396/375 cam for street 454?

[goinforbroke]

Was just wondering if a 375hp 396 cam .520 lift 242 duration 112deg, solids.(3863143) would make make a good street cam in a mild 454. Engine is 2 bolt 454, 820 oval ports, cut for big valves and milled to achieve 10:1 with .125 dome pistons. Dual plane intake, 750cfm 4150 holley, 2" headers. Will go in a 72 nova. th350, 3.73 rear. Current cam is a .520 lift crower hyd with 218 duration. Any help would be appreciated.

[WILMASBOYL78]

It should work great!!! You can't beat that cam for the money...you will have lots of power and that super "solid" sound! Next motor I build will be a BB with oval ports and that cam....good luck!

wilma http://www.yenko.net/ubbthreads/images/graemlins/3gears.gif

[Chevy454]

I would think it would work...our 10:1 L72 went pretty good with the stock cam (12.7 @ 108+ in a 3800 pound car on skinnys)...where those ovals will shine (mid range) that cam works pretty darn good... http://www.yenko.net/ubbthreads/images/graemlins/headbang.gif

[YenkoYS100]

I had a '62 BubbleTop BelAir with a '71 Vette LS5 454 in it with the Vette 4 speed. Car weighed 4000+ lbs. It had the stock '71 8.5:1 ? pistons in it. It had a GM 375/396 cam in it, 780 Vac. sec. Holley on a C396 Edelbrock dual plane intake, 2 1/8" fenderwell Hooker headers, stock GM ignition, had the #820 heads on it. I think it was 3.08 rear axle ratio? Car ran on regular gas (1980's). You could dog it, shift into 4th gear running 25 mph. Put the pedal to the floor, and it didn't buck, jerk, or anything but start gathering up the speed like a freight train. I loved that car and engine combo. Still kicking myself for selling her. Hopefully she's still in the hands of Delmer McAfee in Odessa, Tx.?

[markjohnson]

Hey Rick, it's strange that you had a '62 bubbletop with an LS-5 back in the eighties in Texas. I remember my my father bought a red '62 bubbletop out of Texas back in 1986 that had an LS-6 454 in it. It had a powerglide though instead of a 4 speed but it also had the big 2 1/8 Hookers and a Holley three barrell carb on the stock aluminum pancake manifold. Lots of similarities there. Try to dig up a photo and I'll do the same on my end. Car was red on red by the way.

[YenkoYS100]

I was living in Calif. when I bought mine from an undercover Downey Cop. It was white with red interior. Started life as 6 cyl. stick. I sold her to the guy in Tx. Tom Jacobsen picked up the car for Delmer from me. I'll try to find my pics.

[Keith Tedford]

I had an L78 cam in a '66 360 hp 396 4 speed Beaumont. It worked fine and got excellent gas mileage as well. In our L78s and especially the L72, this cam is excellent for the street. The cam lift specs include the valve lash, so you are actually running slightly under .500" lift. If you plan on turning 6K plus rpm, make sure that you install better than stock valve springs or you run a good chance of dropping a valve sooner or later. This caused the demise of most L78 and L72 engines, including the original engine in our L78 Chevelle. http://www.yenko.net/ubbthreads/images/graemlins/tongue.gif

[indyjps]

its a good cam, i think youll make more power without sacrificing anything with an aftermarket grind from comp cams or equivalent.

[nuch_ss396]

This is an interesting topic. I can't say I ever thought
about that combo before. Could you basically use this cam
with an L/34 bottom end & heads? What intake would be
recommended?

These L/78 cams are so hard to come by these days. Who would be a good recommendation for a "blueprinted" cam to
match original specifications? (Comp Cams, Crae, etc. )

Steve

[Stefano]

Jim Pace parts Wharehouse has an L78 cam kit for a great price. It is a blueprinted version ground by one of the big names. I have run several of these in the past with no issues.

[Chevy454]

Nuch: go with the GM blueprint cam made by Crane...us Pure Stock guys have already done the leg work and tried the other brands, and the GM/Crane piece is worth the money...the part # from GM will be 12364057...from Crane it's part # 19038.

[Stefano]

Yeah, what he said, same cam.

