1970 impala needs more power - Impala Tech
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post #1 of 17 (permalink) Old 02-23-2013, 11:04 PM Thread Starter
 
 
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1970 impala needs more power

Hey everyone, I've got a stock 1970 impala with a 2bbl 350 and powerglide. It's a rough old beater but I like it a lot, just needs some more power. I'll swap the glide for a th350 but need help on the engine upgrade options. What's a good head/cam choice while keeping the stock bottom end? I've seen plenty of used heads on Craigslist, everything from vortecs to iron eagles, just not sure what to run. Whatever will make the best tq/hp, be reliable and not totally outragous on fuel. Probably asking too much but thought I'd see what you guys thought. I've also picked a 4bbl qjet for cheap I'd like to use as well. I plan on driving the hell out of it this summer!

Thanks!
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post #2 of 17 (permalink) Old 02-23-2013, 11:24 PM
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Vortec heads, Edlebrock Performer to match, Q jet will bolt right on. You should be able to find everything used if you are patient.

Two doors, four doors, wagons, and ragtops.
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post #3 of 17 (permalink) Old 02-24-2013, 12:05 AM Thread Starter
 
 
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Thanks! Any input on a cam?
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post #4 of 17 (permalink) Old 02-24-2013, 02:22 AM
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Welcome to the Team Greg!

You are going to be looking at the RV page of your favorite cam companies catalog for a cam. Your '70 isn't the lightest car Chevy ever made.

Have you considered a 454 big block short block out of a late eighties early nineties pick-up truck. Then you could bolt on some pre-1975 (the dreaded peanut port was introduced in 1975) oval port heads and an aluminum intake topped with a 750 vacuum secondary carb. Grab the TH400 while you at the yard because even a peanut port truck engine is going to break a TH350.

A big block is what you are looking for to make your barge into a Corvette (named for the highly maneuverable lightly armed escort ship that is smaller than a destroyer).



If a BBC is too chalenging to consider think about a direct replacement SBC 400 that was created by Chevy just to move your car and light pick-ups around in the eraly seventies.

Big Dave
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post #5 of 17 (permalink) Old 02-24-2013, 09:26 AM
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Changing out that powerglide will make a world of difference
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post #6 of 17 (permalink) Old 02-24-2013, 12:00 PM
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A few points to ponder while thinking of your upgrade. Two things have rescued the American V-8 from oblivion. The first was the overdrive transmission introduced in 1985 to improve gas mileage.

The benefit of an overdrive transmission is two fold. The first gear is lower than that found in a traditional three speed or a two speed. By making the first gear ratio a 2.74 or 3.06 to one it triples the engines torque to get the car rolling faster. By using a 0.30 or a 0.33 to one final drive ratio you cut by a third, the final cruise RPM there by saving gas and engine wear. Finally the use of a lock up converter eliminates the inefficiency of an automatic that used to constantly slip reducing parasitic drag by up to ten percent.

Here is a description of the various transmission options you have from Chevrolet:

http://www.chevyhiperformance.com/te...e/viewall.html

The second big thing was EFI or Electronic Fuel Injection. It was put in place to reduce emissions as required by law. Now most old car guys balk at the idea of EFI under the hood of their early iron and I do not blame them. I am a carburetor guy myself and EFI is an anathema. But along with computers and fuel injectors came computer modeled heads and intake manifolds that maintain a high air speed without sharp bends that place the air fuel charge into the cylinder efficiently. That measured amount of fuel to air that was injected can now be mixed by the new heart shaped combustion chamber and burned cleanly. The unanticipated side benefit of a clean burn is more power.

From the efforts of millions of dollars in research and design work by hundreds of mechanical engineers at GM's motor division we have some of the best small block Chevy cylinder heads ever made by the factory. Ten to fifteen years ago not even the aftermarket could touch them in terms of making power at 0.450 inch of valve lift or below (where 85% of all cams are ground).

However lately the after market has caught up with their blatant copying (called reverse engineering by lawyers) of the features that these Vortec heads had to offer. Today you can buy an aftermarket head with the same "Quick Burn" heart shaped combustion chamber, the same tall thin intake ports of the "Vortec" head, and the same raised "D" shaped exhaust ports that Chevy invented and used on the ZZ4 350, without the 0.480 inch lift limitation of the stock head.

Cams have improved greatly to reflect the improvements made in heads (the two are complimentary and neither will work well if the one doesn't match the characteristics of the other). Starting in 1987 all Small Block Chevy engines were equipped with a roller cam. Prior to this a roller was an expensive race only component that drivers talked about as a status symbol at car shows. The addition of the roller changed the possibilities available to cam grinders. Lobes that where previously thought to be far to too aggressive became common place with the availability of roller tappets.

Because all production cars have used roller cams since the mid eighties the oil companies stopped adding metal supplements to motor oil (principally Zinc and Phosphate) that prevented wear when you had steel parts riding on cast iron. They were removed to save money and because there was a remote chance (if all the planets aligned and it took a bad bounce) of polluting the catalytic converter found on all cars since 1973. This is of concern to those who own old flat tappet equipped cars like yours because without DZZP in the oil your cam will quickly wear out and destroy the engine in the process (filling the motor with metal filings as a bad lifter becomes a hardened steel tool turning down the cast iron cam lobes as the cam rotates). Because of this you have to add DZZP to your oil at every oil change or convert over to a roller cam on your next cam purchase.

