[dmac]

Any difference in building for max torque vs building for max HP?

I usually see builds that have higher HP numbers than torque numbers at higher RPMs. I just saw a site that reported a Pontiac build with reported 583 ft/lbs max torque and 562 max HP. Didn't see the dyno printout so maybe they cut off at max torque.

Would same general principles apply as far as cam selection and intake/exhaust flow ratios? I'm now thinking about cylinder heads and whether or not paying for extra porting to increase flow will be worth the cost for my purpose.

Would this be a case where using different rocker ratios on exhaust and intake make sense if seeking higher torque numbers with something like the 068 or 041 cams? 455 (467) motor originally came with the 067 in a station wagon. It will be in a 75 Ventura for now, but may end up in a 75 Grandville vert. I plan to set up the Ventura to tow with frame/suspension fixes.

I recall someone posting a few years ago about using his car (1967 GTO maybe?) for towing a car trailer and I'm thinking along the same lines for towing a camping trailer. I want to be able to accelerate quickly while towing to pass trucks and slow traffic on the freeway. while still retaining great drivability when not towing. I really want to keep my 2.73 rear axle ratio to keep rpms lower and mpg higher. With that ratio, freeway rpms would be in the ~3000 range.

[pastry_chef]

For maximum performance target max power at RPM range where your engine spends time.
HP and TQ coexist at all RPM, low, mid and high.

Required valve seat duration is dictated by piston speed.
Intake valve lift by displacement, RPM, inlet efficiency.

[RocktimusPryme]

In my experience when someone tells you "its a torque motor" that's usually just someone's way of rationalizing their slow motor. Maybe the argument is that it feels fast.

You can target build an engine that makes torque with lacking power. Think like a 3rd gen TPI motor. I think they made 345 ft lbs and only 240 HP.

On the other hand I cant think of any motor that made big power numbers and didn't have requisite torque. Once you get way up there with race engines the power curve might be way higher, but the torque is still good. I don't think there is a motor out there that makes 900 Hp and 147 ft Lbs.

[Stan Weiss]

Since this is the street section and you want low cruise RPM. I would build for a lower max peak RPM torque and as wide a torque curve as you can.

Stan

[pastry_chef]

Originally Posted by dmac

I want to be able to accelerate quickly while towing to pass trucks and slow traffic on the freeway. while still retaining great drivability when not towing. I really want to keep my 2.73 rear axle ratio to keep rpms lower and mpg higher. With that ratio, freeway rpms would be in the ~3000 range.

455?

Compression ratio?

[ponyakr]

Your 467 should make plenty of power to your 3000rpm highway speed, with an 068 clone.

May as well go with a bit more lift for a cheaper price & go with a Summit 2801. Some say a 455 will run out of steam at around 4500 or so, with a cam that small. But, if you don't plan to go above that, why use a bigger cam ? As always, most cam opinions are just that--opinions, unless somebody has done EXACTLY what you wanna do, with EXACTLY the same set-up.

[torqhead]

Originally Posted by dmac

I recall someone posting a few years ago about using his car (1967 GTO maybe?) for towing a car trailer and I'm thinking along the same lines for towing a camping trailer. I want to be able to accelerate quickly while towing to pass trucks and slow traffic on the freeway. while still retaining great drivability when not towing. I really want to keep my 2.73 rear axle ratio to keep rpms lower and mpg higher. With that ratio, freeway rpms would be in the ~3000 range.

Saying this " able to accelerate quickly while towing to pass trucks and slow traffic on the freeway" and keeping the gears you should build a motor that has low end torque and good power at least to 5000/5200 RPM. Even hopped up cars downshift to get that immediate power bump. Plenty of factory 389/400/428/455's engines were built from the factory for that RPM.

[Steve C.]

Horsepower Vs Torque
The Difference, Why It Matters, And How To Get It

https://www.hotrod.com/articles/horsepower-vs-torque/


.

[Tom Vaught]

Good article Steve This says it all: "what we are all seeking is the greatest-possible torque value over the broadest-possible rpm range."

Tom V.

[dmac]

Originally Posted by pastry_chef

455?

Compression ratio?

455/467 w/4.25 stroke
compression 8.8:1 with iron heads and 87 cc chamber.
With aluminum I'd be at 9.73 CR with 74 cc chamber.

Questioning whether getting heads ported will help or hurt for desired rpm range . Considering KRE aluminum or a pair of SD performance iron heads. I should maybe go for the aluminum and raise CR some.

I'm a little concerned about detonation on the 91 octane that passes for premium here. Shop left deck at .030 even after asking for zero deck. He was familiar with wider variety of thin head gaskets for chevies and thought .030 would be fine and leaving it would save me some money on labor. I don't really want to disassemble new block and get the block decked due to low budget.

[dmac]

Originally Posted by torqhead

Saying this " able to accelerate quickly while towing to pass trucks and slow traffic on the freeway" and keeping the gears you should build a motor that has low end torque and good power at least to 5000/5200 RPM. Even hopped up cars downshift to get that immediate power bump. Plenty of factory 389/400/428/455's engines were built from the factory for that RPM.

Makes a lot of sense. I had forgotten about the downshifting and resulting higher rpm range I might want. I was thinking that a cam that died at 4500 rpms might be good enough. I'm starting to see some benefits of just having an overall more powerful motor. Last real performance motor I had was 13:1 cr and I couldn't drive it at 25 mph with the 2.73 rear gears it had. Would be just above idle in second (TH400) at 50 mph though. I don't want anything close to that this time.

Just read the article posted by Steve . Looking at that indicates to me that I would want max torque to be a little higher than cruising rpm so I keep efficiency a little above and a little below

Also thinking trailer weight would be a maximum of ~3500 lbs, and not the 6000-8000 lbs some other threads were written about.

