Br1dgeman

Simple question- Building a 400 small block. Plan to use a 165 ecm with MAF, Dart heads, probably a stealth ram, and was thinking about this cam-

Comp Cams 12-423-8 Retro fit Hydraulic Roller (XR 276 HR)

224 / 230 duration .502 / .510 lift, 110 LSA

Catalog says choppy idle.

With the wealth of tuning experience out there, tell me guys, Can I make this cam work with the 165 ECM or has someone already done it and can give me feedback?? I don't mind putting the time in to tune it, I just do not want to chase my tail and throw my money away at the same time...Curious if it has enough vacuum at idle, will it idle smooth enough? will the ecm have a fit?

Opinions anyone??

11sORbust

you don't want to run a 110lsa on fuel injection. 112-114 lsa is a much better choice. There will be more vacuum with a wider lsa.... As you know I have a 400SBC. My cam is 242/250* and it runs fine. I would get rid of the maf system though. You have more "tune-ability" with the 730. With a big cubed engine I maintain the 730 ecm will produce more power under the curve.

No matter what, you'll be much happier with a different profile. I'm convinced it worth paying a living legend $35 to spec the perfect cam. That is what I'm going to do when I try something new on my 400. He claims that just a cam with his specs can net over 100hp. PLEASE share the specs if you get them from him. I'm curious what he suggest for your combo.
http://www.davidvizard.com/camshaft.html


Another thing you didn't mention....the intake. That has a big role on what cam you need.....

Dominic Sorresso

Not sure I agree with that. I am currently running a 108 LSA HR cam with my 350 Xfire. Its pulling between 14-15in Hg at idle. My previous cam had a 112LSA and pulled 16in Hg. The idle isn't all that much different with proper tuning.

And that is where I got the specs for my cam. I did spend the $40 for Motors and Machines to do a cam spec. Got their name from the Vizard article. Be ready with the low lift flow numbers from the heads you'll be using. So far I'm pretty happy with the results but I haven't yet gotten the opportunity to dyno the motor vs the previous cam.
http://www.davidvizard.com/camshaft.html

CaptPicardsZ28

I disagree as well...I am getting ready to install a cam with 109LSA and I am told it can be done. Its a matter of tuning. I do agree that 730 setup would be better as well. I have a 406 and swapped from MAF.

SBNova

The wider LSA's like the 112-114 are more efi friendly, and may take less time to tune. That same cam you are looking at from Comp is available in a 113 or 114 (cant remember which it is), it is known as a "305" cam, for a newer roller block 350. You can use it in a non-roller block by using the correct oem roller cam timing chain set. This cam is also listed for sale right now in the thridgen classifieds. Im not the one selling it though.

Dominic Sorresso

SB,

The Vizard article is very illuminating. Highly recommended reading for those that are considering cam swaps and upgrades.
One of the points he makes is that most people treat duration and LSA almost interchangeably. Meaning that its urban legend that you can increase duration to make up for the wider LSA. Vizard believes that for a given set of heads and rpm range, there is only one optimum cam profile.
Here's excellent reading on gas flow dynamics and the impact on cam specification.
http://www.hotrod.com/techarticles/18218/

91L98Z28

with respect to the total overlap which reduces engine vacuum, both LSA and total duration affect it.

that is to say, a 108 LSA cam with 210/220 duration, is going to have less overlap (and more idle vacuum) than, say, a 230/240 cam on a 114 LSA, everything else being equal.

you have to look at the overal profile and not just a single number.

Dominic Sorresso

91,

The point of the article is not that you would only look at overlap, but rather the correct spec'ing of a cam begins with the correct overlap for a given motor displacement/cylinder head configuration along with the desired rpm operating range. In my particular case, vacuum dropped only marginally even though my new cam has 10d or almost 25% more overlap than my previous cam. Also, you'll want to measure overlap using adv. duration.

SBNova

Yeah, I have read that before. Good link to have though.

It still stands though, that two cams with identical lobe profiles,lift, and duration, yet having two different LSA's, the wider LSA will of course have less overlap. I was suggesting the same exact cam he wants, yet with a wider LSA. The 305 Comp, being fairly well known, is spec'd by Comp as a TPI/EFI cam, the other isnt. Not that either one couldnt be tuned, but the wider lsa should be simpler.

Z69

Intake closing has a large effect on how an engine runs too.
So how the lsa is changed is very important.
Not something most if any of the tech line gurus know more about than it will affect cylinder pressure.
In short, the sooner the intake closes, the less time for reversion. Regardless of lsa. So I fail to understand why no one has tried a 108-110 lsa with a short 262 or so cam & EFI. It will make a lot more mid range torque.
Actually I do "see". Nobody looking for HP runs that small a cam except with a turbo. Or a small CID engine. But that would rule out the looking for HP part.....

11sORbust

Thanks for saving me some typing

Grim Reaper

I was wondering when someone was going to start bringing up this important point.

Grim Reaper

You won't have any problems except some minor tuning issues. I assume this is your "first" time tuning and why you are asking the questions. You probably need to rescale the lower 3 MAF Scalar Tables, but that cam will work very well. In fact, once properly tuned, you will probably find that cam a 'bit mild' sounding and not nearly as "lumpy sounding" as you expected.

ben73

i just tryed to fax the recommendation form to vizard and it rang out.. so i tried to email them and it bounced!! grrr!

Dominic Sorresso

Ben,

Try cammasters@msn.com That's the email address for Motors and Machines where I sent my cam form. Attn Denny.

