Can anyone give me some help on the max rpm I should be turning on my engine. Its a 355, cast Scat crank, reconditioned x-rods w/ pioneer bolts, hyper pistons. The assembly has been balanced. Cam is a XE268, 1.6 roller tip rocker arms. The rpm range for the cam is 1800-5800 but I'm using 1.6 roller tips and a 1" carb spacer so I figure my range has increased to around 6000 or so. I'm going to be putting in a Corvette governer in my 700R4 which is supposed to shift around 6k. I've never had my engine above 5k yet so I want to make sure it'll withstand 6k rpm whenever I feel like getting a heavy foot.

Thanks

should handle 6K easy IMHO.

I don't know the answer to your question but im fairly positive that to answer it properly we would probably need to know the types of valve springs/pressure that you have and if you are using a full roller set up or just the roller rockers.

I think your cam will quit pulling before you get in trouble.

You'll feel it stop pulling well before 6 I betcha.

I wouldn't be afraid of an occasional 6 on a cast crank, but it may flex and kinda scarf up your mains a little if you do it too often.

When the valves float, you've exceeded the rpm limit.......LOL
You won't hurt it doing 6K. Just watch oil pressure to make sure it doesn't run out and pump all the oil to the top.

Rev it till you feel it stop pulling! I turn 7500 occasionally with my .040 under cast crank! :D

Thanks guys. I figured my cam would run out by 6k but I was more worried about the bottom end than anything. The cam is a hydraulic Comp XE 268. I have Comp Mag push rods, guide plates and screw in studs. The spring pressures are a little lower than I wanted but I'll probably replace them or shim them one day. The pressures are 85/290lbs. They are Comp valve springs but I can't recall which springs they are.

Keep raising the RPM until a rod lets loose or a valve hits a piston. Then, shift 500 RPM sooner the next build.

Don't go above the RPM range of the cam. I am guessing you have stock heads. You should see much gain past 5,500 in my best guess.

I would think 5500 would be about optimum with that cam.

Keep raising the RPM until a rod lets loose or a valve hits a piston. Then, shift 500 RPM sooner the next build.

Don't go above the RPM range of the cam. I am guessing you have stock heads. You should see much gain past 5,500 in my best guess.

I have Brodix IK180's. They flow 243/175 @.500 so they're fairly decent heads.

You are getting good advice when guys mention 6,000 rpm.

It's a 268 advertised duration cam along w/ the hy-roller weight/valve spring deal here is all.

Install a decently sized solid lifter cam and matching springs, (say, a 290/250, 108/108, .485" gross lift Isky Z-30), and it will rpm high enough to scare you!!

pdq67

You are getting good advice when guys mention 6,000 rpm.

It's a 268 advertised duration cam along w/ the hy-roller weight/valve spring deal here is all.

Install a decently sized solid lifter cam and matching springs, (say, a 290/250, 108/108, .485" gross lift Isky Z-30), and it will rpm high enough to scare you!!

pdq67

That would better match the heads you have. With a cam that size, that is why I guessed you had stock heads. Why not get a cam that takes better advantage of the head flow? Sometimes having a cam too small can actually hurt performance in respect on a bigger flow head.

That would better match the heads you have. With a cam that size, that is why I guessed you had stock heads. Why not get a cam that takes better advantage of the head flow? Sometimes having a cam too small can actually hurt performance in respect on a bigger flow head.

The specs of the cam are 224/230 @ .050 and .508/.512 w/ my 1.6 rockers. I didnt want a real big cam because I didn't want to turn high rpms (over 6k). I did a lot of research (including asking a lot in here) and came to the conclusion that was the best cam for my set-up.

