Building a 393 low end torque engine

[WheelHorse]

Low end torque less than 2000 rpm....Smells like diesel.

 

[pcf_mark]

Sounds like you made up your mind. Enjoy your combination, post up the dyno sheet.

The dynamics of a stroker are unique.

 

[brewchief]

The enginemasters show on the motortrend app(and maybe on youtube) built a 410" sbf to test if you could run to big of a cylinder head.(ep28)
With a pretty small cam(the don't state brand but by specs it looks like a comp extreme energy XE262H) and a couple different sets of AFR heads they were making 450ft lbs when the dyno graph started at 2500rpm with peak around 500ft lbs at 3900, horsepower was in the upper 4s peaking at around 5500rpm.

This was done with a Performer RPM air gap intake, 850cfm ish carb and 1 3/4" headers, all parts that people think will kill torque.

If you insist on running stock exhaust manifolds and a tiny carb then I wouldn't bother with a stroker, just run a mild 351w.

 

[68ford]

The reason instated my peak HP at 5600 was to show how strokers need more cam and big heads. My cam is a 351w would do 7400 rpm per the manufacturer. But in a 438 the HP is almost dropped 2000 RPM. My point was you can not go off what cams do in a 351w because the increased displacement all of which is from stroke.

 

[nvrstuk]

Wayne, I stated the cam info earlier...

The OP wants a diesel...oh, btw 300 in line 6 cylinders DO fit in a Bronco but they look too much like a Chevy to me... lol

Build what ever you like, enjoy it, keep an open mind.

 

[jckkys]

The lightning cam puts the power curve close to where I want it. More duration would move the power curve to a higher RPM. If anything, I want it lower. It seems nearly impossible to get hotrodders out of the high RPM high HP mindset. As I said, the 300 inline 6 had an ideal power curve with maximum torque at 1600 RPM and maximum HP at 3800. I want the same with 2 more cylinders and nearly 100 more CI. 21 yrs. driving trucks taught me high RPM is useless. As for headers I've been there done that. They are only helpful over 3000 RPM. They cook the engine compartment and they are noisy. UPS experimented with Borla stainless headers in a couple thousand trucks. There was no improvement in fuel economy. I drove one and was happy when they went back to manifolds.
My 351 only rarely winds over 3000. On the interstates I'm only turning about 2600. Around town I average about 2000. Merging on the highway is the only possible place to use more HP.
The Holley 4010 is a cheesy copy of the Ford 4100 and they never made a smaller version than 600 CFM. I chose the 480 for throttle response, fuel economy, and off road operation. It's simply the 2bbl OE 289-302 EB carb with 2 extra barrels, and looks as original using the same air cleaner, fuel lines, and linkage.
After owning 3 stock EBs, I know I want it to look like EBs did while they were in production. These are historic vehicles that worked amazingly well as built. They don't need to be turned into monster trucks, crawlers, or race cars. There are areas that can use improvement but the do anything utility vehicle has to remain so.

 

[68ford]

Still think if you want so much torque you're selling yourself short with the 3.85 crank. After doing some quick searches, a stock 302 piston will make 10.2 to 1 with a 64cc head. What cc are your heads?

 

[68ford]

If you like the way a 300 online 6 runs, just copy it. It's the exact bore and stroke as a 408. Build it with 9 to 1 like a 300. Have a cam ground with the same specs. It will be the same thing plus 25% and same power band.

 

[jckkys]

The 3.85 crank makes about 390 CI with a .020" over bore. It's a lot cheaper to do than a 4.00 crank piston combination by using my 351 rods and 302 pistons. That's close enough to the 4.00 bore/4.00 stroke of the 300 IL6. If I could get a 500 HP engine free, I wouldn't put it in an EB. A Cobra kit car maybe. Gasoline truck engines are an entirely different concept. They have a very wide torque/power curve. They are nothing like a diesel that has a narrow torque curve. An example of a real truck engine is the Ford 534CI. They make only 266 HP at 3200 RPM and 490ft/lb. of torque at 2000. Big cams, heads, and header type exhaust are nowhere to be found. It has just a 600 CFM Holley. A 302 can make more HP but wouldn't do the job a 534 does. The 534 weighs 1300 lbs, so they aren't EB engines. The 300 IL6 is also a great TRUCK engine, but too long and tall for EBs.
For what it's worth '96 GT40 heads have 65cc combustion chambers. The 302 pistons I use need to produce 9.1-9.4 to 1 CR. The short duration cam doesn't like high compression according to Comp Cams. I may want a lower compression ratio further. I'm still researching that.

 

[ntsqd]

I too think if you're going to maximize low speed torque that you need to consider finding a quality set of SMALL tube, long primary length headers or having them made. I get the appeal of stock exhaust manifolds, it's just in conflict with your stated goals for the engine.

I build all exhaust joints like the below image. Design courtesy of MISF. Just in case it needs to be said, the tube on the left is upstream. They don't leak, ever, and only need a small bead of Ultra Copper RTV for a gasket. Use regular steel bolts, but use BRASS nuts. Not lock nuts. Not Stainless nuts (and/or bolts); steel bolts with brass nuts. You'll be amazed at how well this works and lives.

