[shaker455]

Originally Posted by glhs#116

Y’all are great. 703 ordered. I guess I can use the 702 for decoration. I will check where it comes out. I do prefer a stock link chain timing set like I have installed but there is a multi keyway roller chain set on my shelf if it comes to that...

Sell the 702 if you have it already...
plenty guy's here would take it.

[glhs#116]

Originally Posted by Tom Vaught

That was true for many years but the last 10 years or so manufacturers have had to run a Emissions Test (75CVS), a F.E. Test, a WOT Test, a A/C On Test, an Evaporative Emissions test, and in some cases on heavier vehicles a heavy load test.

But the majority of older Performance vehicles only had to do the CVS/FE/Evap tests and as Cliff posted were mostly light load testing. .

Tom V.

Here it’s idle emissions for CO, NOx and CO2

[72projectbird]

Originally Posted by glhs#116

In Qatar? Yes

Man,

On a side note, I was checking out Qatar on Google maps, and it looks like a nice place. I noticed they laid out the roads to the right of North Residential Villa in a really cool pattern. It looks cool from the sky lol!

[glhs#116]

Originally Posted by Cliff R

Most emission testing is done at idle and part throttle cruise rpm's. This is where tight LSA can get one into trouble as pulling the lobes closer together increases overlap and effects cylinder scavenging at low rpm's.

Cam manufacturers go that direction with their camshafts mostly for the "bling" factor as tight LSA puts more "authority" in the exhaust sound. It also pulls power down in the rpm range and narrows up the power curve, so "felt" performance is more exhilarating that a wider LSA cam with similar specifications.

I can't provide a lot of feedback on the Voodo cams because I have very little direct experience with them, and none of it was with Pontiac engines. I did get to spend a LOT of time with a customer in the past couple of years who built what he thought was a very stout running 350 Olds engine using one. It had 9.5 to 1 compression and a smaller Voodoo camshaft, aggressive idle note, "felt" very strong driving the vehicle, easily roasted the tires whacking the throttle, etc. As good as it seemed when the car finally hooked up, which was often well into 2nd gear it was seriously lacking at that moment to the shift point, IMHO. I said nothing to him about it, instead we contracted to have me drive the car to our local track for testing. Good move IMHO, because despite how good a vehicle "feels" by the seat of your pants, the drag strip number will tell you EXACTLY how much power it is making/effectively using.

Anyhow, I was proven correct at our first drag strip outing. The first two runs resulted in spinning the tires most of the way thru the 1/8th mile and lackluster ET and MPH, converting the numbers like high 16's at best a little over 80mph. I then changed tactics and did a "John Force" burnout, which resulted in perfect traction. What a complete TURD all the way down the track. I considered ordering a Big Mac and a Coke and having it delivered so I could consume it before the end of the run, yes, it was that slow!

Jump ahead to the next season, with my help we built a new engine, 10.7 to 1 compression, custom ground cam from Lunati, 222/222 on a 114LSA (basically a copy of the GM 327/350hp cam).

No more "bling" in the idle quality, nearly dead smooth, strong vacuum, smooth/strong power right off idle, power curve flat as Kansas, just keeps on pulling until you feel like moving the shifter. Mid-20's for fuel economy in the owner 1984 442 with 3.73's out back and the rebuilt (done here) 200-4R with one of our custom converters in it.

It's now SOLIDLY into the 13's at the track and I suspect with DOT's or slicks we'd see some high 12's with it. I'd also bet anyone reading this it would pass emission testing w/o the first problem anyplace.

The new found power is mostly linear compared to the first engine, so it doesn't throw ALL of it at you right off idle and roast the tires to death. Instead it just pulls like a freight train clear across the load/speed range, and the car is very quick, and strong in at gear at any vehicle speed.

Now for the bad news, with all that said the owner is NOT completely happy with it......because it doesn't have any "attitude" at idle and it doesn't get any attention at car shows and cruises like it used to with the lower compression engine and tight LSA camshaft!....LOL

As far as how all this relates here, emission testing throws a trump card at you especially with a low compression engine. Camshafts that are going to fully exploit the available power of the good flowing HO heads are NOT going to be less than 230 @ .050" and about 280 @ .006". I've built more of the HO and 455 SD engines that most who will read this. Despite their EXCELLENT potential, the relatively "low" static compression ratio makes it difficult to "have your cake and eat it to" with them.

The best cams I've cam up with for them are all at or over 230 @ .050, and hydraulic roller designs so we can keep seat timing down for improved idle and low rpm power, but have enough cylinder filling abilities at higher rpm's to utilize the excellent flowing round port heads. Most have been ground on either 112 or 114LSA saving the tighter LSA for the stick shift cars as idle quality is not quite as important. We combine these camshafts with 2 valve relief pistons and very tight quench, and cut the heads just a bit to get closer to 8.8 to 9 to 1 compression which also improves power at every rpm plus more vacuum at idle with longer seat timing camshafts.

