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396/375 cam replacement

7087 Views 9 Replies 5 Participants Last post by  bluecarguy
Hi folks,

I am in the process of a tear down over haul of my 396/375 from my 70 Chevelle and would like some opinions... The car is pretty heavy since it has a/c , ps, pb and several other options and it is a cruiser. It is pretty much stock with the exception of a set of Hooker Super Comps ( which are flat on the bottom from hitting about every speed bump it has ever crossed and are likely to be replaced with Heddman Elites) and a Torker R-2. Car is a 4sp with 3.55 posi.

I think I will go back with a stock alum hi rise intake to better fit the cowl induction set up. I will drop the comp to about 10:1 if I have to overbore the engine , otherwise it will be the stock 11?:1 pistons and rods.

I am looking for cam recommendations and any other suggestions u might want to offer. Comp recommended an XR282HR as a roller cam option and a XE268H for a flat tappet suggestion. I want to have enough vac to have reliable brakes along with a good lumpy idle. I would like to get a power boost if possible and like the idea of the hydraulic roller cam but wonder if the extra cost is worth it. I also plan on roller rockers but I want them to fit under the stock valve covers (is that possible?).

Any help you could offer would be greatly appreciated.


edit - good info so far...anybody else want a shot?:thumbsup:
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OK BlueCarGuy,

So you have a 396/375 horse engine with the rect ports in your 70 Chevelle plus you have A/C, 4-spd and 3.55 gears.

I'd shy away from a solid lifter cam simply because of the added work with the occasional rocker adjustments. Also, if you have a cruiser on your hands vs a brawler, really no sense investing in all the hyd roller stuff unless you "gotta have it" and you have a lotta green in your wallet. Certainly some extra lift to be found on less duration but the conversion kits cost quite a bit. The 3.55 gearing does help bring the rpms in quicker....4-spd helps, wide or close ratio? I'm not a fan of Rect Port heads on street engines less than 496 inches. Way too much head/port volume for a 396/402 per everything written since the early 70s. Port velocity is very important especially for a street engine. Having said this, here is my 2 cents into the cam choice discussion and some history to show you where I'm coming from:

Back in 79 I got my first car on the road, two years after HS graduation. She was a rather faded burgandy 1968 Nova. Out with the 307 2v, Powerglide, and 10-bolt 3.08. I'd apprentenced myself to my mega gearhead neighbor since age 14, so I'd built a 427 w/ 4-bolt mains, steel crank, HD dimple rods, 11:1 TRW Slugs, rect port closed chamber heads, factory Aluminum high-rise and 3310 Holley 750 Holley. I also had the L-88 cam, specs are well-known and BIG, lotta duration for top-end power. I had a 10-inch Super Hole Shot torque converter, built TH400 and a 12-bolt posi w/4.56 gears. Big ports, big cam duration, 'soggy' bottom end power and bad manners, an idle that frightened all onlookers with the very short 2.5" pipes and short turbo mufflers. At 3500 rpm it seemed another engine kicked-in. More nuts than an oak grove. Not what you'd call a street car but pretty typical SoCal ride of the era. Pals had 1970 SS Chevelles, whole 'nother story....

Fast fwd to 1991, bought a project car after a long break in the gearhead lifestyle. Got her running/cleaned-up/painted and still have her. My 68 427 RatVette has the M-20 wide ratio 4-spd w/3.36 gearing, I have a Performer RPM intake and Edelbrock Thunder AVS 800 carb. She has oval port open chamber #781 heads with 2.19/1.88 valves and 10.5:1 CR or there abouts.
I run an Erson Hi-Flo spec: .545/.545" lift 235/235 deg dur @.050" and 112 LSA. This vintage grind was in the car when I bought it, discovered during a freshening of the engine. I get 12.5" manifold vacuum for the power brakes and all the vacuum-operated systems. Once warm she idles with authority yet has a strong bottom end pull . The strong bottom end power only gets stronger with more RPM....turbine-like rather than so-so with a surge at 3000 rpm. With 36 deg total advance I run octane boost for insurance against detonation when I know I'm gonna misbehave.....\\I'd almost say the car has excellent street manners. The RatVette has serious attitude when you mash the go-pedal. I'll be removing the factory exhaust manifolds and going to some Hedman Headers this summer.....gee, just what I need, more power!

