Well my 350 (1970) has a pretty loud ticking, happened as I was driving at about 70-75 normal rpm, had a little surge in power, no leaks or gauge changes, had it towed and my mechanic friend said it sounded like lifters, opened it up, no broken springs or rocker arms, so replaced the lifters and noise still there. engine starts easy and idles normal. Looks like a teardown might be in order. Ran great for over 2 1/2 years.
I'm thinking maybe a 403 might be a good switch. I've seen articles saying its a relatively easy swap using my 1970 #6 heads, but it raises the CR higher than 8.5-8.75 which is what I want since I have that small Weiand SC on it now at 5psi.
403 sounds nice, extra 50 cubes for the same size block, but CR might be an issue.
Any comments, swap or rebuild my 350?
Thanks, Frank

 

There's no replacement for displacement. If you are running boost, keep the 4A heads, which will keep CR down. Install 2.070/1.625 valves. Pick an appropriate cam. Enjoy.

 

The cr of the 403 is 8.2.........a little lower than I was thinking of going but it might be okay...........got suggestion for a decent cam, don't need a thumper just a mid range to a little above mid range.........the cam I have now is .218/,218 with .456 lift 110 ls.
Thanks for the info, Frank

 

Less CR and more boost is a better way to make HP. I'd talk to Cutlassefi about a cam for that combo.

 

Actually it is less than 8 to 1 compression and the 4A heads need a lot of work on the exhaust side.

 

Well, less than 8:1, I will have to think on this a bit more.
And yes culassefi, I'm sure, could steer me right on the cam.
If I just took my 350 #6 heads it would be over 9:1, a little too high from what I've read.
My #6 heads have 64cc, the 403 has 83cc, I'm trying for around 70-72, with CR in mid 8 range.
Thanks to both of you for the info.
Frank

 

Don't rely on published CC numbers. Check your specific heads. You also need to account for real compressed thickness of the head gasket (new FelPros are a lot thicker than stock). Also, a small shave on the 4As fixes your problem. Again, a blown motor is MUCH less sensitive to port flow than an NA motor.

 

Yes, I was thinking that a small shave might be the way to go to use the 4A. Also a thicker gasket with the #6 heads, both sound like a good approach.
And yes, checking the heads, specifically is #1.
Now I haven't opened up a stock 403 yet, I think I'm about to now, but did they come with flat top pistons?
And is that why the #6 heads with small combustion chambers on a 403 are running the CR up?

Frank