1997 GMC Jimmy camshaft upgrade - Blazer Forum - Chevy Blazer Forums


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Old 02-16-2018, 08:08 PM
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Default 1997 GMC Jimmy camshaft upgrade

Hey all I'm new to this forum site and was wondering if anyone knows of a cam upgrade options for a 1997 Jimmy with a 4.3l. I'm going to be putting new stock cylinder heads on my engine and was looking for a possible upgrade for the cam. Basically everything is stock and I'm wondering if there is a cam that will give a little better performance and fuel efficiency that will work with a stock ECM. I'm not looking for anything crazy just a basic cam upgrade.

Any ideas?


Thanks for your time and help!
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Old 02-16-2018, 09:25 PM
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I'm in the same search as you right now. i have a 97' 4x4 got some junk yard heads in hopes to refresh them and upgrade the cam to squeeze some hp and torque out of the engine for light/medium towing in the mountains.

so far i've gathered that you cant use a cam that will give more than .450 intake valve lift and .500 exhaust valve lift given your rocker ratio: without modifying the head.

HR-204/286-2S-12 Hydraulic Roller Camshaft for Chevrolet 1992-2002 90 degree V-6, 4.3L

HR-194/271-2-12 Hydraulic Roller Camshaft for Chevrolet 1992-2002 90 degree V-6, 4.3L

these are the two cams i'm considering because of thier lower lift height, im trying to gather information on what all i need to change out aside from cam and valve springs.

i hope someone else that knows more can chime in on your post as well.
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Old 02-17-2018, 01:18 AM
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You can run .500 intake and exhaust lift without machine work on the heads, as long as you run ls6 valve springs with comp cams 787 retainers. I have even heard of a couple people running .525 lift without machine work, however I can't vouch for .525 personally.

I'm running a comp 266hr grind cam. (.500 lift) with that valve spring set up. I chose the cam because it's effective RPM range is something like 1800-5000 As opposed to many others that are made for a higher RPM range- better used with a higher than factory stall converter.(I believe our factory ones are around 16 - 1800 stall)

It is recommended with any cam upgrade to have your .ecu tuned otherwise you're basically pissing in the wind, spending money for the same or possibly worse performance.
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Old 02-17-2018, 05:11 AM
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chevyriders advice is the same that I would give.

BTW. What injection are you running on that COMP 266HR?
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Old 02-17-2018, 07:46 AM
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Quote:
Originally Posted by error_401 View Post
chevyriders advice is the same that I would give.

BTW. What injection are you running on that COMP 266HR?
My marine intake/and injectors are supposed to be here tuesday
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Old 02-19-2018, 09:31 AM
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Quote:
Originally Posted by chevyriders View Post
You can run .500 intake and exhaust lift without machine work on the heads, as long as you run ls6 valve springs with comp cams 787 retainers. I have even heard of a couple people running .525 lift without machine work, however I can't vouch for .525 personally.

It is recommended with any cam upgrade to have your .ecu tuned otherwise you're basically pissing in the wind, spending money for the same or possibly worse performance.
so some springs such as these:
https://www.texas-speed.com/p-1383-l...od-to-550.aspx

and a cam such as the 266 from comp, or a crane cam.

and a tune on the ECU: do you have a suggestion for a place that will do a tune?

that's all that's really required? stock lifters and tappets are fine?

Last edited by mikmac; 02-19-2018 at 09:33 AM.
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Old 02-19-2018, 11:42 AM
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Those should be the ones, but here's the gm part number- i just ordered mine from the dealer.


Comp cams 266hr and 270hr are the ones I know of that have .500 lift. 266 is supposed to keep more of your low end power- but the 270 is supposed to give you more of a performance gain (within it's RPM range.)

You can send your ecu out to wait4me performance or pcm for less for an affordable tune. Most people seem to prefer wait4me out of the two.They are know to do decent tunes, however if you find a reputable local speedshop that can dyno tune it, that will get you the best results. They will probably charge twice what one of the mail order tunes cost, but you get what you pay for- and support local business at the same time.

You can run stock lifter and pushrods, I bought new factory style pushrods just so I had nice clean oil passages- but my lifters were in super nice shape so I kept them.

It would be a good time to replace your timing chain/gears while you're in there. I used a 350 timing chain kit because it's much beefier. The plastic timing chain covers are intended to be one time use. I would replace that as well.

Last edited by chevyriders; 02-19-2018 at 11:46 AM.
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Old 02-19-2018, 01:47 PM
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Quote:
Originally Posted by chevyriders View Post
Those should be the ones, but here's the gm part number- i just ordered mine from the dealer.

Comp cams 266hr and 270hr are the ones I know of that have .500 lift. 266 is supposed to keep more of your low end power- but the 270 is supposed to give you more of a performance gain (within it's RPM range.)

You can send your ecu out to wait4me performance or pcm for less for an affordable tune. Most people seem to prefer wait4me out of the two.They are know to do decent tunes, however if you find a reputable local speedshop that can dyno tune it, that will get you the best results. They will probably charge twice what one of the mail order tunes cost, but you get what you pay for- and support local business at the same time.

You can run stock lifter and pushrods, I bought new factory style pushrods just so I had nice clean oil passages- but my lifters were in super nice shape so I kept them.

It would be a good time to replace your timing chain/gears while you're in there. I used a 350 timing chain kit because it's much beefier. The plastic timing chain covers are intended to be one time use. I would replace that as well.
Thanks for all the info, makes it so much easier to just get all of it together like that from someone who has already done it.

have dealt with pcm4less before for work. will pick up a ecu from the junk yard for a whole 23$ and send to them.
will just do the 266 and refresh push rods since I have 105k on motor and timing kit like you said.
don't want the 270 because of the TQ converter stall and the little loss of low end there.

and as far as the valve spring retainers im assuming the GM retainers for the LS springs will work? or do you have to use the comp retainers?

gm retainers: http://www.jegs.com/i/Chevrolet-Perf...66344/10002/-1

Thanks again.

Last edited by mikmac; 02-19-2018 at 01:59 PM.
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Old 02-19-2018, 03:43 PM
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You have to use the 787 comp cams retainers, they're clearanced differently. They're cheaper than the gm ones anyway.
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Old 03-04-2018, 10:45 AM
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Thanks for all the help and input. Its not every day you get this much info with part numbers by someone who has done this kind of work before. I was also curious if this would also work on TBI heads as well. I have a TBI engine that im hoping to be doing a similar cam swap on this year as well. (1995 4.3l. TBI)
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