[Stan Weiss]

Interesting how people just like to throw terms out there tight and wide LSA. Lets actually look at the listed numbers

The XE256 is 256 / 268 110 LSA

The 066 is 273 / 282 111.5 LSA

Not a very big difference and this would mean the 066 has more overlap than the tight LSA XE256.

[Cliff R]

I LOVE to "throw terms out there" but at least I actually do this sort of thing vs Googling it all up.

While I'm throwing things out there, it was mentioned somplace that Butler uses and recommends Comp cams. Well, until I sent them this dyno chart it was true, they pushed the tight LSA XE lobes pretty hard. I had a nice long talk a few years back with Rodney Butler, sent him this overlapping Dyno sheet, and....well.....you can go to their website and see what happened since that conversation and a few email exchanges.

Of course it's rumored that they just made the switch because of demand from the customer base. Prodding from me, customers or whoever, they now offer a full line of "new"cams with quite a few on 112 and 114LSA's. It any case, my fault, their fault, nobodies fault it's been good for the hobby for sure.........

[Stan Weiss]

Cliff,
Don't need to Google anything. Clearly you have limited understand of what does what when it comes to cams.

I.have explained this to you before but you just don't want to understand. It was the increase in duration that made the difference. With increased duration you sometimes need to widen the LSA to keep overlap in check.

Let look at what Pontiac did
066 111.5 LSA
067 113.0 LSA
068 116.0 LSA

Then when they got to the high performance cams they cared more about HP the idle quality.
744 115.5 LSA
041 113.5 LSA

Stan

[Jay S]

Here are some quick dyno sims for this

066

2000-424 tq
3000-434 tq
3500-414 tq
4000, 290 HP

XE 255, 106ICL
2000-433 tq
3000-449 tq +15 over 066
3500-426 tq
4000 295-HP+5

Here is what it shows retarded 7*, really shows how small that cam truly is in a 400.

XE255, 113 ICL
2000-420 tq
3000-445 tq…-4
3500-431 tq…+5
4000-310 HP+15
4500-315 HP+20 over 106

You would hardly notice a 15 ft lb change in tq and 5 HP over the 066 driving on the street, 20 HP at the top on the last sim would be very noticeable.

[Cliff R]

Stan, I'm on the user end so don't get all caught up in the tech stuff.

I'm actually shocked at how much of it you don't have a handle on being a "tech" guy.

The power improvment and improved idle quality (from the dyno charts above) comes in part from longer seat timing and improved scaveninging but more of it comes from being able to run more timing on the engine at idle speed and more total timing WITHOUT detonation. I've told folks on here for many years how POORLY many of these engines run once they get between the fenders of the car when you make poor cam choices.

The wider LSA pushes peak power (VE) higher in the RPM range and spreads out power at the same time. Since the events at higher RPM's occur more times per second once we get past peak VE (peak torque) the engine will not ping even though we have improved cylinder filling considerably. Therefore we are nicely rewarded with a LOT more upper mid-range and top end charge PLUS a nice smooth idling engine with excellent street manners. That fact alone should throw out the comments from folks about not caring how much power their engine makes past 4500rpm's or so because is doesn't matter. If excellent idle quality, throttle response and good street manners were at the top of your list you have them. Then, if you choose you are now making a BUTT LOAD more power in the upper RPM range as a byproduct.

You "tech" boys don't get any of that since you aren't out on the front lines actually having to tune some of these engines after poor cam choices were made for the CID and static compression ratio. I tried to tell your buddy up in Canada that but his experience was solely limited to Google so just wanted to search in vane for folks who agreed with his twisted line of thinking instead of actually going out and doing some of this.

I was hoping you had put all that behind you but you were the first one in line in that "linch mob" that ended up getting him canned permanently from this Forum in the first place.

My experience with these engines covers nearly half a century, and it amazes me to this day with all the good infor out there, and the technology that folks still make poor choices with parts selection, especially camshafts, then have to come on the Forums and look for help that isn't there to try to get past fundamental issues in the engine build.