For what you are doing here staying small with the cam will greatly improve emission test results, but certainly is not going to exploit a lot of the potential of the excellent 455 HO engine..........IMHO...........Cliff

Cliff,

It sounds like you are confirming the thinking that was in my head when ordering the 702. Basically, as much as I was hearing good numbers and great reviews from the 704 it was clear that a cam that big wasn't going to work well for me with either the "fuel economy" nor the "pass emissions" goals. And with the higher lift I suspected I might even need longer pushrods for the smaller base circle. And then I saw that the 703 was on the 110 which just seemed too tight. The 702 is on a 112. So I figured to myself, it's close in .050 numbers to the 068 and with the fast open/slow close "new style" lobes maybe it might be a bit more "awake" than stock but still idle enough like stock for emissions and pull a tall gear.

Cliff, I hear you about the tight LSA and the super narrow power band that impresses the butt but doesn't make much power. But I saw some dyno charts here somewhere of the 702 and it looked like a pretty broad torque band which (I recall) went longer and higher rpm than the 068. So it didn't look to me like the narrow peaky band I remember being associated with the XE grinds. But happy to be corrected.

Really, this thread started when I started reading of 703s and 704s in engines like 350s and people being happy and I feared the engine making too much dynamic compression and giving me headaches. I've definitely heard of that as a problem to avoid with too "small" a cam in too "big" an engine. As Cliff says, I'm definitely trying to have my cake and eat it here.

Well, anyways. It looks like I have both 702 and 703 coming so I have a while to convince myself which to run. I think Cliff has me worried again about the bigger cam. Not just because it is bigger, but also because it is tighter. If the car was just a "toy" I would throw a big lumpy cam in and not care. But I have to pass emissions here in Qatar and I plan to have a T56 with .50 overdrive by the time I get it back to the UK. And in the UK I'm seriously going to have to be able to get decent highway mileage to afford the petrol. So those two goals are pretty important.

So, consensus. The 702 is going to be a step up from the factory 068? And do you reckon it should get similar or better vac, economy, emissions? Anyone with any experience of idle emissions testing and/or fuel economy in a 455 with the 703? Any reason not to be worried about the tighter LSA?

Sam

[pastry_chef]

Originally Posted by glhs#116

But I saw some dyno charts here somewhere of the 702 and it looked like a pretty broad torque band which (I recall) went longer and higher rpm than the 068. So it didn't look to me like the narrow peaky band

Wise observer.

Regarding emissions a concern is valve overlap area.
BOTH duration and LSA factor in that overlap.

X-factor, how strict is the emissions test?
Do you have target numbers?

[77 TRASHCAN]

Originally Posted by glhs#116

In Qatar? Yes

What octane ratings of gasoline to you have, there?

[Cliff R]

"Cliff, I hear you about the tight LSA and the super narrow power band that impresses the butt but doesn't make much power. But I saw some dyno charts here somewhere of the 702 and it looked like a pretty broad torque band which (I recall) went longer and higher rpm than the 068. So it didn't look to me like the narrow peaky band I remember being associated with the XE grinds"

I haven't even looked up the specs of any of the cams in question here, just making "general" comments on the subject since I do this for a living, and the information that I provide here is from direct testing, not regurgitated from previously posted info, theory based on currently available information, or what someone else did or tried to do with or couldn't do with one of these engines.

I'm also trying to stay out of an LSA debate, which my "fan club" on this website more than any other will try to throw in my face every single time the subject of cam selection comes up.

LSA is only a small part of a big plan, but even today you will continue to see the factory engines showing up with very wide LSA camshafts in them. This is done in part to help those engines meet emission standards currently in place, but also to provide the end user with an engine having excellent idle, off idle, fuel efficiency and broad/flat power curve. All of these things are beneficial for everyone involved, except you aren't going to get a "nasty" idle note sitting at a stoplight or car cruise to impress all your friends.

The broad/flat power curve provides quite a few positives with these engines including LESS octane required all else being equal. Think about this subject in dynamic terms, not static. When the engine rpm' are relatively low and we have narrowed up the LSA and yanked power DOWN in the rpm range it will reach peak VE sooner.

Peak VE is the rpm where highest torque will occur and also highest cylinder pressure. I've mentioned this many times, but have worked on several 455 engines with lower compression that pounded like SLEDGEHAMMERS on pump gas with "normal" timing/fuel curves in them. These engines and not by coincidence used camshafts with short seat timing AND tight LSA. So the well meaning engine builder was trying to stay at or under the proverbial "brick wall" of 9.5 to 1 compression for pump gas, then follow all the nonsense in print about using a "modern" cam profile to bring back all the lost power.

