3A vs 5A heads on 79 350

[Escalus2k4]

Hi guys, im back again with another question........ I have been searching and searching for a set of good flowing heads and I ran across a guy who told me that 5A heads will outflow the 3A heads that I currently have. Luckily I still have my 5A heads from my 307, but is what this guy saying true? If they do flow better and I will pickup atleast a little gain from them, then I will bolt them on for the time being while I continue looking for a set of better heads. What should I expect from them compared to my current 3A heads?


Thanks!!

[W403]

If your looking for better flowing ports and still want unleaded fuel capability anything from the #7 heads up from 1972 can and should work. #7s would be the best choice and still have good availability in some older salvage yards. With some basic head work, clean up, knurled guides and valve job you could be back on the road for cheap. Mind you there are lots of choices of course. Also, the #4/4A heads from 403 Trans Ams, and some tow package cars and such( without going into grave detail) have the 2" intakes and 1.5" exhausts. A great tool to obtain that would be able to fully explain all the cylinder heads and they're specs would be the engine tech manual offered by Mondello. And I mean it is very technical and will cover pretty much any questions you may have and then some for the entire Oldsmobile engine. It was the best $25 I spent many years ago.

[captjim]

The 307 5A head is not an upgrade from the 3A head, it is worse. The chamber is smaller and it will boost CR. The 4A head has a huge chamber and will significantly lower CR. A #5, #6, #7, or #7a head will flow better and raise cr, try and find a pair of those.

[Redog]

You want 5 heads, not 5A.

Also there are 2 types of 7A heads, be careful not to get the 1985 to 1990 7A heads, casting number 0142

[Escalus2k4]

Thanks for the info guys, back to the salvage yards!!

[88 coupe]

Originally Posted by W403

........ knurled guides ........

Nothing but a half azzed band-aid.

If you want to do it right, there are two choices: Oversize valve stems or, new bronze guides.

Originally Posted by W403

........ tech manual offered by Mondello ........

Yes, at the bottom of page 46, it says "knurl the guides to eliminate sticking".

But, on page 12, it also says:



Norm

[W403]

Really now, don't scare the 'poor' guy. I have well over a 100k on a set of #6 heads that were knurled by a competent machine shop back in 1986 during a basic rebuild. Trust me although I wasn't kind to it in my younger years I kept the oil changed regularly and always tuned properly. Also, after machining, the valve train was properly set, oil restrictors used ( both an important part ) and high quality components used; rings, bearings and oil pump. Again, mine was never any race motor, but it always ran strong and was fun. The motor still holds 170-175 psi cranking compression ( I realize this isn't always reliable per books and others but can still be used as a reference) . When fresh back then after breaking in it was only 185-190. The motor although leaks some oil, does not burn it. I've since only replaced the valve guide seals and freshened up some gaskets and such over the years. I only turn it up to around 5200 or so at most on shifts as you should know Olds motors make great low end torque. More than anything else, it's been a blast to own and drive all these years and I too have always been on a budget. Yeah, maybe I've been lucky and there are a lot better ( more expensive ways ). I've hung around machine shops in my younger days that performed work on several others thru the years that turned them out like this as well as full blueprint and race. The budget motors done by them never came back from these guys, nor did the hi-po stuff. Unfortunately old school machine shops that are truly reliable and reasonable are getting harder to find. I remember when they had they're own race cars and motors side by side with everything else, man they sounded cool. Good luck once again and most of all enjoy your olds on whatever budget you can afford, I have. Mine is now due for another rebuild, this time it will be a more expensive project.

[88 coupe]

Originally Posted by W403

........ don't scare the 'poor' guy ........

Nothing to do with scaring anyone. Everything to do with posting factual information.

Originally Posted by W403

........ I have well over a 100k on a ........

Congratulations.

Originally Posted by W403

........ after machining, the valve train was properly set ........

Exactly what one would expect from any competent machinist.

Originally Posted by W403

........ oil restrictors used ........

An unnecessary expense.

If less oil to the cam bearings is desired, one could drill a .062" hole in each cam bearing, instead of waiting for those "restrictors" to be delivered. Since the flow is already restricted by the cam bearing clearances, nothing is accomplished, either way.

Originally Posted by W403

........ I've hung around machine shops in my younger days ........

I am sure, everyone is properly impressed.

Norm