[nuch_ss396]

[ QUOTE ]
Nuch: go with the GM blueprint cam made by Crane...us Pure Stock guys have already done the leg work and tried the other brands, and the GM/Crane piece is worth the money...the part # from GM will be 12364057...from Crane it's part # 19038.

[/ QUOTE ]

Rob,

Thanks for the input. Just one other associated question
for you. I have heard a number of opinions about the solid
lifters for these cams and which ones to use. I've been
told that the NOS GM lifters are the best by far. Man, they
do go for major bucks on eBay. http://www.yenko.net/ubbthreads/images/graemlins/headbang.gif

I was informed that the aftermarket lifters aren't ground
properly on the bottom face ( rides against the cam lobe ).
What's your take on this issue? http://www.yenko.net/ubbthreads/images/graemlins/dunno.gif

Steve

[nuch_ss396]

[ QUOTE ]
It should work great!!! You can't beat that cam for the money...you will have lots of power and that super "solid" sound! Next motor I build will be a BB with oval ports and that cam....good luck!

wilma http://www.yenko.net/ubbthreads/images/graemlins/3gears.gif

[/ QUOTE ]

Tom,

Would you have the oval post heads incorporate the use of
the bigger valves as well? What size valves are we talking
about here anyway? BTW, what casting ( head ) would you
recommend?

Steve

[WILMASBOYL78]

As for valve size we are talking 2.19 Intake and 1.88 Exhaust....heads choices for stock GM are open to discussion, depending on your preference for open or closed chamber dsign and what kind of piston/compression ratio you are running. I like the 290 closed chamber head..it has very good flow potential and can help make decent compression. There is probably more power potential with open-chamber design, but your pistons have to be set up to work with the larger chambers. The 820 casting would do a good job. All of these heads benefit from some "massaging" on the exhaust side to improve flow. Use quality valve train parts and make sure you check valve to piston clearance during assembly. The oval port heads will perform better on the street and provide crisper throttle response and more low end TQ....Weiand makes an oval port dual plane manifold "Stealth" that looks a lot like a factory hi-rise and even has the choke setup....this manifold or the Edelbrock Performer RPM are good choices..add the Airgap if stock appearance is not imporatnt. Good luck..wilma

[nuch_ss396]

Tom,

A couple more questions if you don't mind.

With those valve sizes, would some porting need to be done
for flow? If so, how much? Got any target numbers?

If open chamber heads are used ( Like the #820 ), what
compression ratio should I be after? 9:1 or so? What if
the closed chamber heads are used?

Again, it is an interesting topic to be sure.

Steve

[Chevy454]

Steve: the Crane/GM lifters that come with the blueprint cam are fine...I've tried regular Comp and Crane solid lifters, and had no problems...(knock on wood)

[WILMASBOYL78]

Depending on what you start with you will definately have to machine for larger valve seats for the 2.19 and 1.88 sizes. As for porting I think some mild blending and smoothing to improve std flow will be fine. The exhaust side on the BB heads responds well to some improvement. I'm no machinist but any compentent shop should be able to help.
As for compression..10.0 will do the trick..maybe a little more???. Depending on piston configuration and other factors you can use pump hi-test with modest timing. You may have to experiment a little with total advance...not sure if combustion chamber style will impact how much compression you can get away with..but at 10.0 to 10.5, I don't think it will be a major factor. Will check with one of my engine buddys for his thoughts. Most of the aftermarket suppliers like Edelbrock offer their performance heads with some style of open-chamber design. This design is superior to the original closed chamber head for the way the head flows and allows for "better breathing". Some might say that you can even make more horsepower with less compression. This is important if you want to run your car on pump gas...any engine that performs really well, usually has the right combination of parts and technology. hope some of this helps... http://www.yenko.net/ubbthreads/images/graemlins/3gears.gif

wilma

[nuch_ss396]

[ QUOTE ]
... This is important if you want to run your car on pump gas...any engine that performs really well, usually has the right combination of parts and technology. hope some of this helps... http://www.yenko.net/ubbthreads/images/graemlins/3gears.gif

wilma

[/ QUOTE ]

Tom,

What you finished your last post with sums it up in a
nutshell.
http://www.yenko.net/ubbthreads/images/graemlins/worship.gif