With that said I've found that we can quit wasting time worrying about lowering compression and use it to our advantage instead. It allows for larger cams and when correctly chosen they lower dynamic cylinder pressure at lower rpm's, push peak torque up in the rpm range, and spread out the torque curve. With VE occurring later rpm's past VE will allow LESS time for cylinder filling. So if the engine doesn't ping at the rpm where peak torque occurs, it is NOT going to increase it's octane requirements past that rpm. Good new for everyone involved here.

So for the subject at hand, 455 HO and their close counterparts the excellent 455 Super Duty engines have tremendous potential. The factory knew this and wanted to put bigger camshafts in them, but quickly found that with their relatively "low" compression the negatives they faced at idle and low rpm's were simply too much to overcome as far as the EPA was concerned. What a bummer because those engines are just begging for a 230 @ .050" or larger cam to be installed in them to see the benefits of the much better flowing round port cylinder heads.

I see your build as not really a problem since it doesn't appear that it needs to focus on making optimum power on pump fuel, spends a lot of time as a daily driver, and you won't be taking steps to increase the static compression ratio a bit, not to mention someone is going to sniff it for emissions. So going with a smaller cam on wider LSA will get the job done. The smaller Lunati camshaft for sure isn't going to make much top end charge or even come close to seeing the full potential of the HO heads, but for what you are doing and the limitations imposed you'll be happier all the way around with something at or close to the factory cam......IMHO......Cliff

[b-man]

If you're worried about passing emissions then put the 702 in there and don't look back.

The engine will be happier at low RPM when cruising in overdrive and fuel mileage will be a bit better too.

[Cliff R]

+2

I attached a cam card and dyno sheet which may be of interest to some reading this thread.

The engine was a 1973 455 Super Duty we did here a few years back. Pretty much "stock" aside from us installing Icon forged pistons (zero decked), 4340 "H" beam rods, .039" thick head gasket, and cutting the heads .020" to clean them up. Stock intake was used (unported), original 1973 factory Super Duty Q-jet, stock distributor (recurved by us), and a custom ground HR cam.

Even with this much camshaft being used notice how early the engine makes peak power, how broad/flat the power curve is, etc. I'd also note that this engine idled dead smooth, not even a hint of "lope" even slowing it clear down to 600rpm's where it was still making over 13" vacuum!

So look at the cam number, and consider it is a modern roller profile, and then think about how much power will not be made using a much smaller flat cam with less of everything everyplace.........FWIW.......Cliff

[geeteeohguy]

Originally Posted by glhs#116

Here it’s idle emissions for CO, NOx and CO2

At idle, only CO and HC are usually measured. NOx needs to be measured on a dyno, under load. And CO2 is merely an indicator of combustion completion, as is 02. They aren't considered pollutants. The biggest effect a large cam will have on emissions is high CO (carbon monoxide) and high HC (hydrocarbons) due to a richer fuel charge. Rich running engines almost never have high NOx readings......NOx is caused by high combustion temps usually resulting from very lean mixtures.

[glhs#116]

Originally Posted by geeteeohguy

At idle, only CO and HC are usually measured. NOx needs to be measured on a dyno, under load. And CO2 is merely an indicator of combustion completion, as is 02. They aren't considered pollutants. The biggest effect a large cam will have on emissions is high CO (carbon monoxide) and high HC (hydrocarbons) due to a richer fuel charge. Rich running engines almost never have high NOx readings......NOx is caused by high combustion temps usually resulting from very lean mixtures.

You are correct. It is CO, CO2 and HC

[gtofreek]

Not sure why anyone would think the 703 at 227/233 would be considered big in a 455. It is small by my standards, and idles really good in a 455. The 110 LSA isn't going to cause an issue in that engine, but it could always be ground on a 112 if you like. Either way, it would be fine. It would have a mild lope in a 400, but not in a 455. I put it in a 428 and it wasn't even lopey in that.

[Cliff R]

+2, small cam for a 455 by my standards as well.

Still throws a trump card at you for getting thru emissions. The basic rule of thumb here is that the longer the duration and tighter the LSA the more pollutants you will see at idle speed and in the "normal" driving range. Just a simple matter of physics with these things.

If getting thru emissions without pulling out all the stops is the goal here, the smaller the camshaft that you install into that engine the easier its going to be for you.....IMHO.......Cliff

[Gary H]

I recently built a 4.250 stroked 400 engine with 6X-4 heads using the Vodoo 702 cam. The customer really wanted low end power and couldn't care less about the upper RPM range. He does't hot rod the car much, just likes to lay into it from stop light to stop light occasionally. Compression ratio wound up around 9.6 if I remember right. The engine made 453 hp @ around 4900 and 590 lbs of torque. Very responsive on the street and with the seat of the pants feel, but it's done power wise at around 5000 rpm. Really what he was looking for in this situation.

