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Used camshaft selection for stock short block 360

Posted By: SANDYinNS Canada

Used camshaft selection for stock short block 360 - 05/15/09 02:40 AM

I'm putting a budget 360 together for my 84 shorty truck. Street and stip use no hauling or towing. just a bracket rig and tire burner. Getting tired of the current slant6!

The truck has 3:55's and a sure grip 833 od tranny. The 360 short block is a mid 70's low comp version that will only be treated to a re-ring and bearing.

I'm using a set of ported heads of the same vintage only they have 202 valves in them. Again left over from another project that was upgraded to eddy heads.... I'm going with an edelbrock performer as the truck a/c and it is the only intake I have fits with that.


Here is my real question. I have 3 camshafts left from various other projects all are used but in fine shape with lifters in order.

One is comp cams 268 and another is comp 272.

The wild card is an old purple shaft I once took out of a 340. It has to one of those old 108 centerline cam as we had an issiue with detonation and swappimg it out for a wider centerline cam solved the problem.

Wouldn't this work well in my low comp 360 by building up the cyl pressure? Or would one of the more modern comp cams be a better choice.

This is basically a junk motor with me using up some old parts that are laying around.

Posted By: goldmember

Re: Used camshaft selection for stock short block 360 - 05/15/09 02:57 AM

Comp 268 if thats all you have.
Posted By: MR_P_BODY

Re: Used camshaft selection for stock short block 360 - 05/15/09 04:02 AM

I dont know the LSA on the 268 or the 272 but if they
are wider than the purple I would use the purple and
install it at 102 to 104 centerline just for the purpose
you stated... upping the cyl pressure
Posted By: goldmember

Re: Used camshaft selection for stock short block 360 - 05/15/09 04:08 AM

The only problem is the MP hyd cams with 108 lsa are over 290 degrees(I know they don't list them as such),so you can advance them all you want and not produce cylinder pressure with under 8 to 1 comp. The old standard comp 268high energy is ground on a 110lsa and most install it around 106lca,much closer to usable than the larger duration MP cams,IMO.
Posted By: MR_P_BODY

Re: Used camshaft selection for stock short block 360 - 05/15/09 04:36 AM

Quote:

The only problem is the MP hyd cams with 108 lsa are over 290 degrees(I know they don't list them as such),so you can advance them all you want and not produce cylinder pressure with under 8 to 1 comp. The old standard comp 268high energy is ground on a 110lsa and most install it around 106lca,much closer to usable than the larger duration MP cams,IMO.



Your talking 290 advertised which is about a 246 at 50
then advance it to 102 CL then you still have enough
RPMs to play with, as you advance the cam you kill
the upper rpm range. If you use the 268(which I
am guessing its a 268 advertised) which would be
about a 228 at 50 and if you advance that you dont
have much for top end RPM... JMO BUT it will have
better low rpm cylinder pressure for torque
Posted By: goldmember

Re: Used camshaft selection for stock short block 360 - 05/15/09 04:51 AM

With no comp,not enough gear,somewhat heavy truck I would not worry about top end and kill it dead where it needs to work.
Posted By: patrick

Re: Used camshaft selection for stock short block 360 - 05/15/09 12:04 PM

the 268H is 218/218 .050 dur, .454" lift

the 272? do you mean the magnum 270H? is 224/224, .470 lift

I have an XE262 in my stock long block 360, pulls real good from about 1800-2000 up to 5500. if you've got a loose (2500-2600 stall converter, and don't care about idle quality, I'd probably go 270H. if your converter is more in the 2200-2300 stall range or lower, the 268H

use comp 901 springs with either.
Posted By: SANDYinNS Canada

Re: Used camshaft selection for stock short block 360 - 05/15/09 12:21 PM

I'm going to check what I have I think both were xe cams?
The mp is an old 284/484 purple shaft/108 I'm fairly sure of that one!

Truck is 4 spd..no worries on stall speed.
Posted By: patrick

Re: Used camshaft selection for stock short block 360 - 05/15/09 01:06 PM

what first gear ratio is it? unless it's a 3.09 first gear tranny, I'd stick with one of the two comps, probably the smaller one.
Posted By: SANDYinNS Canada

Re: Used camshaft selection for stock short block 360 - 05/15/09 02:30 PM

Quote:

what first gear ratio is it? unless it's a 3.09 first gear tranny, I'd stick with one of the two comps, probably the smaller one.



I have no idea what the 1st gear is? whatever came in a slant 833 od 84 truck?

I looked it up somewhere on the net and it does look like a 3:09 1st gear

The cams i have are a
268 h could be an xe not sure but i think it might be

Second one is a 274 xe which looks like it is discontinued?

both appear to be on a 110 center line

Is there much difference? I know the old 108 dc shaft detonated badly with a 9.7 :1 motor ( I measured it before and after the rebuild )
Posted By: patrick

Re: Used camshaft selection for stock short block 360 - 05/15/09 05:16 PM

Quote:

Quote:

what first gear ratio is it? unless it's a 3.09 first gear tranny, I'd stick with one of the two comps, probably the smaller one.



I have no idea what the 1st gear is? whatever came in a slant 833 od 84 truck?

