Fuelie 461X Iron Heads #1

[Joe C.]

Re: Fuelie 461X Iron Heads #1

Duke - I agree, with your comments using the 327 the best choice for power as I'm convinced. But I'm using his little brother 283 .030 over that makes it a 289 and lowering my compression ratio from 11 to 1 to 10.5 to 1 flat top pistons. I need to keep the compression high do to the lower CID. Of course will be using 461X 194 int 1.5 exh using a higher lift camshaft. I selected dual pattern version giving more lift & duration on the exhaust side because of the original exhaust manifold restrictions.

Crowers 00242 462int/470exh lift @ .050 duration 220/226 Advertised duration 280/286 overlap 59 (that is 8 degrees less overlap then the solid Duntov cam), LSA 112 & LIC 108 this cam will produce 285php @ 5500 RPM, 347.9pt @ 3000 RPM I would like to try the smoother ideling cams LT-1 but believe they take a little to much of the nostalgic idle away. I'm willing to make a slight trade off in idle quality besides a 4.11 posi with a close ratio 4 speed should be just right for this application. I would really like to run the solid lifter cam but hate to be removing the valve covers once a month to adjust. The new Comp cam hydraulic lifters have a check valve that mimics the solid lifter sound as it restricts over oiling at higher RPM. I'm still experimenting and haven't made up my mind with anything as of this time. Of course I value your comments immensely.

Bill

1961 Black/Silver/Red Int. 283/315 FI
power windows. Frame off 65% completed.
1989 hard top daily driver 165,000 miles

Bill,

The cam you're looking at sounds like a fairly mild one, with very gentle flanks, what with the whopping 60 degree difference between seat-to seat and .050 duration. The LT1 cam has, I think 300+/300+ and 242/254, also producing a very gentle flank. What is Crower's recommended SCR with that cam? Also, 112 is probably a bit tight for a 283. You might look into having that cam ground on a 114 LSA.

[Bill B.]

Re: Fuelie 461X Iron Heads #1

Joe - Interesting, I agree that doesn't make any sense....You can get the details from Stan himself: srweiss@erols.com Please keep me posted of your findings.

Bill

[Duke W.]

Re: Fuelie 461X Iron Heads #1

I would really like to run the solid lifter cam but hate to be removing the valve covers once a month to adjust.
Bill

If this is the kind of BS you really want to believe, then there is nothing I can do to help.

Duke

[Bill B.]

Re: Fuelie 461X Iron Heads #1

Bill,

The cam you're looking at sounds like a fairly mild one, with very gentle flanks, what with the whopping 60 degree difference between seat-to seat and .050 duration. The LT1 cam has, I think 300+/300+ and 242/254, also producing a very gentle flank. What is Crower's recommended SCR with that cam? Also, 112 is probably a bit tight for a 283. You might look into having that cam ground on a 114 LSA.

Joe - I was hoping for a logical explanation, this was my newest find so I wanted some new input I downloaded Comp cams Camquest 6 its free from their sight. Found it helpful. Its like having your own dyno....well its fun anyhow. I will take your advice on the LSA 114 I was hoping that the LSA 112 would bleed off some of the compression at mid RPM's with the overlap at 59 so I can run pump gas without any problems and boosting the top end. The bottom line the peak hp went up and the peak torque, but couldn't understand as you stated that whopping 60 degrees and showing low .050 numbers. I will look at the LT1 cam as you stated it also has a gentle flank. Do you know what the .050 numbers are for this cam?

I appreciate it,
Bill

[Joe C.]

Re: Fuelie 461X Iron Heads #1

Joe - I was hoping for a logical explanation, this was my newest find so I wanted some new input I downloaded Comp cams Camquest 6 its free from their sight. Found it helpful. Its like having your own dyno....well its fun anyhow. I will take your advice on the LSA 114 I was hoping that the LSA 112 would bleed off some of the compression at mid RPM's with the overlap at 59 so I can run pump gas without any problems and boosting the top end. The bottom line the peak hp went up and the peak torque, but couldn't understand as you stated that whopping 60 degrees and showing low .050 numbers. I will look at the LT1 cam as you stated it also has a gentle flank. Do you know what the .050 numbers are for this cam?