Rusty Brodix lists your head with hydraulic cam as idle-6000 rpm. Operating max range is usually based on cross sectional area, a dimension that establishes the velocity of the air/fuel charge as it is measured at the narrowest cross section of the intake port, usually the area where the port passes near the pushrods. The cross sectional area actually tells as much if not more about how the head will behave than the intake port volume does (a very long and narrow intake port could measure the same volume as a very short and wide intake port, so cross sectional area becomes an important number to consider when determining the airflow characteristics of a given head. For example non Eliminator AFR 180 heads have a cross sectional area dimension of 2.05 sq in. The Dart Pro 1 210 heads have almost the same dimension at 2.06 sq in. So the AFR is going to behave differently than many of the other 180 port heads since it has a large cross sectional area. While we don't know the cross sectional area for you Ik180s because Brodix doesn't provide that, they do provide you with the operating range which is what you're really after anyway.

Your 700 carb should be plenty for operating a 355 to 6000 rpm, even with a higher VE like 90 or 95%. I know a 750 cfm carb will support a 377 sbc at 95% VE to 7200 rpm, so the 700 is a good choice for you I think.

Don't forget to look at mid lift flow numbers from .200 to .400. These are as important as max flow numbers. The piston is accellerating down the bore with the intake valve open when max vacuum is created and you want really good flow numbers in the mid lift as well as max lift while the piston is accellerating before it slows at BDC. The mid lift numbers for the Ik180 are also decent, I think you'll be happy with this head for your application.

There's a lot of things to look at for the big picture, but carb and heads should both support you operating to 6000 on this build.

The specs of the cam are 224/230 @ .050 and .508/.512 w/ my 1.6 rockers. I didnt want a real big cam because I didn't want to turn high rpms (over 6k). I did a lot of research (including asking a lot in here) and came to the conclusion that was the best cam for my set-up.

Not to bust your chops I am legitimately asking...Why did you pick a split lift/duration cam for such a balanced street head? My calculations show the IK 180 to have a 72% intake/exhaust ratio in flow. You would usually use a cam with even intake/exhaust numbers to compliment a head that has a good street flow percentage. 75% is what I have always understood to be the street target.

Not to bust your chops I am legitimately asking...Why did you pick a split lift/duration cam for such a balanced street head? My calculations show the IK 180 to have a 72% intake/exhaust ratio in flow. You would usually use a cam with even intake/exhaust numbers to compliment a head that has a good street flow percentage. 75% is what I have always understood to be the street target.

I called Comp, Summit, and Crane as well as posted on this board for cam selections. All three recommended a split lift/duration cam for my setup. Comp recommended either a XE268 or XE274. Crane recommended their version of the same and Summit recommended the Edel Perf RPM cam.

Not to bust your chops I am legitimately asking...Why did you pick a split lift/duration cam for such a balanced street head? My calculations show the IK 180 to have a 72% intake/exhaust ratio in flow. You would usually use a cam with even intake/exhaust numbers to compliment a head that has a good street flow percentage. 75% is what I have always understood to be the street target.

Maybe he has restricted exhaust. Maybe he likes the sound of larger duration exhaust cams. Maybe its is motor to do what he wants. Ive noticed a few times you bust chops for guys doing something. If his head is what it is let him or his builder pick what they want/think is best. Lets face it, we might have more influence if we built engines for a living...(like I used to do part-time before moving to Cali).
I think that cam is a GREAT choice for his particular setup and unless your a gigolo bigger is not always better when it comes to bumpsticks.

I like your cam fine Rusty.

Not everyone wants solids and a 6° split just ain't a big friggin deal to go actin like you're a cam and head analyzin/condemning expert lluciano.

I thick you picked the right cam :) go have some fun!

1 RPM before it blows! It should handle 6k ok.

Dad gum all I ever wanted to know is whether you guys think my bottom end would hold up to 6k or so. I've never had any doubts about my cam, head, intake set-up. Thanks anyways.:)

A stock bottom end will handle 6500 so yours will be no problem.

Assuming it was built correctly, your bottom end will be just fine. I've been running a stock cast crank, stock rod (with upgraded bolts), cast pistoned XE268 cammed Vortec headed 355 for over 8 years now, with the occasional 6K rpm blast. My setup will rev to 6K with a 600cfm carb very easily.

