people cry about 5000rpm converter on the street
My hunk of junk Hq Holden Ute Runs pump swill friendly 383 sbc
Turbo 400, 8inch. 5600 rpm converter
4:1.1 rear gear 255 drag radial tyre
11.10 @ 121 consistent
Yes the engine only makes 510 -520 hp
But it is

nearly 2 hr drive for me highway driving to my local track sitting on 60 mph @3200-3300 rpm

Yeah I probably should put a gearvendor overdrive on but at $3000 plus $ Australia
Forget it
I would rather spend the money on a new dart block so I can make 600 hp
Drive it, drive it, who cares

Steve C

Sh!t Steve, i would have slashed my wrists about 20 mins into that drive! Lol

Hey Craig
I am 47 years old and probably should be over this sort of behaviour
But hey its fun and still learning

[cjperformance]

Steve, mate im only 45 , and a half! Haha, no ya never get over the power rush i dont think. I have many older friends and family that are petrol heads, one mate at 84 about to get back onto his Yamaha XS650 that i have fitted a turbo to ! They all say they may have gotten a bit more sensible as to where they use the power but all still love it.
Dont get me wrong i love fast stuff but i was always into big block stuff when strokers were costly and got used to the big lower down grunt and 3.25/3.5/3.7 gears. I think due to that, whenever i get something street wise that runs hard but is alwats up on the rpm im always thinking of how i can make it just as fast but drop the rpm at cruise etc. Which did make me pretty proficient in
n2o and overdrive trans conversions!
Nowadays i do like the mild engine with boost route aswell.
All horses for courses i guess.

[rfoll]

I can tell you from the current setup on my car with a well built 415, you will not like a 5000 rpm converter on the street. At the track it is a serious yahoo.

Hard to drive on the street? Does the tranny get hot.

Nothing gets hot but the passenger compartment, no flooring and a pair hot of 3" pipes running under the floorboard. The reality of 5000+ converters is that you are always turning lots of rpm. Every stoplight means leaving with the engine rpm way up until you hit the next stop, which could be 2 blocks or less. With a really loose converter, engine braking becomes a thing of the past. If your not careful, the tires will go up in smoke under acceleration, at anything under 60 mph, and that tends to get the attention of people you would rather avoid. Did I mention how incredibly loud things get with the engine rpm always over 3000? The novelty wears off really quick.

[turdwilly]

[/quote]
The reality of 5000+ converters is that you are always turning lots of rpm. Every stoplight means leaving with the engine rpm way up until you hit the next stop, which could be 2 blocks or less. With a really loose converter, engine braking becomes a thing of the past. If your not careful, the tires will go up in smoke under acceleration, at anything under 60 mph, and that tends to get the attention of people you would rather avoid. Did I mention how incredibly loud things get with the engine rpm always over 3000? The novelty wears off really quick.
[/quote]

Sounds like you need to find a new converter company.

[hoffman900]

The wider LSA for an n2o cam has real advantages for higher n2o use, the wider lsa effectively retards the intake events and advances the exhaust events ( decreases overlap figure) and the real advantages here for more n2o are, the retarded intake giving a lower cylinder pressure at the beginning of the n2o pull making the engine less detonation prone, the advanced exhaust events open the exhaust valve earlier in the exh cycle to start getting the much increased volime of exhaust gas out early to reduce pumping loss later in the exhaust cycle, and the resultant reduction in overlap leaves less in/ex valve open time and flow area to reduce overscavenging (unless your exhaust is extremely restrictive) caused by the higher gas velocity thru the header pipes due to the increased gas volume created from using n2o.

According to Billy Goldbold, Comp Cams lobe designer, the reason for wide LSA on higher N2O set-ups is strictly about knocking down the mid range, when the car may not be able to put it down, and shift the power curve up a little where the car can.

[autogear]

Im a hack when it comes to engines; but I don't need the bragging rights of "XXX hp all motor and OH YEAH I added a kit of N20"
Maybe Im different, but I'd over-build the engine for durability, knock the compression and cam down a peg; and just throw the bottle at it on the strip, using one of the nitrous controllers on the market. Sneak up on the tune and you can have a car thats probably more manageable on the street (and absolutely rugged); and an absolute beast at the strip.

Im probably way off base LOL

[CamKing]

The wider LSA for an n2o cam has real advantages for higher n2o use, the wider lsa effectively retards the intake events and advances the exhaust events ( decreases overlap figure) and the real advantages here for more n2o are, the retarded intake giving a lower cylinder pressure at the beginning of the n2o pull making the engine less detonation prone, the advanced exhaust events open the exhaust valve earlier in the exh cycle to start getting the much increased volime of exhaust gas out early to reduce pumping loss later in the exhaust cycle, and the resultant reduction in overlap leaves less in/ex valve open time and flow area to reduce overscavenging (unless your exhaust is extremely restrictive) caused by the higher gas velocity thru the header pipes due to the increased gas volume created from using n2o.

According to Billy Goldbold, Comp Cams lobe designer, the reason for wide LSA on higher N2O set-ups is strictly about knocking down the mid range, when the car may not be able to put it down, and shift the power curve up a little where the car can.

That makes no sense.
The mid-range power actually picks up on the wider LSA with NO2.
It does flatten out the torque curve, but it makes more power above peak torque.

[Ericnova]

The reality of 5000+ converters is that you are always turning lots of rpm. Every stoplight means leaving with the engine rpm way up until you hit the next stop, which could be 2 blocks or less. With a really loose converter, engine braking becomes a thing of the past. If your not careful, the tires will go up in smoke under acceleration, at anything under 60 mph, and that tends to get the attention of people you would rather avoid. Did I mention how incredibly loud things get with the engine rpm always over 3000? The novelty wears off really quick.
[/quote]

Sounds like you need to find a new converter company.
[/quote]

I thought the same thing when I read it......get a better converter, sounds 30 years out of date technologically.