Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine> please critique cam choice
User Name
Password
lost password?   |   register now

Thread: please critique cam choice Reply to Thread
Title:
  
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
10-02-2008 05:23 PM
eric32 Trust the guys that have built many motors. I have four previous builds with three different cams and and several types of heads and intake and carb setup. If you go too big of a cam you will regret it. Trust me I was there I had a stock 350 with 882 stock heads 76cc chambers with an edelbrock torquer 2 intake with a 600 holly carb for street use. It had around 8.5 to 1 and I used a comp cam 292h with 244/244 @ 50 duration with 501/ 501 lift. Talk about over camming a motor that was bad on my part but that was what I wanted. I did not get what I thought I should of had. This was in a 86 s-10 so it did run fast but man I was getting valve float at 4500 rpm with the stock heads and springs etc.

After I went with way bigger world product heads a bigger dual high rise intake manifold with more compression over 9.3 to one did I get a bigger amount of boost from the cam. You need to get what would be good for street. I right now have a really nice setup with a cam that I don't like to well. I have a comp big mutha thumpr cam wich specs at 243/257 @ 50 with 531/517 lift. That is with a Quickfuel drag racing q-series carb ($650 Retail) with an edelbrock rpm air gap performer intake, Dart iron eagle 200cc heads fully ported with 2.02 1.60 valves with all matching components for the cam. I have estimated 450hp with around 380ftlbs of torque by 6200rpm.

I have had nothing but problems with trying to get it tune with my carb. I had a somewhat smaller cam previously and it was a crane powermax. It was a 234/242 @ 50 537/559 lift. That cam did not give me the choppy idle that I like and I switched to the big mutha thumpr cam and it was a big mistake. They both give me good take off and the other perks of hotrodding but the smaller cam gave me way better street manners and mostly likely gave me better hp and torque number cause it was way better for my setup. Trust me be carfull of what you select.
Eric
10-02-2008 04:48 PM
spinn if you have a big heavy truck with big heavy tires. thats going to be driven around.

get a 4 bolt main 350 crate HO ,and 4.88 gears with your 31's.
10-02-2008 01:25 PM
ap72
Quote:
Originally Posted by jbvcw71
Your best cam selection is one that you initally feel is WAAAAAY too SMALL.

NO REGRETS!
Well, going with a cam that is too small leads to detonation problems, especailly with high compression- which is one reason why I'm going with a unusually large cam.

As far as the bull headed engineer thing, I'm actaully fairly quiet when it comes to giving suggestions, when it comes to work I only speak up when they need the right answer.

Seriously though this thing is not meant to set records on the track nor on the mud runs. Its built to be a fun toy to drive. Some people like cruising in an automatic od car with a torque curve as flat as a pool table and an idle speed at 500 RPM... If I wanted that I would buy a diesel.

To me running with a 4500 RPM torque peak, banging gears on a stick shift, and the absolute nasty sounding idle that comes with engines like these is a good time.

The only thing I'm worried about is running it on 93 octane VS having to switch to E85 because of too much effective compression, and an idle speed over 1,000 RPM (just a number I set as my own standard), and wearing through springs (which with modern designs isn't more than a little more initial capital investment).

My effective displacement is still about 276 ci, and compared to a stock 4.3L which comes in around 237 ci I'm still coming out ahead on power with the big cam- even at idle! (I'm comparing it to the largest enigne that came in the S-10 for reference- also the one many people use with stock gearing, auto transmissions, and 30" tires- factory size tire is right around 28-29")

Oh yea, effective compression is up too... along with intake and exhaust flow...

Are there ways to build engines that idle lower and pull more vacuum and can run on watered down gas- yes, hell you can even buy one from GM for a fairly low price. But where is the fun in that.

Lastly, don't blame relying on the numbers as a fault since they don't support your opinion. I understand your opinion- I really do and there's nothing wrong with it. I just don't like being that conservative when its not at all needed.

