Cam comparison: hydr. FT vs hydr. Roller

[BigBlockMopar]

I'm running a hydr. FT cam in a 360ci Mopar LA SmallBlock. 11.3:1cr.
100% 'spirited' street car. Transmission: stock convertor auto+OD - 3.55:1 gear.
Converted the lifters to solids.

CompCams XE256H
Adv.Dur. - Int 256° - Exh 268°
Dur. 050 - Int 212° - Exh 218°
Lobe lift: Int 0.298" - Exh 0.303"
Valve lift @ 1.5:1 ratio: Int 0.447" - Exh 0.455"
Valve lift @ 1.6:1 ratio: Int 0.476" - Exh 0.485"
Lobe Sep: 110° - Int Cent: 106°
Valve timing: Int 22°- 54° - Exh 20° - 68°


Now I ended up with a reground retrofit hydr. roller recently for another (318ci) engine.
Supposedly reground to following specs:

HR-279-MSBS-360
Adv.Dur. - Int 258° - Exh 264°
Dur. 050 - Int 206° - Exh 212°
Lobe Lift: Int 0.320" - Exh 0.325"
Valve Lift @ 1.6:1 ratio: In. .512" - Ex. .520"
Lobe Sep: 112°

* RV and tow applications
* Good low-end
* 8:1+ compression, intake, headers, gears (for better performance)
* Stock stall
* Noticeable idle

---

Started wondering how these two cams would compare, and maybe if/how much the roller would be an improvement in the 360ci over the flat tappet cam?

[ProPower engines]

They are both small cams by comparison but they would be better then a FT.
While there is also cams of similar @50 timing in a FT I am not really sure why you would consider a FT cam when you
have both rollers available to you. The tighter LSA cam may yield better lower end power but I would worry about it under heavy towing loads with that CR and would concern me for a towing application as detonation is more likely under heavy loads. Unless you have an unlimited supply of high test fuel to run.

[MadBill]

I'm running a hydr. FT cam in a 360ci Mopar LA SmallBlock. 11.3:1cr.
100% 'spirited' street car. Transmission: stock convertor auto+OD - 3.55:1 gear.
Converted the lifters to solids.

Maybe it's just me, but I see both of those cams as about 15° duration short of "spirited", unless perhaps you have a 2:71 gear, big tires and a stock converter. They won't help detonation resistance with that high CR either...

[BOOT]

I'm no cam expert but I rem seeing somewhere that FT had the advantage in smaller cams, up to something like .480 lift then roller was the way to go.

[BigBlockMopar]

The FT cam is currently in use in the 360-engine in the car.
The car (1973 Dodge Dart) is a daily driver and runs on LPG / Propane.
Tight quench, closed chamber heads. Haven't been able to make it ping yet. Digital timing table.

I agree the current cam could use some duration but I was afraid this would impact economy and low-rpm city driving a bit. But I've let that worry go already. And some lopey idle won't mind me at all.
With 'spirited' I ment more that I don't drive like a granny.

If the roller cam, (which was ment for the 318-engine at first) would be a better one, I might be tempted to convert the current engine to roller cam.

[PRH]

I'm running a hydr. FT cam in a 360ci Mopar LA SmallBlock. 11.3:1cr.
100% 'spirited' street car. Transmission: stock convertor auto+OD - 3.55:1 gear.
Converted the lifters to solids.

Maybe it's just me, but I see both of those cams as about 15° duration short of "spirited", unless perhaps you have a 2:71 gear, big tires and a stock converter. They won't help detonation resistance with that high CR either...

I’m in this camp as well.
Your current cams fall more into the “tow vehicle” catagory than hot street car for me.

If you’re thinking of stepping up to a hyd roller for the 360, I’d be looking at something like the XR268HR as the low end of the suitable range.

If the car has headers, and you stepped up to something like a factory high stall converter, and I was looking for a noticeable improvement in power from the midrange and up, I’d step up to the XR274HR.

[Krooser]

Why the solid lifters on a juice cam?

[BigBlockMopar]

Collapsing hydraulic lifters.
Got sick of them and decided to make them solid. My faith in hydraulic lifters is pretty much gone.

I’m still on the fence of getting a ‘proper’ chosen roller cam for this engine, instead of just using what I just ended up with.
But turning a FT (Mopar) engine into a roller cam easily comes close to a grand, from past experiences.
The car has full length headers. X-pipe and Borla street mufflers.

I also want/need the car to be able to idle in a traffic jam without issues.

[PRH]

Just get rid of the hydraulic stuff altogether....... SFT.....Comp XS268S........ it’ll be a pussycat.

I had a 9.8:1 360 on the dyno recently with a bigger cam than that, and it was very docile.

It wouldn’t have been great with a stock converter, but with the CR you’re running the XS268S would be fine with a factory high stall type converter.

[ProPower engines]

The FT cam is currently in use in the 360-engine in the car.
The car (1973 Dodge Dart) is a daily driver and runs on LPG / Propane.
Tight quench, closed chamber heads. Haven't been able to make it ping yet. Digital timing table.

