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Im thinking going mild with the Comp Cams 456/268 cam in a 350.
Hows it sounds and does it run good on the street.
useal add ons carb, intake, exhaust, stall, gears.
Last edited by s i 442; November 18th, 2022 at 10:37 AM.
I have always thought that cam was low on lift for the .050 duration - most of the 204 cams have that amount of lift.
But I have never used that cam, so no first hand experience.
Im thinking going mild with the Comp Cams 456/268 cam in a 350.
Hows it sounds and does it run good on the street.
useal add ons carb, intake, exhaust, stall, gears.
That is a lot of cam for a 8 to 1 Olds 350. I ran a 214/214 cam with and without a higher stall and 2.78 gears and 9 to 1 compression. It had 150psi cranking compression, it was pretty gutless with the factory 1600 stall. I ran equal to mid 15's, 9.9 in the 1/8 with a 8 to 1 Olds 350 with an Edelbrock Performer 204/214 cam advanced 2 degrees, it had 140 to 142psi cranking compression, 1900 factory stall 2004R and 3.42 open gears in a 3750 pound 88 Cutlass. The ignition was breaking up around 4500 rpm. I would do a compression test on your 350, see where you are starting.
Look at the head flow numbers in the spreadsheet below (this info was compiled by kitfoxdave), based on this info anything with <.500" lift you're giving up flow (power) per the table. I don't know why COMP has so many Olds Cams with <.500" lift. SBC have a Valve Angle of 23* where the Olds has 6*, because of this the SBO can run more lift than a SBC (I know nobody asked that but I think it's worthwhile to point it out). Pretty much any Dyno result will back up the >.500" lift cams make the best power. I have yet to see anyone recommend a sub .500" lift cam for an Olds yet (not saying it hasn't been done I just haven't seen it published), Lunati Cams offers a lot of Olds cams with greater lift and similar grinds to Comp.
The Bulk of Shelf Cams for Oldsmobile also seem to be offered more often in wider LSAs 110-112. That might be because people who drive these cars want a smooth idle but that should be able to be achieved by decreasing overlap. Every dyno test shows that the tighter LSA produces a greater average torque per Cubic Inch than the same cam otherwise (lift & duration) on a wider LSA. The renowned Engine Builder and Author David Vizard came up with this formula LSA = 128-(CID/8/Intake Valve dia x .91) assuming 10.5:1 CR, (correction factor is .6* added to LSA per extra point of CR; so going to 12:1 you'd widen the LSA lower compression tighten the LSA). So a 10.5:1 355 with 7a heads would want a 107 LSA (per that math) 50-75 Overlap would be street performance overlap (per DV's book) and using his math to calculate duration .(LSA + overlap/2) x 2 (107 + 37.5)x2=289* (on the high end) or 264* on the lower end which is right in the ballpark of the Advertised 256/268 of the XE256. If a smooth idle is important a tight LSA with some overlap might not be for you here's a 455 with 108* LSA 230/236* @.050
(one sounds wicked the other very mild and I doubt any of the experts would recommend either one).
These calculated numbers are for average Joes building a street motor for pump gas, to gain a better understand of what a decent cam would be for their engine to make power vs asking the internet or calling Tech Support at Comp. If you give your exact engine specs and combo to an Experienced Olds Engine guy like CutlassEFI, BTR, Olds Perf & Machine etc they can spec out and order you the best cam for your combo. I think most will dissuade you from the Hyd Flat Tappet as well, and for good reason as the reported failure rate is pretty high and today there's only 1 company making Flat Tappet lifters in the USA (Topline Hylift) and they recently had to swap to a brand new Foundry because the one they had used for 60+ years closed (forever) during COVID (I got that info from a Topline dealer). Confidence in Hyd Flat Tappet lifters and Cams is at an all time low.
It would be AWESOME if one of the Oldsmobile Vendors could do a similar round of testing using the SBO. You're not going to see it on Engine Master's or Hot Rod Magazine, Dulchich himself even said when asked about making power for the Olds 350: "I don't think I'd ever build one of those engines".