Techinspector posted the numbers- to me they look great. 6,000 RPM hp peak is my idea of ideal for this project.
10-02-2008 12:20 PM
jbvcw71 Your best cam selection is one that you initally feel is WAAAAAY too SMALL.

NO REGRETS!
10-02-2008 10:59 AM
PutPut72 Hey guy's don't mess with him, he's an ENGINEER. Not to be a @$$hole, but you fit the profile of an engineer (I have worked with TONS of them). No matter what anyone suggests you still think your way is the best, and that's fine because most things are learned through trial and error (unless you heed peoples advice). Just like the Guy who lived next to me with a 327 Chevy that he built, and him & his smart buddies knew that it was over 600 hp. That thing sounded nasty & was pretty cool in his 72 nova, but too bad he got his ***** kicked by my mild 383 in a 3700# 72 Chevy pickup which sounds decent but not radical like his beast (hahahah ).
These HotRodders on this forum are very smart and have information that CANNOT be ignored. It pisses me off when someone gives you good advise and you don't listen because you know better. If you are so set on this combo, build it, but don't keep asking for advise and then blatantly turn it down.
(No Offense to any Engineers who aren't bull-headed, I actually am one but a piece of paper with your name on it doesn't give you the right to be stubborn).
10-02-2008 07:32 AM
ap72
Quote:
Originally Posted by curtis73

Then you, sir are a master. I retract everything I said. Can you build me one of those 6000-rpm torque peak 4-bangers that gets 27 mpg? I'd love to have one for a rock crawler with 40" tires with a 3.08 rear.
Well thank you for the compliment, and I'd love to help you buidl an engine like the one I had, it won't do well with that gearing and tire combo in a full size truck though. Mine was with 30" tires in a 5-speed S-10 with 4.10's. 3.08 gears with 40" tires needs nothign short of a big block. To match the displacement/revolution of the tire you'd need a 600 inch big block to match me putting my 350 in this S-10. A 262 would be about comparable to my origianal 2.5L...

Oh and Tech Inspector did a dyno sim of my engine combo... I don't think it looks bad at all- 495 hp, 475 tq... 355 ftlb at 2000 RPM... That's big block territory (not a well built big block, but still impressive for factory heads and NA on pump gas with stock displacement.)

I know what you'll say next- its a SIMULATOR... yes it is and its as valid on this combo as any of the other ones.

As far as critiquing, I was looking for suggestions on simmilar cams... running something like a 262H cam compared to this one would be as close as running a solid roller... And to risk sounding like a ******* I actaully like arguing about things like this, if nothing else it forces me to reconsider and evaluate my own opinions... even if I decide to still stick to them.
10-01-2008 11:12 PM
curtis73
Quote:
Originally Posted by ap72
I really don't understand why everyone is getting so miffed over a little duration. Here's a setup very simmilar to what I'm building except he has heads that were ported better than mine will be, and a cam with MORE duration that is still streetable.... Wow, imagine that... There's a lot of people running bigger cams on the street. hell my hp peak will probably end up around 6,000 or maybe a hair under. And that's not streetable? Granted its not a deisel, but what's the point of building this stuff if you're just going to stick with stock, or near stock parts?
First of all, my problem is not that you want to use 250* on the street... its that you want to do it with 4.10s in a truck with 31" tires. You also just said what many of us said days ago... "except he has heads that were ported better than mine will be". You have to match everything together. You are planning to use a cam that will shine from 3500-7000 with heads that shine from 1500-5500. Streetable also has A LOT to do with the rest of the car. If its a 3000-lb Camaro with a 3500-stall and 26" tires and manual brakes, great. If that is your idea of streetable, then do it.

Quote:
and yea, I know I'll be getting around 14 MPG, but I'll live with it.
My guess is 10 mpg on the highway if you spend lots of time tuning.