[pastry_chef]

Originally Posted by Gary H

I recently built a 4.250 stroked 400 engine with 6X-4 heads using the Vodoo 702 cam. The customer really wanted low end power and couldn't care less about the upper RPM range. He does't hot rod the car much, just likes to lay into it from stop light to stop light occasionally. Compression ratio wound up around 9.6 if I remember right. The engine made 453 hp @ around 4900 and 590 lbs of torque. Very responsive on the street and with the seat of the pants feel, but it's done power wise at around 5000 rpm. Really what he was looking for in this situation.

Thanks Gary, excellent results!

[Formulajones]

Originally Posted by Gary H

I recently built a 4.250 stroked 400 engine with 6X-4 heads using the Vodoo 702 cam. The customer really wanted low end power and couldn't care less about the upper RPM range. He does't hot rod the car much, just likes to lay into it from stop light to stop light occasionally. Compression ratio wound up around 9.6 if I remember right. The engine made 453 hp @ around 4900 and 590 lbs of torque. Very responsive on the street and with the seat of the pants feel, but it's done power wise at around 5000 rpm. Really what he was looking for in this situation.

Very respectable power for a little cam. That would be a fun street engine. Those Voodoo cams really do work well.

[1968GTO421]

Originally Posted by gtofreek

Not sure why anyone would think the 703 at 227/233 would be considered big in a 455. It is small by my standards, and idles really good in a 455. The 110 LSA isn't going to cause an issue in that engine, but it could always be ground on a 112 if you like. Either way, it would be fine. It would have a mild lope in a 400, but not in a 455. I put it in a 428 and it wasn't even lopey in that.

Paul, thanks for posting this info, esp. re: 428

[Cliff R]

"I recently built a 4.250 stroked 400 engine with 6X-4 heads using the Vodoo 702 cam. Compression ratio wound up around 9.6 if I remember right. The engine made 453 hp @ around 4900 and 590 lbs of torque"

Most 6X-4 heads will make closer to 10 to 1 compression on a 455 unless a pretty thick head gasket was used or pistons pretty far down in the holes at TDC, or may had pretty big valve reliefs in them, etc.

What were the head flow numbers if you don't mind my asking?

Do you have or can post the dyno charts as peak numbers don't tell us about average power or where peak power was made at.

Good power numbers for sure, but I'm looking to compare them to what we've done here as I've built a good many 455's with 6X-4 or iron heads with chambers in the 88-96cc range.....tks.....Cliff

[Gary H]

Originally Posted by Cliff R

"I recently built a 4.250 stroked 400 engine with 6X-4 heads using the Vodoo 702 cam. Compression ratio wound up around 9.6 if I remember right. The engine made 453 hp @ around 4900 and 590 lbs of torque"

Most 6X-4 heads will make closer to 10 to 1 compression on a 455 unless a pretty thick head gasket was used or pistons pretty far down in the holes at TDC, or may had pretty big valve reliefs in them, etc.

What were the head flow numbers if you don't mind my asking?

Do you have or can post the dyno charts as peak numbers don't tell us about average power or where peak power was made at.

Good power numbers for sure, but I'm looking to compare them to what we've done here as I've built a good many 455's with 6X-4 or iron heads with chambers in the 88-96cc range.....tks.....Cliff

The heads were hand ported by me. Nothing too exotic, matched to RA IV intake gasket, bowls done, a little short turn radius work. Probably wound up around 240 CFM. Intake was a Crosswinds intake, port matched. Checking back on my notes the compression ratio was 9.7. 94 cc heads, 5.5 cc piston reliefs, .039 gasket, pistons, .010 in hole, 4.160 bore. Don't have the dyno sheet, I gave it to the customer, but peak power was at 4900 rpm.

[Cliff R]

Was most interested in where peak torque was at. When I see a high number like you made I like to know where it happened, and how much torque was still being made around 4900-5000rpms.

Usually with a high peak number the LSA will be 110 or tighter, it will occur around 3400-3600rpms, and the numbers out near 4900-5000rpms will be considerably lower than if a wider LSA cam was used.

Anyhow, your numbers are right on par for a 455 build with 240cfm heads and cam around 230 @ .050".

With 6X-4, 4X, 7M3, and 1974 #46's with 230 to 240cfm flow all of our engines have been at or just over 1hp/cid using cams with 230 @ .050". They also idle very good, and strong power in the "normal" rpm range, and pump gas friendly even closer to 10 to 1 compression or a tad higher.

We have done one engine with stock untouched heads, not even a port match and it made 440hp/530tq. It also had 96cc chamber heads, the largest of any that we used for any of them, so the head porting and compression will help the power numbers with those engine builds.......Cliff