We see this ALL the time , and not just with cam choice. Here you admitted have zero experience with an XE256 cam, but I have worked with several engines with that cam in them and it's a big TURD every single time. Folks with all this vast knowledge of cam lobe profiles should be the FIRST one in line to tell us that installing a tiny little cam in a big CID engine doesn't just keep making it better and better at idle and low RPM's. Doesn't make "more" torque either, and advancing cams doesn't always improve low end torque, even though we here those things regugitated frequently on the Forums.

My guess is that the intake closing point is a very important player in how all this works, but I 'll leave the theory to you tech boys and continue to help folks out here on the user end of the deal recover from making poor choices with this sort of thing....FWIW......Cliff

[Stan Weiss]

Originally Posted by Jay S

Here are some quick dyno sims for this

066

2000-424 tq
3000-434 tq
3500-414 tq
4000, 290 HP

XE 255, 106ICL
2000-433 tq
3000-449 tq +15 over 066
3500-426 tq
4000 295-HP+5

Here is what it shows retarded 7*, really shows how small that cam truly is in a 400.

XE255, 113 ICL
2000-420 tq
3000-445 tq…-4
3500-431 tq…+5
4000-310 HP+15
4500-315 HP+20 over 106

You would hardly notice a 15 ft lb change in tq and 5 HP over the 066 driving on the street, 20 HP at the top on the last sim would be very noticeable.

Jay,
Thanks that is some good information. Which sim program do you use?

Stan

[PAUL K]

I have no idea why we are posting dyno sheets in a thread about an 8:1 compression 400 needing more throttle response. But here are a couple of low compression, pump gas, iron headed Pontiac engines using fast open and closing lobes. The 600 HP engine used a 106 LSA and the other used a 104.... Both engines had above average throttle response.

[KCTurbo]

I ran a very similar setup in one of my 400's. All depends what you want to do with the car. At the time I was running a 2004R and a 390 gear 27in tire. I will admit that it sounded good and was pretty snappy on the throttle, but it was done making much at about 4800. The butt dyno liked it but ran out of steam fairly fast.

[Stan Weiss]

Originally Posted by Cliff R

Stan, I'm on the user end so don't get all caught up in the tech stuff.

I'm actually shocked at how much of it you don't have a handle on being a "tech" guy.

The power improvment and improved idle quality (from the dyno charts above) comes in part from longer seat timing and improved scaveninging but more of it comes from being able to run more timing on the engine at idle speed and more total timing WITHOUT detonation. I've told folks on here for many years how POORLY many of these engines run once they get between the fenders of the car when you make poor cam choices.

The wider LSA pushes peak power (VE) higher in the RPM range and spreads out power at the same time. Since the events at higher RPM's occur more times per second once we get past peak VE (peak torque) the engine will not ping even though we have improved cylinder filling considerably. Therefore we are nicely rewarded with a LOT more upper mid-range and top end charge PLUS a nice smooth idling engine with excellent street manners. That fact alone should throw out the comments from folks about not caring how much power their engine makes past 4500rpm's or so because is doesn't matter. If excellent idle quality, throttle response and good street manners were at the top of your list you have them. Then, if you choose you are now making a BUTT LOAD more power in the upper RPM range as a byproduct.

You "tech" boys don't get any of that since you aren't out on the front lines actually having to tune some of these engines after poor cam choices were made for the CID and static compression ratio. I tried to tell your buddy up in Canada that but his experience was solely limited to Google so just wanted to search in vane for folks who agreed with his twisted line of thinking instead of actually going out and doing some of this.

I was hoping you had put all that behind you but you were the first one in line in that "linch mob" that ended up getting him canned permanently from this Forum in the first place.

My experience with these engines covers nearly half a century, and it amazes me to this day with all the good infor out there, and the technology that folks still make poor choices with parts selection, especially camshafts, then have to come on the Forums and look for help that isn't there to try to get past fundamental issues in the engine build.

We see this ALL the time , and not just with cam choice. Here you admitted have zero experience with an XE256 cam, but I have worked with several engines with that cam in them and it's a big TURD every single time. Folks with all this vast knowledge of cam lobe profiles should be the FIRST one in line to tell us that installing a tiny little cam in a big CID engine doesn't just keep making it better and better at idle and low RPM's. Doesn't make "more" torque either, and advancing cams doesn't always improve low end torque, even though we here those things regugitated frequently on the Forums.

