[Cliff R]

Skip, I do have a couple of pretty high compression iron headed 455's out there on pump fuel, on is 11.5 to 1, and it's been fine so far. I haven't talked much about it publically, as both were done recently and don't have a lot of street or track time on them. Besides, I really didn't want to jinx myself. About the time I start ranting and raving about how good it works the guy will surely put a couple of pistons in the oil pan! But, so far, so good.

I also help out quite a few folks with Stock Eliminator, Pure Stock and FAST Class cars. I agree the Stock Eliminator "low" compression set-ups run amazingly well for what they are. I support more folks in Pure Stock and Fast these days than Stock or Super Stock classes.

Just got off the phone with one of those folks yesterday, he's running a couple of 68 Firebirds, the Pure Stocker has went 11.18 and the FAST Class car deep into the 10's. We were trying to find a few more HP someplace to get the FAST Class car into the 9's this season, so tossing some ideas back and forth......Cliff

[68azbird]

Maybe if that was 110 octane coming out the pump.

[llwta76]

Originally Posted by Cliff R

Skip, I do have a couple of pretty high compression iron headed 455's out there on pump fuel, on is 11.5 to 1, and it's been fine so far. I haven't talked much about it publically, as both were done recently and don't have a lot of street or track time on them. Besides, I really didn't want to jinx myself. About the time I start ranting and raving about how good it works the guy will surely put a couple of pistons in the oil pan! But, so far, so good.

I also help out quite a few folks with Stock Eliminator, Pure Stock and FAST Class cars. I agree the Stock Eliminator "low" compression set-ups run amazingly well for what they are. I support more folks in Pure Stock and Fast these days than Stock or Super Stock classes.

Just got off the phone with one of those folks yesterday, he's running a couple of 68 Firebirds, the Pure Stocker has went 11.18 and the FAST Class car deep into the 10's. We were trying to find a few more HP someplace to get the FAST Class car into the 9's this season, so tossing some ideas back and forth......Cliff

A iron headed streetable car over 11 to 1 ? I'm assuming on 93 pump gas? I'd like to hear how you've managed that trick. We all know about quench and smoothed chambers and such but there must be more in your engine building techniques for you to accomplish this. I'm all ears if you're willing .

[Steve C.]

Terry Walter Precision Engines:

Pontiac .030-over 400
unported #16 heads - 2.110 / 1.770
9.2 compression
Comp XE262H hyd flat tappet cam
Factory cast iron intake
Holley carb
Factory long branch exhaust manifolds

365 hp at 5400 rpm
445 ft.lbs. torque at 3400 rpm

Chevy comparision:

Comp XE262H cam tested with Chevrolet 350
Bore+4.040" Stroke=3.480" 9.25:1Compression ratio
Dart S/R Heads Edelbrock Performer Manifold
Holley #3310 Vac. Sec. Carb 1 5/8" Headers

Max Torque 411 ftlbs @ 3600 RPM
Max Horsepower 330 HP @ 4700 RPM
Vacuum 18.5" Hg @ 800 RPM
20" Hg @ 1000 RPM


.

[bendutro]

Thanks for sharing Cliff, the firsthand experience is invaluable to guys like me that can't afford to build 5 different engines to sort the truth from the BS.

Not to throw a wrench in the discussion, but in all the CL/duration/SCR/DCR talk, I can't help but wonder if Rhoades lifters would help or not.

[JLMounce]

Originally Posted by Skip Fix

"I didn't build the engine in my bird so I couldn't tell you exactly what cam is in it, "however it runs on pump gas just fine. It's a 462 topped with #62's which should put it between 10.8-11.2 SCR depending on how it was built."

Just because you cant hear detonation does not mean it is not happening. Go put it on a chassis dyno and load it make a pass, then drain the gas run it on 104 race gas and see what it does. Bet it picks up a bunch because it needs more octane

Cliff you got many 455s running 11.2:1 iron heads on pump gas for a street car?

Those 11.5 NHRA stockers using low compression 78 motors sure got it figured out! But the chassis and cam are definitely not too street friendly

I admit this is a possibility. However, I've had a bore scope up it's skirt and at least with the crappy resolution from the camera the piston top doesn't show any signs of damage. I was even able to pull the part number off the piston.





L2359 which corresponds to the Sealed Power forged slugs for 4.181 bore.

