i have a 396 chevelle with 325 hp. i would like to increase the power but i do not want to change the heads. what cam would work best for this. i would also be willing to change the carburetor if this would help. i have already ordered my headers. any help would be appreciated
irlene
I read this post and my mind takes me back to the day when I first got a bbc 396, all hung up on the "stock" specs of this and that gross and net this or that cam makes this much.
Zoom forward 22 years and I will tell you this none of it makes a difference unless you dead set on a number matching engine for a numbers matching car.
Bottom line a 396 needs convertor 2500 plus, 10 to 1 compression and decent 230/240 @ .050" cam, some stock ported heads, small tubed headers, dialed in timing curve and some RPMS to make decent power.
After several years and many combos this is my list for minimum requirements, I have spent to many days at the track with under performer combos that just don't put enough power out.
I comes to this you need to turn up the rpms to get decent hp out of a 396
Zoom forward 22 years and I will tell you this none of it makes a difference unless you dead set on a number matching engine for a numbers matching car.
Bottom line a 396 needs convertor 2500 plus, 10 to 1 compression and decent 230/240 @ .050" cam, some stock ported heads, small tubed headers, dialed in timing curve and some RPMS to make decent power.
After several years and many combos this is my list for minimum requirements, I have spent to many days at the track with under performer combos that just don't put enough power out.
I comes to this you need to turn up the rpms to get decent hp out of a 396
While i am back here i forgot to also rec installing a lrger higher flow .135" needle & seat to replace stock for bbc .125" needle & seat and a lighter fuel pump rod.
You can run the carb out of fuel smaller needle & seat setup & i have also found the heavy stock pump rod in soime cases can cause stock f-pump with lighter pump are spring to float at 4500-5k rpm reducing fuel flow to carb which is an issue with perf cams running up to 5,500-5,600rpm.
And today some rbld kits actually have an even smaller .110" needle & seat SBC used.
Scott
You can run the carb out of fuel smaller needle & seat setup & i have also found the heavy stock pump rod in soime cases can cause stock f-pump with lighter pump are spring to float at 4500-5k rpm reducing fuel flow to carb which is an issue with perf cams running up to 5,500-5,600rpm.
And today some rbld kits actually have an even smaller .110" needle & seat SBC used.
Scott
The Cam specs for the FT hyd cam GM used in stock 396/325hp & 350hp & 360hp (1 yr only),402/350hp,427/385hp,390hp,LS5 454 365hp & 390hp,among a few other bbc's is:
214 int/218 ex deg dur @ .05,.461"/.480 gross lift,on i believe a 115 deg LSA.
Even though porting the heads would nice its expensive and not nededed a all to inc perf he quite a bit.
Since the stock 396/325 hp motor has decent lrg oval port heads with small chambers for decent 10.25.1 comp in stock form if his motors in good cond not using much oil with good compression all he has to do is :
* INSTALL AN AFTERMARKET HYD FT PERF CAM (with proper matching springs & retainers,maybe valve seals while your at it too) THATS MORE CAM THEN STOCK 396/350HP & 360HP HAD IN APPROX RANGE OF 218-224 INT/226-230 EXT DEG DUR @.05,.510"-.520" /.530"-.540" GROSS LIFT ON A 110-112 DEG LSA .
With a properly dialed in dist/timing curve a cam in that range will still be very streetable and idle decent in a smaller 396-402cid bbc motor.
* SETUP MECH ADV IN DIST FOR 18 DEG MECH ADV ALL IN BY APPROX 2500-2600RPM MAX.
TO RUN WITH APPROX 18 DEG BASE TIMING THE AFTERMARKET PERF CAM NEEDS.
THEN YOU HAVE 18 DEG BASE TIMING + 18 DEG TIMING FROM MECH ADV IN DIST = 36 DEG TOTAL. THATS A GOOD PLACE TO START FOR A STREET PERF TIMING CURVE WITH A CAM IN THAT RANGE THAT SHOULD RUN WELL RIGHT OUT OF THE BOX ONLY NEEDING TO TWEAK THE TIMING A COUPLE DEG EITHER WAY TO FIND THE SWEET SPOT.
* RUN A VAC ADV LIMITED TO A MAX OF 10-12 DEG & HOOK IT TO FULL INT VACUUME TOO.
* TWEAK/ADJ THE Q-JET FOR BEST PERF ESPCIALLY WHEN IT COMES TO PROPERLY ADJ SECONDARY UPPER AIR VALVE SPRING TENSION TO ENSURE ITS OPENING FULLY AT THE PROPER RPM AND THAT THE LOWER MECHANICALY OPERATED SECONDARY THROTTLE PLATES IN CARB BASEPLATE ARE ALSO OPENING FULLY TOO.