[Half-Inch Stud]

Yes, i feeel very strongly about this.

Try to make high TQ at all the RPMs that you can.

HP will become a mere "calculation" to you.

[pastry_chef]

pounds of force to the wheels now = (horsepower now * 375 ) / MPH now.

Not factoring for aero or rolling resistance.

--------------------------------

Torque vs Horsepower, which is more important?
http://performancetrends.com/blog/?p=7

[pastry_chef]

Originally Posted by dmac

Questioning whether getting heads ported will help or hurt for desired rpm range .

Unless you go way overboard it will help a 467.
If you never plan to exceed 4000 RPM don't bother.

[Sprocket]

Use the following cam, it combines the best the factory 066 and 068 offer:

Lunati 10510700 (60900) 207/213 .437"/.455" 112 LSA 108 ICL

No need for porting unless you are doing a lot of 5,000 rpm mountain pass climbing. This cam is max torque yet has good top end power. Should work with stock valve train and idle like butter in your engine. We used this in a stock 455 tow vehicle and it worked like a dream. Previous cam used was the 067.

[Cliff R]

Before choosing a camshaft, heads and compression ratio decide on the goals for the vehicle. Although you can make great power in a 455 build with relatively "low" compression it takes higher compression ratios to make optimum power on pump gas. Higher compression ratios also open the doors for larger camshafts with less negatives at idle and in the "normal" driving range.

Don't think that you can simply pick a compression ratio then install a smaller camshaft to boost power and make the engine pump gas friendly at the same time. The worst engines we've tuned here far as 455's were concerned had small camshafts in them. I've seen them pound like sledgehammers on pump gas well below 9.5 to 1 compression.

Aluminum heads don't make more power and allow you to run higher compression ratios all by themselves. They work a little better because out of the box they flow the same amount of air as well ported iron heads do, and they also have "modern" combustion chamber designs improving both airflow and combustion efficiency so they make more power at the same compression ratio as iron heads and require less timing and fuel to do it.

A street engine always works best when it has good idle quality, smooth off idle and good power in the "normal" driving range. Ported heads will NOT hurt that scenario and they will greatly improve upper mid-range and top end power with a larger camshaft. So with a little increase in compression, more head flow, and well chosen camshaft you really can have your cake and eat it too with a well thought out 455 build.

WAY back when KRE first came out with their new aluminum "D" port heads we built several of the first engines with them, dyno'd them, track tested and several excellent articles followed from HPP and Popular Hot Rodding. Using my own 6X headed engines as a test platform we installed KRE heads and changed NOTHING else.

Both the iron headed engine and KRE headed engine made great power, drove fine on the street, idled well and ran good at the track. Either one was fine with a steady diet of pump gas, even lower octane ratings. This happened because we built that engine with very tight squish, big cam on a wide LSA, and very precise control of timing/fuel curves.

No reason anyone reading this couldn't do the same thing, and not go broke in the process. I'll add here that with our KRE headed 455 we ran as quick as 11.64 at the track at 116MPH in full street trim on DOT tires. That engine also produced a relatively smooth idle, strong low end power and excellent street manners. At a glance if you looked at the car and heard it run you'd think it wouldn't run much quicker than 14's or maybe dip into the 13's on it's best day.

We've exploited that basic concept and with later engine builds have used higher compression and much larger camshafts combined with CNC ported KRE heads and made even more power but still equally as docile and fine on pump gas.

So the "recipes" for success are out there, and very well outlined on this Forum. I'd add here that we've also built iron headed 455's that run pretty close to the aluminum headed 455's and even at higher compression ratios we have yet to experience any issues on pump gas......Cliff

[Half-Inch Stud]

As a corollary to CLIFF's writ, 9.0:1 is too low Compression ratio with iron heads.

I shot too low on that because i wanted to add BOOST, but decided to stay NA.
So shoulda hit Compression somewhere in the 9.5 to 10.5.

[torqhead]

Originally Posted by dmac

Shop left deck at .030 even after asking for zero deck.

This is total BS, what a lame a$$ shop! Too bad you didn't know this prior, I would've used someone else.

If you are considering it and can afford it, my opinion since you're looking for good power is to get a set of aluminum heads. There are a number of benefits but one is tuning can be a little less finicky.

[dmac]

Originally Posted by Sprocket

Use the following cam, it combines the best the factory 066 and 068 offer:

Lunati 10510700 (60900) 207/213 .437"/.455" 112 LSA 108 ICL

No need for porting unless you are doing a lot of 5,000 rpm mountain pass climbing. This cam is max torque yet has good top end power. Should work with stock valve train and idle like butter in your engine. We used this in a stock 455 tow vehicle and it worked like a dream. Previous cam used was the 067.

With that cam, what would using 1.65 ratio rockers do? Working off Jim Hands model of the the 041 with Rhoads lifters, and the 068 using Rhoads AND 1.65 ratio rockers, I'm open to using both Rhoads and 1.65. The 'tick' doesn't bother me at all and I really like the concept of using the variable lifters to broaden the curve.

IF I decide on aluminum heads, they will come ready for more lift and ready for 1.65 rockers. I personally prefer getting more lift through higher ratio rockers vs getting more lift from a higher lift at the cam. Higher ratio rockers in general allow a slower 'ramp' to achieve the same lift. I'd even consider using 1.7 or 1.73 ratio rockers. The higher ratio extends the effective duration compared to same cam with lower ratio.

[pastry_chef]

Originally Posted by dmac

IF I decide on aluminum heads, they will come ready for more lift and ready for 1.65 rockers.

If you purchase from someone who will setup for your combination, like Dave Wilcox.

https://headsandmanifolds.wordpress....orting-prices/