I have the XE262H cam in my 383. When I changed from 1.5 to 1.6 rockers (all 16), I didn't see any change in idle quality, and I didn't expect to. Duration and overlap affect idle, not lift, and they are not affected by changing rockers. On the performance side, I believe the 1.6s took about a tenth off my 1/4 times.

 

One thing fun about asking for a camshaft recomendation by the time everyone checks in you can end up even less sure of whats right lol.

 

 

Yeah, one nice thing about camshafts is that there are so many to choose from........of course, one bad thing is that there are so many to choose from........


Keep the shiny side up!
Scott

 

True but I for one have learned a little more about cams from following this thread i still don't have a real great understanding of them but it's certainly better than when I started reading this.

 

You have some good street performance gearing and enough overdrive to still do good highway work at very reasonable rpms. But overall you have a wide spread from low to high gear in your trans especially when you consider a small 350 engine. Bigger engines pick up wide ratio spreads much easier then smaller ones. Chevy originally used mostly wide 114 LSA cams for a reason even if it was not the most overlap for power. Lunati's vodoo cams were done by a very good cam designer offer a little more lift without gimicks used of increased rocker ratios and use a 112 LSA. There you go some more confusion lol.

 

i asked jeff to compare the 270H and XE268!



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Re: xe268?
Sent: Sat Nov 17, 2012 12:08 am
From: jeff swisher
To: Matt Gruber*
The XE268H gave up at 6500rpm.. and the 270H was fine to 6900 and pulled harder through the mid range..If you need the R's the 270H or 280H is the way to go...I actually like the 280H best.
Check the opening and closing on the intake side of the XE268H vs the 270H
The XE268 intake opens 28 before tdc the 270h is 29 degrees before TDC..so it opens a bit sooner.
Now look at closing..XE closes at 60ABDC and the 270 is at 61...I feel this tad bit longer time the intake valve stays open helps feed the engine....Maybe maybe not..overlap is 54 for the XE268 and 50 for the 270H.
The added overlap from the 268 is comIng from an ex lobe that is almost the same as the 280h
Now if you analyze this SBC head deal through the years you will see that the vortec head makes much more power than the old double humps.. what is it???? not the ex port because they left that the same crappy port.
But the intake port is very effecient ,,,, So better intake port makes more power..
Take it further..notice a bunch of people run a 1.6 rocker on the intake side only because a bunch of engines either gain no power with them on the ex or they sometimes loose power...
Sometimes 1.6 on both work... but usually the intake side responds best....
OK!!! so why do you want to run more exhaust duration as in a dual pattern..
Give me more intake duration or the same...Bigger ex lobe or larger split will help carry the RPM further past peak power....But would you not possibly make more power with more intake side..a tad shorter ex to control overlap ..
Even with more overlap of the XE268h i feel the intake valve is just not open long enough for old ported iron heads..or maybe it is that tad bit earlier closing...
Either way both cams will make great power the 270 just inks it at the mid and top..and better MPG for me...that may be due to the 50 overlap vs 54....but the 280h has 60 overlap and MPG the same as the 270H....who knows....
My pic for best power and mileage for daily driver if the guy can tune will be the 280H.
If you need revs to 7200
Can't go wrong with any of them though..either one he picks will be great.
and not all engines act the same..and for sure my stuff does not act the same as anything i have seen..unless it is a roundy round hand grenade...
jeff swisher
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Quote jeff swisher
Re: xe268?
Sent: Sat Nov 17, 2012 12:08 am
by jeff swisher
The XE268H gave up at 6500rpm.. and the 270H was fine to 6900 and pulled harder through the mid range..If you need the R's the 270H or 280H is the way to go...I actually like the 280H best.
Check the opening and closing on the intake side of the XE268H vs the 270H
The XE268 intake opens 28 before tdc the 270h is 29 degrees before TDC..so it opens a bit sooner.
Now look at closing..XE closes at 60ABDC and the 270 is at 61...I feel this tad bit longer time the intake valve stays open helps feed the engine....Maybe maybe not..overlap is 54 for the XE268 and 50 for the 270H.
The added overlap from the 268 is comIng from an ex lobe that is almost the same as the 280h
Now if you analyze this SBC head deal through the years you will see that the vortec head makes much more power than the old double humps.. what is it???? not the ex port because they left that the same crappy port.
But the intake port is very effecient ,,,, So better intake port makes more power..
Take it further..notice a bunch of people run a 1.6 rocker on the intake side only because a bunch of engines either gain no power with them on the ex or they sometimes loose power...
Sometimes 1.6 on both work... but usually the intake side responds best....
OK!!! so why do you want to run more exhaust duration as in a dual pattern..
Give me more intake duration or the same...Bigger ex lobe or larger split will help carry the RPM further past peak power....But would you not possibly make more power with more intake side..a tad shorter ex to control overlap ..
Even with more overlap of the XE268h i feel the intake valve is just not open long enough for old ported iron heads..or maybe it is that tad bit earlier closing...
Either way both cams will make great power the 270 just inks it at the mid and top..and better MPG for me...that may be due to the 50 overlap vs 54....but the 280h has 60 overlap and MPG the same as the 270H....who knows....
My pick for best power and mileage for daily driver if the guy can tune will be the 280H.
If you need revs to 7200
Can't go wrong with any of them though..either one he picks will be great.
and not all engines act the same..and for sure my stuff does not act the same as anything i have seen..unless it is a roundy round hand grenade...
Quote Matt Gruber
xe268?
Sent: Fri Nov 16, 2012 11:19 pm
by Matt Gruber
Jeff
could u give more details on that older cam swap?
was it a 270H to an XE268? which is faster in the 1/4?
Thanks!
a friend wants to buy a xe268. is that a mistake? 355 sbc, good heads 10.2:1