Last edited by rogue_ryder; November 22nd, 2022 at 04:11 PM.
Well I laid out 3 Isky cams and 3 Comp Cams specs and when I was done I have the Comp Cams Magnum 490/280 coming in the mail. This will be the 3rd time using it so I know what it sounds like and what will work with it.
The 350 the cam is going in is a stocker 4 barrel engine, below is
the last car I used that cam in ( 350), it was all stock when I started, you talk about power!
Agree. I don't think a 2500 stall will be enough with that cam, of course depending where it actually stalls. Mine usually flash mid way in the rating range. I would love to see a before and after compression test with this cam in this 8 to 1 motor.
Im not racing it ever, its all for cruise-ins and dragging Main attention and bragging rights.
But im pretty sure if that cam can run fine with a 600cfm Holley and manifolds it only has to be better with a 750cfm Holley and headers. Did ya listen to the above youtube vid when I used the cam last time, started right up, idles and held in gear with no pull whats so ever, drove the car everywhere.
Last edited by s i 442; November 26th, 2022 at 09:49 AM.
If it ends up gutless, what are you bragging about?
Because it sounds cool! Myself, not a fan of a rough idle, music to some peoples ears. If it is his thing, sure why not. I personally like a smooth idle and something that turns tires into smoke. Comp is very vague on their site, just a 2200+ stall recommended. Usually they suggest something like 9.5 to 1 at least and 3.55 or better gearing, pretty vague.
If it ends up gutless, what are you bragging about?
Gutlass how, if it makes it to the cruise-in, draws attention and makes it back home thats a win!
Speed limit on Main st is 30MPH, you can really do some loping at that speed!
Around here trying to build something fast is a waste we have 5 second street cars and a 75 Cutlass is never going to be one of them.
... people who post soliciting opinion and advice only to argue against it?
Just because you give advice doesn't mean its right.
you think im not going to run that cam because someone says it won't work when I've ran it twice before and it ran great and not defend it?
Most of you talk on here recommends a puny 204@50 cam and 2 barrel with iron intake and stock manifolds and try to convince people a points distributor is all you need, sometimes you have to sift thru it for something useful.
Just because you give advice doesn't mean its right.
you think im not going to run that cam because someone says it won't work when I've ran it twice before and it ran great and not defend it?
Most of you talk on here recommends a puny 204@50 cam and 2 barrel with iron intake and stock manifolds and try to convince people a points distributor is all you need, sometimes you have to sift thru it for something useful.
My point being: if you already know what you're going to do, why bother asking us?
My point being: if you already know what you're going to do, why bother asking us?
Because maybe I forgot something or a valid point comes up I can use but at the end of the day I'll make my own decisions and choices but include the opinions of this site.
Because maybe I forgot something or a valid point comes up I can use but at the end of the day I'll make my own decisions and choices but include the opinions of this site.
Just because you give advice doesn't mean its right
There's nothing wrong with his advice.
A Cam that is designed to run on an engine with 9.5:1+ CR is going to be a dog in a 8:1 CR engine, and that's because you won't build enough cylinder pressure, things get even worse if you have a tall rear gear and heavy car. There's actual science behind this, and you can run all the numbers. For a healthy street engine you should have a DCR of 7.5-8:1 https://www.gofastmath.com/Compressi...tio-Calculator Having driven a combo of parts that the biggest difference was Compression Ratio I'll take the Cammed up Higher CR over the low compression engine with a Cam that sounds cool ANY Day. Not ONLY will the big cam low CR combo be a dog on the street it'll use more fuel because of the lowered cylinder pressure.
Comp gives vague advice but Lunati's very similar Voodoo https://www.lunatipower.com/voodoo-h...8-268-276.html actually gives specific information on CR, Gearing, Stall Speed and Headers for a very similar grind. Olds Performance Products Cam in that size says "Deep pronounced chop in exhaust. Suggested compression ratio 9.6-10.1. Dual exhaust a must, headers, enhanced power with aftermarket ignition, aftermarket intake manifold. Gear ratio with automatic 3.55 to 4.10. Manual transmission gear ratios 3.73-4.10. Factory oem rocker arms acceptable. Roller tip or true roller rocker will add enhanced performance. RPM range 2200-5800"
[QUOTE=rogue_ryder;1466488 There's nothing wrong with his advice.