If/when you get sick of the XE's constant ticking noise, then I would consider a single pattern cam. I prefer single pattern cams for most everything anyway...especially street motors.

The heads would do better with a single pattern grind. The Performer RPM is an outdated grind by todays standards. I don't bust chop I speak the truth. Yes I would consider myself a cam expert or I wouldn't be posting.

77wolf you have consistently been wrong on the facts on many posts, and done nothing but attack. Even when I prove the facts to you, no apology.

If you guys want to keep posting your mis-information and attacking someone for raising a legitimate suggestion or comment, you can have this board.

I came on here to aid in my extensive knowledge of engines and theory. wrsjr asked for a critique of his combo, I gave it not to offend, but to point out what might improve his combo overall. You guys can't debate or discuss like adults and have no interest in the truth being told. You do a general dis-service to all the people that come on here.

To all on this board,

LATER

Hay everyone play nice :)

I used to have same cam and similar set up and would shift it right at 6k.

...Crickets...

Luciano, he asked what rpm his engine would handle safely. You were the first one to criticize his heads and intake after you found out what he had. If you are as experienced as you say you are, then you would have had the intellegience to not 'bust someones chops' over the choices of engine components.
Truth be told you seem like a good person with a little knowledge, but you act like a 28 yr old man that just graduated from an engine school of somesort and are plum full of knowledge that you feel the need to let everyone know about.
This board was just fine w/o either of us so if you dont come back its your loss not ours.
Have a great day. :D
Rusty, its obvious we all agree your combo should handle 6K blasts during street bruisin and cruisin.

Awe, come on wiskee....

pdq67

Awe, come on wiskee....

pdq67

Yeah, maybe your right. BUT, too many times hes blasted on someone for making a mistake or setting something up that wasnt done the way he would have done it. When this happens he comes across as the ifinite authority on engines.
Luciano, hate to see you go bro, but lighten up, eh?

We're supposed ta be having more fun here than wiskee has playin' w/ his lovely wife so lighten up!!

pdq67

We're supposed ta be having more fun here than wiskee has playin' w/ his lovely wife so lighten up!!

pdq67


Pd, you are a RIOT!!

The heads would do better with a single pattern grind. The Performer RPM is an outdated grind by todays standards. I don't bust chop I speak the truth. Yes I would consider myself a cam expert or I wouldn't be posting.

77wolf you have consistently been wrong on the facts on many posts, and done nothing but attack. Even when I prove the facts to you, no apology.

If you guys want to keep posting your mis-information and attacking someone for raising a legitimate suggestion or comment, you can have this board.

I came on here to aid in my extensive knowledge of engines and theory. wrsjr asked for a critique of his combo, I gave it not to offend, but to point out what might improve his combo overall. You guys can't debate or discuss like adults and have no interest in the truth being told. You do a general dis-service to all the people that come on here.

To all on this board,

LATER

Couldn't agree with Harley more.

And Paul we all know you love solid cams(I relish when you talk about them), wasn't attacking you and hope you didn't take it thataway. I was in a hurry to get to work this morning and should have phrased that part a little different.

Rusty, we know you didn't have any doubts about your combo. But I could tell from your posts 13 and 16 that you were feelin a little chomped on about your top-end pieces and it wasn't even in the context of your thread. Sorry your thread got crapped on a little.

Oh and lluciano, ... Go outside and actually work on something dammit. It will help you to comprehend the words you read all day on the internet.

Ouch! This is starting to sound like a Mustang forum I used to visit! Someone asks a question and the thread would turn into a 'bashing board'! The original question may or may not get answered but there would be numerous posts ranting and raving about things that had nothing to do with the actual answer. I do like multiple opinions since it does give options but bashing isn't necessary.

Ouch now that really hurts being compared to a Mustang sight LOL

Geez!!

The "F" word was mentioned!! Boy, this thread's going down hill fast now!!

He, He!!

pdq67