The gearing in the Nova makes any comparison to the Vette skewed. I would tell you the Vette can go cross-state no problem or down to Cali and get maybe 15 mpg. A sweet combination that would take someone a lot of money to beat or a bunch of money and a big shot of giggle gas. RatNova took 1/2 tank of gas to go from Carson to Manhattan Beach, Gardena, and back. I'm sure a lot of this is the gearing and the loose torque converter and not all the engine's fault (right!).

I'll be building a mild 454 for my 70 Elky. I'm looking at a budget-brawler vs trick/more expensive components. I have a Perf RPM Air-Gap intake and a 3310 Holley. Engine will be 40-over 454 so 462 cubes with KB small dome Hyper-E slugs with milled 781 heads, guess 9.8:1 cr. I'm also torn, if I run the original 68 closed chamber oval port heads of the Vette on the Elky's 454, I could have 10.5:1 CR instantly and the heads have only 2000 mi on them (machinework/assembly by Nascar's Cope Bros). So, gotta decide closed chamber and more compression (plus no need to have another set of heads built/save bucks) or to run open chamber heads with a bit more flow and modest compression (plus upgrade and assembly costs or purchase of a ready made set). Comments appreciated on head choice. Anyway, this combo should be good for 450 horse /500 ft lbs no problem. Elky has a built TH-350 and the 12-bolt will get 3.42 gears and a new posi (has 2.56 gears and posi now) and most likely a mild stall torque converter.

Cam choices:

Cam #1 is a Summit "house brand" K1302 grind
.540/.540" lift 228/238 deg dur @.050" lift and wide 114 LSA.
2500 rpm-5500 rpm, over 6000 with good valve springs. Only $70 with lifters.
If you browse the GMPP pages, pn 12353920, this is the same cam Crane grinds for GMPP yet you get charged $180 for......hmmmmmmm

Cam #2, I've also looked at the Edelbrock Torker-Plus cam #7162. Far bigger numbers than their Performer-Plus cam yet not as ragged as the Perf RPM cam. Specs:
.527/.553" lift 224/232 deg dur @.050" lift, also the wide 114 deg LSA for good street manners. $182 at Summit. Dunno if I'm really gonna pick up a lot of power difference for the extra $110 bucks I'd have to spend for a 'name' brand cam. Crane, Comp Cams, and Lunati have cams similiar to this, all about $180 with lifters

I'll probably catch hell for what I'm about to say.
In a street cruiser cam, considering the wt of the Chevelle and the modest 396 engine size, go "small." You'll be happy with the torque and good manners.
By small, I don't mean the weak-suck factory HP Hyd cam. I think the .500 lift Performer cam or equivalent cam could be a bit too small for your goals which I assume to be; good power, good sound, something like good street manners. With your static compression ratio being so high, a 'small' cam will build too much cylinder pressure and you'll be rattle central and on your way to a cracked piston or worse. Any of the cams I listed are on the Large to BIG end of 396 cams and in the ball park for what I'd be looking for if I was in your shoes simply because your high compression will pump up bottom end power somewhat lacking in a 396 with rect port heads..... ....

BTW, you've probably read that the new oil formulas no longer contain Zinc. Ensure you use a Diesel formula oil that still has Zinc when you break-in your new cam in addn to break-in lube from your cam company. I understand after a few oil changes you can switch to the new oil formulas with no issue.


Advise on what you come up with after all the sage advice on this site. I'm more frequently on El Camino Central.
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