* INSTALL HEADERS (OR EXTRUDE HONED EX MANIFOLDS IF YOU DOINT WANT TO RUN HEADERS) ALONG WITH GOOD FLOWING MUFFLERS AND 2.5" MANDRELL BENT EX PIPES & TAILPIPES TO ENSURE GOOD BREATHING ON EX SIDE OF THE MOTOR.
Doing all the above (esp using a cam in range i suggested thats larger then stock 396/350 & 360hp cam is along with headers & good breathing ex system) should increase your 396 from its stock 325hp/415lbs trq rating to roughly 365-370hp/430-440lbs trq without removing heads for expensive porting though it could add an additional 25-30hp ro a bit more .
I have done this type mod to quite a few stock 396-402bbC's like yours over the yrs and it really wakes them up when done properly esp when running man trans and decent street perf gear with reasonable cruise rpm like 3.31 or even 3.42 if running non OD old school 4spd trans.
With a 5 spd man trans or Od auto trans then you can run 3.55-3.73 gear for more getup 7 go .
Scott
214 int/218 ex deg dur @ .05,.461"/.480 gross lift,on i believe a 115 deg LSA.
Even though porting the heads would nice its expensive and not nededed a all to inc perf he quite a bit.
Since the stock 396/325 hp motor has decent lrg oval port heads with small chambers for decent 10.25.1 comp in stock form if his motors in good cond not using much oil with good compression all he has to do is :
* INSTALL AN AFTERMARKET HYD FT PERF CAM (with proper matching springs & retainers,maybe valve seals while your at it too) THATS MORE CAM THEN STOCK 396/350HP & 360HP HAD IN APPROX RANGE OF 218-224 INT/226-230 EXT DEG DUR @.05,.510"-.520" /.530"-.540" GROSS LIFT ON A 110-112 DEG LSA .
With a properly dialed in dist/timing curve a cam in that range will still be very streetable and idle decent in a smaller 396-402cid bbc motor.
* SETUP MECH ADV IN DIST FOR 18 DEG MECH ADV ALL IN BY APPROX 2500-2600RPM MAX.
TO RUN WITH APPROX 18 DEG BASE TIMING THE AFTERMARKET PERF CAM NEEDS.
THEN YOU HAVE 18 DEG BASE TIMING + 18 DEG TIMING FROM MECH ADV IN DIST = 36 DEG TOTAL. THATS A GOOD PLACE TO START FOR A STREET PERF TIMING CURVE WITH A CAM IN THAT RANGE THAT SHOULD RUN WELL RIGHT OUT OF THE BOX ONLY NEEDING TO TWEAK THE TIMING A COUPLE DEG EITHER WAY TO FIND THE SWEET SPOT.
* RUN A VAC ADV LIMITED TO A MAX OF 10-12 DEG & HOOK IT TO FULL INT VACUUME TOO.
* TWEAK/ADJ THE Q-JET FOR BEST PERF ESPCIALLY WHEN IT COMES TO PROPERLY ADJ SECONDARY UPPER AIR VALVE SPRING TENSION TO ENSURE ITS OPENING FULLY AT THE PROPER RPM AND THAT THE LOWER MECHANICALY OPERATED SECONDARY THROTTLE PLATES IN CARB BASEPLATE ARE ALSO OPENING FULLY TOO.
* INSTALL HEADERS (OR EXTRUDE HONED EX MANIFOLDS IF YOU DOINT WANT TO RUN HEADERS) ALONG WITH GOOD FLOWING MUFFLERS AND 2.5" MANDRELL BENT EX PIPES & TAILPIPES TO ENSURE GOOD BREATHING ON EX SIDE OF THE MOTOR.
Doing all the above (esp using a cam in range i suggested thats larger then stock 396/350 & 360hp cam is along with headers & good breathing ex system) should increase your 396 from its stock 325hp/415lbs trq rating to roughly 365-370hp/430-440lbs trq without removing heads for expensive porting though it could add an additional 25-30hp ro a bit more .
I have done this type mod to quite a few stock 396-402bbC's like yours over the yrs and it really wakes them up when done properly esp when running man trans and decent street perf gear with reasonable cruise rpm like 3.31 or even 3.42 if running non OD old school 4spd trans.
With a 5 spd man trans or Od auto trans then you can run 3.55-3.73 gear for more getup 7 go .
Scott
From a 1970 Motors Auto Repair Manual I found some information;
It state's that valves spring installed height is 1.88 for 2 396's listed in 1966.
spring pressure psi
325 hp = 220@ 1.46"
360 hp = 315@ 1.38"
It skip's the shp engine but list's the 427's spring pressures at the same as the 360 hp 396 however the 390 hp is hyd and the 425 hp is naturally a sft but according to this book keeps the same spring pressure as the 360hp 396.