89gta383

iTrader: (5)

I have a 242-254 .555 .585 110 lsa cam in my 383 with maf, gets 9-10" vacuum and needs a canister if you want the idle lower than 1200, but other than that it drives fine after tuning.

ben73

Thanks Dom.

funstick

I think there are just to many variables to even begin to try to build a model for the proper cam. usually i use rollers. rollers are good for sevral reasons. cams swaps are less exspensive, no break in hassles. if your building a motor and dont expect to change the cam timming, cam, rockers etc i think your fooling yourself. i always tell my engine customers that there might be 3,4,5 cams to really hash the thing out to satisfaction. but youll need to collect data etc.

Also more important then the cams are the heads and manifolds intake and exhuast. they play such a large role in power production. if everything is properly optimized then ideally the camshaft should only set the stage for the power band. the heads and manifolding realy control the mazimum output.

Grim Reaper

I couldn't agree more Sean.

Remind me let you know what a buddy and I discovered about high rpms, big cams, and hydraulic rollers.

11sORbust

I totaly agree with evrythig you said. Right now I'm on the second cam. In 6 months I might change it again.

Grim Reaper

Tim, aren't you glad you installed that 2-piece timing chain cover?

funstick

ahhh depending on the spring retainer etc etc etc. ive seen hydroulic rollers goes as fast as 7200rpm. takes a very light valve titanium retianer,keepers and conical/behive springs with lightwiegth pushrods. plus using the ligthest hyrualic rollers you can find.

typically if the tune requires loads of timming all around the cam is just way to big.

TRAXION

I had a total of 4 different cams in my stock 350 shortblock .. ranging from short duration to mid 230/240 duration. I've played with big LSA cams and low LSA cams. I never had any problem tuning them to run. There was a difference in the amount of time required to make them run really good. The low LSA cam required more time ... but rewarded me with much more performance. The old myth of using big LSA cams (112+) is dead. It's just that nobody knows this since most people continue to spout off that garbage about needing a 112+ LSA cam in an EFI vehicle. I'm currently working on another car with a 108LSA cam. No problem. If you are looking for big power then go with a lower LSA cam as long as you have the knowledge and some experience tuning chips. You run the potential of losing your power brakes. You might need a vacuum pump. But, once you get the tune worked out ... the car will be unstoppable.

Tim

CaptPicardsZ28

Thanks for clarifying Tim...I agree 100%. People are tuning all kinds of cams with efi these days. Its a matter of knowing how to tune. I tried your link to the 1990 iroc and none of the links there work except for the tgo ones. Any way to fix? Thanks.

Z69

I said that wrong...
Intake opening point determines how much reversion you'll get.
For instance, a number of years ago a mag ran an article on a 475ci BBC that made 19" vac at idle with an 108 lsa cam.
Not a normal "truck" lsa number.
Asymetrical grind cams make this stuff even more confusing.
Since the cam lobe will not be symetrical on both sides of the CL.

From what I can tell from my carb experience. The bigger the cam, the harder the idle range will be to tune. The 600-1200 range.
as you go up in duration, then the part throttle will need more attention. For instance, my 383 doesn't reach max vacuum at cruise until about 2300rpm. I cruise on the idle circuit of my 750DP. Converter and gears will affect this too. I'd imagine that a 3k stall makes it a little easier.

Dominic Sorresso

In fact, Tim, its because of tuning and EFI that you can get an narrower LSA cam to behave. When I first started thinking about upgrading my camshaft, the words of wisdom were always "Don't go less than 112d for computer controlled motors". So I bought one with 112LSA. Made good power BUT, my new cam has 10d more overlap and 4d less LSA. It still idles in the mid 800's with 14-15" Hg. And what a difference in top end. Bottom end has been beefed up too unlike what you would expect. I was skeptical when I first submitted my cam form to Motors and Machines and they came back with a 108 LSA. I put it in largely based on Vizard's article. I am definitely not sorry.

Grim Reaper

Actually, your original post (intake closing) is correct from what I have read. While the exhaust closing/intake opening has a great affect on the vacuum and idle, the most critical time event is the intake closing from all the articles I've ever read about camshafts and design.

Before anyone starts to jump on my throat and say "That's wrong", I want to make it clear that I do notT profess to be a camshaft designer or an expert on the science. But all camshaft designs try to have the intake close a particular point just after BDC for maximum cylinder filling. Everything else, moves from there. That is why I agree with your original comment.

If people are interested, I will try and dig up some of the web sites I have found on this subject.

I also agree with Tim aka Traxion's comments that "once a person has learnt eprom burning and tried a couple of different setups, that narrow LSAs are not a big deal for tuning".

11sORbust

I suggested to use a 112* lsa. It's not based on a myth. As you even stated, a wider lsa is typically easier to tune. That is why I suggested it. Some people don't want to run a vacuum pump. My 406 has a big cam (242/250*_114*lsa), the idle is at 850-900rpms and vacuum reads 19-20". I have a stealthram. Tim, you had a miniram. That tighter lda might have worked well with your intake......

laiky

19-20" of vacum????

11sORbust

Yes.

and to clarify, I never said a tight lda cam wouldn't work. I never gave a cam spec for Al's engine because I'm not in the guessing game. David Vizard has TESTED hundreds of cams. His program (cam master) can help make over 100hp just by a cam change. Vizard is a living legend and you can actually have him spec a cam for you. I could be building engines for 20 years and never compare to his program or knowledge (for cam selection)....I would say $35 is a steal!