is comp cams 268H good for Olds 455

[kcsteck]

I had 280H cam in my Olds with headers,vicotr intake and just lost cam lobe for some reason. Maybe I adjusted incorrectly is my guess.everything checks out except cam lobe and the lifter. I need new cam and comp cams tech suggested use the 268H with about same lift and better rpm range 1600-5800
what ya all think.
Casey

[DelawareDave]

I had a 268H in a 502 chevy and it worked good.
Proper break-in will make or break a new cam. I have installed new cams, and wiped a lifter within 10 minutes, during the break-in period. Replaced with another new one, and no issues after that, doing everything the same way. Go figure.

[396_WAYS_TO_SPIT]

keep the comp 280h. It is a good cam and will pull hard. When you breakin the new cam put a bottle of gm's "EOS" in the oil. It will help keep the lobes on the cam. also, run about 2qts of oil more than capacity. This will allow hot oil splash on the cam......

[Taylorman]

Another option when breaking in the new cam is to run Shell Rotella 15W-40 diesel engine oil.

[396_WAYS_TO_SPIT]

Another option when breaking in the new cam is to run Shell Rotella 15W-40 diesel engine oil.
yup, that too;)

[396_WAYS_TO_SPIT]

Another option when breaking in the new cam is to run Shell Rotella 15W-40 diesel engine oil.
yup, that too;)

[malcolm]

I would run the 268 cam if you have the low compression pistons. I went with the 280 in mine because my comp. is 10:1. I am a little disappointed in the smooth idle of the 280. I thought it would at least have a little lope to it.
396, did your 280H have a lumpy idle? Mine almost sounds like an RV grind.

[kcsteck]

i had lopy idle with 280 but i do not know what compesion ratio my pistons are. they are flattop 30 over is about all i know. since they are flattop does that mean low compresion?if low compresion 268 or 280
casey

[PANTHERJET]

since your on the subject i have a 292h in my 455 and seems to idle fine i thought it would have been a little rough anybody else running that cam

[kcsteck]

mine with the 280 was a slug out of the hole. did good once got to upper rpms. i need better out of the hole. maybe the 268 would be better? i want better acceleration from a deadstop to get on plane and all.im pretty sure my pistons stock compresion ratio and i have big valve heads(Ka) heads.victor intake demon 750 and headers.
casey

[HotDogz]

I run a 292 CompCam in my .060 over 455 and I have no prob getting on plane. Had the 280 before my buildup and that cam was also stout enough for the 455. Check your timing curve and make sure your all in at 2800 -3000rpms. IMO...
Like the idle sound with the 292, nice and lumpy. :p

[kcsteck]

what kind of pistons you runnin stock or bigger then stock? how much diff does it make to run stock pistons with 280 or 292 then with bigger pistons ? guess what im asking is with stock pistons should the 280 or 290 still be good cam with the other componets that i am using?

[malcolm]

Not sure what you mean by flat tops. All Olds pistons are dished. The amount of dish dictates the compression.

[Daytona100]

Post some stats of your engine, compression, heads, valve size, intake style, carb size, any port work, impeller size, rpm range, etc and I can run it on a computer program and see what comes out.

[Daytona100]

Ran the numbers came out with two choices comp-280H and 268H. 280H rpm range 2000 to 6000 rpm 493HP at 5500rpm and 538 torque at 4000rpm and 268H rpm range 1500 to 5500 rpm 457HP at 5000rpm and 543 torque at 3500rpm. :)

[malcolm]

Those numbers are at least 75 hp too high. ;)

[Daytona100]

I had to improvise some of the numbers not knowing his actual comp ratio carb size valve size etc. Results still came back with the two cams that he was questioning about. The rpm spreads should be close best I could do with the limited info I have.

[gregr1971]

if you want a nice radical idle,comp 305h works great! with that victor, more compression, and some good ,ported,big valve heads, you'll be happy, run that cam in mine and i'm(was) satisfied.

[Taylorman]

Ran the numbers came out with two choices comp-280H and 268H. 280H rpm range 2000 to 6000 rpm 493HP at 5500rpm and 538 torque at 4000rpm and 268H rpm range 1500 to 5500 rpm 457HP at 5000rpm and 543 torque at 3500rpm. :)
I doubt he will see those numbers with stock unported heads.
Im running a 280 Isky cam with .517 lift and it idles pretty smooth and pulls pretty good from idle.
I doubt you need anything more than a 280 on an Olds since your running it under 5000. Anything more in duration is a waste on a stock Olds. Sometimes smaller is better. Some head work would do you some good.

[kcsteck]

all my info was there Daytona. except piston comp ratio? I have455 olds bored 3o over (461) Victor intake,750 demon carb,big valve heads (KA) Heads,Headers,electronic ignition. I dont know how to get the size of pistons? I had the 280 cam in it and it didnt run right but might be because I adjusted valves incorrectly and wiped out cam lobe on #3 exhaust.or cam might have been bad when i got it . I bought it used on ebay. Bad idea! it went 4900 rpm at 60.1 mph on GPS boat does not have hook but might be cavitating for wear ring bad?
Casey

[396_WAYS_TO_SPIT]

396, did your 280H have a lumpy idle? Mine almost sounds like an RV grind.
Mine was a little lumpy but not that much. It idled pretty smooth. My throttle response was really crisp

[HotDogz]

Kcsteck,
I think the stock piston size in an Olds is 4.125, .030 over would be 4.155, .060 over would be 4.185.
I run .060 over Speed Pro Forged .142 dished pistons. Unported heads will be your major hold back even with large valves. I put in Ferrea SS I 2.075 E 1.710 valves in stock Ga heads and only make 410 HP @ 5300rpm and 502 ft/lbs of torque @ 3800 rpms with a 292 cam. Desktop Dyno says that with just an Edelbrock head swap, HP jumps to 525 HP at 5350 rpm and 602 ft/lbs of torque at 3800 rpm with no other changes.

