Rebuilding a 307 - Impala Tech
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post #1 of 7 (permalink) Old 03-07-2013, 06:08 PM Thread Starter
 
 
Join Date: Sep 2010
Location: Edmonton
Posts: 29
 
Rebuilding a 307

Hi Team Impala,

Well I took about a year off from my 1968 4 door HT Impala to get hitched to a very special lady (that went smoothly but really put a damper on my car fund money!), but now that it's done, I can get back at it!

I was originally going to swap in an LS motor, but have since decided that the modified drive shaft, new tank, mounts, etc., plus the cost of the motor itself, would be prohibitive in both costs and time. I have visions of driving this gloss black beauty to Vegas next year so I gotta get going!

The car came stock with a 307 pumping out a BLISTERING </sarcasm> 200 HP. The more I read about these 307s the more I realize that they aren't a bad engine (they are a stroked 283) but they just don't breathe very well.

A lot of folks have had luck swapping on Vortec headers from a late-model chevrolet truck, adding a different cam, and some headers -- and gaining significant horsepower -- 270 +, which is adequate for my build at the moment. That is what I want to do as all of those upgrades are within my time and budget.

A bit about the build:

1) I don't care at all about numbers matching for this car -- it is my first and is a 'learner'.
2) I want to drive it on long trips -- fuel economy matters.


So, my question is this:

1) Which Vortec heads should I be looking at (i.e. what are good source vehicles? Does it make a difference if I pull them off the 305 or the 350 (5.0 or 5.7L))
2) If I'm going to a scrapyard for the Vortec heads, whats stopping me from using the whole Vortec engine and benefiting from a newer, more powerful 5.7 Liter Vortec 5000 -- as in, can this be carboreted and will it drop in without too many problems with fuel, drive shaft, etc. that you'd get with the LS?

I've found conflicting knowledge on the above, and this will be my first time tearing down an engine so I want to be as sure as I can be.

I leave these two questions to the god-like knowledge of Team Impalas. Ritual sacrifice to follow

Cheers
Craig
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post #2 of 7 (permalink) Old 03-07-2013, 08:47 PM
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Craig you have the correct idea. Buy a 5.7 liter 1996-'01 pick-up truck motor. That way you get the last generation of Vortec heads (there were three castings some using pressed in seats others using flame hardened seats). Earlier heads have a bad rap of cracking (but I attribute that to poor maintenance more than a poor design).

All you would need to bolt it in is a car oil pan as the truck oil pan won't fit in your chassis. You will also need to get it running is a Vortec carburetored intake manifold, a 600 cfm vacuum secondary carburetor (notice I don't recommend one brand over another) and a small cap aftermarket HEI distributor to get the car running. To enjoy the full benefits of the motor you want a hydraulic roller cam that is limited to 0.480 inches of valve lift and 210 or less degrees of duration measured at 0.050" valve lift. A set of Headman or Flowmaster headers should maximize your fun.

The 307 has value if and when you sell the car (as it is the "Born With" motor that might interest a museum curator), so I recommend draining the fluids and bagging it to keep out moisture. Store it away for some future day.

Big Dave
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post #3 of 7 (permalink) Old 03-07-2013, 10:35 PM
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Location: Lewisburg, Ohio
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The flexplate on the later 350 is different as that motor has a one piece rear main seal. Also I doubt it will have a provision for a manual fuel pump.
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post #4 of 7 (permalink) Old 03-07-2013, 11:26 PM
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Quote:
Originally Posted by dadstoy View Post
The flexplate on the later 350 is different as that motor has a one piece rear main seal. Also I doubt it will have a provision for a manual fuel pump.
Both true but easily remedied.

I never use a mechanical fuel pump because the pump is the same temp as the oil, or about 240 degrees. I don't want that heat going into the fuel as cooler air and fuel makes more power. The flex plate is eight bolts to replace and I always recommend a SFI part as even a flex plate can explode (especially if it is cracked by excessive flexing).

Big Dave
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post #5 of 7 (permalink) Old 03-08-2013, 01:45 AM Thread Starter
 
 
Join Date: Sep 2010
Location: Edmonton
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Thanks very much for the information, Big Dave and Dadstoy!

One more question for you -- for Transmissions, if I keep the 307 I was going to go with the 200 R4. If I go with the Vortec 5000 with the car oil pan, would that same trans be a good bet? Or should I pull the truck transmission also?

Regards
Craig
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post #6 of 7 (permalink) Old 03-08-2013, 08:00 AM
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You would need to retain the EFI to use the overdrive 4L65e that the truck used (there are much better EFI systems than the TBI which is basically just an electronic carburetor). If you want EFI the long runner sequential fire TPI off of a 1989-'91 L98 Corvette (the Camaro used a 305 motor which is not going to be able to feed a 350).

The 200R4 will work with the 5700 Vortec motor just fine once it is carburetored and given an HEI distributor.

Big Dave
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post #7 of 7 (permalink) Old 03-08-2013, 11:42 AM Thread Starter
 
 
Join Date: Sep 2010
Location: Edmonton
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That makes my day -- I just found a 200R4 out of an allegedly well-running Monte Carlo for 300 bucks, I'm going to try to jump on it before someone else does. I figure even after a Master Rebuild I'll still be ahead for that kind of money.
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