I appreciate it,
Bill

LT1 cam, GM 3972178
Speed ProCS1145R

lobe lift in/ex .3057/.3234
valve lift (with rocker ratio, ACTUAL @ 1.5:1 @ POML) .4590/.4850
lash: .020/.025

LSA 116
ground 6 degrees advanced (110/122/116)

Dur @ .050: 242/254
Dur @ .006: 295/310

The LT1 cam was optimized for a SBC of 350 CI, and may not be the best cam for a smaller displacement engine, like 289.

When these cams were designed, they were primarily required to provide durability, paramount, coupled with as much top end horsepower development that was possible within those constraints. These engines carried a factory warranty, right? In order to provide sufficient "high" lift, together with gentle flanks, durations (seat-to-seat) had to be HUGE. This, consequently required the designers to open-up the LSA in order to make them streetable with those big durations. Additionally, they designed them with large clearance ramps, which meant large tappet clearances (lash).

Aftermarket cams do not carry the long warrantees like GM, Ford, etc............usually 1 year or less. The cam designers understand that the engines that these cams are designed for will probably not see day-to-day use, with 1000 miles/year being about right. With this in mind, the designs are quite a bit more aggressive. As long as you are willing to accept the above premise, then you will be well served to use an aftermarket cam in any engine that you build. If you use the correct oil, with sufficient ZDDP (if using flat tappets OR VERY AGGRESSIVE roller tappets), keep idling to a minimum, and yearly driving to reasonable limits, then you can expect long life from your engine's valvetrain.

"Performance" aftermarket cams, especially those marketed as "fast action", "high energy" etc have differential between seat-to-seat and .050 lift in the vicinity of 30 degrees plus/minus 5 degrees or so. This indicates that less duration is needed to accomplish a given amount of lift. Tighter lash, in the vicinity of .012/.012 is used, which means smaller clearance ramps, and valves jerked off/on the seat at faster rates.

All of that said, if choosing an aggressive aftermarket flat tappet (whether it be solid or hydraulic) cam, or mild hydraulic roller, the following applies regarding optimal LSA based on V8 cylinder displacement:

406 cu-in : 106
383 cu-in : 108
350 cu-in : 110
327 cu-in : 112
283 cu-in : 114

If you want to use a vintage camshaft, then you should probably stay with the original Duntov (3736097) in your application. If you are looking at the LT1 cam, then keep in mind that it was designed for a larger displacemnt engine than yours. If applying the above analysis, then that would mean (in theory) adding an additional 4 degrees to an already huge LSA of 116, to end up with 120. Someone would have to "model" this design for you, but in theory, it would make a nice running 283.

Don't believe what you heard about solid lifters. If your car is not a daily driver, it means that the tappets would need looking at, perhaps every 5-6 years!

Joe

[Duke W.]

Re: Fuelie 461X Iron Heads #1

There is no optimum LSA! Most of what you read about cam design on the Web and hot rod mags is BS.

The first thing you need to establish are some basic operating parameters like maximum allowable revs, idle characteristic, and the minimum engine speed to acheive 80 percent peak torque. I use 2000 for a road engine. If it's significantly above that the engine will be soggy and unresponsive in normal road driving and get lousy fuel economy.

To design a cam you can start by establishing the EVC and IVO points to duplicate the OE cam. This will result in about the same effective overlap, which will yield your idle characteristic target.

The most significant valve event is EVC. The later it is the higher the top end power at ever increasing revs, so you must take into account the maximum allowable revs and your 80 percent torque point.

EVO is determined by I/E flow ratio. The lower it is the earlier the exhaust valve needs to be opened. If the E/I ratio is about 0.75 the optimum timing numbers will yield close to equal duration. If less, the EVC point will have to be advanced and the exhaust duration will be more. OE SB big port heads are typically about 0.65, but typical "massaging" increases it to 0.75-0.80. Think about what effect that will have on your exhaust duration relative to inlet duration!

High overlap can work against you on a road engine due to exhaust back pressure. Even the Duntov and LT-1 cams, which have about the same effective overlap have too much (and most aftermarket cams have way too much), but reducing it smooths out the idle, which may not be desireable if you are trying to duplicate the OE idle characteristics.

