Building a 393 low end torque engine

[pcf_mark]

Finally got some piece of mind after 14 years that is awesome. Nothing to worry about is always good news. I bet that runs great on the street.

 

[jckkys]

There is a repeated theme I see on this forum. That is "anything worth doing is worth over doing". I like a stock or near stock appearance in the engine compartment. I've done that with my 351W. No way to do that with a 300, FE, diesel or Y-block. I'm not reverting to a chrome plated after market collection of parts including headers either. The 351 works well but I think a little more grunt may help in some situations. The 3.85 crank wouldn't cost much more than a normal short block rebuild. I'm only considering it in the event the short block needs rebuilding.
The drive train has suffered no breakage or unusual wear with the 351, C4, 28 spline 9" axle, 3.50 gears, and 31s for at least 25 yrs. This combination works very well. I am interested in keeping things quiet and want to know about how to keep the valve train quiet. The few engines I've seen with roller tip or full roller rockers didn't seem to be unusually noisy, but they had headers and loud exhaust. Comp Cams said my very mild cam won't make noise regardless of rocker type. This needs to be verified.
My point about the 534 was, a real truck engine is not a high revving peaky performance engine. By the way, they are derived from the Lincoln 462 Y-block. They are not FEs. Moving heavy trucks for hundreds of thousands of miles takes a flexible power band. Unfortunately we just can't get past the hot rod mentality here. Too bad since EBs make lousy and dangerous hot rods.

 

[pcf_mark]

Moving heavy trucks for hundreds of thousands of miles takes a flexible power band. Unfortunately we just can't get past the hot rod mentality here. Too bad since EBs make lousy and dangerous hot rods.

I'm not sure how you define flexible power band. A power band from 1000 rpm to 2000 rpm is not flexible - it is peaky.

You have your mind made up but if you run that on a dyno I would like to learn something from it if you care to share it. My math tells me it will be down on power compared to a stock 351 at every point on the curve from idle on up. You made the engine 12% bigger but used a smaller cam. All else being equal it will make less power and torque. A slightly longer strong changes the mechanical relationship but you only make more power with efficient cylinder filling not stroke.

 

[68ford]

When was the last time merging on the interstate on a 1940 John Deere sounded like a good time? ;D

 

[68ford]

https://www.instagram.com/p/BPTmO2zAdwu/?utm_source=ig_share_sheet&igshid=iyzpx7nwm5pm
I'll argue EBs do make great hot rods.
https://www.instagram.com/p/BrbMQqlgTOl/?utm_source=ig_share_sheet&igshid=psrm8pxesegi

 

[AZ69EB]

68ford,

Your Instagram vids just makes real men smile!

 

[pcf_mark]

https://www.instagram.com/p/BPTmO2zAdwu/?utm_source=ig_share_sheet&igshid=iyzpx7nwm5pm
I'll argue EBs do make great hot rods.
https://www.instagram.com/p/BrbMQqlgTOl/?utm_source=ig_share_sheet&igshid=psrm8pxesegi

NICE! Really snappy for a 302 with an iron head! 10.5:1 helps a lot with that.

 

[jckkys]

The idea is maximum torque at about 2200 RPM with max HP at around 4400. That's a broad power band that idles at 500 RPM and pulls hard at 1500. The new cam has more lift and about the same duration as the Lightning cam. The 4 degree advance should help the low RPM torque. It, as I said, is very close in specs to the Lightning, 1969 Mustang, and Explorer cams. All these are mild easy to live with cams.
Today I talked to local engine builders and all agree the roller rockers with this cam won't make any noise, as I suspected. They also agree a 9.2-9.4 to 1 compression ratio with regular gas is about right.
If you want a 10 sec. 1/4 mi. EB, go for it. There are an infinite number of better places to start.

 

[68ford]

If you want so much low rpm torque but don't want to spend the money for a 4in crank which is guaranteed to make noticeably more torque, why spend money on roller rockers which with such a small cam, the valve spring pressure will be light and rpm so low that roller rockers likely won't help anything?

 

[nvrstuk]

I'm with 68 Ford...EB's make great hot rods...just can't postup my video on CB...

...and roller tipped rockers on a cam that is that small is a TOTAL waste of money AND no, they don't make ANY more noise that regular rockers...

 

[68ford]

So looking online, a set of rods(a cost he is saving doing a 393) are about 300 bucks. A set of roller rockers are over 100.
I would build a 408 and reuse the stock rockers.
30% more stroke will make torque where the rockers will do nothing. And torque seems to be all that matters.

 

[pcf_mark]

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

The dynamics of a stroker are unique.

Just saying this part again.

Also HP does not exist. Torque at an RPM is horsepower. We are all making torque. If you want to make torque you need to fill the cylinder efficiently. You want low end torque fill it well at low rpm. With an engine that is 12% bigger than a 351 with the same intake runner and intake valve you need to adjust your cam specs. You also need to consider very long intake runner like a dual plane. Then you need a long tube exhaust just like the intake for optimal filling. That is why a street headers have very long tubes - 24-32" - to tune the exhaust for low RPM. A very short intake (single plane) and very short headers move the power up in the rpm band. Stock manifolds are super short hurting torque production.

 

[ntsqd]

Given the ratio ambiguity and inconsistency of stock rockers I can see using a quality true roller rocker (in my mind that's a set of SS Crowers & nothing aluminum) if you're trying to extract the most from the least. Yeah, you're not going to see a huge gain from them, but it's one less variation from cyl to cyl. Getting closer to having all of the cyls producing the same amount of power is worth something.

I'd want aluminum cyl heads with an intake runner volume in the 160cc range. Then you can put a little more CR in it (cylinder pressure is where the power is) and still run on low octane pump fuel and be less detonation sensitive.

 

[jckkys]

I guess using a mild cam that works at low RPM is sacrilege to hot rod mind set too bad none of you can think outside this orthodoxy.

 

[68ford]

Running too small of a cam, limiting what goes in, is the same as not opening the throttle all the way. The result is not miraculously a lower torque peak, it's simply less power.
You're being every bit as close minded and not realistic.

 

[ntsqd]

Some people only see what they want to read.

Nowhere do I see recommendations to put in a .750" lift, 380° duration cam. What I am seeing is suggestions that the cam(s) chosen will be limiting the engine from reaching the desired goal. The chosen cam may work fine, but it will leave power within the desired RPM range, on the table.
In other words, a larger cam may still meet the stated RPM band & idle characteristics while delivering more than the chosen cam.

 

[Montoya]

Some people only see what they want to read.

Nowhere do I see recommendations to put in a .750" lift, 380° duration cam.

To be fair to jckkys, I was kinda implying it and definitely thinking it.

 

[nvrstuk]

Like 68Ford, ntsqd and Montoya both posted (and I'm sure many others are thinking but are too nice to post)

....NOBODY has posted to put in some huge cam...I just don't understand your never let up attitude about our thoughts about HP and how you feel NONE of us understand anything about engines, HP and torque...WOW... usually, like 1x/year I rant about someone's posts on a subject but you just won't give up on the "how slow and inefficient can I make my engine" and never listen to advice that YOU are asking for.

My sincere response again is...good luck on your engine build. I hope you like it.

 

[68ford]

At what point do you just buy a Scout with a 392 instead? You'll always be behind, so no one will see you ;D

 

[ntsqd]

oooh! MISF* says those are fightin' words......




* My Infamous Scout Friend


;D