new 350, not much power?

[DRobb's_85]

A few months ago I swapped the old 305 out in my 85 K10 4x4 and put a new crate gm goodwrench 350 paired to a new edelbrock 600 cfm carb in its place. The new 350 runs fine, but I dont think its running at its full potential. I mean, it feels just slightly more powerful than the old 305 that was in it, and Its almost like I can barely keep up with traffic. Also, the other night when a cold front came through, I was entering a freeway and gave it about half to 3/4 throttle and it bogged down for a second and then backfired (popping noise). It doesnt do this when it is relatively warm (anything over 55-60 degrees) only on really cold days. I know I shouldnt expect much as it is a heavy 4x4 but I need to at least be able to keep up with traffic lol. Do you think the carb just needs to be tuned or what. Any suggestions on what I could do to make it run a little better? Also, on warm starts (like 10-15 min after it is turned off) it is a little hard to start. I have to give it a little gas and it will crank for a few seconds, then I let it sit for a sec and crank it again and it will fire up. Any ideas what that could be? Someone reccommended I get a carb spacer? Anyways thanks

[Prong]

Are you running a carb spacer on it? It'll help cut down on the heatsoak and make hot starts a little better. As far as the power issue goes, what's your timing set at? How do the plugs look? You might have to go a bit bigger on the metering rods and jets if it's running on the lean side.

[79blazer]

what he said. I'm think you can find the tuning kits at checker/vatozone.

Now I'm not sure if this is related... but I bought a new goodwrench like you, and used TBI on it on my Caprice. Lots of power, but had bad intake back fire. I was assuming that was because the cam was for a carb.

[84 400]

yeah I have the same thoughts. U might need to kit the carb up a bit. Timing is also important as was said. Did you put on a better manifold???

[maxreps]

You have a lean mixture problem... running poorly and popping on cold days but fine on hot days means you need to richen your fuel mixture. If you have a manual choke you can prove me right by partially(not all the way though) closing it while driving on those cold days, to effectively richen the mixture.
First I'd suggest turning your mixture screws before changing jets because it doesn't sound like you're too far off. They're on either side of the vacuum port on the front side of it(under the "E" and the "K" in the edelbrock sticker). They have a slot for a flat blade screwdriver.
But if that doesn't help the total problem you may still need to go up a size or 2 on your jetting.

[wicked_sky_gazer]

I had a similar issue along with many others also (on my 355), I changed to a holly 740 or 750 don't remember.... Tuned it up and advanced my timing to about 6 or 8 degrees at idle and it runs like a stripes ape now

[DRobb's_85]

No carb spacer on it now, what type would work, the wooden ones, aluminum? What size would work with my carb (e-brock 1406)? Its not like it runs horribly, runs decent actually, it just doesnt seem like its running as good as it could possibly run, which is important to me. It just seems like I have to give it more throttle than I should just to keep up with traffic. Also the only time it backfires (which is very rare, only happened twice) is when it is really cold outside and I give it more than half to 3/4 throttle, which isnt very often. Also another thing I forgot to mention..Whenever I park it in the garage and come back outside 5-10 min later, there is a pretty strong raw gas smell.. running rich maybe or what? I'm very nervous about messing with the carb, never done it before and its my DD. We'll see though..

[Prong]

You want a 4 hole spacer, preferably Phenolic (plastic type), not the big "open" spacer. What do the plugs look like? Bone white, tan, or ? I'll bet they're white (a lean condition).

[vtwinsport]

Had the same problem as you d robb.
crate 350 with edelbrock 1406 600cfm and edelbrock 2101 intake. carb was flooding due to heat sink of aluminum after running then sitting. Always took gas and more cranking than usual. there was usually black smoke upon startup at these times.
Fixed that with a phenolic spacer (brown fiber colored) and adjusting my floats downwards. they were sitting too high and allowing extra fuel in. If you check your #5 & 6 plugs they're probably black on one side or all round. I have the electric choke finally adjusted now too. It took half a dozen time to get it right.

That bog at the freeway on ramp is a lean condition alright. You may have to adjust your pump (see manual) or change the step up springs, needles. Your engine vacuum can affect this.

[gchemist]

Retune your carb. The old 305 settings won't work on the new engine. Use a vacuum guage. http://www.centuryperformance.com/tu...e-spg-148.html

I use on vacuum guage on my 1406. The carb is so easy to tune.