Any thoughts on using a 305 for a V8 swap instead of a 350? Thinking how many of these powered several vehicles with the 7.5/7.6 rears that are also very common in the s-series and will bolt to the 4l60s. Plus the 4x4s tiny front diff. Was thinking could still gain an extra 100hr/tq over the 4.3 but maybe not as potentially as damaging to rest of the stock components as a 350 can be.

 

By the butt dyno in an S-chassis, I don't think anyone would notice the difference between the two, assuming you're talking about a bone stock 305 vs a bone stock 350.

BUT, if you're plan is to try to build up the 305 for more power than stock, I think you'd be better off just sourcing a 350 to start with. There would be more potential for HP gains out of the same size package (dimension wise in the engine bay) with the higher displacement 350, and for the same amount of work to complete the swap. There's plenty aftermarket support for either (probably more for the 350), so the sky is the limit on how crazy you want to get with it. You could certainly build a 305 to outperform a 350, but to get to let's say an end result of a simple 300hp, you'd be better off starting with the 350.



I'm sure you've already been asked before if you've brought this up to anyone else, but is there anything keeping you away from an LS swap? A stock 4.8l would outperform either and are EXTREMELY plentiful in junk yards, are proven reliable. 5.3l would be ever better and are still plentiful. 6.0l if you're feeling frisky. Or 6.2l if you really feel like going HAM lol

 

Yeah, thought of it. And yes I agree there's no replacement for displacement for sure. And though yes you can pretty much get the same performance upgrades for the 350s and ls familys. I was looking at the whole package of the vehicle it self. Most the s10/blazers 4x4s have the 7.6 rear end and front just as small.

A 350 bone stock or likewise, well let's face it, if going with one of those your gonna put upgrades on it while rebuilding it, cause while your there!? Sure more fun always not disputing that, just the snow ball effect that has... engine upgraded then your gonna want/need a better trans, cause that 4l60 ain't gonna take it for long(dosent on a stock 350 either), let alone that small 10 bolt behind that. So now you looking at finding at least a 8.5, Ford 9 or dana. Same goes for the front. Once that's out of the way you'll also more then likely need the drive shafts made to fit. Now you've added all that extra weight and power so you know the suspension is gonna be right there with it too.

Just thinking a built 305 might provide a little better then the 4.3 that almost all us 4.3 owners are wanting out of it but having more aftermarket support. Where you can get good numbers out of a 305 it looks to be a bit more mild then the big brother 350 and eases into the numbers from other articles I've read on. The idea retaining most of stock equipment but yet getting that little something extra out of it. So a 305 might be a better application

I have 2 96 s10 blazers 4dr 4x4 lt plus a 3rd 96 ls spare parts, and 96 Tahoe. (Don't ask how that worked out like it just did.) Tahoe has a bad trans(4l60). Was thinking easy put that 350 in one of the s10s.(bb the Tahoe later). In stock form probably ok, even a mild cam a tune max might be ok. But anything more then that after researching everything, other components are gonna have be replaced with it. And still not convinced a 10 bolt will hold for very long.

So looked at what else could we do to the 4.3. well for the same dollar..... Rather have the V8(no offense to the 4.3, it's a cool little engine). But yes being somewhat lazy and thinking lots of cheap stock parts. What application could run on that but make it a bit more fun. So a 305 will respond well to the same typical $ build of the 350, but might allow the stock parts to live.

Still I got 2 so could make one of each lol,.... Just thought what others think. Of course bigger is better, but for these little s10's that 305 that ran in so many heavier vehicles with the same 10 bolt and 200-4r/700r4s that also have a good torque curve through most of it's rpm range. Might be a more appropriate application assuming your not trying for 10s quarter miles every weekend at the drag strip with all 4s spinning

 

The Chevy 305 is such a boat anchor. Throughout it's entire production run from 1976-1995, the only 305 c.i. RPO to hit 200 horsepower was the LB9 (tuned port). Aftermarket for the 305 is not there because the heads are VERY poor and the bore is too small for todays modern big-valve aluminum heads with modern combustion chambers (how you make power these days). Furthermore, the 305 takes very small chamber heads (not generally made or sold) to have a decent compression ratio with flat top pistons. They do not respond to mods like a 350 does..

The L35 V6 in the 2006+ blazer is 190hp/250ft.lbs stock. The heads are the V6 version of the infamous Vortec heads - same ports - same valves. I don't understand why anyone would modify an existing 305, much less swap it in place of a decent-headed V6 and then modify it.

The only swaps that make sense for a 96+ blazer are the 1996+ Vortec V8 and the LS motors. This is because the PCM in the Blazers can be made to run the fuel injection system found on these motors, as well as the rest of the many systems found there. For example transmission won't shift without a PCM. Gauges/speedo won't work without a PCM Many other systems like BCM, TCCM, ABS, SIR, etc need to interface with the PCM. So I recommend to keep the PCM and fuel injection if you aren't making a racecar out of a second gen Blazer. The fuel injection system / engine in your Tahoe is made for this swap.

p.s. I have a 4L60e in my Avalanche behind a LS motor and I tow my racecar and trailer with it. I drive it easy and watch the trans temperature on my scanner.

Any differential will not take spinning one wheel under power for very long. Even a 7.5/ 7.65 rear will take a lot of power if you're not spinning one wheel and you don't shock it too badly. Originally I ran my 89 S10 for an entire race season with 28.0 x 10.0 x 15 wrinkle-wall slicks, a warmed over 350 that came in it, and an open 7.5 rear. Never spun a tire and never broke it before upgrading the entire driveline. However, with 150 more ponies I did manage to trash (split/break/destroy) the pinion gears in an 8.5" Eaton Posi differential the very first time I tried using a trans brake.