Most engine simulation and "cam analysis" programs are worthless because they only simulate SAE gross with no road exhaust system or front end accessories. I've been through them all.

The only simulation program worth a damn is Engine Analyser, and IMO the old versions 3.0 and 3.2 are more accurate than the "Professional" verison that shows cylinder pressure at every crank angle and takes longer to run.

EA computes effective overlap in sq-in-degs, which is what really counts, not LSA. Maintaining constant effective overlap means LSA increases with more duration and vice versa, so LSA cannot be used as a useful comparison between cams unless all the durations are the same. For example the Duntov and LT-1 cams have very nearly the same effective overlap in sq-in-deg (which is why they have the same idle characteristic), but the Duntov LSA is 110 and 116 for the LT-1 cam. So much for LSA offering any useful insight into the how a cam performs! Also, valve sizes are taken into account in the effective overlap calculation, so small valve 283 heads will show less effective overlap than 327 heads for the same EVC/IVO timing points.

Another very useful parameter in EA is Mach index. Most configurations won't make much more power above 0.55 no matter what you do with valve timing without a significant loss at the low end.

If the configuration shows 80 percent peak torque at 2000 and a Mach index of about 0.55 at maximum allowable revs, you've got a well optimized cam design, and the timing numbers may not look anything like any OE or aftermarket cam, particularly if the heads have been massaged which typically raises the E/I ratio well above OE.

Of course, the above requires that you have accurate head flow data, accurate models for you inlet and exhaust systems (which requires a good estimate of exhaust system flow characteristics) and front end accessory configuration.

Once you establish the basic timing points, you can further refine the design by individually advancing or retarding each lobe in two to four degree increments, then the whole cam in similar increments. If you have reasonably accurate input parameters you will likely end up with a cam that doesn't look anything like what is available on the market, including OE, especially when the heads are massaged.

That's when I decided to design my own cams using the various OE lobes and mixing and matching them as required to get as close to my optimized valve timing points as possible.

Duke

[Bill B.]

Re: Fuelie 461X Iron Heads #1

Joe - You covered it all and then some, and put some of my concerns into prospective. I really appreciate it! The more input received brings me one step closer in choosing the 'perfect camshaft'. What seems to be the case today other then what was previously stated by Joe, that most cam manufacturers grind their cams for the majority CID 350, 383, and have little selection if any for the smaller 283 understandably so,(cam manufacturers can't turn a profit selling to the 1%). So selection is very limited and settling for a cam that was profiled for a larger engine or finding one that 'may' work doesn't really cut it for me. Original factory performance camshafts are always a possibility, they have been proven.

Now with all that being said, and applying what I learned, I'm shifting gears and now looking into custom grinding. I want the best of both worlds with a little give and take mixed with an experience grinder could make the 'perfect 283 camshaft'.

Thanks, again Joe
Bill

1961 Black/Silver/Red Int. 283/315 FI
power windows. Frame off 65% completed.
1989 hard top daily driver 165,000 miles

[Michael H.]

Re: Fuelie 461X Iron Heads #1

I sure enjoy the cam wars here. Some folks have WAY too much free time.

If you just keep on grindin hell outa the intake ports, the flow numbers will increase but I gotta tell ya what. The efficiency goes down when the size goes up.
There's a lot more to it than just more air flow. Remember, the air volume stops and starts. It's not a continuous stream of air like on a flow bench. That may give ya a hint.

[Duke W.]

Re: Fuelie 461X Iron Heads #1

Like valve timing, most guys have no real engineering level understanding of port flow.

On a road engine the objective is not to "hog the ports out". The objective is to improve the isentropic flow efficiency. This is accomplished by blending the rough machined area above the valve seat to the as cast portion of the port, which eliminates the annular ridge and matching the head ports to the manifold ports. No material other than significant casting flash should be removed from the interior of the port. This removes only a few cc of material so port velocity is not materially effected, but significantly more mass will flow at any given depression due to the greater achieved flow efficiency.

Typical SB heads as machined by Flint have inlet/exhaust flow efficiencies of 44/41 percent. The above rework, including typical three angle valve seats will increase the flow efficiencies to the 50/60 percent range.