One thing of course working in my favor here is my location. I'm 4500 ft above sea level.

[Skip Fix]

I looked at my post and to clarify I meant 11.5 second 1/4 low compression 78 stockers. They allow 89cc heads for the "stock" 6X chamber.

[Will]

Originally Posted by neill

So Will, would you install it @106 or retard it to 110 to match the intake closing angle of the 270 magnum? How octane sensitive was your 400?

Heh, we're way off-topic for this thread but I wouldn't mess around trying to retard it. All that will do is kill off low-end torque and may not make any more higher up.

350s need all the help they can get in the lower RPMs.

That 400 drank a steady diet of 87 octane with no complaints.

The XE262 seems like it would be decent in a low-moderate compression 350. Not the best choice, but it shouldn't be bad. I wouldn't run it in anything larger.

[Matt Meaney]

many years ago, I had the original Rhoads lifters on a RA IV cam in a 455. I don't remember them as really loud. standing next to the fender with the hood open, you could hear a light tick, but from the drivers seat, driving, nothing. had a full exhaust with dyno max super turbo's, which was not a loud exhaust at idle/light throttle. Now, the comp 857 HR lifters, are very noticeable all the time.

does anybody have a video of Rhoads lifters, from the drivers seat, with the hood down? how about one of a XE grind (with regular lifters), that closes the valve so fast it bounces off the seat and makes a tick? it would be interesting to compare noises and give people a better idea of what they would be getting into with either choice.

[Will]

I've run Rhoads on a couple different cams and you can't hear them from the driver's seat. Hood open, yeah there's a little ticking but I didn't find them to be all that loud really.

[72LuxuryLeMansLa.]

Originally Posted by Matt Meaney

many years ago, I had the original Rhoads lifters on a RA IV cam in a 455. I don't remember them as really loud. standing next to the fender with the hood open, you could hear a light tick, but from the drivers seat, driving, nothing. had a full exhaust with dyno max super turbo's, which was not a loud exhaust at idle/light throttle. Now, the comp 857 HR lifters, are very noticeable all the time.

does anybody have a video of Rhoads lifters, from the drivers seat, with the hood down? how about one of a XE grind (with regular lifters), that closes the valve so fast it bounces off the seat and makes a tick? it would be interesting to compare noises and give people a better idea of what they would be getting into with either choice.

You'd be amazed at how many ticking issues from the driver's seat are just a bad manifold or manifold to down pipe gasket!

[AdamIsAdam]

Originally Posted by Matt Meaney

does anybody have a video of Rhoads lifters, from the drivers seat, with the hood down? how about one of a XE grind (with regular lifters), that closes the valve so fast it bounces off the seat and makes a tick? it would be interesting to compare noises and give people a better idea of what they would be getting into with either choice.

I have the XE274 with hydraulic lifters. The first video is before I bought the car with the CAT rockers and the after video is with new Harland Sharp*rockers.


https://youtu.be/9hK-3r_gLk0

https://youtu.be/TKkWQtrZ2Mw

[Cliff R]

With the Rhoads V-Max lifters we can choose the amount of leak down, so they can be "tight lashed". I like them and use them over the std version so we can bottom out the plungers with a feeler gauge between the rocker and valve. This sets them all at the same place, so the noise is consistent and so is the amount of bleed down they provide at low rpm's. They will also run like a solid lifter at high rpm when tight lashed, as it pretty much takes most of the hydraulic action out of the equation.

I usually start at .010" for lash setting, which minimizes noise but still provides improvements in idle vacuum, throttle response, and power in the "normal" driving range.....Cliff

[grivera]

Originally Posted by Matt Meaney

does anybody have a video of Rhoads lifters, from the drivers seat, with the hood down? how about one of a XE grind (with regular lifters), that closes the valve so fast it bounces off the seat and makes a tick? it would be interesting to compare noises and give people a better idea of what they would be getting into with either choice.

My #'s matching engine (currently on stand) has an XE-268 with CC 852-16 lifters and didn't tick any more than a non-XE engine.

[77 TRASHCAN]

Bumping this up, in case some missed it!!!

