My 305 is a 350

American Muscle 79

Apprentice
Thread starter
Jan 29, 2018
65
33
San Diego, CA
Personally, I was never really a fan. Just wanted to brag about my brush with greatness. I think the chrome looks good against the aluminum and black.
I wasn't either, which is why I ended up replacing them here. I will be building a smog motor to swap out with this one if the need arises. Which is where I'll repurpose these.
 
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64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
2,237
113
Upstate NY
So that's what I thought as well. With the smaller combustion chamber, it should have upped the compression. But after combing through the forums for that specific head casting, I found a lot of people saying that the flow on those heads are awful. From what I understand, in actuality, the combustion chamber isn't much smaller than a stock 350 head, and the intake and exhaust ports are too small to flow a meaningful amount of air. That combined with the fact that I'm setting aside most of the CARB compliant components should give the engine enough room to breathe.
Be careful of internet garbage/misleading info. Small runner, low flow heads only affect performance once they get out of the rpm range that requires more flow to continue to make power. Those heads should have given a bump in performance below 3500-4000 rpms over a set of smog era heads and it should have been more than noticeable.

So the question of did you figure out what was wrong because the heads aren’t the issue until it’s over 4000rpms, and maybe higher. If you’re this far in, you might as well pull the cam to see the grind number.

Saying ^^^ because I hate to see you put it back together with the same problem present.

Good luck and congrats. You also might want to measure the stroke - maybe someone threw in a 327 crank that they had laying around.
 

American Muscle 79

Apprentice
Thread starter
Jan 29, 2018
65
33
San Diego, CA
Be careful of internet garbage/misleading info. Small runner, low flow heads only affect performance once they get out of the rpm range that requires more flow to continue to make power. Those heads should have given a bump in performance below 3500-4000 rpms over a set of smog era heads and it should have been more than noticeable.

So the question of did you figure out what was wrong because the heads aren’t the issue until it’s over 4000rpms, and maybe higher. If you’re this far in, you might as well pull the cam to see the grind number.

Saying ^^^ because I hate to see you put it back together with the same problem present.

Good luck and congrats. You also might want to measure the stroke - maybe someone threw in a 327 crank that they had laying around.
Thanks for the tip! The engine didn't have any major issues with running, it just didn't have enough power to outrun my wife's mini. The only available performance was through the RPM range you suggested. Over 4000 wasn't even an option. This wasn't the only thing holding the engine back. Between the heads, the EGR system, cruddy exhaust manifolds, smog equipment, etc., the car was being asphyxiated. I suppose it wasn't terrible performance considering the state that I got my Malibu in when I was 14, but it just feels terribly slow now. It's capable of kicking off a one-tire-fire, I just wanted a little more from it now that I found out it's a 350, and I had some parts just sitting around.

I'll let you know how it goes!
 

American Muscle 79

Apprentice
Thread starter
Jan 29, 2018
65
33
San Diego, CA
And that's why I asked the first question - a 3.8 runs better than that.
Not in my experience. My Malibu ran like a champ when I first got it and it couldn't break 17 seconds in the quarter. Honestly, I'm not even sure how a 3400 pound car with a bad gear ratio and somewhere around 130 wheel horsepower could do much better than that.
 

bracketchev1221

G-Body Guru
Jan 18, 2018
849
93
Not in my experience. My Malibu ran like a champ when I first got it and it couldn't break 17 seconds in the quarter. Honestly, I'm not even sure how a 3400 pound car with a bad gear ratio and somewhere around 130 wheel horsepower could do much better than that.
I doubt they were 130 at the wheel. They were like 140 at the crank. You’re right my friend had a 305 78 and it ran in the 17’s. But your new engine will be a big improvement. My 229 v6 has a hard time making it some of the hills in pa without slowing down!!!
 
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American Muscle 79

Apprentice
Thread starter
Jan 29, 2018
65
33
San Diego, CA
I doubt they were 130 at the wheel. They were like 140 at the crank. You’re right my friend had a 305 78 and it ran in the 17’s. But your new engine will be a big improvement. My 229 v6 has a hard time making it some of the hills in pa without slowing down!!!
I was definitely being generous with that number. No way was this thing getting 130 to the ground. 😅
 

American Muscle 79

Apprentice
Thread starter
Jan 29, 2018
65
33
San Diego, CA
Quick update:

I got the 350 in and ran into a few different issues that were self-inflicted. After hooking up the MSD SF ignition box and the HEI distributor, I tried firing this bad boy up, to no avail. I noticed a pretty sizable fuel leak from the accelerator pump right off the bat. It also seemed like the carb was puking fuel. Long story short, the needle and seat on the rear bowl was stuck and the accelerator pump diaphragm was cracked. Needless to say, some rebuilding was in order there.

Still, with spark and fuel, it should have fired up. To eliminate all factors, I replaced the R45TS plugs that were in it with some longer plugs that were recommended for this angle plug application (GMPP Fastburn aluminum heads). But this thing sounded like it had no desire to fire. It would just sneeze fuel back up through the carb. Timing. I pulled the valve covers and checked TDC but still nothing. At least that's that I thought. After triple checking myself, I noticed I was 180° out. After pulling the distributor and orienting it correctly, it fired right up.

The idle took off to around 2500 RPM. I backed out the idle screw with no changes. I also checked the idle mixture screws and didn't find a problem. No open vacuum ports. I checked the perimeter of the intake and the carb with carb cleaner and didn't notice any change in RPM. At that point, I knew what it was. I pulled the intake and there was the "good enough" gaskets I used for the intake. Sized to match the intake runner on the head, and not the manifold, they left little room for error. It was pulling air from under the intake on at least two cylinders. I ended up ordering a properly sized set.

In the mean time, I rebuilt the carb, wired the electric fans, and replaced the crossmember to facilitate the dual exhaust I'll be running.

With any luck, I can get this thing broken in this weekend. Let's just hope I didn't mess anything else up.

Gee. I guess this wasn't a really quick update after all.
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