CR, keep it low and use as short of a con rod in the engine as you can find COTS pistons to work with them.
Long rod engines are great where detonation isn't a concern. If you're going to work it hard and get it thoroughly warm then a long con rod is not what you want. True, they build better (not more!) power because the piston dwells at TDC (& BDC) longer, but that longer dwell makes such an engine more sensitive to detonation. Experienced this first hand with an Early & late 22R, Early is a tall deck, long rod and it detonated much more when working hard (& when isn't a 100HP engine in a ~4500 lbs truck not working hard?) than the later short deck, short rod replacement long block.

 

[bmc69]

The 408 I built for my '69 had a peak torque of 496 ft-lbs at 2900 RPM and was already past 400 ft-lbs at 1500 or so..very "diesel like" performance, and it liked to break stuff.

It was "all done" by about 4500 RPM though, and peak HP was only 340 or thereabouts if I recall correctly.

 

[JWMcCrary]

Here's a pdf of the engine build in my 73. The engine was built and installed in 2005, upgraded to Holley fuel injection in 2013. The only thing I would do different is the comp cams roller rockers, they are noisy as hell.
C4 with 4.30 gearing. Has 33s, then went to 35s, now has 37s.

 

[jckkys]

2 questios
1 to bmc69; what cam/grind did you use?
2 to JW are you talking about Comp Cams roller tip rockers? What makes them noisy?
If the Comp Cams roller tip rockers are noisy, would stainless full roller rockers fix the noise problem?

 

[DirtDonk]

Interested in that as well. Usually it's the full roller rockers that people complain about the noise with, but I don't believe I've heard that with roller tip only versions.
But I could be wrong.

I have a set of Magnum roller tip/ball pivot rockers I'll be using, so very curious too.

Paul

 

[pcf_mark]

Here's a pdf of the engine build in my 73. The engine was built and installed in 2005, upgraded to Holley fuel injection in 2013. The only thing I would do different is the comp cams roller rockers, they are noisy as hell.
C4 with 4.30 gearing. Has 33s, then went to 35s, now has 37s.

Some Comp hydraulics are just plain noisy. The hydraulic lifter has adjusters with a limited range and they rattle on some cam profiles. If the rockers are making noise they may be worn out (trunnion fatigue) or perhaps improperly adjusted. They have no extra lash or movement to make noise.

 

[Rustytruck]

I fear you will make too much torque for 31 inch tires. Then you will need lockers all around to evenly share the torque. Then if you do get traction especialy sudden traction you start busting stuff. This is why a stock 351works so well for a street and trail rig. A little more but not too much. Plan on upgrading the driveline too. I think you will not like a Bronco with an engine with a very narrow pratical operating range of 1 to 2,000 rpm after that its just too much torque just as bad as having a 6500 rpm motor thats usless in a 4000 rpm truck.
i wish you the best in your endeviour.

 

[nvrstuk]

It's your build but reading things like "...Merging on the highway is the only possible place to use more HP."... I realize there's nothing anybody can tell you about a Bronco that you don't already have your mind made up about...that being said... a couple quick questions...

1- why do you say a 300 six is too long and too tall for an EB? Have you seen them in an EB and don't like the look? or what? I've seen several and they fit. You keep saying you love that bore and stroke so just wondering??

2- never need more rpm... your quote..."Merging on the highway is the only possible place to use more HP."...ok, but some people might drive their Bronco differently... is that OK?.. I am not saying this to be mean or whatever, but it's like there isn't ANY OTHER use for a Bronco besides YOUR use?

3- list of questions could go on but I feel it's, well...what's the use...btw, headers DO NOT leak and my Bronco thank our Lord, is not a UPS truck but it might drive like one with a 1300# cast iron 534 powering it.

All in good fun... enjoy your build, let us know how you like it and what you came up with... all our builds are different and that doesn't mean anybody's is wrong...well, except for that one guy with the "LS" in his... lol

 

[68ford]

I have worked on a few of those 534 FE engines. That thing is about the king of inefficiency, less than 1 foot pound of torque per cubic in. I think that is impossible to do with a 408w ;D
The 534 is just a large 361 or 391 truck engine. Same FE engine as a car but has forged crank, machined combustion Chambers and sodium filled valves.

For what you want, I think a 390fe stroked to 445 with all stock 361/391 truck parts would make probably a 100 more foot pounds of torque than a 393 always starving for air because the valves barely open.

 

[JWMcCrary]

Some Comp hydraulics are just plain noisy. The hydraulic lifter has adjusters with a limited range and they rattle on some cam profiles. If the rockers are making noise they may be worn out (trunnion fatigue) or perhaps improperly adjusted. They have no extra lash or movement to make noise.

They are just noisy, not noise you hear from improper adjustment or worn. I was told I would get used to it 14 years ago.
I worried myself sick over it when I first put the engine together, adjusted numerous times trying different methods, was my first experience with roller rockers.
In 2016 I upgraded to Holley's dual sync distributor. After I got it installed and the EFI dialed in the best I could I took it to Big 3 Racing, well known speed shop near Cleveland, to make sure everything was OK and synced properly.
One of the first things out of the techs mouth was " no mistaking those roller rockers, how old are they?". He said they were fine and that's how they are.
It was at that point I started not hearing them as much.

 

[Montoya]

"...Merging on the highway is the only possible place to use more HP."

To each their own but you and I have completely different driving styles!

I'm the guy standing on the loud pedal with open headers burning rubber at every stoplight and giving a finger to the old lady in the Prius...I can't help it but my bronco makes me act like a dumb teenager and I wouldn't change it for the world.

I wish you luck with your build.