I would prefer to run on pump gas, and get a brute of an
engine in the process. But, I want it to appear stock.
The L/78 cam with the oval port heads sound like an
interesting combination. I'd love to test drive one of
these before I build it. BTW, I have a 402 +.040 ( L/34 )
just sitting here waiting for such a project. http://www.yenko.net/ubbthreads/images/graemlins/beers.gif

Steve

[Jim Ferron]

Just a couple notes, my brother has that cam in his 454 and it's fine...maybe a little small. Second, I'm not so sure 820's are the head to use...781's or 049's are the perferred OC smog head, I believe the intake runner are the big difference..Dirt cheap as well, couple hundred bucks a set.
Third, certainly you don't have to change the valve seats to go to the bigger valve no matter which of the three heads you use. Just hog out what's already there.

What will be VERY inportant will be to unshroud the valves in the combustion chamber. You'll see with the big valves, when they are open, they come very close to the wall of the chamber. ANY machinest will/should know to use a grinder to remove material around the edges...to allow for better flow with the big valves.

[nuch_ss396]

Jim,

DO you have the full part numbers for the heads you
mentioned? I want to look into these a little more.

Steve

[WILMASBOYL78]

Good info Jim...I'm not a machinist and I was tryin to say what you mentioned about the valves and the grinding. I have always been kind of in the closed chamber world and should have deferred to the OC users. I'm going to check some of the heads I have in the shop to see if I have any of those numbers. What's your opinion on the hardened seats?? some folks don't use them..they say a good stainless valve is sufficient. I really enjoy the discusson of BB ideas....always good stuff. Thanks for setting me straight. tom

[Jim Ferron]

353049 or 356781 both are pretty much interchangable...smog pick-up truck OC Oval port heads. [OC is the only way to go...]

Just put big valves in 'em and go run high 10's.. The heads on my 496 in my GTO came off a 454 that ran high 10's and had never been ported, just unshrouded..

Wilma knows Nelson, my engine guy [he built my 496, my L-88 and my brothers 454] and another place for ultra solid advice is team Chevelle. Those guys won't steer you an inch off course..I'm 'L-78 Guy' over there....

[nuch_ss396]

[ QUOTE ]
353049 or 356781 both are pretty much interchangable...smog pick-up truck OC Oval port heads. [OC is the only way to go...]

Just put big valves in 'em and go run high 10's.. The heads on my 496 in my GTO came off a 454 that ran high 10's and had never been ported, just unshrouded..

Wilma knows Nelson, my engine guy [he built my 496, my L-88 and my brothers 454] and another place for ultra solid advice is team Chevelle. Those guys won't steer you an inch off course..I'm 'L-78 Guy' over there....

[/ QUOTE ]

Jim,

Can Nelson perform the larger valve installation and the
unshrouding you mentioned when I find a set of these heads?
I would rather go with someone that is well versed in this.

Lastly, I was planning on doing this to a 402 + 0.040 L/34
that is just waiting for something like this to happen. Do
you see any issues with valve unshrouding aginst that bore?


Steve

[Keith Tedford]

With the 396 it is a good idea to add the flow notches in the tops of the bores as well for better air flow. Without using a flow bench, any grinding in the ports can just as easily hurt the air flow numbers as increase them.

[Jim Ferron]

Nelson can perforn the work but truly ANY quality engine machine shop that has has ever built some BBC engines will be well versed in this procedure.

Unshrouding the valve in this case really, in my mind, doesn't constitute, 'chamber work'. Certainly notching the bore to match the whatever you do to the head ala 'gasketmatching' could only help as Keith mentions...all neatly done. All could be done at home with a die grinder.

[nuch_ss396]

Tom, Jim & others,

Can any of you tell me the flow differences between the
oval port heads mentioned in this thread? I don't need
actual numbers, but I am trying to understand if what makes
one oval port head better than another was the combustion
chamber, and/or the intake runners, and/or the exhaust
ports.

Stated another way, do any of the oval port heads of
interest here have significantly different intake or
exhaust flow numbers? I always wondered about all the
different heads Chevy developed and more importantly - why.

Steve

[Jim Ferron]

Open Chamber vs. Closed ...Open was Chevies answer to a Hemi...OPEN allows better spark travel..as far as port design... Ihave no idea as to why GM made so many versions of the same thing except to assume it affects the RPM which peak horsepower is made.

Open Chamber also lowered emmisions dramaticly..