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!!

 

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.

 

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.

 

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

 

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

 

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.

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

But, on page 12, it also says:



Norm

 

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.

 

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

Congratulations.

Exactly what one would expect from any competent machinist.

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.

I am sure, everyone is properly impressed.

Norm

 

I was recently looking at a 307 with the 7A 0142 heads, do you know what the issue is with them?

Thanks,
John

 

Tiny ports, similar to those on the 2A from the 260's. The 5A's will raise compression, the 3A's have 79cc combustion chambers whereas the 5A's have 64cc or something. Yes, I hear they flow better, but does anyone have anything quantifiable on this? Consider upgraded valve springs and rockers while you're in there if you're not gonna change the cam. Heads aren't really a "time being" thing...for me at least. I mean, that's 6 hours out of my day that I could be doing something else. If you're gonna upgrade, upgrade, no use in spending $30 in gaskets twice. Oh...ARP head bolts while you're at it...if you weren't gonna do it anyway...

 

I think the 7A caution was for the two 7A heads. 72 7As have a subscript a while the later 7As have the 7 and the A the same size. The older heads have a smaller cc and can increase the CR on the later 350 s

I don't think there is anything inherently wrong with the later 7A heads

 

Thanks, I was looking for heads to put on a 350 in my boat and came across these freshly rebuilt, after some research though I don't think they will be good for what I want...this thread was old and I was surprised to get any response, appreciate the info...

 

I guess it's time for SBO Heads 101
I have photos, anyone want to do the writeup and photo hosting?

I perceive the general assumption these days is that if you are building an Olds V8, you are interested in an occasional driver with as much power as you can get, not a fuel sipping smog compliant daily driver.

Therefore, compression to suit a more enthusiastic cam, and good flowing heads are in order. With that in mind, then, the 7A heads come up short. While they presumably have small chambers [from the 307], they certainly have the half-height inlet ports similar to the 2A and 6A castings. Nothing "inherently wrong" with that, but not what we assume a person is seeking these days.

There are indeed two distinct "7A" castings, thus the need for a visual course. Years ago, all we had was text, so I adopted the practice of writing "7a" with a lower case "A" to indicate the tiny and subscripted upper case "A" that appears on the 1972 350 heads. As opposed to writing "7A" for the later puny port smogger head, whose ID looks exactly like that- an upper case A adjacent to and the same size as the "7".

I don't see the early 307s' 5A smogger heads being much different from 3A 350 smogger heads- possibly smaller chambers on the 5A, almost certainly smaller valves. Probably what the feller meant what that #5 heads [-not- "5A"] would flow better.... Yes, the 1968-9 #5 castings make a great choice for performance. Also #6, #7, and 7a [not "7A"]...

Surely the Heads wiki has this ironed out and somewhat error free by now?

http://www.oldsmobilewiki.com/index.php/Category:Heads


"
================================================
ID/ Use Casting
Code Year(s) CID CCs Number Notes
1 '64 330 385101 Used ROCKER SHAFTS rather than
pairs on PEDESTALS.
2 '65 330 ?????? All V-8s now using PEDESTALS.
3 '66 330 60 389394
4 '67 330 60 394497
5 '68 - '69 350 64 397742 Excellent candidate for use today.
Good flowing, and high compression.
6 '70 350 64 403859 W-31's had larger 2.000 intakes. '69
W-31's?
7 '71 350 64 409147 W-31's had larger [2.000] valves.
7a '72 350 64 409147 The 'A' is a subscript, like �"
tall, to lower right of the '7',
like | 7A.
8 '73 - '76 350 79 411929 Smog heads. Have huge bb-sized 79cc
chambers yielding poor compression
ratios without extremes of
compensation.
10 '76, '77? 260? 57 550362
2A '76 - '81 260 554715 Easy way to ID a 260 engine.
3A '77 - '80 350 75 554716 1/2" bolt holes.
4A '77 - '79 403 83 554717 Matches the 4A or 4B block, get it?
Easy way to ID a 403. 1/2" bolt holes.
5A '80 - '84 307 64 3317
'85 also???
6A '85 - ?? 307 67 5844 Non-ECM Canadian cars?
7A '85 - '90 307 67 0142 This 'A', and the others from 2A to
6A, is a large capital letter equal
in size to, and immediately adjacent
to the 7, like | 7A.
D3A 350 3948 Diesel.
==================================================

 

Other than being totally inadequate for a performance application. Also, not positive, but I don't think 350 intakes will fit.

BTW, you guys do realize that this thread is REALLY old, right?

 

Well someone still had a question about it...so it was brought back to life. I thought that's what this place was for?? haha

 

From Octanias post
"8 '73 - '76 350 79 411929 Smog heads. Have huge bb-sized 79cc
chambers yielding poor compression
ratios without extremes of
compensation."

This has resulted in many 73-76 Olds 350s being scrapped. My are they "smog" heads? They had larger exhaust valves, yes, the ex side needs some work, but in reality so do all of them.
"Extremes of compensation"??
Flat top pistons and #8 heads result in 9 to 1 compression, which is just right for a DD mild street application.

 

That was written a long time ago.
It is a wiki now, so feel free to edit it and clarify this aspect, right?

As I understand it, #8 heads are so huge they are good for
-used larger-valve donors
-Diesel to gas conversion
-403's w/o changing to smaller dish pistons
-Flat top W31 piston 350's with much less than W31 compression.

Pretty much the worst of the pre-smog era choices.

 

IMG_0377.jpg

 

IMG_0375.jpg

 

Except that back then 102 octane fuel was available. 9 to 1 Cr is pretty close to optimum for using 87 octane fuel. There is nothing wrong with flat top pistons and #8 heads in a fun daily driver. IMHO. Much beter than #7 heads and 23 cc dished pistons.

 

IM doing a #8 head flat top piston build. All im doing to the heads is a little exhaust work taking the egr bump's out and doing a little bowl work.

 

Well if you just use #4 heads on a 23cc dish, wouldn't it yield the same results? #8 head is 79cc, a 29cc difference from the #4. My next motor will just be a 403 with #4 heads and a mild cam.

 

Your #4 heads CC out at 50??? Not likely. Most are in the 64 cc +/- neighborhood.