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Old 07-15-2012, 04:54 PM   #1 (permalink)
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legitimate suggestions? performance increases?

I've had my car since high school(im 27). It's a 1970 Impala with a small block 400 that has been rebuilt and fitted with an Edelbrock intake, carb(1406), and cam(2103). Headers, dual exhaust, and an old HEi that does now have 12 volts going to it.The original TH400 is in it and has been rebuilt. I guess my question is for the experienced drive train builder. I know little about heads and rear end gears. Heads are stock and so is the rear end.any cheap upgrade ideas? also does anyone have any idea what hp i may be getting currently?comments about a similar application welcome as well. Thanks in advance.

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Old 07-15-2012, 08:32 PM   #2 (permalink)
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Hard to say, alot depnds on what was done during the rebuild. What comp. ratio you are running etc, etc, ... top HP for a stock '70 400 was 265...at the flywheel. You are probably a little over 300. Again, depending on the rebuild, and since I assume it's running, than the heads would probably like some new springs & some roller rockers, maybe go up to 1.6. rearends are not cheap...period, but a gear change & a good T. convertor in that TH400 would wake it up a bit. A 700R4 would be a better yet upgrade.

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Old 07-16-2012, 10:03 AM   #3 (permalink)
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I would also dump the HEI for a solid state unit. Some reuse the stock housing

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Old 07-16-2012, 11:17 AM   #4 (permalink)
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Wtf? Why would you change out the HEI? As shaft driven distributors go, you can't really do any better.

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1978 Caprice Classic Landau
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Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
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Old 07-16-2012, 01:38 PM   #5 (permalink)
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Wtf? Why would you change out the HEI? As shaft driven distributors go, you can't really do any better.
Agreed.

Find out what your axle ratio is (stamped on passenger side axle tube facing front of car) and let us know. I just switched my 3.07 gears for a set of 3.73 gears and swapped out my powerglide for a 200-4r in my 65 SS.

Dollar for dollar, a rear end swap can be hard to beat if you are in the 2's right now. If you do much highway driving, an OD tranny would also be a good call.

As far as heads go, a nice set of vortecs (with correct manifold) can add almost 40hp off the bat with your current setup, and not too expensive. This also might be a good option for you.

-Nick

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Old 07-16-2012, 08:30 PM   #6 (permalink)
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no i just meant that when i replaced the original distributor with an hei i changed the main power to 12v as opposed to the resistance lower voltage wire that comes stock with the original. is this not a good thing? is HEI not preferable to the original? and i could not find the ring gear stampings where you suggested. ill look again though.

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Old 07-16-2012, 08:38 PM   #7 (permalink)
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Quote:
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As far as heads go, a nice set of vortecs (with correct manifold) can add almost 40hp off the bat with your current setup, and not too expensive. This also might be a good option for you.

-Nick
I don't think you can bolt Vortec's on to a 400 without drilling some some steam holes in them. IIRC that was a big issue BITD when guy's would throw a set of heads on a 400 from another SB engine, they would crack.

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Old 07-17-2012, 08:29 AM   #8 (permalink)
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Quote:
Originally Posted by kingnutin View Post
Wtf? Why would you change out the HEI? As shaft driven distributors go, you can't really do any better.
Change it out to one with external coil, more spark.
Yes as stock units go the HEI was one of the better one.
Sorry for the confusion.

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Old 07-17-2012, 11:20 AM   #9 (permalink)
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I don't think you can bolt Vortec's on to a 400 without drilling some some steam holes in them. IIRC that was a big issue BITD when guy's would throw a set of heads on a 400 from another SB engine, they would crack.
Yea, you are correct. Any heads besides the 400 heads will need the steam hole provisions drilled, which is why 400's get a bad rap for overheating.
Almost every good machine shop can make these adjustments to the heads.

-Nick

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Old 07-17-2012, 04:11 PM   #10 (permalink)
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You will not need more spark than an HEI provides, leave it alone, anything else is wasting money.

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1978 Caprice Classic Landau
350 2-bolt, stock 4bbl
Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
4 wheel disc brakes!
16x8 American Racing Baja's with 225/60/16 Pirelli P4's

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Old 07-17-2012, 08:29 PM   #11 (permalink)
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I put one of these on my last 1st gen 355 that was pushing about 375 HP, made a big difference all around, but above 5500rpm & starting was alot better than stock.

http://www.summitracing.com/parts/SUM-850030/

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Old 07-17-2012, 08:58 PM   #12 (permalink)
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rock on i get it. but back to the rear end, mine is a completely stock 4 door's rear end. should i leave it alone? or is there more fun i could be having? within reason, im blue collar, and this is my daily driver

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Old 07-18-2012, 10:24 AM   #13 (permalink)
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Gregg, that's cool, but for another $20 you can get their entire distributor, which includes new bushings and pigtails, that's what I've been considering.

As for your rear end, it depends on what your current ratio is, you will only be able to go so low before you will need an overdrive and/or lock-up converter.

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1978 Caprice Classic Landau
350 2-bolt, stock 4bbl
Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
4 wheel disc brakes!
16x8 American Racing Baja's with 225/60/16 Pirelli P4's

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Old 07-18-2012, 12:18 PM   #14 (permalink)
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Gears and stall make for huge seat of the pants improvements but how much you can stand with a 3speed tranny meaning no OD and no lockup.

Actual power production is all about airflow. HP is all about burning fuel at the right air fuel ratio, getting more fuel in the cylinders is easy, getting more air in the cylinders to burn it is the hard part.


Edelbrock parts are often a genuine improvement over the OLD stuff like what you had stock BUT at the same time there is a LOT of room for improvement on the old stuff and Edelbrock does not take you as far as it could for the effort involved.

I mean the cam is single pattern, for a naturally aspirated gen 1 or even gen 2 smallblock that is a joke, these engines have always been comparably stronger on the intake side than exhaust which is why you will find most cams for them have more exhaust duration.

I understand using Edelbrock matching stuff to simplify emissions inspection, but at the same time nobody can see a cam during inspection.

Heads are a HUGE part of the HP equation since all the airflow in and out goes through them, heads would be a good place to look BUT I would probably stay away from Edelbrock, well made products that do not actually offer as much gain as they could. This is not to say go the other end of the spectrum and look at AFR either, they are FAR more marketing than anything else. I think the Vortec suggestion is decent, they are inexpensive and a lot of shops all over the country know how to make them work even better.

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Old 07-18-2012, 02:59 PM   #15 (permalink)
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thanks. i'll keep that in mind.

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