305 TBI Header (?)s

[89Sierra305]

If you're willing to go as far as camming a Tbi 305, I would suggest saving up and waiting to do a 350 swap and proceeding from there. Period. The shorties and Ultimate Tbi model are just nibbling around the edges. Start with a good power plant.

Now if you're unwilling or unable to swap the 350, Shorty headers are only one part of the very restrictive exhaust. They won't get you much on their own. You need to do the Y pipe and rest of the exhaust to see any gain from doing the headers. After the exhaust you can do the TBI mod, maybe take the heads off and have the intake side ported. Then you can worry about a new cam.

Stepping aside from the motor for a moment, if your rear end is a 3.08, you can step up to a 3.73 to give it some more acceleration. Won't help your fuel economy at all, but it's something to consider.

What all do I need to swap the gears in the rear end? If you have some part #'s or links I and a few other newbies would surely appreciate it. I'm going to do some research of my own and see what I can find. Thanks for the info.

 

[Sean Buick 76]

What ratio gears do you have? The code is in the glove box

 

[Das Hatt]

What all do I need to swap the gears in the rear end? If you have some part #'s or links I and a few other newbies would surely appreciate it. I'm going to do some research of my own and see what I can find. Thanks for the info.

The simplest way to go is go to a treasure yard and grab an entire axle assembly that has 3.73 gears off a C series truck. ( the K series trucks have a track width that is slightly larger.) The yard in my area has axle assemblies for $95 and a $20 core.

If you take it off of 1500 it's a simple procedure. If you want to upgrade to a 2500 axle, you get more splines on the axle shaft and the 11 inch duo servo drum brakes instead of the 10 inch leading/trailing brakes that come in the 1500. You will need a conversion ujoint. That I do not have a part number for. Also the 2500 rear end comes with either six or eight lug flanges, you would either have to get wheels that would fit, or have the axle flanges plugged and re-drilled to fit the five lug wheels on your current truck.

(All this is moot if you already have 3.73 gears, but the brakes and sturdier axles would still be an upgrade)

 

[PlayingWithTBI]

What all do I need to swap the gears in the rear end? If you have some part #'s or links I and a few other newbies would surely appreciate it.

here's what I got over 4 years ago and, as mentioned pinion preload is critical, even with new stuff. The Timkin bearings I bought were for setting up the rear end. I ground out the inside race so they'll slide on and off easily instead of pressing the bearings every time. The crush sleeve eliminator is a way better way to go. Here's the manual too...

Pinion Bearing	TMK-M802049	Timkin		Summit Racing	$14.99​	1​	$14.99​	Y	Ground ID for slip fit to
Pinion Bearing	TMK-M88048	Timkin		Summit Racing	$8.99​	1​	$8.99​	Y	set preload on pinion
Crush Sleeve eliminator	YGA-55048	Yukon Gear		Summit Racing	$33.06​	1​	$33.06​	Y
Rear End Overhaul Kit	ZKGM8.5	Yukon Gear		Amazon	$57.00​	1​	$57.00​	Y	Total:
4.11 ring & Pinion	ZG GM8.5-411	USA Standard Gear	Convert 3.42 to 4.11	Amazon	$145.11​	1​	$145.11​	Y	$259.15

 

[L31MaxExpress]

Upgrading a 305 is not peeing into the wind. They can make a lot of power and still be a nice cruiser. It is still a SBC, it still responds to anything a 350 responds to. The biggest restrictions are exhaust, intake and camshaft in that order.

 

[Erik the Awful]

The crush sleeve eliminator is a way better way to go.

If you look for a "crush sleeve eliminator" you're going to pay about $60. If you look for a "steel shim kit" you can score it for about $25. At least that's how it was when I rebuilt my Mustang's 8.8.

Upgrading a 305 is not peeing into the wind. They can make a lot of power and still be a nice cruiser. It is still a SBC, it still responds to anything a 350 responds to.

If you can score a 350 for under $200, is it worth it to rebuild a 305? That's a 15% increase in displacement for next to nothing.

 

[L31MaxExpress]

If you look for a "crush sleeve eliminator" you're going to pay about $60. If you look for a "steel shim kit" you can score it for about $25. At least that's how it was when I rebuilt my Mustang's 8.8.


If you can score a 350 for under $200, is it worth it to rebuild a 305? That's a 15% increase in displacement for next to nothing.

Except you will not score a decent 350 block for under $500 where I am. The only time you even see one still in a wrecking yard vehicle is with a rod hanging out of it. ATK buys all the GM engines they can from the local yards for cores. I literally asked a couple of my local yards why they never had GM V8s and that was their answer. My last L31 I built actually came out of my aunts Escalade, I paid the $100 GM core charge to keep it a few years ago. Both Mexican 062 heads were cracked on that ~110K mile Goodwrench L31, but the block itself was solid.

 

[Kens1990K2500]

I would do exhaust(shortys and a high flowing y pipe or true duals), tbi mods(fuel spring and maybe a spacer), give it some timing and a set of 3.73 gears. It would be a decent running truck that will spin the tires at will. A cam will require tuning for it to run correctly.

I have a 305, and installed shorty, stainless steel headers, and had a complete custom exhaust system installed. My truck already had 3.73 gears.

Had a new distributor installed, but have not done any mods to the TBI, yet. Not a race car by any means, but starts and runs well, with good throttle response. It doesn't feel underpowered.

 

[Kens1990K2500]

Except you will not score a decent 350 block for under $500 where I am. The only time you even see one still in a wrecking yard vehicle is with a rod hanging out of it. ATK buys all the GM engines they can from the local yards for cores. I literally asked a couple of my local yards why they never had GM V8s and that was their answer. My last L31 I built actually came out of my aunts Escalade, I paid the $100 GM core charge to keep it a few years ago. Both Mexican 062 heads were cracked on that ~110K mile Goodwrench L31, but the block itself was solid.

I ran into a guy that combs the salvage yards and buys up starters, alternators, etc., and resells to rebuilders of those components.

Not sure how I feel about that, since it reduces the chances of backyard mechanics or Joe six pack on a tight budget finding a used component to get their ride back on the road.

 

[89Sierra305]

Thanks for all your info and help guys. I've been a bit busy with the ol' 9-5 and haven't had a chance to look at anything. If I were to take a guess the rear is not a 3.73 gear. I'll take a look when I have some down time. The last time I did some highway driving was before I got the new motor. It felt like it was a little slow on acceleration but that could have been the old motor on its way out. Again I'll take a look when I do some maintenance work on the rear on my day off. Thanks guys.