Looking for direction and info to upgrade 327 - Impala Tech
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post #1 of 8 (permalink) Old 10-25-2015, 09:18 AM Thread Starter
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Looking for direction and info to upgrade 327

I have a 65 Impala with a 327. I'm keeping it mainly stock inside with stock crank boring it 30 over but putting a hydraulic roller cam in it.
I'm looking for some information on going to a fuel injection system and also an electronic ignition.
Can someone point me in the right direction on what items are needed and the processes?
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post #2 of 8 (permalink) Old 10-25-2015, 01:58 PM
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You build the 327 just as if you where going to put a Holley crab on top of the motor (except your cam choice is limited by the fact that you can not use a long duration cam or one with a short LSA), only you substitute a Throttle Body Injection unit in place of the carburetor. You use a stand alone HEI as it will not be controlled by the engine control unit the way it would be on a port injected EFI motor as there are not enough sensors or software to complete the conversion to EFI beyond the electronic carburetor that is a TBI. The only three sensors a TBI uses is manifold vacuum, water temp and a narrow band oxygen sensor. In some models the TBI senses manifold vacuum and temp needing only an added oxygen level sensor in the exhaust just by bolting on the TBI. These models also include the EPU right in the TBI body. The only other change is the requirement of a higher pressure electronic fuel pump placed in your gas tank.

I see no real gain going TBI over a carburetor other than the slight increase in fuel economy at the expense of performance. Converting over to a LS-3 5.3 liter (324 cubic inches) fully evolved EFI motor makes sense to me if you want the full benefits of computer control of your engine (ignition spark advance control, fuel air ratio control and variable valve timing plus displacement on demand where it converts from a V4 to a V8 by stepping on the gas pedal). A 5.3L or better yet a 6.0 liter out of a truck, or the newer 7.0 liter LS engine out of the Corvette has fourteen computers and twenty three sensors sampling the engine ten times faster than the speed of the piston. TBI is nothing more than a glorified electronic carburetor.

Big Dave
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post #3 of 8 (permalink) Old 10-25-2015, 09:40 PM Thread Starter
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Well that's the kind of input I'm looking for Dave...thanks!
One question though, you said not a long duration cam? Did I already limit myself by going with a hydraulic long duration cam?
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post #4 of 8 (permalink) Old 10-25-2015, 10:09 PM
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TBI and EFI if it uses a MAP (Manifold Air Pressure) aka vacuum sensor are limited in their sensitivity. Hot EFI set ups as found on the Corvette and Camaro use a MAF (Mass Air Flow) sensor to measure the volume of air being sucked into the motor to calculate the time setting for the injectors to stay open. If you use a long duration cam with a TBI it thinks you are running at WOT while the motor is actually at idle and dumps in way too much fuel due to low manifold vacuum due to a long duration cam. A EFI or TBI cam usually has an LSA of 114-116 degrees. A hot carburetor can will have an LSA of 108 or 110 degrees. (Oh as I read what I just wrote I forgot another sensor used by both TBI and EFI rely on: a throttle position sensor (TPS), that tells the computer if you foot is in it or not, or if the car is at idle, or anywhere in between).

Shortening the LSA increases the amount of overlap which means both valves are off the seat at the same time for a longer period of time. This plays all (nether region) with the MAP sensor and confuses the computer which is being told one thing by the MAP sensor and another by the Oxygen sensor and yet a third by the TPS. (hot EFI cars also rely upon a wide band oxygen sensor that can more accurately measure the amount of oxygen that has gone through the motor without combining with a carbon atom), than the older narrow band oxygen sensors do.

You are restricted to very few if any cams other than stock TBI profiles with a TBI set up. You can look on the cam pages in the catalog and look for a grind that works with a TBI and then compare that grind to a carburetor cam. There is no rumpitty rump rough idling cams available for a TBI motor. The computer would roll over and put itself in limp home mode. (think of the commercial with the young mother with her daughter in the their Japanese station wagon crawling down main street a 12 mph with cars behind her honking their horns as she apologizes to them. Then the very young daughter says "^%$(&^@## sensor" to the tech at the service center when the car is finally fixed. That is an example of limp home mode, and the fact that kids pick-up the strangest things!)

Big Dave

Last edited by Big Dave; 10-26-2015 at 10:01 AM. Reason: thick finger typo removed
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post #5 of 8 (permalink) Old 10-26-2015, 07:52 AM Thread Starter
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That makes sense to me. I have already begun on my motor and its prepped for the hydraulic roller cam. I like what it will do for me and am satisfied with the carb set up after your comments.
Any in put on going to an electronic ignition? I would like to get away from the points etc.
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post #6 of 8 (permalink) Old 10-29-2015, 11:37 AM
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Just buy a Summit brand HEI, they work great and very cost effective. no need for MSD box and all that unless you are racing.
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post #7 of 8 (permalink) Old 11-02-2015, 05:57 AM Thread Starter
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That looks pretty good to me. I think I was over complicating it. Thanks
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post #8 of 8 (permalink) Old 11-08-2015, 07:53 PM
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Just grab a HEI out of a older rig 74 up run a new 12 gauge + wire and roll on .If you want it to look like a stock dist. get a Pertronix unit .
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