A call to a Cam Grinder or Professional Engine Builder would have gotten you a much better Cam suited to your application than that Comp Magnum.
Any one of these guys would have recommended something better than that Comp Cam:]
Funny thing is I first picked a small cam 456/268 Comp Cam and someone said it was too big, now come on, much smaller and it would be a stock cam, Im beginning to believe maybe somebody doesn't like Comp Cams no matter what grind it is?
But anyway did you listen to the vid up in the thread? Same 490/280 cam, stock 71 engine, 600 Holley, 308 posi, 3000 stall. block long burn outs, if thats a dog in your book you must have your own TV show Monday nights at 7:00!
I think the 3000 stall is key to that launch you had. My 70S was 9 to 1 Olds 350 with a 214/214 cam, did 1/4 block burnouts with a 2350 flash stall, 2200 to 2500 rated and 2.78 gears. The 2004R was ran low, lost 3rd and 4th, in went the stock TH350 with the 1600 flash stock stall. It wouldn't even peel the skin off a grape. Hopefully it gives the idle you want with acceptable performance. The good part is, you should be able to run regular gas with very aggressive timing, which should help low end and part throttle.
Last edited by olds 307 and 403; November 28th, 2022 at 08:42 PM.
I think the 3000 stall is key to that launch you had. My 70S was 9 to 1 Olds 350 with a 214/214 cam, did 1/4 block burnouts with a 2350 flash stall, 2200 to 2500 rated and 2.78 gears. The 2004R was ran low, lost 3rd and 4th, in went the stock TH350 with the 1600 flash stock stall. It wouldn't even peel the skin off a grape. Hopefully it gives the idle you want with acceptable performance. The good part is, you should be able to run regular gas with very aggressive timing, which should help low end and part throttle.
Well hell if the stall lets me have the cam I want its a win/win!
Last time I ran timing 15 initial and 36@ 3000 and the car started and didn't ping, I only run 93 in my old cars, that may help and sometimes when I get to the track I get me 5 gl of 110 and add a gallon for the smell!
Question, I hook the vacuum pod up to full vacuum, is that your pick or what?
I experienced low speed bucking with 22 initial with a 30 degree vacuum advance canister off manifold vacuum witb 87 octane that has 10% ethanol. I now run 91 non ethanol in my 70S. Timing was in by 2800 rpm and 38 total without vacuum advance. Of course it was an actual 9 to 1 compression with 150 psi cranking compression. You will be much lower on both counts. I would bet the timing I ran would be no issue for you. I used a 20 degree adjustable vacuum advance canister to fix the low speed bucking. It made part throttle less responsive.
Last edited by olds 307 and 403; November 29th, 2022 at 06:31 PM.
Interesting idea for a build: low compression, big cam and as much timing as you have the ***** to dial in. Match that with a 200R-4 with its 2.74 low and a 3200 RPM stall torque converter and 4.33 rear.
Wonder how that would run ... low-octane regular gas stormer?
Gutlass how, if it makes it to the cruise-in, draws attention and makes it back home thats a win!
Speed limit on Main st is 30MPH, you can really do some loping at that speed!
Around here trying to build something fast is a waste we have 5 second street cars and a 75 Cutlass is never going to be one of them.
If you would have said that’s what you wanted in the first place,, you could have just pulled 2 plug wires and punched a hole in each muffler with a screw driver.
or stuffed an even bigger cam in it to “draw attention”. 🤣🤣
If you would have said that’s what you wanted in the first place,, you could have just pulled 2 plug wires and punched a hole in each muffler with a screw driver.
or stuffed an even bigger cam in it to “draw attention”. 🤣🤣
I guess if all you can afford is junk then yea that might be your answer.
November 18th, 2022, 09:34 AM
... people who post soliciting opinion and advice only to argue against it?
