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tbi to cpi

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Old 09-08-2008, 10:33 PM   #1
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tbi to cpi

my 4.3 is going downhill FAST!

different cylinders have different problems... half my engine is running too rich, the other half is running to lean, and ive got oil on 1 or 2 of the spark plugs...

its loosing power drastically by the day, and its making me sad hahaa!

so my questions is: easier to rebuild my engine, or pick up a 4.3L CPI and swap that in? what all would be involved in swapping to CPI? just a different wire harness? any and all help is appreciated guys, thanks!
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Old 09-09-2008, 06:06 PM   #2
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Re: tbi to cpi

Easiest would be to pick up a CPI and put your TBI heads and intake on it. Get a valve job done on the TBI heads while you have them out.
Old 09-09-2008, 06:31 PM   #3
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Re: tbi to cpi

yeah the cpi is shitty anyways, injectors go often

tbi is reliable, just bad head design (slow flow)
Old 09-09-2008, 07:18 PM   #4
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Re: tbi to cpi

Quote: Originally Posted by FxsX24
yeah the cpi is shitty anyways, injectors go often

tbi is reliable, just bad head design (slow flow)
so i was reading somewhere that the CPI had a better cam... can i use the CPI cam in my TBI truck to gain the extra ponies?

i like the idea of keeping my TBI (because i love it, easy to fix and shiz)

so what would be a good thing to do to my heads? could i get them ported so they flow better?
Old 09-09-2008, 08:09 PM   #5
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Re: tbi to cpi

Quote: Originally Posted by Golana
so i was reading somewhere that the CPI had a better cam... can i use the CPI cam in my TBI truck to gain the extra ponies?

i like the idea of keeping my TBI (because i love it, easy to fix and shiz)

so what would be a good thing to do to my heads? could i get them ported so they flow better?
If your TBI is a balance shaft motor, then yes, you can use the CPI cam. You can get the TBI heads ported but it's prolly going to be too expensive to make it worth it.
Old 09-09-2008, 08:42 PM   #6
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Re: tbi to cpi

Quote: Originally Posted by Yogi
If your TBI is a balance shaft motor, then yes, you can use the CPI cam. You can get the TBI heads ported but it's prolly going to be too expensive to make it worth it.

or get a tbi manifold for vortec heads ( or a 4bbl for vortec heads and a tbi adapter)
Old 09-09-2008, 08:47 PM   #7
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Re: tbi to cpi

Quote: Originally Posted by FxsX24
or get a tbi manifold for vortec heads ( or a 4bbl for vortec heads and a tbi adapter)
Good ideas!
Old 09-09-2008, 09:02 PM   #8
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Re: tbi to cpi

whats the point of a cam that is ment for a set of faster flowing heads, just to be slowed by tbi heads
Old 09-09-2008, 10:27 PM   #9
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Re: tbi to cpi

why dont you just put your tbi intake on a longblock cpi. they have same bolt pattern. now if newer 4.3 with csmfi (?) than you will need diff intake
Old 09-09-2008, 10:30 PM   #10
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Re: tbi to cpi

Quote: Originally Posted by S15vortecpwr
why dont you just put your tbi intake on a longblock cpi. they have same bolt pattern. now if newer 4.3 with csmfi (?) than you will need diff intake
did the cpi not have votrec heads?????
Old 09-10-2008, 12:49 AM   #11
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Re: tbi to cpi

Quote: Originally Posted by FxsX24
whats the point of a cam that is ment for a set of faster flowing heads, just to be slowed by tbi heads
thats why i asked about porting
Old 09-10-2008, 03:07 AM   #12
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Re: tbi to cpi

Which years had Vortec heads or how do you tell? Also where would you get a TBI Intake for Vortec heads(did chevy put TBI on a Vortec motor)?
Old 09-10-2008, 12:10 PM   #13
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Re: tbi to cpi

Quote: Originally Posted by stomperz71
Which years had Vortec heads or how do you tell? Also where would you get a TBI Intake for Vortec heads(did chevy put TBI on a Vortec motor)?
In 1992, Gm started building the CPI motor with "Vortec" on the intake manifold cover:


The heads were changed in '92 but then in '93 they were changed again for 10% more airflow. About this time, GM started putting "Vortec" on all valve covers, CPI and TBI. Here is a description of those changes:

Quote:
CYLINDER HEADS
There have been several cylinder heads used on the 262 since it began in ’85. Some of the changes appear to be minor, but most of them will create problems if the wrong head is used in the wrong place. Here’s an overview year by year:

1985-’86: The 1985 and ’86 engines used a 14079248 casting. It had two holes on one end and three on the other end.
1987-’91 TRUCK, EXCEPT HEAVY DUTY AND ’87-’93 CARS: These heads were the same as the earlier ones except that they had three bolt holes on both ends. The intake surface above the ports was quite narrow; it’s only about 0.250" wide. The unmachined, cast ledge on the top edge of the head was 0.600" wide. Look for c/n 14094768, 10144103, 14099067 or 12553050. All of these heads had adjustable rockers.
1992 TRUCK WITH TBI AND NO BALANCE SHAFT: These heads had a wider surface for the intake gasket even though they didn’t need it because all of the tooling was changed to accommodate the new heads for the VIN "W" CFI engines that were introduced in ’92. The 10144103 casting was carried over from ’91, but it had the wide intake with straight ports on the top. It can be used along with any of the earlier 14094768, 10144103, 14099067 or 12553050 castings from ’87 through ’91.
1992-’93 TRUCK WITH CFI, BALANCE SHAFT: When the high output VIN "W" engine with central fuel injection was introduced in ’92, the heads were redesigned for the application. They had "eyebrows" added to the top of the intake ports to make room for the injector nozzles, so the intake surface above the ports was increased by 0.250˝ for improved sealing, and the cast ledge above it was narrowed down to 0.350˝ to provide more room for the intake manifold.
The 10077626, 14099064, 10240209 or 10238181 castings were used, but be sure to check them over carefully because there are two versions of the 10238181 and 10240209 castings with an important difference. In ’92 and ’93, they came with an 8° top angle on the intake seat and a 75° throat, but that was changed to a 30° top angle with an 80° throat in ’94. Separate the 8° heads from the 30° heads and use them only on the ’92 and ’93 engines.
The most significant changes occurred in 1996, and when most people talk about "Vortec" heads, they are referring to the 1996+ heads. While not technically correct, that's just the way it is.

Edelbrock makes a TBI manifold for the '92-'95 heads.
Old 09-10-2008, 12:14 PM   #14
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Re: tbi to cpi

Quote: Originally Posted by FxsX24
whats the point of a cam that is ment for a set of faster flowing heads, just to be slowed by tbi heads
A better cam is a better cam. It may be restricted by the TBI heads, but it will still flow better than the TBI cam.
Old 09-10-2008, 10:34 PM   #15
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Re: tbi to cpi

that looks like my eng exept all my intake is gray.

any cam is better than a tbi cam
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