Inliners International Forums General Discussion Hi Performance Cam recommendation

Hello.
I'm putting a 250 in my Nova wagon and wondered what can I should go with. The car is street driven and not raced. Nothing too radical just something more than stock. Thanks.

3:31 rear gears 3000 at 65mph.

I would suggest a Compcams 252H with a stock engine. Works with stock springs.

Recheck you rear ratio, 10 bolts in Chevy had 3.36 ratio. But you were close.

That's probably what it is.

I should also mention that I have a T5 speed, plan to use an Offy two carb intake with two of Langdon's Carter-Weber carbs. I also plan to tow my 1250lb travel trailer with it.

Same cam, should work with stock springs, but worth putting in new ones with the added lift.

http://www.summitracing.com/parts/cca-61-232-4/overview/make/chevrolet

strummin67 I.I.,

is your 250 engine a stock build?
Compression ratio?

MBHD

It's stock inside. I plan on using the 194 head I have with the 60cc combustion chambers. That should bring up the compression a bit.

Oh no, Martin. You didn't bring up the 194 head thing again did you? We need to add a can of worms to our "smilies"

OHH yes he did!

Great choice on using the 194 head to gain some compression B.T.W.
Stock , you will be lucky to have 8:1 compression. Factory tolerances are not the greatest.

You can mill the head to get the cc's in the 50's also.

I would get a custom grind camshaft from Comp Cams. 210-220 range degrees duration @ .050 .550" lift on a 114 lobe separation.

MBHD

With the stock 60cc you should get around 9-1 If you go with a flat top you will be closer to 10-1

So that would be either the 260H or the 268H.

With those two choices I would get the 260H, but I would like a wider lobe separation, that is why I recommended a custom grind, not off the shelf grind.

MBHD

[quote=CNC-Dude #5585 [/quote]

I think he's about to get up!! Just needs a little more beating!

What does widening the separation of the lobes do?

I like a wider separation because of these things mainly:
Broadens Power Band
Decrease Chance of Engine Knock
Idle Vacuum is Increased
Idle Quality Improves
I also think you will get better mileage w/a wider separation camshaft.

Also, w/a tight lobe separation camshaft, power will come in quickly & in the lower RPM range, then it will be like hitting a wall,, power will just shut down abruptly & not rev anymore,, where as a wider lobe separation camshaft will give you more overev capabilities, a wider power band if you will.

http://www.compcams.com/Pages/413/cam-timing-lobe-separation-angle.aspx

It seems that most camshaft made for our inlines always seem to have a tight lobe center.

I know B.B.C.'s like a wider lobe separation camshafts, they seem to make more power, some engines are just that way.

The camshaft I currently am using has a lobe separation of 114.
& it just pulls & pulls on the top end. Could not be happier with how it works.

Most LS engines have wide lobe separation camshafts from the factory up to about 122-124, have a lot of duration, & they just rev & rev.
Pretty sure it works better for emissions also, makes less.


MBHD

Hank,
You are correct in all you say, the LSA can have a great effect on how you make the power that you do. Type of driving and gear splits have an effect on LSA choice too, a tight gear split and many gears, a tighter LSA is useful. Tight LSA cams "feel" quicker because of the rapid ramp of the torque curve like you said. They also have the torque peak and HP peak closer together too. For boosted applications you want a wide LSA. Circle track cars like a tight LSA. Not one "wide" or "Narrow" fit all driving. We all have our preferences, I happen to like 108-110 LSA my self. But Martin for your car with a wide LSA would probable be best

you would need the tighter LSA for an engine that you can't easily get the CR high enough on. Tighter LSA "is like" higher compression. Whis results in better throttle response and more power, higher efficiency. Until you go too far and have knock issues.

Wider LSA reduces compression and generally the valve overlap, so less compression or mixture is bled through the exhaust, so it's better for turbo applications. But it makes an engine lazy down low and a big cam withwide LSA and not enough compression, would be a pig to drive until it gets "on cam". Which is the #1 reason people are afraid of big cams. You have to give them compression.

BUT it's not quite as simple as that, there are other factors that affect the outcome. Like Overlap. It is not directly linear or directly linked to LSA.

If you can't get your compression ratio high enough, you need to make compression with a cam that doesn't bleed compression out.

Much, much more complicated...

Sounds like it.

Perhaps. But not incomprehensible. I think that LSA is a useful metric in drawing a comparison between two cams with otherwise equal duration/lift specs. But I agree with MBHD - its best to have a cam ground to meet your needs.

In this light LSA simply becomes an outcome of timing-event choices for IVO/IVC and EVO/EVC.

Worth reading in this regard:
SpeedTalk-circa'09
Mechadyne

In addition, with a custom grind one need not settle on a single duration. With a dual-pattern grind the exhaust duration can be elongated without necessarily inheriting more overlap (which is the case with a single pattern grind).

regards,
stock49

I'm looking at the middle one. Engle Cams.

That one should work good with your 194 Cyl head.

MBHD

I've decided on a cam.
After much discussion I'm going with this cam. http://www.crower.com/camshafts/chevy-194-250-6-cyl-compu-pro-hydraulic-cam-8322.html

Sounds like a good choice.
I added your car to the Gonkulator database, assumed a 3000lb curb since my hardtops weigh 2800 with a six.
Also, I took the liberty of adding Landon iron and dual 2" pipes.
My stock 250 measured to 8.3cr, with a 60cc head it would have 9.2cr so that's what I used for yours. I did NOT do any "work" to the little 194 head so there is more potential there.

Torq 238 at 3400
Powr 200 at 5100
2.31
10.04 at 68.7 1/8 mi
15.72 at 86.2 1/4 mi
7.6 0-60mph
Should give about 28mpg highway, better REAL mpg than many of today's Super-Heavy "Crossovers", which are really just 1960s station wagon wanna-be mutations.

Let us know if you get the cam in and bring it to the CA Mini-Nats I would like to hear it run!

I did a comp cams custom grind 268H 219@ .050 .486 lift on a 110 lobe center for my 292. That's a fairly mild cam for the 292 and a more radical cam for the 250.

My current plan is to go with an Offy intake and two Carter/Weber carbs from Langdon's Stovebolt. Is this going to be enough?

Should be plenty.
Note the Gonkulator predicts 200hp for your build.
My rule is roughly you need 2cfm (at 1.5" Hg) of carb for each HP, then subtract 10%

So 200hp needs
200x2=400cfm - 10% = 360cfm.

Each of the 32/36 webers (old Pinto 2000 carbs) makes about 280 cfm at 3.0" Hg, or 200cfm at 1.5" Hg, so the pair is 400cfm.
Just perfect.

These are the Carter/Weber ones. Tom said these were each designed for 100 cubic inch engines. So I believe I am undercarbureted.

Put 3 on then!