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head swap on 90 caprice LO5

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Old 01-04-2005, 02:06 PM
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Car: 1990 caprice 9c1
Engine: lo5 350 tbi with 416 heads
Transmission: 700r4
head swap on 90 caprice LO5

well started on the head and cam swap,going with a set of 305 h.o. heads with the big valves and 58cc chambers i went through and polished the ports and chambers and claned and replaced the valves ,i noticed that on my spare set of iron LT1 heads the exhaust valves where thinner all the way to the head unlike the 305 valves which flared out to meet the head and seemed like they could be blocking a bit of flow so i swapped them in with some new drop in replacement valve springs and installed new valve seals ,the exhaust side was suppose to have the crappy *** umbrella seals ,and i just put the new style vitron seals on the intakes and i bought a second set and used em on the exhaust so it should be smoke free and i'm gonna swap in a staock 95 f body lt1 cam while i'm at it ,i thought these LO5's had dished pistons ,but mine had flat tops as you can see in the pics ,guess this combo is gonna need a bit of tuning..lol






new heads are on ,cam is in ,now its just the headers ,intake and front assy's..



and my ported thottle body ..lol


wound up not useing the edelbrock intake right now,just went with the stocker to get it running had a chip burned by www.tbichips.com real good job ,with 10.0 to 1 compression i detect no knock with 93 octane and a 160 t stat. :lala:

Last edited by ironroad9c1; 01-04-2005 at 04:22 PM.
Old 01-04-2005, 04:50 PM
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Car: '90 RS
Engine: 377 LSX
Transmission: Magnum T56
Looks good but your will need to burn your own chips. TBIchips will not even begin to cover what your car needs tune wise.
Old 01-04-2005, 04:57 PM
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Car: 1990 caprice 9c1
Engine: lo5 350 tbi with 416 heads
Transmission: 700r4
well its a lot better than with the stock chip..lol,you also need to remember the lo% caprice police cars had bigger injectors than the 350 trucks and i run a differnt ECM,but the pres of my impala club is gonna do some data logging for me to see how close it is.
Old 01-05-2005, 07:53 AM
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Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
Unless your running a really thick head gasket your probably way over 10 to 1. I ran a similar setup on my car a while back when I was poorer than I am now and with a .042 head gasket (std felpro) and a .020 head saver shim and a rather deep .032 deck height I was at 9.8 and had 200 psi cranking compression. It ran on 93 but I had to be carefull with timing. I'm guessing your relying on the knock sensor right now.
Old 01-05-2005, 09:46 AM
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Car: 1990 caprice 9c1
Engine: lo5 350 tbi with 416 heads
Transmission: 700r4
well i checked everything with the keith black CR caculator and everything added up to 10.0 to 1 ,with the chip he burned me ,i'm running stock base timing of 0 degrees ,and a 160 t stat like he instructed. i'm going to try and get some datalogging in this week and see if ther eis any small knocking cause i'm not hearing anything so if there is any its very slight.
Old 01-16-2005, 08:54 PM
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Car: 1990 caprice 9c1
Engine: lo5 350 tbi with 416 heads
Transmission: 700r4
well checked today and its getting 15 mpg around town ,thats up from the 14 thats estimated in the 9c1 factory brochure and cruises all day at 75 no problems ,great swap.only bad side is that you definatly have to run 94 or better in it..
Old 01-16-2005, 10:14 PM
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You have the exact same combo I have down to the injectors even. SOME vans came with the Roller cam and 65 lb/hr injectors as factory equipment. I am running the 081 tpi heads on mine though.

I run 89 in my van with 10.3 : 1 compression and run 32* total timing. I have that exact same combo in it and love it. My cranking compression is at 210 in every cylinder. 305 heads are great to keep detonation at bay. They just don't ping like a 350 head would at the same compression.

Right now I am running a CCC Q-jet on it but ran TBI on it for a while although like you stated it ran not so good with the factory chip.
Old 01-17-2005, 04:43 PM
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Car: 1990 caprice 9c1
Engine: lo5 350 tbi with 416 heads
Transmission: 700r4
yea i had a chip burned by www.tbichips.com he came highly recommended, i think my highway milage problem is that my t stat was too low had a 160 not going in or going in and out of closed loop,swapped in a 180 today gonna see how that does.
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