Quote:
As far as expierence goes, no one who commented ahs tried anything like this-
Uh.... yeah, because its mismatched. If we were inexperienced enough that we HAD tried this, you wouldn't be asking our advice. There's a reason why experienced people like the one's you asked DON'T do what you suggest.
Quote:
just the same with the last engine build that I did with a "cam that was too big" as it turned out my milage was twice what they speculated and the torque curve was damn near flat with a peak around 6k RPM again. Oh, and as far as the numbers go I had it down to the exact jetting before I even put it together. I underestimated my milage by 2 MPG's last time (I got an easy 25- 27 on the highway) and I was off on the timing with 1 degree too much advance. Before I even turned a bolt.
Then you, sir are a master. I retract everything I said. Can you build me one of those 6000-rpm torque peak 4-bangers that gets 27 mpg? I'd love to have one for a rock crawler with 40" tires with a 3.08 rear.

Quote:
I really just wish you were here for the big "I told you so." I guess the only people that can really comment on this would be budget oriented roundy round racers, since they actaully do have expierence on setups very close to this.
Firstly, no. Roundy-round racers wouldn't build this for a race. Secondly, they are restricted by very specific rules. They are building a purpose-built engine to run at an insanely specific RPM range. You are building a street engine for a large-tire mud truck. Those two couldn't possibly be more different.

Secondly, I WILL be here for the big "told you so." I've been here for years and I plan to stay. Post your numbers after you get it dynoed... or can you just magically predict that like you predict jetting and torque curves?

Is your combo terrible? No. Could it be worlds better? Yes. I just have to laugh that the TITLE of your thread is "please critique my cam choice," then you have spent the last three days insulting us and defending your original choice while citing a 4-banger that was a "blast to drive" as your last build.

If you think a 4-banger with a 6k torque peak is a blast to drive on the street, then enjoy your overcammed 350 that is built with a no-name Ebay cam.



Done.
10-01-2008 09:10 PM
Stroke I'd do it like a CORR motor, you know...

450cid 820HP Championship Off-Road Racing Small Block Chevy


Really though, a .480ish 218*@.050 on a 112 would be nice.
10-01-2008 06:46 PM
spinn if your off roading my friend did his 79' prospector up with a edelbrock performer cam, 750 carb, and performer intake. the summit cam is .420/440". the heads were magnums converted for a LA block. gears were 4.88's with 31's.

made a powerfull combo.
10-01-2008 04:44 PM
techinspector1
Quote:
Originally Posted by ap72
Okay, I conceeded, I decided to step down a bit on the cam and am going with an ISKY grind.

http://www.iskycams.com/timingchart...._number=201524

which has only 244/248 duration @.050" and .524/.534 lift... I figure buying from Isky is proably a safer route.
OK, assuming 1.94/1.50 valves, 10.5:1 c.r., 750 carb and Performer RPM manifold, 1 3/4" headers with mufflers and the Isky solid lifter cam, here's how it works out on my software....(1 5/8" headers will drop power, any smaller carb will drop power)....
rpm tq hp
2000 355 135
2500 360 170
3000 385 220
3500 435 285
4000 460 350
4500 475 410
5000 475 450
5500 460 480
6000 435 495
6500 390 485
7000 345 465
Retarding the cam timing 2* will make 500 peak hp @6200 and 475 peak tq @5000..... 2* retard and 850 carb will make 505/480.
10-01-2008 03:03 PM
ap72 Okay, I conceeded, I decided to step down a bit on the cam and am going with an ISKY grind.

http://www.iskycams.com/timingchart...._number=201524

which has only 244/248 duration @.050" and .524/.534 lift... I figure buying from Isky is proably a safer route.
10-01-2008 01:30 PM
ap72 I really don't understand why everyone is getting so miffed over a little duration. Here's a setup very simmilar to what I'm building except he has heads that were ported better than mine will be, and a cam with MORE duration that is still streetable.... Wow, imagine that... There's a lot of people running bigger cams on the street. hell my hp peak will probably end up around 6,000 or maybe a hair under. And that's not streetable? Granted its not a deisel, but what's the point of building this stuff if you're just going to stick with stock, or near stock parts?

and yea, I know I'll be getting around 14 MPG, but I'll live with it.

