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Old 09-24-2012, 08:44 PM
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BBC Roller no bottom end

I have a 396 Roller motor in my 67 nova. I bought the car with this motor with a fresh build. I know it's a roller cam but have no specs. This motor sounds so damn mean, it has a pretty loopy idle. Anyway when I get on it it just doesn't have any low end balls at all. It has a great top end but even brake torqueing it just don't respond like it should. It has cast heads and a TH350 trans with a 2400 stall. I know it has a lot more any ideas?

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Old 09-24-2012, 08:49 PM
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Need to know cam and head specs.

I see a lot of guys over camming 396 engines and using 115-119 cc. big port heads on them. Makes for a bad drivability, turd.
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Old 09-24-2012, 08:58 PM
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Short of tearing it apart I don't have cam specs. The heads are pretty stock besides springs and roller rockers after about 2500 rpms it goes. I can say that for some reason there are days this motor responds pretty good but most days it's just flat at start.
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Old 09-24-2012, 09:09 PM
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It has a 750 DP holley with mec secondarys. it's an automatic with a 2400 stall. I'm just thinking wrong carb, wouldn't a vacuum secodary carb work better with they auto trans.
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Old 09-24-2012, 09:13 PM
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It really don't make sense to me to install a big roller cam with stock heads, heads are where the power is made. This is just a guess but I would almost bet that it has a Mother Thumpr cam in it. Those cams sound really wicked but they leave alot to be desired when it comes to performance. I have been told that with a proper tune, they perform fairly well but it takes a good tuner to get them there. There are retro fit kits available to install a roller cam into a standard block but a true roller cam will have roller cam bearings. Do you know what gear the rearend has? What intake and carb setup it has?
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Old 09-24-2012, 09:21 PM
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It has a 12 bolt 3.73 gears eaton posi diff,Edelbrock air gap intake with a 750 DP Holley. This motor has days it reponds fairly well but most days it's off, that's why I think carb. Would a Vacuum secondary carb be a better choice?
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Old 09-24-2012, 09:27 PM
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Quote:
Originally Posted by boobert View Post
It has a 12 bolt 3.73 gears eaton posi diff,Edelbrock air gap intake with a 750 DP Holley. This motor has days it reponds fairly well but most days it's off, that's why I think carb. Would a Vacuum secondary carb be a better choice?
A vacuum secondary carb would be better in my opinion IF the cam will allow sufficient vacuum to operate it. This may be one reason it has a mechanical secondary carb on it. You would need to check how much vacuum the engine has with that cam before changing the carb.
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Old 09-24-2012, 09:28 PM
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A BB with a little 750 X should go bananas even with a bigger cam.If on some days it seems better then its time to tune it.put plugs in it,take the bowls off the carb lets check the jets and timing at idle and total timing.Im sure you have a minor problem
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Old 09-24-2012, 09:31 PM
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It has the vacuum, from what I understand the 4150 mec carb shoud be used with a 4 speed or an auto with a stall of atleast 4000 rpm
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Old 09-24-2012, 09:35 PM
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a 750 double pumper is a small carb for a rat.you have minor issues,maybe lots of them.carb size or double pumper is not an issue
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Old 09-24-2012, 09:36 PM
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Quote:
Originally Posted by boobert View Post
It has a 12 bolt 3.73 gears eaton posi diff,Edelbrock air gap intake with a 750 DP Holley. This motor has days it reponds fairly well but most days it's off, that's why I think carb. Would a Vacuum secondary carb be a better choice?
Pull the carb and see if the intake is a single or dual plane. If it's a single plane, that could be your problem. You need a dual plane for low end torque. Does it have a carb spacer and if so, how tall?
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Old 09-24-2012, 09:42 PM
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No spacer would that help?
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Old 09-24-2012, 09:43 PM
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you have a bb,torque is not an issue,,,lol
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Old 09-24-2012, 09:53 PM
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you have a bb,torque is not an issue,,,lol
Regardless if a BB or not, with the wrong parts or setup, a torque monster diesel can be turned into a turd.
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Old 09-24-2012, 09:57 PM
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I wouldn't call it a turd but definitely something wrong.
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