Big Dave

Last edited by Big Dave; 02-24-2013 at 12:16 PM.
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post #7 of 17 (permalink) Old 02-24-2013, 03:15 PM
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Quote:
The first was the overdrive transmission introduced in 1985 to improve gas mileage.
OD was introduced in 1981 in GM RWD.

Two doors, four doors, wagons, and ragtops.
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post #8 of 17 (permalink) Old 02-24-2013, 07:20 PM
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Quote:
Originally Posted by jayoldschool View Post
OD was introduced in 1981 in GM RWD.
True Buick had the 200R4 well before the first Chevy getting the 700R4 in 1985.

Big Dave
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post #9 of 17 (permalink) Old 02-24-2013, 07:45 PM Thread Starter
 
 
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Thanks for the reply Dave. I'd love to toss a big block in but really want to keep it simple and avoid as much downtime as possible. I've got a history of going overboard and spending more time wrenching than driving and want this to be the opposite. Was thinking I'll do the tranny first then pick a weekend to do the heads/cam/intake/carb. Leaning towards stock vortecs.

Might consider the 200/700r4 over the 350. I'm guessing mileage would be better.

Anyone have YouTube videos of their impala ripping around with vortecs heads?
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post #10 of 17 (permalink) Old 03-03-2013, 10:27 PM Thread Starter
 
 
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Well guys I came across a 358 hobby stock motor that I just couldn't pass up. It's got eagle crank/rods Keith black flat top pistons, mild comp cam and stock vortec heads. Compression is 9:5:1 I need to find an intake and carb for it yet. Any suggestions? Also picked up a th350 for next to nothing.

I have a few questions:

Can I reuse my flywheel and tq converter from my stock setup?
This motor has one of those larger 7 qt pans with a kickout, will it fit in the impala?

This is pretty much an opportunistic budget build. So much for the heads cam idea, hopefully this is an easy swap for me. I'll try and post some pics of the old beast soon!
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post #11 of 17 (permalink) Old 03-03-2013, 10:56 PM
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Even though what you have will bolt up (flex-plate and the torque converter out of the PowerGlide), I never, ever reuse a torque converter. They are too cheap to get a clean new one to slap into the tranny. The flex-plate I would replace with an SFI version for a few bucks more as they are a lot stronger than the stock ones.

The kickout oil pan should clear your chassis without any issues (only problem might be headers being close to the pan).

I recommend a VORTEC version of Edelbrock's RPM Air Gap intake manifold and a 650 or 700 cfm Holley carburetor with vacuum secondaries. You can frequently find a running used Holley 650 for around $50 and rebuild it for another $30.

Big Dave
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post #12 of 17 (permalink) Old 03-04-2013, 08:20 PM Thread Starter
 
 
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Thanks Dave, I'll go with those items. Now for some pics of the old beast!

I'm gonna dig out the cam card and post it up later tonight, hopefully someone can describe how it'll behave.

Thanks!
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post #13 of 17 (permalink) Old 03-04-2013, 09:09 PM Thread Starter
 
 
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It's a custom comp cam, how would you describe it based on the cam card?
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post #14 of 17 (permalink) Old 03-04-2013, 11:31 PM
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That cam has a lot of overlap in my opinion for a Vortec head. You do not need it, and it actually hurts your motor's bottom end performance to have the valve off the seats for so long a period of time (242 degrees @ 0.050" of valve lift is the duration which is a measure of valve dwell, or time the valves are open).

In the old days (thirty to forty years ago) you needed a lot of duration because the heads were poor at moving air compared to today's computer designed heads. The lift is limited in a Vortec head to 0.480" at the valve with a 1.5; ratio rocker (it jumps to 0.512" if you use a 1.6:1 rocker). I am assuming this cam was designed for a roundy round car running Vortec heads (the LSA is 106 degrees which is also pretty tight and favors high RPM operation). It is designed to be installed straight up at 102 degrees which is normal.

Big Dave
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post #15 of 17 (permalink) Old 03-11-2013, 10:14 PM Thread Starter
 
 
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Should be interesting to see how it gets around. Thanks again for all your responses. I just started a new thread in the drivetrain section, hopefully I'll see ya there!
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post #16 of 17 (permalink) Old 05-10-2013, 07:49 PM
 
 
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Just going cheap and external (and keeping the original motor with very little teardown), changing over to a 4bbl carb and adding exhaust headers/dual pipes would make a decent difference. Other old school tricks such as a fuel line "cool can", adjusting the timing a little, hotter ignition coil, flex or clutch fan would squeeze out a couple more horses.
If you have the money, as previously mentioned, Edelbrock has good matched heads/cam packages.
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post #17 of 17 (permalink) Old 05-23-2013, 11:07 PM
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LSx swap.. Toss a carb on it or LS6 intake and ls6 cam, headers, tune and you'll be close to 400whp..

-1970 Impala: LSx/th350/12bolt/4:10
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