SBC 383 500ft/lb torque build

[Scotthatch]

My last thought is about gear ratio

If you have 500 ft lbs at 3000 rpm and gear to be at 80 mph at 3000 then you have an 3.12 rear gear with 1 to 1 on the transmission in last gear ... this puts 1560 foot lbs at the axle
If you have 500 ft lbs at 4000 rpm and gear to be at 80 at 4000 rpm you will have a 4.17 gear ...that puts 2085 ft lbs at the axle .. to get that same axle torque but at the 3000 rpm deal above you would need to make 668 ft lbs at 3000

Gear is a wonderful thing ... my nothing sbc in the shop truck with 4.56 gears does great ... drawback is at cruse it's a little high in rpm (th350) ..... this is part of why newer trucks have more gears

[GARY C]

My last thought is about gear ratio

If you have 500 ft lbs at 3000 rpm and gear to be at 80 mph at 3000 then you have an 3.12 rear gear with 1 to 1 on the transmission in last gear ... this puts 1560 foot lbs at the axle
If you have 500 ft lbs at 4000 rpm and gear to be at 80 at 4000 rpm you will have a 4.17 gear ...that puts 2085 ft lbs at the axle .. to get that same axle torque but at the 3000 rpm deal above you would need to make 668 ft lbs at 3000

Gear is a wonderful thing ... my nothing sbc in the shop truck with 4.56 gears does great ... drawback is at cruse it's a little high in rpm (th350) ..... this is part of why newer trucks have more gears

Yeah in the old days a granny geared work truck would tow a house with a limited powered straight 6 and do a whopping 45 mph top end but they did what they were designed to do, now days we want our cake and eat it too, thank you GM for my 6 speed 3/4 ton.

[Scotthatch]

I had a navy supply truck like that ...5.13 gears straight 6 3 on the tree with a granny first ... hauled some big loads out to the dock with that truck but was never meant to leave the base ..

[mtmvette]

I received some interesting information from a old time engine design engineer. He says over 450ft/lbs is highly probable. And furthermore, approaching 500ft/lbs is not out of the question. All under 3500 rpms. I have some parameters, can anyone Dynosym it for me?

[Scotthatch]

The build I posted above is 460 at 3500 ....

But what are your perimeters?

[mtmvette]

Do you have a program that can play with cam timing?

[groberts101]

Do you have a program that can play with cam timing?

Why don't you just buy pipemax? It's highly informative, especially pointing out where the exhaust system needs to be and will surely fall short once packaged into a vehicle. Will quickly show you some of the lower compression combo's posted here are getting up near 120% ve. Also points to much larger carb cfm requirements too.

Imo, most of what was said very early on is where you'll likely end up in reality. Then consider where all the info and spec's are coming from with respect to magazines and dyno charts. Everyone has an agenda when money's involved. Never hurts to dream and work towards one though.

[NewbVetteGuy]

Serious question to other engine builders here. Who is honestly prepared to build a tow engine (not talking diesel) going into a heavy load situation where you know it will be subject to extended WOT-( because thats what will be required to do the job , not fairy tale it will do it at 1/4 throttle etc) - usage on a regular basis in possible high ambient temps and driven by possibly some one who has no sense of things like pinging let alone knowing what station has decent fuel etc AND send it out the door with warranty?
I will say that I certainly am not. Fact is that given these parameters a small cammed engine will do the job, and a small cammed engine with good heads (for the rpm range ) and intake, exhaust etc for the rpm range does not require a high C/R to pull WOT at lower rpms and fact is that if you sit an 'on the edge' CR engine in these conditions with joe average behind the wheel and have him WOT pull it up thru a hilly/maintain area in high ambient temps with heck knows what fuel he dumped in out of the fuel can for the stationary generator as he could not be bothered stopping for fuel on the way home ,, that you are asking for trouble. Even then if you can refuse the warranty due to proving that it was due to abuse you will still look like a dick in the eyes of the all knowing customer.
Build as much TQ safely as the engine parameters allow and gear it right for the actual road speeds and use that it will see and it will do the job well for a long long time.

Not remotely an engine builder, but it's 2018: High CR Torque Build + EFI w tuned Knock Sensor: Done.

The cost of a new towing-focused truck today is pretty shocking; an engine build of a tow vehicle, even if using an old Gen1 SBC should be able to absorb the cost of EFI. The combo gets you better longevity, fuel economy, and torque: all seriously important goals for a comercial tow vehicle.
Although not super common, it seems like a pretty ideal situation to add EFI to an old rebuilt engine. -No?

-ESPECIALLY if SAE's current plans to dramatically increase the octane of regular pump gas in a 5 year timeline come true- then you can add timing back in as regular pump gas moves to 98 - 100+ octane and you'll be really glad you pushed the static and dynamic CR boundaries.


Adam

[Scotthatch]

I have no agenda .. link to the build was just one I found online that fit what you are doing ....

I do agree with the pipemax idea ... I have been very impressed with the numbers posted here from that program ...

As for having a program .... no I do not .. I do all the math by hand as I feel it gives you a better view of how it all works ..

If you are crunching cam specs there is not much to look at with a torque build because the rpm is so low overlap is going to be a bad thing .... the duration is going to be low so port efficiency is only going to be like 85% of what the heads flow and your biggest problem is getting enough valve exposure at peak piston velocity

IMAG2297.jpg

[NewbVetteGuy]

Do you have a program that can play with cam timing?

