305 to 350 swap

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Gramps

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305 and 307 for that matter can both be made to run very well. The 305 has almost identical bore to the 265 and the 307 is a 283 bore. My 1999 Tahoe has a L30 305 with a 218/218 @ .050 cam, ported intake base, Volant CAI, long tube headers, 2.25 pipes to 2.5" high flow cats and a dual in/single out magnaflow. It put down 267 rwhp through a 4L60E and 9.5" 14-bolt.

A factory stock Marine 305 Vortec is also a 260 NET HP engine with the tiny 395' Marine cam in it and very restrictive water cooled manifolds.


I’m not disagreeing with a 305 being made to run well, hell they run very reliably in stock form. But, I don’t see a 305 putting out 267 to the ground with a few bolt ons. That would need to be making 320 at the crank. That little cam I don’t think so. Let’s see a dyno sheet? I’d love to eat my words.
 

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L31MaxExpress

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I’m not disagreeing with a 305 being made to run well, hell they run very reliably in stock form. But, I don’t see a 305 putting out 267 to the ground with a few bolt ons. That would need to be making 320 at the crank. That little cam I don’t think so. Let’s see a dyno sheet? I’d love to eat my words.

I do not have a copy of the Tahoe one at hand but the L30 can be woken up very well. I tuned a stock 100k mile L30 long block with a few bolt ons and a 350 exhaust years ago that I had in my Express van for about 2 years. Stock cam, 1.6 full roller rockers, shorty headers and a 350 dual cat exhaust. Not hard to know a fresh almost no mile engine, with thinner head gaskets and .020" milled heads, 24° @ .050 more intake duration, 22° more exhaust duration, .073" more intake lift, .059" more exhaust lift, a ported lower intake, cold air intake, underdrive pulleys, and electric fans would be 42 hp more.

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L31MaxExpress

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For comparison purposes K&N dyno tested a stone stock 96 4x4 and got 185 hp at the tires and another 10 with their FIPK cold air intake. That was with the stock exhaust manifolds, TBI style Y-pipe, restrictive single cat and restrictive OEM muffler. Most factory stock 350 Vortecs dyno in the 190-200 hp range. I think the bottem end torque suffered a little in my Express van dyno above because of the OEM dual 3" piping to the muffler. It is also plainly evident how bad the stock Vortec cam is with the HP being table top flat for 1,000 rpm before is simply chokes the engine. Tahoe made 267 whp @ 5,400 for comparison. Also made right at 300 tq from 3,000-4,500 with a peak of 308 @ 4,000. Cam is a Lunati High Efficiency 268 with 1.6s and LS6 springs/787 retainers now, stock springs when dyno'd.
 
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To get back at the original question, !00% bolt up, You will need to change the EGR, Injectors, PCV, ESC(if you have it) and the tune in the PCM. The PCV may be the same one not sure. Edit, sorry seemed to have stroked out mid sentence.
 
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I do not have a copy of the Tahoe one at hand but the L30 can be woken up very well. I tuned a stock 100k mile L30 long block with a few bolt ons and a 350 exhaust years ago that I had in my Express van for about 2 years. Stock cam, 1.6 full roller rockers, shorty headers and a 350 dual cat exhaust. Not hard to know a fresh almost no mile engine, with thinner head gaskets and .020" milled heads, 24° @ .050 more intake duration, 22° more exhaust duration, .073" more intake lift, .059" more exhaust lift, a ported lower intake, cold air intake, underdrive pulleys, and electric fans would be 42 hp more.

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Thats alot of work for 42hp.
 

L31MaxExpress

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To get back at the original question, !00% bolt up, You will need to change the EGR, Injectors, PCV, ESC(if you have it) and the tune in the PCM. The PCV may be the same one not sure. Edit, sorry seemed to have stroked out mid sentence.

Actually the 305 exhaust will not work with a 350 tune. 02 sensor placement and number of cats are different for a 305 and 350 tune. You need someone with Tunercats OBD2 to correctly configure the cats and sensors. HP Tuners and EFILive cannot do it.

EDIT-Disregard just remembered we were talking a TBI truck not Vortec. i will leave the info above for anypne considering swapping a Vortec 305 to 350 and vice versa.

For that you need a knock sensor, injectors and prom chip from the same year 350 truck with the same trans. EGR is usually the same.
 
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Its a 93. so tbi. Only one cat and one o2 sensor on that truck 305 or 350. Keep the original pcm, run a plain jane 350 chip for said pcm from the junkyard, change aforementioned parts and run it.
 
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