My guess is that the intake closing point is a very important player in how all this works, but I 'll leave the theory to you tech boys and continue to help folks out here on the user end of the deal recover from making poor choices with this sort of thing....FWIW......Cliff

Cliff,
I am done with you. The only thing that will happen is I will get banded from PY because of you like others have. I will let the people reading these posts decide which one of has a true understanding of cam events.

Stan

[Cliff R]

You've been done with me for a long time, as your comments have continued to display your dislke for me and what I do.

"Cliff,
Don't need to Google anything. Clearly you have limited understand of what does what when it comes to cams."

Clear example right here, trying to indicate to the readers that I don't get it when it comes to this topic. "Limited understanding"? Ya, you are right. I'll just crawl back under my rock now, or rather go to the shop and actually help out a dozen or foiks this week who bought into all the BS associated with camshaft selection and now need to run the timing clear off the scale to get their engines to idle plus add a butt-load of idle fuel and bypass air to "crutch" their poor cam selection..........

[Stan Weiss]

Stan

[John Milner]

I have had good luck with the Summit 2801 and Crower 60240 camshafts in 8:1-9:1 compression engines. For me, both of these camshafts resulted in a smooth idle, good low-end power and made for a reliable engine. I also know of a local 8:1 400 that runs a Summit 2800 camshaft. It is a smooth running engine with good low end power. In an 8:1 engine, I think I would lean towards something 204/214 @.050 or the Crower 60240 camshaft.

[PAUL K]

I seriously have no idea how one could have an idling issue with a 212 @ .050 camshaft in an 400 CID 8:1 compression engine regardless of the LSA.

[Skip Fix]

The Summit 2801 worked a little better -smoother maybe a little better power than the XE262 in the second 400 I put in the 81. It was dead nuts on degreeing dot to dot. Both were 112 LS. Teh first XE they sent the outer cam journal was 0.002 too big and would not fit!

[mrmark1957]

Thanks for everyone's opinions. When I've got the motor out this winter to replace the rear main seal and other gaskets, I will swap this XE256 in (along with new valve springs) because I already have it and I know it runs quietly. Maybe trim the heads .030" also to get a little more efficiency. The XE being so small might make no measurable improvement over the 066 in it now. These cams were made for low compression smog motors, so I was just wondering if it would help this 400 out. Mark.

[78w72]

im sure you know this or hope you do, but when pulling the cam, be sure to mark the lifters so they go back in on the same lobes of the cam. less important but do the same for the pushrods & rockers as well as the rocker balls.

.030 off the heads is a good idea, should be ok without messing with intake or bolt alignment.

[mrmark1957]

Thanks for the heads up, but I had an auto repair shop for 37 years after I left the dealership. I've had hundreds of motors apart and together. Now I look for things to do with my own stuff to keep myself busy. As for intake bolt alignment after cutting the heads, I will get the intake side of the head cut the same amount to keep the bolts lined up.

[Jay S]

Dyno numbers were from an older Sim5plus.

[78w72]

Originally Posted by mrmark1957

Thanks for the heads up, but I had an auto repair shop for 37 years after I left the dealership. I've had hundreds of motors apart and together. Now I look for things to do with my own stuff to keep myself busy. As for intake bolt alignment after cutting the heads, I will get the intake side of the head cut the same amount to keep the bolts lined up.

ok wasnt sure where you were at with engine/cam experience.

thats fine to mill the intake too, just mentioning that at .030 its usually OK to leave the intake alone, ive done a few heads at .030 & even a little further, never had an issue with bolt alignment on factory intakes or edelbrock performers, if they are off just a tad its easy to elongate the holes a little. head port alignment was fine too, especially on unported intakes that can be all over the place.

[mrmark1957]

You might have misunderstood what I mentioned about cutting the heads. I don't cut the intake manifold if the if the heads have been milled, then the intake is "married" to the heads. I would cut the intake side of the head where the manifold matches up to it if the alignment was off. Then the intake can still be used with other heads without bolt line-up mismatch.