1968 300 camshaft questions

brunickw

brunickw

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Im new on here, so I have been searching and searching looking for a good camshaft that I would like. I think I might have it narrowed down to two. Either the XE275HL, I have been reading a lot about that one, and comp cams recommended the PP280H. Which one would you guys think? Its going in a 440, its got a pertronix distributor, edelbrock performer intake, holley 750 carb, stock convertor right now but can upgrade, It has the stock 3.23 ratio but I think im gonna go a little lower. Its got the stock heads on it right now but I plan on upgrading them sometime. Im looking to have a good lopey idle, not going to race it so i think the rpm range is fine with those two cams? Any input will help.
Thanks
 
Both cams are too aggressive for a big heavy car.
Too gassy and always have to keep the RPMs up.
68 440's have ZERO deck height at 10:1 compression.
Too much overlap and you lose compression.

You need torque to get moving.
Best to go with the Comp Magnum 270H (part # 21-306-4)
Largest cam that will still work with 750 carb,stock heads with stock rocker arm and stock convertor and have a noticeable idle.
You will need the complete kit with matching valve springs.

Alternate choice is the High Energy 268H cam. (# 21-215-4)
Really good torque band through all RPM ranges.
Both cams will work great with a light stall 2300-2500 and 3.23 gears. Even 2.94 works with both.
Very popular cam choice with minimal fuss.

hope this helps.
 
cbarge said:
Alternate choice is the High Energy 268H cam. (# 21-215-4)
Really good torque band through all RPM ranges.
Both cams will work great with a light stall 2300-2500 and 3.23 gears. Even 2.94 works with both.
Very popular cam choice with minimal fuss.
hope this helps.
Click to expand...
The Extreme Energy 268 is as close as you'll get to using the old Road Runner cam without putting one in. Good Luck
 
When I had my 68 NYer with 440 I installed the Mopar Purple cam shaft 260/260.
Worked great with stock convertor,750 carb,Pertronix ignition,3.23's and TTi 2.5 exhaust system
DSC01432.JPG

DSC01433.JPG
 
brunickw said:
Im new on here, so I have been searching and searching looking for a good camshaft that I would like. I think I might have it narrowed down to two. Either the XE275HL, I have been reading a lot about that one, and comp cams recommended the PP280H. Which one would you guys think? Its going in a 440, its got a pertronix distributor, edelbrock performer intake, holley 750 carb, stock convertor right now but can upgrade, It has the stock 3.23 ratio but I think im gonna go a little lower. Its got the stock heads on it right now but I plan on upgrading them sometime. Im looking to have a good lopey idle, not going to race it so i think the rpm range is fine with those two cams? Any input will help.
Thanks
Click to expand...

I recently installed a rebuilt 440 in my '66 300 convertible. The cam I selected was a higher torque Comp Cam. The cam specs are here:

21-222-4(Single Bolt) - Xtreme Energy™ Hydraulic Flat Tappet Camshafts

I have fantastic throttle response and good vacuum. I'm running stock carb, 3.23 gears and stock converter.
 
Last edited:
Thanks for the help guys, I thinking about going with the 270H, 268H or the XE268H now. I seen that CBARGE said I will need valve springs with the 270H. What about the 268's? I would rather not change the valve springs now if im gonna go to different heads in the future. I was thinking some kind of aluminum heads unless you guys think I should put some money into mine. Im not sure on the head casting numbers on the stock ones now.
 
brunickw said:
Thanks for the help guys, I thinking about going with the 270H, 268H or the XE268H now. I seen that CBARGE said I will need valve springs with the 270H. What about the 268's? I would rather not change the valve springs now if im gonna go to different heads in the future. I was thinking some kind of aluminum heads unless you guys think I should put some money into mine. Im not sure on the head casting numbers on the stock ones now.
Click to expand...
What springs are on your current heads? Performance cams should use new matching valve springs or something comparable in specification.

The XE cams have faster opening and closing rates than non-XE cams of comparable lift, so they produce smoother idle and better vaccuum. You need to ensure there is enough spring pressure to prevent valve float (lifter not following the cam lobe on the closing ramp) at all RPMs that the engine will be operated at.

When I got my Edelbrock heads, I checked with Comp to confirm that the springs that came preinstalled on the heads would be compatible with the XE268H cam.

My convertible has a 383. I used a Comp High Energy 256H I think, and new Mopar "HP" springs on 516-casting iron heads.
 
They are just the stock springs on them, the motor has never been into other that changing the intake, dis, and carb. I will get casting numbers off the heads when I get a chance to open them up.

So Im thinking maybe the XE268H would be a decent one? Then I was doing some more research and I think the lifters would be the COMP Cams High Energy Hydraulic Lifters 822-16, and the Springs would be the COMP Cams Valve Springs 911-16. Does anyone know if this would be the correct setup? I heard that the heads wouldn't need machining with those springs and I could use the stock rockers and pushrods with those lifters?

Thanks
 
I did see the notes, that's why I was concerned. That's when I started searching about that camshaft on the forum. Comp recommends their 924-16 valve springs which will require machine work, guys on here were telling people who had the same questions as me to use the 911-16 springs because they don't require head work and will work fine with that cam and application.
 
muh build sheet says 822-16 lifters and 924-16 springs it says regrind crank, honed, resize rods, balanced, resurface heads - i dunno what machine work you heard tell of but thats whats listed on my ticket. this is the 1st and only motor ive ever had rebuilt so i dont know whats SOP and whats not.

https://www.waynecalvertengines.com/history

wayne calvert built my motor. local texas boy done good.
 
The XE268 sounds like a good cam. For your application I wouldn't go any bigger.
The 911-16 springs are single springs and 925-16 are double springs, the double springs need the spring pocket machined larger around. I would use the single springs.
The 504-16 seals are standard umbrella seals, the 505-16 are positive stop seals and require the guide to be machined for seal fitment. Standard seals are good for your application.


21-223-4(Single Bolt) - Xtreme Energy™ Hydraulic Flat Tappet Camshafts
 
brunickw said:
They are just the stock springs on them, the motor has never been into other that changing the intake, dis, and carb. I will get casting numbers off the heads when I get a chance to open them up.

So Im thinking maybe the XE268H would be a decent one? Then I was doing some more research and I think the lifters would be the COMP Cams High Energy Hydraulic Lifters 822-16, and the Springs would be the COMP Cams Valve Springs 911-16. Does anyone know if this would be the correct setup? I heard that the heads wouldn't need machining with those springs and I could use the stock rockers and pushrods with those lifters?

Thanks
Click to expand...

Just go ahead and get the entire kit. Yer gonna need most of the stuff in it anyway. That way you'll have compatible components and no worries.
 
Ok now that I have the cam figured out, I have some exhaust questions. I wanna change the exhaust because it hangs down to low and the previous owner had someone do it for him and none of it was done right. They used 3" into flow masters and then dumped it right before the rear axle, and they welded the pipes directly to the stock manifolds, and there is no x or h pipe underneath. I have been reading to go with either some stock HP manifolds or go with some headmen shorty headers. After the manifolds or the shorty headers the local exhaust shop is going to finish the exhaust all the way back from them. And I know I will need the mini starter for the headers.
 
Where do you guys think I should be at for timing for this camshaft? I have read anywhere between 10-15 BTDC, does this sound right? Its the XE268H
 
brunickw said:
Where do you guys think I should be at for timing for this camshaft? I have read anywhere between 10-15 BTDC, does this sound right? Its the XE268H
Click to expand...
Give it all that it can handle without pinging under acceleration. Mine with a older Hughes 3032 cam likes it at 14*, it wants more but will ping. Good Luck
 
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