Why don't you just buy pipemax? It's highly informative, especially pointing out where the exhaust system needs to be and will surely fall short once packaged into a vehicle. Will quickly show you some of the lower compression combo's posted here are getting up near 120% ve. Also points to much larger carb cfm requirements too.

Imo, most of what was said very early on is where you'll likely end up in reality. Then consider where all the info and spec's are coming from with respect to magazines and dyno charts. Everyone has an agenda when money's involved. Never hurts to dream and work towards one though.

+1 on PipeMax. You can find free downloads of old copies of "Desktop Dyno" that will show you how the HP / torque curve will move with different cams, you can play with any of the "Dynamic Compression Ratio" calculators for another view of cam sizing/timing chart, but Pipe Max can show the impact of induction and especially exhaust changes, too and will even give quite conservative (IMHO, anyway) estimates of the required octane to run a given combo safely. -PipeMax gets very close to an ACTUAL "dynamic compression ratio" calculator as it's estimating actual cylinder pressures- which translate very closely to combustion temperatures which are I think the best indicator of detonation risk. (A couple more tweaks based upon intake air temp, head material, any thermal coatings, oil temp, & AFR and estimate combustion temp / exhaust gas temps would be even dreamier, but I'm pretty sure I couldn't afford it.)

Don't forget if you are really going to push your static and dynamic CR to the edge to maximize torque, and you're NOT going to go with EFI and a knock sensor, cooler air temperatures are even more important (and will also slightly help hp and that torque you're looking for @ 1% every 10 degrees F temp drop?? (I think that's right...)). I think an old Vizard quote is that every 7 degrees of intake air temp drop is equivalent to an 0.5 increase in fuel octane. A cold air intake should be included in every torque-focused / towing build, IMHO.

-Focusing on exhaust velocity may also help keep knock at bay -haven't seen this discussed much here, but I remember an article from some Mazda engineers talking about trying to keep knock at bay on the new very high static CR Mazda SkyActiv engines and they found that a tri-y style exhaust pulled the heat out and away from the head faster and helped keep more timing in longer, so I can't help but feel like there's something there. (Mazda wouldn't have included the extra expense of a tri-y style headers on an $18,000 car, if they didn't need to/ it wasn't a big help.) -Maybe read up on the Calvin Elston "school" of header/ exhaust design and focus on exhaust velocity and "blowdown length" to help an engine on the ragged edge. -Very relevant to a towing build, appropriately sized tri-y headers may help increase low rpm torque for the same reason. Seems worth considering in a torque / towing focused build especially with a dynamic CR pushing the limits of 93 octane....



Adam

[B Original]

Do you have a program that can play with cam timing?

Post away I have a copy of David vizard torquemaster I build a dozen engines off have it it's been spot-on with a predictions every time. It is way beyond the inferior programs like desktop dyno

I need your valve size, your Rod length, you're bore and stroke, RPM you want the engine to idle at, the peak RPM you want your horsepower to nose over at and the fuel you want to run, and desired compression ratio.

To get everything the way you want it you may have to be flexible with your compression ratio, intake valve size, and idle vacuum and desired fuel octane.You have to massage these items to get the optimal outcome. If your compression ratio is fixed you may have to compromise on one of your desired inputs.

[HDBD]

People forget how well just a blueprinted 295hp 350 ran. Even stock they were a strong pickup motor geared right. At 383 or 400 similar parts at the same cr and cam better yet.

[77cruiser]

Do you have a program that can play with cam timing?

Post away I have a copy of David vizard torquemaster I build a dozen engines off have it it's been spot-on with a predictions every time. It is way beyond the inferior programs like desktop dyno

How does one get that? How much is it?

[B Original]

Do you have a program that can play with cam timing?

Post away I have a copy of David vizard torquemaster I build a dozen engines off have it it's been spot-on with a predictions every time. It is way beyond the inferior programs like desktop dyno

How does one get that? How much is it?

Unless you hang out at Terry Walters machine shop. You have to attend one of his seminars in Charlotte. He gives it and the porting software (IPO) away for free as part of the seminar. The software is still in evaluation form it is complete for Gen I SBC's and near complete for SBF's but he still has a lot to go before the other engine groups are done before he can release it for sale.

Carnut know a lot more than I about the Porting software he has been posting post for a couple years about it
I know this is may be off subject but here is a video on the porting software I think there may be one on the torquemaster somewhere but I cant seem to find it
https://www.youtube.com/watch?v=GaEvJykjH9U

[77cruiser]

Post away I have a copy of David vizard torquemaster I build a dozen engines off have it it's been spot-on with a predictions every time. It is way beyond the inferior programs like desktop dyno

How does one get that? How much is it?

Unless you hang out at Terry Walters machine shop. You have to attend one of his seminars in Charlotte. He gives it and the porting software (IPO) away for free as part of the seminar. The software is still in evaluation form it is complete for Gen I SBC's and near complete for SBF's but he still has a lot to go before the other engine groups are done before he can release it for sale.

Carnut know a lot more than I about the Porting software he has been posting post for a couple years about it
I know this is may be off subject but here is a video on the porting software I think there may be one on the torquemaster somewhere but I cant seem to find it
https://www.youtube.com/watch?v=GaEvJykjH9U

Thought it might be something like that.