 

I've almost forgot what my original question was. Alot of info - thanks to you all for your responses, advice, opinions, etc. When I get this thing together, I'll have ya'll over for a beer or two.

 

I never quoted the entire post but if you read it, it goes along with what I said in this post ? or another. People get caught up in the "sounds right to me" philosophy when in fact most of it is what I refer to as intelligible BS.
The "sounds right to me stuff".

Why do you think Ron Capps and John Force have won so many championships. Do you think their crew chief's are reading Hot Rod Magazine or do you think they are coming up with their own theories.

That's why I go all the way to taking motors out of the car to see for myself. I have never read a Hot Rod magazine ( I have read technical books for putting together engines and so on ) or listen to bar room crap. I see for myself, with my own eyes what is going on.

There is nothing wrong with dual pattern cams except for the now universally accepted BS "Oh the exhaust is staying open longer and the the exhaust port flow lousy" Compared to the intake that will never change. These are myths and old wives tales. A single pattern cam is alive and well and I will say the same thing about dual pattern cam just don't get caught up in someone's theory (BS) about them

 

Ron Capps has never won a Championship

 

The thing is car weight, gearing, trans and intended use are not even addressed. You were recommending a XE262 with 1.6 rockers. Jeff, whoever he is, recommended a 280 and is talking reving it to 7200 RPM. Thing is faster in the 1/4 mile could be a xe262, an xe268 or a 280 H depending on gearing, trans, convertor and build specs. For many people what is faster in the 1/4 mile has absolutely no bearing on cam selection especially if they need race gas to run it or timing backed down to 21 total.
The XE268 cam is a good choice for what he has. Others will work some better for some intended uses some worse.

 

What!!!!!

 

mako
good to see u chime in again. i took your Q's seriously and came up with a 2nd recommendation. Backed up with STREET and drag experience from jeff. the 270H. it does sound good for the OP And if he wants a smooth idle, the xe262 1.6 Intake, would be great too, since he does not shift above 6000. But, like jeff says, these are all great cams
.
a word to everyone on tuning. my 72 355 xe262 would ping at 36 total WOT. There are several "cures".
1. reduce CR
2. larger cam
3. higher octane
4. reduce timing.
I set timing to 34 and ping is cured. A larger cam or a lower CR pose a serious risk. Will it still spin the tires easily w/3.08? That is a risk i chose not to take.

 

whats the mpg like with a xe268h?

 

It seems to me like MPG on one of our cars is going to be hard to quantify. By the time you upgrade to a cam like this, most guys have probably made several other significant modifications. The original poster here has an overdrive automatic, performance 3.73 rear gears and has changed the top end of the motor as well.

The xe268 is probably not a "green" cam. What makes it even harder to measure MPG is the way we drive these cars. Yesterday I had 3/4 tank of gas. I drove about 60 miles and have about a quarter tank of gas now. I am going to guess 12 MPG.

However, much of that trip was spent at an air fuel ratio of 12.5:1 which is what I get at WOT. I have a 3 speed auto and on a lonely Texas toll way, I never found the end of this cams power curve.

 

So you tried out that new 85 MPH speed limit on that tool road the wife wants to take her new SRT 8 on it

 

Watch out for pigs. Its pretty much a redneck autobahn.

ps. No seriously, real pigs.

 

LOL, I had a flashback to the 70's for a second there

 

Who is Jeff? What makes him an authority.
You have a 3.08. OP has a 3.70 gear and a 2400 convertor. You don't think this warrants the next size larger cam in the series?

 

NO! he has overdrive. He will turn MUCH LOWER rpm cruising around in 4th. Does his converter LOCK? Even less rpm.
I'd expect the xe268 to surge at 1000-2000 rpm in 4th locked due to excessive overlap. Maybe that can be tuned out, maybe not. No problem with the XE262H or the 270H with a fully divided dual plane. Excessive overlap (xe268) causes poor MPG, long warm-ups, and less power at normal street rpm's.
I'm an ASE certified mechanic(retired). Certified in ENGINE PERFORMANCE. People proud of their accomplishments use their real name, like Jeff(and me, and many others )
What are mako's qualifications?