[67GTO4SPEED]

It's kinda funny to me that a lot of people automatically consider wide LSA cams as school technology and lazy lobes. Besides the the Thumper line of cams, (which most people realize is a cam series that sounds big but are not anything impressive) you can't get an off the shelf Comp cam for a Chevy LSx engine with a LSA tighter than about 112. These cars are flying with those cams and are making some stupid numbers. The same is true for the new Chrysler Hemi's. The cams for all those engines fall in between 112 - 116 on the LSA. These engines all come with pretty healthy CR and aluminum heads and there is no need for a small duration cam with a tight LSA that tricks the engine into have more dynamic compression.

Below is a cam card for a pretty healthy LSx cam. This is recommended for a big cube (420+ cu in), high compression LS engine.

[77 TRASHCAN]

Sorta makes ya wonder if one or more of the LS engineering crowd may have read some stuff from Mac Mckeller....

[hurryinhoosier62]

It's a simple answer: fuel injected engines need LSAs of 112-116 degrees.

[gtofreek]

Wide lobe seps are not considered old school. There are engine combos that need them, or run better on them. Long stroke engines can benefit from them to keep the engine in a wide power band to pull the car. Engines that need to make power at 9000-10,000 RPM's NEED wide lobe seps[sometimes as wide as 119°-120°], and big duration cams. Narrow lobe seps run out of steam too soon to make power up there.

We all know that narrow lobe seps make more peak power than wide lobe seps, but do it in a narrower RPM range[when compared to the same lobe ground on a wider lobe sep].

We all know that wider lobe seps make less peak power than narrower lobe seps, but in a broader RPM range. More average power. Certain lobe designs, by nature, benefit from wide lobe seps, while other lobes benefit from tighter lobe seps. If you have a lobe design that when ground on a 110° LSA, has a power band as broad as another lobe design ground on a 112° or 114° LSA, why not take advantage of the extra power if your not running the cam out of it's power band in the first place?

As far as dynamic compression is concerned, well, IMO, you can throw those calculators out the window. They have no real place in engine building. They are just a computer program someone came up with because they had an idea that sounded logical. They DO NOT predict dynamic compression accurately because they have one design flaw. When it comes to the cam, they only look at intake closing point. Here's a good example of why they do not work:

You put all the specs of your engine in the dynamic compression calculator.

You are looking at two cams.

Cam #1 is a HFT cam that has an intake closing point of 56° ABDC.

Cam #2 is a SR cam with an intake closing point of 58° ABDC.

You run the calculator and, of course, it shows the SR cam #2 has a lower dynamic compression ratio than cam #1, since the valve closes later. When, in reality, cam #2 has considerably more dynamic compression than cam #1 since it filled the cylinder with a lot more air and fuel.

The factory's use wide lobe seps because they can run more duration and still have mild manners. The bigger cams with wider lobe seps will still make good vacuum, and have better driveability than if they ground them on tight lobe seps. The factories are looking for smooth idles, and good driveability, NOT mean sounding hotrods. They also need them to pass strict emissions laws. Something that is not going to happen with 220° @ .050", ground on a 108° LSA. I understand why the OEM did what they did. I don't argue with it. I just don't think it's always the best way to go for everything.

[72LuxuryLeMansLa.]

Originally Posted by gtofreek

As far as dynamic compression is concerned, well, IMO, you can throw those calculators out the window. They have no real place in engine building. They are just a computer program someone came up with because they had an idea that sounded logical. They DO NOT predict dynamic compression accurately because they have one design flaw. When it comes to the cam, they only look at intake closing point. Here's a good example of why they do not work:

You put all the specs of your engine in the dynamic compression calculator.

You are looking at two cams.

Cam #1 is a HFT cam that has an intake closing point of 56° ABDC.

Cam #2 is a SR cam with an intake closing point of 58° ABDC.

You run the calculator and, of course, it shows the SR cam #2 has a lower dynamic compression ratio than cam #1, since the valve closes later. When, in reality, cam #2 has considerably more dynamic compression than cam #1 since it filled the cylinder with a lot more air and fuel.

If dynamic compression calculators have no real place in engine building how do you figure out how much pressure will result from a cam? Do you use static compression ratio calculators? Static in my opinion doesn't help since you get no compression until the Intake Valve closes........

Jim Hand and David Vizard are two engine builders that I believe are knowledgeable and considered expert engine builders by most. They seem to think Dynamic Compression ratios are to be considered........

http://pontiacstreetperformance.com/...mpression.html
http://www.hotrod.com/events/coverag...power-squeeze/