I agree the current cam could use some duration but I was afraid this would impact economy and low-rpm city driving a bit. But I've let that worry go already. And some lopey idle won't mind me at all.
With 'spirited' I ment more that I don't drive like a granny.


The fact that this is an LPG engine it will benefit from less over lap if economy is the goal thus building more
low end. I have had many fleet tow trucks from our wrecking yard that were LPG fueled and I tried
everything with in reason to get the best power and economy from them. Both sm amd bb engines and they all
enjoyed less over lap. Any sign of lumpy idle and the fuel mileage suffered badly while they seemed to make better
power and different RPM's but the bottom line was they were commercial trucks and while they ran 10-14 hrs/day
and hard work towing It turned out to be a better option to just go more inches which gave the best of both worlds.
All our trucks had BBC or BBF 385 engines in them and while the cost of fuel remained under .020 cents/liter for many
years back in the 80's it slowly when through the roof to the point where gasoline was cheaper to buy and run based
on the fuel demands of the trucks I tried for years to get then right and better on LPG but the fuel was getting worse
here and would not take the higher comp. it did 10 yrs prior then came the cost per trip thing.

While engine wear was much less on LPG fuel and oil looked like it was just changed I just don't see it being better economy with more overlap. Some of the best MPG we got was done with custom cams made with less then a factory
stock cam had. They would run out of power at about 4500 rpm but that was the point of the exercise.

Better fuel MPG and less wear and tear.

[BigBlockMopar]

The fact that this is an LPG engine it will benefit from less over lap if economy is the goal thus building more low end. I have had many fleet tow trucks from our wrecking yard that were LPG fueled and I tried everything with in reason to get the best power and economy from them. Both sm amd bb engines and they all enjoyed less over lap. Any sign of lumpy idle and the fuel mileage suffered badly while they seemed to make better power and different RPM's but the bottom line was they were commercial trucks and while they ran 10-14 hrs/day and hard work towing It turned out to be a better option to just go more inches which gave the best of both worlds.
All our trucks had BBC or BBF 385 engines in them and while the cost of fuel remained under .020 cents/liter for many years back in the 80's it slowly when through the roof to the point where gasoline was cheaper to buy and run based on the fuel demands of the trucks I tried for years to get then right and better on LPG but the fuel was getting worse here and would not take the higher comp. it did 10 yrs prior then came the cost per trip thing.

While engine wear was much less on LPG fuel and oil looked like it was just changed I just don't see it being better economy with more overlap. Some of the best MPG we got was done with custom cams made with less then a factory stock cam had. They would run out of power at about 4500 rpm but that was the point of the exercise.

Better fuel MPG and less wear and tear.

That's mostly the reason I went with the XE256 cam when I put this engine together. It appeared to be the most logical cam to go with.
To be honest, the current cam works very nice as it is; Stock idle, very good vacuum, pulls good in mid/upper range...
The car currently makes 234hp on the chassisdyno.
It's just that... I want more.

The mileage however still sucks badly. I can't get it over 12mpg. 15mpg if I baby it on the highway.
Partly I think this is because of the heavy (Dodge truck) transmission (A518/46RH) which has OD only, and a 'late 60s 727 stock stall convertor from a fullsize Chrysler.
The transmission will be changed for a lighter (A500/42RH) version in time with OD+Lockup, and matching smaller diameter lockup stall convertor. First gear on these transmissions is a bit deeper than the 46RH. I really expect this to have some effect on mileage.
So because is bad as it is, I decided to have some more fun out of this engine, while keeping this an every day driver.

A head change is planned too. I have a pair of 65cc SpeedMaster alum. heads waiting.
I will mill them to similar cc as the current castiron heads and give them a nice multi-angle valvejob and hopefully gain some low lift flow as well.

[PRH]

That fuel mileage seems pretty bad to me.

My “all around” mileage with an 04 Chevy 2500, 6.0, 4.10’s is around 13.5..... and highway only is about 15-15.5.

It’s like a 5000lb 4wd extended cab truck.

Doesn’t seem like it would be that hard to get a Dart to use less fuel.

How much cheaper is propane than gas where you are?

[BigBlockMopar]

A little more then half the price of gasoline.

[Roundybout]

I think any increase in engine efficiency is not going to show a large gain in the mileage. You're already there in my opinion with what you've done. You're losing it someplace else that would make a bigger difference such as areodynamics, running gear, tires, driving style all would come into play more than getting some more HP through engine efficiency. Not that doing all you can engine wise would hurt though. It sounds like the drivability is important to you. I don't think a slightly bigger SFT cam would hurt mileage or drivability at all. Being on propane, couple that with some more compression and you'd gain some performance without giving up mileage/drivability you have now. I think you'll find bigger gains with the above mentioned areas in the drivetrain and make it more fun to drive.

[PRH]

I realize parts availability for this stuff must be crap over there compared to here........ but I would think a pretty basic low cr 360 with bowl blended 1.88/1.60 heads, small-ish solid cam, headers, something like a sniper EFI along with a factory high stall converter with a 904 and 2.76’s........ would be a pretty decent daily driver type combo that would still pull down better than 13mpg on regular unleaded.

Anyplace near you with a dynojet dyno?