Newp
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Last edited:
Big Block Into a Small Block Sub Frame
- Thread starter BDR529
- Start date
commando1
Old Man with a Hat
LMFAO!!!!!! No, let's not go there again...
commando1
Old Man with a Hat
Nope. Ain't gonna happen. I shouldn't have even mentioned the part about the heads.
BDR529
Member
I was considering running headers but it's my understanding no one makes a set of long tubes that fits. I know everyone says that any performance modifications done to a motor are useless if you don't let it breathe properly. Also better breathing equals better gas mileage. Has anyone every tried shorty headers on a formal?
BDR529
Member
Well I got the motor stripped down to a bare block today. Gonna talk to a few shops this weekend about pricing and suggestions. All things considered everything looks really good. The only problem I ran into was the two bolts that hold the rear seal in place. The head was stripped out on one of them and needed some "convincing" to break the torque. No stripped threads though so everything's clean. And, just for verification, the heads are in fact 452's. Next step, get the block cleaned and honed, figure out my camber CC's, and decide what to do about pistons!
has2bmopar
Senior Member
Put a little grease on your plug threads, and around your valves, then wipe off any excess. To seal the plexy glass, put a fine layer of grease evenly around the chamber. Block the head at an angle and put the outside hole right at the top edge of the of the chamber.
I would use the large syringe to get up to 80ccs, then use the small one to finish. Cleaning up your chambers will make a very small increase in volume, and if you deshroud your valves mildly, it may increase about 1/2 of a cc.
.
BDR529
Member
Just a small update, I climbed under the car and the little tab with the gear ratio is on it and it says 2.71. This number seems a lot lower than what everyone else was suggesting, and I have no reason to believe the gears have ever been changed out.
has2bmopar
Senior Member
I would start searching for a 9.25" differential with 3.55s.... 3.21s would not be the worst either if you keep your engine moderate.
I'm guessing that you have an 8.25" with the oval cover.
The 9.25" has a stop sign shaped cover.
I'm guessing that you have an 8.25" with the oval cover.
The 9.25" has a stop sign shaped cover.
commando1
Old Man with a Hat
He needs the whole rear drivetrain, not just the differential. He'll never find one from a c-body with 3.55's. He'll have to swap them in new or used from a Jeep or Dodge truck. 3.23's are only a little less rare. C-bodies w/factory installed tow packages more likely.
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BDR529
Member
So what are the benefits of 3.55's or 3.23's over the 2.71 I have now? And if I do need a new differential, what's interchangeable I see a lot of postings for rear ends out of newer Dakotas. Or are they interchangeable between older C Bodies like the 65ish Monaco or the fuseys?
commando1
Old Man with a Hat
First of all, unlike the idiots over at Moparts and they all chime in using the shotgun scatter approach, I like to get the right answer by asking the right questions first, one at a time.
And that first question is - which rear do you have.
Let's I.D. that rear first and from there we can move on...
And that first question is - which rear do you have.
Let's I.D. that rear first and from there we can move on...
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BDR529
Member
I counted 10 bolts and I would have to say an 8 1/4...
commando1
Old Man with a Hat
OK. Forget about putting in a 9 1/4. You're not going drag racing.
The lower the number - the higher in ratio.
The higher the number - the lower in ratio.
Lower ratio Pros: Faster acceleration and response to the throttle.
Lower ratio Cons: Revving like a bastard at highway speeds, running at higher RPMS, and gas economy sux.
If you have 2.71's and want to feel what 3.55's are like, simply drive around the city then the highway in second gear all day. You ain't going drag racing. You don't need higher gears.
All around compromise: 3.23's.
Can you get 3.23's for an 8 1/4? Dime a dozen. No problem. You may want to go new. Used ones have been grinding away for a looong time now.
All you need is to swap out the ring & pinion gears and use a master rebuild kit.
That being said (whew...) my argument is to stay with what you have. It's not a Roadrunner...
The lower the number - the higher in ratio.
The higher the number - the lower in ratio.
Lower ratio Pros: Faster acceleration and response to the throttle.
Lower ratio Cons: Revving like a bastard at highway speeds, running at higher RPMS, and gas economy sux.
If you have 2.71's and want to feel what 3.55's are like, simply drive around the city then the highway in second gear all day. You ain't going drag racing. You don't need higher gears.
All around compromise: 3.23's.
Can you get 3.23's for an 8 1/4? Dime a dozen. No problem. You may want to go new. Used ones have been grinding away for a looong time now.
All you need is to swap out the ring & pinion gears and use a master rebuild kit.
That being said (whew...) my argument is to stay with what you have. It's not a Roadrunner...
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has2bmopar
Senior Member
This would only be true on opposite day.
4.10 turns of a driveline to 1 turn of the wheel is a higher ratio than 2.76 to 1.
I think you are mixing street talk with actual ratios, as something with 4.10s would be referred to as a low geared vehicle and 2.76s as high geared, or tall geared.
Excellent guide to axle identification that you posted. Definitely should take the guess work out for those that aren't fluent in the older Mopars.
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commando1
Old Man with a Hat
You're right. My defintions were clear as mud. Hopefully, tween the 2 of us he gets the gist of the message.
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has2bmopar
Senior Member
I would expect that you will be beating on this car once in a while, and the 8.25" is not going to hold up to the torque of a decent running 440, ecspecially in a heavy vehicle, so I would recommend getting some measurements... axle flange to axle flange and leaf spring perch width.
The '69 -'73 C-body 8.75" may be another option, and I have a couple out that I can get measurements from for a reference. Many 1/2 ton pickups had the 3.21s and 3.55s in the 9.25" axle, and I can get an overall width measurement from one of these also, but you will certainly have to replace the spring perches, even if the overall width will work.
If you are settling on a cam that will work with your stock exhaust manifolds, and will be doing some interstate driving, I would go with 3.23s. If you will be doing minimal driving up to and over 65mph, and plan on headers and a bit larger cam, I would recommend 3.55s. Between this and Stan's discription, you should get the gist of how the different ratios will affect the drivability of your car and this will determine how you build your engine also.
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So, can you stick some decent gears in the 8 3/4? Somebody makes good aftermarket stuff for it?
has2bmopar
Senior Member
Tons of options for the 8.75"... I would check out Randy's Ring and Pinion.
I will, thanks.
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