350 Olds Motor/Heads Need Info

[KCEE442]

found an ad for a 350 olds, the guy thinks its out of a late '70s caddy.
Says its got 3A heads.. are these good heads? also found another ad that a guy is selling #6 Heads from a'70 350
Is this motor worth looking into? and what are the best heads to put on a motor?
Im looking to do a complete build up, (possibly pistons) stock rods, maby 330 crank
mill heads, valve job, port heads also and full roller (lifters,rockers) and a cam, ignition etc etc.

Thanks for any feedback!

 

[Oldsmoletick]

Very well could have been in a caddy, is it fuel injected? Some were. The 3A heads were used from 77-80, made by PMD for olds 350's, has 1/2 head bolts, the block has windowed mains, not as good of a possible performance engine as the earlier ones, but is just fine for a daily driver. Mine is a 77 block, and I put the #6 heads on it, had to have the head bolt holes reemed to accept the 1/2 bolts (earlier engines had 7/16 head bolts). As far as 3A's being good, not from a performance stand point, they have somewhaere around a 75cc combustion chamber, 5, 6, or 7's (somewhere in the 64-70cc area) would be a much better starting point. If building up an engine, I would look to an earlier block as well, the later would work, but why spend the cash on a weaker block, when a 76 or older block can be had for the same price (in some cases). If the guy with the #6 heads has the the whole engine, that would be worth looking into.
Just fyi, putting the #6 heads on my engine really didn't make a big difference, I had a noticable gain on the bottom, but little to nothing up top (the 6's had slightly smaller valves than the 3A's). Good luck.

 

[MULL0140]

Hello:

As the previous reply, I have also built and am running an OLDS350 small block in a 1978 Pontiac TransAm. With the Melling Hi-press oil pump, oil pressure is 40 - 50 psi most of the time. This engine does not overheat like the OLDS403 I had, and is the primary reason for sticking with the OLDS350. The heads are 3A, also known as "716" castings by PMD. The casting is very thin ("smog" heads). The OLDS403 heads are MUCH BEEFIER, and will also bolt on, but with lower compression. The OLDS403 heads are marked as "717" castings by PMD. As noted by the previous reply, even with my 3/4 race cam (214/224 @ .050), I have a fair bottom end, but no top end, even with all the goodies (headers, alum intake, etc.).
problems: Do not reuse the stock cast aluminum rocker girdles. Purchase all new valve/rocker arm running gear (anti-pump lifters, 8.4" pushrods and STEEL girdles). Only use ARP studs for the rocker arms, since the bolts can break off in the head due to heat, etc. Use the premium FEL-PRO head fiber head gaskets, not the metal gaskets by Cometic. REASON: Since this motor only has 10 head bolts per head, the seal has to be perfect (note the 130 ft-lbs of torque required). Also, do NOT use the Valley Pan metal gasket. Get a good after-market intake manifold gasket set. The metal valley pan will leak vacuum. Initial and advance on the timing is critical and difficult to obtain without experimentation.
This OLDS motor was originally designed as an industrial engine and will run mega-hours if not over-revved. Good luck.

 

[joe_padavano]

Also, do NOT use the Valley Pan metal gasket. Get a good after-market intake manifold gasket set. The metal valley pan will leak vacuum.

You were doing great until this statement. I've used the sheet metal turkey tray gasket exclusively on my Oldsmobiles for over 35 years and I've never had one leak. I can't understand why people seem to have some much trouble with them. They didn't leak from the factory and Olds used them with aluminum W-30, W-31, A4, and A5 intakes. I've also used them with aftermarket aluminum with no problems.

 

[MULL0140]

Hello:
I have also used valley pan gaskets in the past on OLDS motors (low performance). Began to see a loss of vacuum on high performance, and JUNIOR.Mondello-OLDS confirmed the metal valley pan gasket will leak vacuum. Went to a fiber intake gasket and the problem went away. Also note that it appears that the metal valley pan gasket "traps heat" underneath the intake maniforld which could hurt performance. #1. Also read another article to start initial timing on these motors at 20 deg BTDC to run properly. This seems to conflict with some motor manuals. #2. Stock starter "touches" header pipes and results in no-start when hot. Went to smaller mini-starter which does not touch header pipe and problem went away. #3. OLDS coolant flow to water pump is almost 100% through one small pipe to pump. To manage water temp, I went with a 165deg thermostat, which seems to maintain coolant temp below 180deg at all times, even in traffic/idle. Mark

 

[joe_padavano]

Hello:
I have also used valley pan gaskets in the past on OLDS motors (low performance). Began to see a loss of vacuum on high performance, and JUNIOR.Mondello-OLDS confirmed the metal valley pan gasket will leak vacuum. Went to a fiber intake gasket and the problem went away.