The best engines today, both racing and road (like the LS7) have flow efficiencies at or exceeding 70.

Duke

[Bill B.]

Re: Fuelie 461X Iron Heads #1

Most engine simulation and "cam analysis" programs are worthless because they only simulate SAE gross with no road exhaust system or front end accessories. I've been through them all.

Duke - The program that is in question CamQuest 6 by Comp Cams does have road exhaust systems from factory manifolds to open headers I believe you can choose approximately six or eight settings. I'm not saying that this program is the most accurate. but its up there. I'm not sure to what degree of accuracy it displays. But then how does one come to a conclusion on a calibration standard?
In your opinion what do you consider is the best overlap for my application?

Thanks, Bill

[Duke W.]

Re: Fuelie 461X Iron Heads #1

If you want results you can count on, get EA. Joe can send you a copy.

I don't know what is the best overlap for your application for one because you have never laid out a set of requirements.

I did do some research on improving my "327 LT-1" configuration by reducing overlap. I was looking for even better low end torque without affecting top end power.

What I ended up with was the 30-30 lobe on the inlet side and the Duntov exhaust lobe on the exhaust side with an LSA of about 121 degrees and about half the effective overlap of the LT-1 or Duntov cams, which would have yielded an idle characteristic somewhat less lopey that the L-79 cam.

Alas, there was not enough material on the cam blank for Crane to grind it, and the improvement in bottom end was not dramatic, so I wrote it off.

The LT-1 cam should work well on a 283 with massaged 461X heads. The shorter stroke relative to a 327 will shift the torque curve up the rev range by about 8 percent, which will move the beginning of the 80 percent torque bandwidth to somewhat above 2000 and peak power close to 7000.

A little less duration/overlap than the LT-1 cam would be best, but there are no OE lobes in between.

What should also work okay is retarding the Duntov cam inlet POML a few degrees, which will widen the LSA, but result in a smoother idle that may betray that it's not a real Duntov cam.

The L-79 cam would also work pretty well, but it limits revs to no more than about 6500, and the combination of massaged 461X heads and FI on a 283 means it will make peak power at about 7000 with that duration, so you need a mechanical lifter cam to get there. Reindexing the Duntov lobes to POMLs 110/114 is effectively a mechanical lifter version of the L-79 cam, albeit with less lift. Both have .050" inch lifter rise durations (above the tops of the clearance ramps on mechancial lifter cams) of 220 degrees. The LT-1 lobe is 231 and 239 for the 30-30 lobe.

Again, you have to establish your objective, and I use three simple parameters than anyone should establish up front.

Then use EA with accurate inputs to work out the timing that best meets your objective. Anything less is just stumbling around in the dark.

As far as simulation programs are concerned, accuracy demands than you be allowed to input exhaust system flow data. I use 500 CFM for the 2.5" C2 exhaust system in EA, and IIRC the flow is measured at 1.5" depression - just like a 4-bbl. carb. This provided good correlation to chassis dyno test results and resulted in only about 3 psi backpressure on a 327, which is a good limit to target on a high performance road engine. (Due to greater displacement/power/exhaust flow, the L-72 generates about 6 psi, which is high. The L-72 needs a better exhaust system to maximize as-installed performance. Exhaust backpressure increases with the square of flow, so the 40 percent greater exhaust flow volume of the L-72 relative to a SHP 327 doubles back pressure.) The documentation provide some guidelines based on pipe size. For 2" systems I believe I used 350 CFM.

I don't think the program you refer to allows this. I did evaluate it, but never used it due to its limitations.

Duke

[Joe C.]

Re: Fuelie 461X Iron Heads #1

There is no optimum LSA! Most of what you read about cam design on the Web and hot rod mags is BS.

EVO is determined by I/E flow ratio. The lower it is the earlier the exhaust valve needs to be opened. If the E/I ratio is about 0.75 the optimum timing numbers will yield close to equal duration. If less, the EVC point will have to be advanced and the exhaust duration will be more. OE SB big port heads are typically about 0.65, but typical "massaging" increases it to 0.75-0.80. Think about what effect that will have on your exhaust duration relative to inlet duration!