I looked it up somewhere on the net and it does look like a 3:09 1st gear

The cams i have are a
268 h could be an xe not sure but i think it might be

Second one is a 274 xe which looks like it is discontinued?

both appear to be on a 110 center line

Is there much difference? I know the old 108 dc shaft detonated badly with a 9.7 :1 motor ( I measured it before and after the rebuild )



268H is 268/268, 218/218@.050, .454" lift, 110 LSA, 48 deg overlap

XE274 is 274/286, 230/236@.050 .488/.491 lift, 110LSA 60 degrees overlap.

268H will make more torque, XE274 will make more HP. using comp's camquest6 software, assuming 7.8 compression, 600 CFM carb, dual plane intake, headers, and flow data taken from hughes website for '576 heads w/2.02's, it's predicting:

308HP@4500 & 387 TQ@2500

switching to an XE274 yields

331HP@5000 & 382 TQ@4000,

one thing to remember is your gear spread and RPM drop. A833 OD's are 3.09, 1.67, 1, so your 1-2 shift will drop RPM's 46%, 2-3 will drop RPM's 40%. ideally you want to shift at or slightly above your HP peak, and drop to near your torque peak.

I think the numbers & RPM's are off on the comp simulation, I'd wager the 268H will peak HP at ~5200 & TQ at ~3000, and the XE274 more like 5800-5900 and 4000-4500. with the wide gear spread and the heavy weight of the truck I think I'd still look at the 268H, and shift ~5700 RPM (will recover at ~3100 & 3400...with the XE I'd say you'd probably need to shift near 7k to get to a decent shift recovery point for the cam (7k shift would recover at 3800 & 4200) and by then I'd wager you'd be too far past your HP peak that you wouldn't be gaining anything. if you had a closer ratio 4 speed with deeper gears, or an automatic with a loose converter, I'd go with the XE.
Posted By: Paul_Fancsali

Re: Used camshaft selection for stock short block 360 - 05/15/09 05:49 PM

Speaking from experiance DO NOT USE THE 284 cam the truck will be a dog period no matter which way you install it.It plain kill cylinder pressure I'm using a very similar setup using a LD340 and 750 Holley dbl pumper. The Cam is a comp 268 high energy. I have tested seven cams and the Comp-268 has given me the best times in a 4350 racing weight car. With the 284 cam the car ran a 15.8 with 3.55s. The car ran 15.0 to 15.2 same gears Comp268.
The key to getting your truck going is in the timing and carb by tuning and gearing I got this car to go 14.30. The comp cam is out of steam at 5700 but will rev to over 6000. So key here is do not over gear!.Also run the total as high as you can and not detonate try 45 total. By the way this car is another example like you are doing using parts from my other car and making it run Have fun !
Posted By: goldmember

Re: Used camshaft selection for stock short block 360 - 05/15/09 06:35 PM

But I'll add a few bits,hope it helps someone. Even at 3100lbs with 3.91 gears and 3000 stall converter the 268he gave near identical times to the 284mp cam low 12's 110-112 mph. The 268he cam was shifted at 5200rpm,the mp284 6000rpm. The MP really liked more converter and gear to wake up. I'd bet the peak torque with the 268he would be 3500-3800 rpm and peak hp 5000rpm for a close ballpark.I found the 268he also favored small carbs over carbs that work with hotter combo's.
Posted By: 71valiant

Re: Used camshaft selection for stock short block 360 - 05/15/09 10:01 PM


I built a simliar engine for my valiant. Stock 360 pistons and heads. I used a 480/480 lift 292/292 duration 230@.050 109 centerline. It runs well with 4:30 gears and a 2600 stall.
Posted By: emarine01

Re: Used camshaft selection for stock short block 360 - 05/15/09 11:07 PM

We had a .030 over 360 9to1 comp with a erson 214 @ .050 with mid.400s lift in a pick up with a 2500 vert and 3.55s I think it was 108 on 104, air gap and 660 holley , ran good 2500 to 5500 in 4500 # 4x4
Posted By: thecarfarmer

Re: Used camshaft selection for stock short block 360 - 05/15/09 11:24 PM

Got an OD; gears can be changed.

Go big cam and don't look back!



Bet if you had 5.13's that purple shaft would be the clear winner...

Then again, I'm NOT known for having anything resembling common sense regarding comfort/drivability.

-Bill
Posted By: SANDYinNS Canada

Re: Used camshaft selection for stock short block 360 - 05/15/09 11:30 PM

Wow going have to let this all sink in!
Posted By: SANDYinNS Canada

Re: Used camshaft selection for stock short block 360 - 05/16/09 11:40 AM

So it sems that I go with the 268. I'm assuming that I should install it at 106?
Posted By: 7D9LRE

Re: Used camshaft selection for stock short block 360 - 09/24/09 01:59 AM

So how did it work? I'm going through my Lil Reds 360 and still undecided on cam and pistons. Thinking KB232 and comp cams 268 or 270. Going to install a 2000 stall, what's the better cam for a heavy truck?
Posted By: SANDYinNS Canada

Re: Used camshaft selection for stock short block 360 - 09/24/09 12:11 PM

My rebuild is getting put off till winter.I managed to pick up a v8 wiring harness as well as a few other pieces to finish the swap just need to free some time to get her underway. . My shop has been busy with paying customers lately !
Posted By: RUNCHARGER

Re: Used camshaft selection for stock short block 360 - 09/24/09 06:02 PM

That OD trans has huge spreads between the gears. You want the 268H I would wager.

Sheldon
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