As far as expierence goes, no one who commented ahs tried anything like this- just the same with the last engine build that I did with a "cam that was too big" as it turned out my milage was twice what they speculated and the torque curve was damn near flat with a peak around 6k RPM again. Oh, and as far as the numbers go I had it down to the exact jetting before I even put it together. I underestimated my milage by 2 MPG's last time (I got an easy 25- 27 on the highway) and I was off on the timing with 1 degree too much advance. Before I even turned a bolt.

I really just wish you were here for the big "I told you so." I guess the only people that can really comment on this would be budget oriented roundy round racers, since they actaully do have expierence on setups very close to this.
10-01-2008 12:51 PM
curtis73 DoubleVision... let's just let him build it how he wants and learn for himself. He's not listening to experience, fact, or reason. He wants that cam, period.

AP72, if you seriously think that a cam with 250 degrees duration at .050 and a 106 LSA is what you call streetable with 31" tires, then you are deluded. That's not what most people call streetable in a 2300-lb stripped Nova with 26" tires and 4.56s.

I'm 34, I've built just as many "new" engines as I have old ones, and VE theory is the same regardless.

You're right, numbers don't lie, but dynos don't race. You can guess and hope and simulate torque figures, but unless you are a master tuner, you're not going to get anywhere close to the torque that you guess will be down below 3000 rpm. You also probably don't understand that VE below the peak falls off at a much faster rate with anything less than WOT. So all of this torque you speak of in the lower range is ONLY there at WOT. If you've never driven a combo like you talk about on the street, it gets absolutely tiring.

Oh... you can also skip the electric fans. They might work on a stock output engine, but you're talking the need for absolutely serious heat, and you'll be doing it while thermally punishing the engine at anything below 3000 RPMs.

Even at its most fundamental, you have to see the major mismatch between a cam that is larger than some NASCAR cams, and a factory iron street head that flows 230 cfms.... or do you just not want to look at the numbers in that case.

The worst part is, you're going to build this engine out of stubbornness, put it in, then a week later you're going to post the following threads:

"350 overheats all the time - I have electric fans"
"More mileage from 350 - I'm only getting 4 MPG"
"Carb running super rich - It burns my eyes"
"Can't get 350 to idle below 1200 - I've already tried 30 degrees initial"
"No power brakes - why do I only have 6 inches of vacuum?"
"350 not as powerful as I had hoped - I used Vortec heads, but..."

Mismatch. Big time. Have fun tuning it. It will take an absolute master. I'm out.
10-01-2008 12:32 PM
GMC boogie Seems like you have it all figured out, contrary to what everyone else has to say.

Experience is often gained the hard way.
10-01-2008 11:07 AM
ap72 I'm not running mud bogs, 3.08 gears is what killed your ability to use the high RPM power, and people said the same damn thing when I put a 11.5:1 a 2.5L with a 232/235 cam in the first s10, which was one hell of a blast to drive.

I'm not saying this will be a torque monster, it won't be. But it will be plenty streetable, pull above 2500 like a freight train and be more than enough to get my truck through anything.

Also, because of the changes in the automotive world I am slow to take anyones years in the bussiness as evidence- recent build in the past 10 years sure, but more often than not, old timers (which Im' not saying you are) have clouded judgement of what is and is not possible because 20 years ago things weren't possible that are today. As such I follow the numbers on most aspects of engine building. Numbers never lie, nor are they opinionated.

calculate the DCR adn the effective displacement on the engine I'm building adn you'll see that even with the big cam the low end stomps the 4.3L which came in the truck along with 3.23 gears and a 700R4...
This thread has more than 15 replies. Click here to review the whole thread.

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -6. The time now is 08:12 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.