[malcolm]

Mine was a little lumpy but not that much. It idled pretty smooth. My throttle response was really crisp
OK, I think that describes mine as well. Thanks!

[kcsteck]

anyway I can tell if I have deep or not deep dish pistons. Id like to know if I have the low or high comprsion pistons? anyone have pics of the 2 diff pistons so I can tell by visual?
Casey

[Taylorman]

This is the high comp pistons.
http://i22.photobucket.com/albums/b334/vidrinek/Boat/DCP_6317.jpg

[73WriedtCustom]

My Olds 455 is bored .030 over. I use forged 9.5:1 pistons, comp cams 268 grind, pushrod guideplates screw in studs, 1.6 ratio roller tip rockers. It seems to wind up pretty quick. The intake is a 750 dual feed on an Edelbrock Torker manifold. I'm thinking of switching to a performer dual-plane manifold.
Mark
*edit* A2 impeller cut, no bowl stuffer, no droop.

[MACHINEHEAD]

Any of these flat tappet hyd. are going to die durring break in if the valve spring seat preasure is higher than 130 lbs and 315 open! A recent call to Harvy Crane confirmed the use of straight 30wt oil at all times for these newer flat tappets. Rotella is also a good recomondation. These oils have higher zink levels which helps the lifters survive. GM EOS is a good pre assembly lube, but I believe it says not to add it as an oil supplement. I use moly assm. lube from Crane only, on all brands of hyd. flat cams. Breaking in the cam on the outer springs only is also a good idea. Run the 280H and start saving for the E-heads 525hp seems real.

[pce680]

i had lopy idle with 280 but i do not know what compesion ratio my pistons are. they are flattop 30 over is about all i know. since they are flattop does that mean low compresion?if low compresion 268 or 280
casey
Flat top pistons in a 455 Olds (460 with a .030 over bore) is around 11 to 1 compression ratio.I would run a MP-560 cam by Joe Mondello.

[MACHINEHEAD]

If that comp ratio is the case as 680 has said, I would go with that cam and run 104 oct. fuel!

[Taylorman]

Flat top pistons in a 455 Olds (460 with a .030 over bore) is around 11 to 1 compression ratio.I would run a MP-560 cam by Joe Mondello.
You mean Engle?

[pce680]

You mean Engle?
YES Engle grinds the cams for Mondello

[kcsteck]

11 to 1 how do you figure? these pistons are flattop pistones with a little dish as most olds have I was told like 8.25 to 1 or 9.50 to 1 how do we make sure. I wish it was 11 to 1 this has me realy confused as everyone is sying something diff.
casey

[kcsteck]

yeh talorman my piston's look just like those pics what size were those?
Casey

[pce680]

11 to 1 how do you figure? these pistons are flattop pistones with a little dish as most olds have I was told like 8.25 to 1 or 9.50 to 1 how do we make sure. I wish it was 11 to 1 this has me realy confused as everyone is sying something diff.
casey
Flat tops ( NO DISH ) is 11 to 1 compression ratio.With a dish they are NOT flat top pistons.

[kcsteck]

sorry then. Guess you dindt read all the post I called them Flattop I guess but also said they had a small dish to them. I dint know they made pistons for the olds without the dish. My mistake. my piston's look exactly like the pics Taylorman put on the post. small dish. what size would those be 9.5 to 1?
Casey

[75MillerJet]

those are the high comp pistons? those are stock tho correct? cuz my previous olds had those same pistons. Do they put pistons dished more than that from factory?

[Taylorman]

My pistons are TRW 2323's. They have an 18cc dish. Your actual compression ratio will depend on other measurements. How far piston is below deck, bore size, gasket thickness and diameter and chamber volume. Without all these numbers you can't acurately calculate comp ratio.

[kcsteck]

ok well mine look like those so I go with the 280 cam vrs the 268 correct?
Casey

[malcolm]

I would say so. That's what I went with, same 2323 pistons. Kinda wish I went a little bigger. :)

[Taylorman]

I think a better choice would be Comps part # 42-224-4. You don't want a cam with duration to high cause your not spinning an Olds that high so alot of duration is a waste. IMO you want duration around 235 @.050 and a 110 lobe separation. Going with duration over that puts the peak rpm way above what an Olds will ever see.

[kcsteck]

taylorman whay cam is that?
Casey

[malcolm]

That's the XE274
520/523 lift
230/236 dur @ .050
That's a little bigger than the 280, but probably still a good choice. That's the one Timminator likes for log exhaust.

[kcsteck]

thanks malcolm,
I will get this cam. im sure will be good with headers as well. prob should get matchin springs as well as stock ones prob will float!
thanks guys you all have been alot of help!!!!
Casey
Happy Boatin