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Question for you camshaft gurus

I would disagree as he asked for the Maximum. For that figure, it's all relative, but I would put it about 9:1 or 9.5:1 IMHO
 
Whats your altitude, and what brands do you have out there? There can be a significant difference brand to brand. Im guessing mid 9's. Check the factory cam and compression ratios of the 69 RB big block c bodies. Low lift, low duration, moderate compression. Add to that the advantage of a modern rebuild. Technology and parts have come a long way.
 
To me that's to small, that's even smaller that what Mopar put in 440's originally. I would at least go with the XE268 as that's really close to what Mopar used. Good Luck
 
This cam is probably well suited for 8-8.5:1. Don't be fooled by the lift and duration numbers because that's not even close to giving you the whole picture. The valve events on this cam are sure to be much different than stock and will likely boost cylinder pressure so your CR can't be too high or it will ping. My guess is this cam will give you excellent off idle power that can only be enhanced with a set of headers as well as superb drivability in general. Factory carb (TQ?) and intake will be great - and cheap.
 
that xe250 cam closes the intake valve at 51 degrees ABDC. very early. in fact 7 degrees earlier than the factory 256 cam that was used in 361 2bbls. the engine will make too much cylinder pressure with 9:1, pump gas, and towing with that cam.
 
9.0-1 is pushing the issue. Quality of fuel is another issue. If you push the ratio, the need for a higher octane comes into play. You are much better off staying at 8.0-1 so you can use 87 octane without any issue what so ever.
 
69a100 said:
To me that's to small, that's even smaller that what Mopar put in 440's originally. I would at least go with the XE268 as that's really close to what Mopar used. Good Luck
Click to expand...

I just put a XE268 in the 67 GTX 440 I just picked up.
 
all of those short duration comp cams hydraulics, magnum/xe/or whatever, close the intake valve too soon. comp in their "infinite wisdom" grinds 4 degrees of advance into these cams, whether they need it or not, and they're all ground on 110 lobe centers. they're not good 440 cams. maybe 383 or less.
 
lewtot184 said:
all of those short duration comp cams hydraulics, magnum/xe/or whatever, close the intake valve too soon. comp in their "infinite wisdom" grinds 4 degrees of advance into these cams, whether they need it or not, and they're all ground on 110 lobe centers. they're not good 440 cams. maybe 383 or less.
Click to expand...

i beg to differ on that opinion, but each to there own, the XE series are way better then the MP cams.

at the end of the day, you dont really need to target a compression ratio, you need to target cylinder pressure.

for any cam in a pump gas 440 with iron heads, 160 to 170 psi is the goal, the trick is figuring out what you need to do to get it.
 
mentor70 said:
i beg to differ on that opinion, but each to there own, the XE series are way better then the MP cams.

at the end of the day, you dont really need to target a compression ratio, you need to target cylinder pressure.

for any cam in a pump gas 440 with iron heads, 160 to 170 psi is the goal, the trick is figuring out what you need to do to get it.
Click to expand...
an iron head 440 won't blow 160-170psi with those short cams, unless the comp ratio is down around 8:1. a 9.3:1 440 i have blew 195psi with one of those short cams. too high for reliable pump gas use,very short winded, and believe it or not the mopar 272-.455 out performed it. those cams are worthless.
 
Call the cam tech at comp. They don't want you disappointed in their product. Then find a similar grind from another company and get their recommendation for cylinder pressure/comp ratio.
 
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