Again, never had any sort of a vacuum leak problem with the stock gasket in nearly 40 years, including on an 11 second 455.

Also note that it appears that the metal valley pan gasket "traps heat" underneath the intake maniforld which could hurt performance.

As for "trapping heat", that's really insane. The whole point of the metal tray is to keep hot oil OFF the bottom of the intake. Of course, Mondollars couldn't very well sell their expensive oil-deflecting valley tray if you were getting the same function for free with the stock gasket, could they?

#1. Also read another article to start initial timing on these motors at 20 deg BTDC to run properly. This seems to conflict with some motor manuals.

Initial and total timing depend on how the motor is configured. The Motors Manuals only cover totally stock applications. Use what works at the track or on the street.

#2. Stock starter "touches" header pipes and results in no-start when hot. Went to smaller mini-starter which does not touch header pipe and problem went away.

Depends on the headers. I've used about half a dozen different brands in A-bodies over the years. Some touch, some don't. The mini starter is still a good idea.

#3. OLDS coolant flow to water pump is almost 100% through one small pipe to pump. To manage water temp, I went with a 165deg thermostat, which seems to maintain coolant temp below 180deg at all times, even in traffic/idle. Mark

Huh? Are you talking about the bypass tube? That is not the only flow passage to the pump, nor is it even the main one. The pump takes coolant in from the bottom of the radiator and sends it through the block, just like on any other V8 (except the LT1 backwards cooling system). Coolant flows from the block to the heads and out the thermostat to the top of the radiator. The bypass tube is only used when the thermostat is closed. Once the engine is at operating temperature, the bypass tube hardly flows anything. You might want to take a look at a diagram of the cooling system of an Olds motor. It looks a lot like the cooling system of any other V8 from the same period.

 

[MULL0140]

HELLO:

Note that the majority of the issues with the OLDS motors involve cooling issues. From the factory, an effort was made on the Firebird/TransAm to keep coolant system pressures down by using an "open" coolant system. Although a pressure-rated radiator cap is used, the unpressurized overflow reservoir vents coolant pressure from the radiator. Attempts to defeat/improve this stock coolant system have resulted in excessive coolant system pressures and blown freeze plugs.
Some mechanics indicate "movement" of coolant visible in the radiator shows water pump activity, but this may/may not be true. Movement of coolant in the radiator could also be an indicator of combustion chamber gases in the coolant resulting from a leaking/blown head gasket. There is an exhaust gas detector for coolant systems available to adapt to radiators.
Factory engineers normally don't deviate from known good systems. The OLDS motor was dropped from production early-on. If the OLDS motor is the only GM motor to have the water pump bypass tube in place, that indicates the engineers felt an issue at hand with the coolant system on the OLDS motor. Note that the Chevrolet small block water pump takes coolant directly off both sides of the block and does not have a bypass tube. This is a dramatic departure from the OLDS design.

Mark

 

[DrRansom442]

You were doing great until this statement. I've used the sheet metal turkey tray gasket exclusively on my Oldsmobiles for over 35 years and I've never had one leak. I can't understand why people seem to have some much trouble with them. They didn't leak from the factory and Olds used them with aluminum W-30, W-31, A4, and A5 intakes. I've also used them with aftermarket aluminum with no problems.

try as I might I couldn't get the turkey tray to fit under my Performer intake.

 

[Oldsmoletick]

try as I might I couldn't get the turkey tray to fit under my Performer intake.

:?: That's odd, which Performer? The felpro one fits just fine under my RPM small block intake.

 

[MULL0140]

HELLO:

Several varieties of the Edelbrock RPM line, RPM, RPM Performer and RPM Performer/AirGap. With the RPM
Performer on the OLDS350, on disassembly, I noted the "turkey tray" had contact marks scorched into the tray where it had touched the intake manifold.
This scorching again goes back to the HIGH importance of the intake manifold in carrying coolant to/from the cylinder heads and engine block. ALL of the coolant to the radiator goes through the front of the intake manifold, so the manifod gets HOT!
I noted that the center water/coolant ports in the FELPRO fiber intake gaskets were blocked off. These could assist in cold-weather warmup if you opened them up.
An interesting note is that on the Firebird/TransAm OLDS versions, the TEMPERATURE gauge starts at 220 degrees! Gives you an indication of how HOT the factory expected these to run! My AUTOGAUGE reads 165 degrees most of the time.
Mark