It state's that valves spring installed height is 1.88 for 2 396's listed in 1966.
spring pressure psi
325 hp = 220@ 1.46"
360 hp = 315@ 1.38"
It skip's the shp engine but list's the 427's spring pressures at the same as the 360 hp 396 however the 390 hp is hyd and the 425 hp is naturally a sft but according to this book keeps the same spring pressure as the 360hp 396.
Irlene,You have what I started out with. My upgrades are:Hedman Elites with a custom exhaust,702's with nice valve job with a little bowl work and clean up,3310 750 Holley,Isky 270 Megacam,all Isky valve train components. This put me past where you want to go. I still have a C-396 intake to install in the next few weeks...Bob
Irlene, if money is available, I would remove the heads, have them ported - valves enlarged by someone with a reputation, adn then add a hydraulic roller cam. You can get with Chris Straub if you prefer to leave the cam selection to a professional.
WARNING! this will set you back near 2K.
Between the fresh valve job, porting, bigger valves and esp the cam, you ought gain a ton of TQ/hp and still be able to use the original qJet.
You'll have to get rid of the tiny hole snorkel air cleaner lid though. That is made for the stock .385 lift camshaft!
WARNING! this will set you back near 2K.
Between the fresh valve job, porting, bigger valves and esp the cam, you ought gain a ton of TQ/hp and still be able to use the original qJet.
You'll have to get rid of the tiny hole snorkel air cleaner lid though. That is made for the stock .385 lift camshaft!
The 360 hp and 350 hp 396 are practically the same engine from 66-67. The 350/360 hp 396's and 385/390/400 hp 427'S and 270/365/360/390 hp 454 all used the same cam.
The 265/325 396's and 240/300/310/330 hp 402's and 335 hp 427's 235/245/275/345 hp LS-4 454'S had the baby cam with .398 lift.
The 265/325 396's and 240/300/310/330 hp 402's and 335 hp 427's 235/245/275/345 hp LS-4 454'S had the baby cam with .398 lift.
The #291's were the last Closed Chamber Head, and the only heads used on the production LS6's, I used a hydraulic cam from a 390 HP 427 in my fathers station wagon. Was originally a 325 HP, Qjet with leaking welsh plugs. I don't remember if the 360/396 and 390/427 used the same cams. Too long ago. Pop liked the way the new cam ran. As mentioned, I'd go with the 220ish intake Voodoo.
As a side note, there was a dicussion on Speedtalk recently where the question posed was "Who makes the best "off the shelf" cam?" Mike Jones, aka: Cam King, reply was one of the VooDoos. Mike only grinds custom cams.
As a side note, there was a dicussion on Speedtalk recently where the question posed was "Who makes the best "off the shelf" cam?" Mike Jones, aka: Cam King, reply was one of the VooDoos. Mike only grinds custom cams.
Pull the heads and have a GOOD head porter do a lil bowl work /gasket match them and your intake, do some flash cleanup. I'd have the valves unshrouded and chamber opened up a bit to lower the 10+ compression. If the guides are good put some good flowing performance valves in them. If the guides are bad get some 11/32 liners put in, and run the better flowing/lighter valves in them. The voodoo 60202 and 60203 mentioned above are nice 396 cam's, get the correct springs to match. That and the timing mods ( 2500 stall if it's an auto ) should make it a different car
With the engine that mild I wouldnt go to a higher stall torque converter, it makes it feel sluggish at low RPM. Keep the q-jet if you have one. Headers, good exhaust and good distributor curve will help a lot
Depending on the model year, the 325 and 350 horse 396 were essentially identical other than camshaft.
May have had minor differences in carb or distributor, but the "real" difference was cam.
May have had minor differences in carb or distributor, but the "real" difference was cam.
Intake, carb, and headers/2.5" mandrel bent exhaust and a performance ignition curve will pull more power out of the existing combo. Try of perf rpm with 3310 750 vac sec. Auto or stick car? If auto, a little more converter will help it out of the hole-- 2200-2400rpm stall. Alot to be gained without removing the front cover.
Sent from my Autoguide iPhone app
Sent from my Autoguide iPhone app
I think a Crane Energizer 272 216 duration @ .050 with .515 lift might get you by without changing anything possibly. I don't know how old your valve springs are so you need to pay attention to that on a cam change. I forget what lift you can have before cutting the valve guide bosses down. If you don't have that done your retainers will come crashing down on them and probably break push rods, rockers and such. The stock 350 hp cam was around 460 lift on intake and 480 on exhaust and your stock 325 is around .398 lift. If it has the Q-JET leave it on there. With the amount of power your wanting to get it will supply the fuel you need.
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