The only simulation program worth a damn is Engine Analyser, and IMO the old versions 3.0 and 3.2 are more accurate than the "Professional" verison that shows cylinder pressure at every crank angle and takes longer to run.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>

Hi Duke,

That did not come from the web.
It came from your protege', David Vizard.
My Engine Analyzer Pro v3.5 bears it out.
My old, but "more accurate" (?) v3.2 does, too.
The word "analyzer" is spelled with a "z", unless written in British, where an "s" is used.
Isn't an "EVO" a Ford rally car?

[Duke W.]

Re: Fuelie 461X Iron Heads #1

David Vizard is not my protege, nor am I his. Most of his work is good, but some mystifies me. As backpressure increases overlap does more harm, especially to low end torque, so there is no way in hell that some "magic overlap" number exists for a given displacement.

Overlap is merely the result of properly selected valve timing for a specific configuration and torque bandwidth spec, including accurate exhaust flow modeling, not an input variable.

Most road engines with conventional exhaust manifolds operate best on very low overlap. This includes OE SHP engines that had fairly high overlap. Lower overlap offers better torque bandwidth at the same peak power level. Look at the valve timing/overlap on current engines like the LS7 - very little overlap.

Overlap is important and can be a significant tuning parameter on racing engines with properly designed header/exhaust systems. Without the benefits of a tuned exhaust system, backpressure is essentially constant and is working against inlet pressure which delays the beginning of cylinder filling as long as the exhaust valve is open.

That's one of the biggest problems of all these hot rod magazine dyno tests. They're almost always done on lab dynos with headers and open exhaust. Take the same engine and put it in a chassis with manifolds and a reasonable street exhaust system, which is going to have significant backpressure, and the valve timing required to optimize performance completely changes.

If you don't know what EVO, EVC, IVO, and IVC mean, then you have no business in this discussion.

If you want to have a serious discussion, fine. If you keep injecting cynicism into your responses you reduce you own credibility and reduce the quality of the discussion.

Duke

[Joe C.]

Re: Fuelie 461X Iron Heads #1

I sure enjoy the cam wars here. Some folks have WAY too much free time.

If you just keep on grindin hell outa the intake ports, the flow numbers will increase but I gotta tell ya what. The efficiency goes down when the size goes up.
There's a lot more to it than just more air flow. Remember, the air volume stops and starts. It's not a continuous stream of air like on a flow bench. That may give ya a hint.

Hey, Michael,
So...............where did ya find the time to put up 4904 posts?
Joseph

[Joe C.]

Re: Fuelie 461X Iron Heads #1

David Vizard is not my protege, nor am I his. Most of his work is good, but some mystifies me. As backpressure increases overlap does more harm, especially to low end torque, so there is no way in hell that some "magic overlap" number exists for a given displacement.

Overlap is merely the result of properly selected valve timing for a specific configuration and torque bandwidth spec, including accurate exhaust flow modeling, not an input variable.

Most road engines with conventional exhaust manifolds operate best on very low overlap. This includes OE SHP engines that had fairly high overlap. Lower overlap offers better torque bandwidth at the same peak power level. Look at the valve timing/overlap on current engines like the LS7 - very little overlap.

Overlap is important and can be a significant tuning parameter on racing engines with properly designed header/exhaust systems. Without the benefits of a tuned exhaust system, backpressure is essentially constant and is working against inlet pressure which delays the beginning of cylinder filling as long as the exhaust valve is open.

That's one of the biggest problems of all these hot rod magazine dyno tests. They're almost always done on lab dynos with headers and open exhaust. Take the same engine and put it in a chassis with manifolds and a reasonable street exhaust system, which is going to have significant backpressure, and the valve timing required to optimize performance completely changes.

If you don't know what EVO, EVC, IVO, and IVC mean, then you have no business in this discussion.

If you want to have a serious discussion, fine. If you keep injecting cynicism into your responses you reduce you own credibility and reduce the quality of the discussion.

Duke

I believe in your sincerity, and I am neither a misanthrope nor a pessimist. I do, however, have a tendency to be sarcastic.
IVO is a guy who was best known for his dragster with 4 engines.