I have a 1969 Firebird convertible getting painted right now. New interior gets put in when that's done. Then its time to look at the engine. When I bought the car last year, it was a driver with a spare motor that had been pulled because it overheated at stop lights. After reading many posts, I'm leaning toward it having the wrong water pump or the spacer hadn't been "massaged" to fit better. The water pump has been changed. Either way, I have it on a stand and the car has another 350 in it that is a dog. In running the numbers, the one on the stand appears to be a 1969 350 HO with "48" heads. Different carb, distributer and water pump has been changed. I'm hopping it has not been touched internally. Plan is to pull it apart next fall and see what I have and what it needs. Reason for this post is from what I have read, there are not too many of these around and this might be a chance to answer some questions and dispel some myths so if anyone has a question, or a comment on what to look for when pulling it down, feal free to post or send me a message. Of all the Pontiac forums, this one seems to have some members that are really smart and know there stuff. Not sure where I'm going with the distributer. One in it is not OEM, it's HEI and I have heard of clearance issues. Hell, I don't even know if it works. The other thing is the carb. Have read that I need one that is factory correct and I will be happy, but those are hard to find and lots of $$$ so we shall see.
Congrats on a '69 convertible. But even more if it is a true HO car. That is really rare. This chart shows the #48 heads as big valve 10.5 compression.Pontiac HeadsThere are many reasons for it to overheat so I would check the basics first.
Original is always best, but, you can use a different carb if it has the right jets and rods inside. I prefer a post 1973 Q-jet because I can convert it to electric choke. Look up your factory carb specs here> Carb specs
If you open the engine, check the cam out for sure. The Wallace Racing site has the cam codes too. And block codes.
I prefer the HEI distributor. No points maintenance, hotter spark. It is a tight fit against the firewall, nothing a small sledge won't correct. You can bench test it by clamping it in a vise and rigging it like it was in a car. Just watch out for the spark. It can reach a foot away and bite like a MF.
Thanks for the tips. Im just guessing water pump because it has been changed. First thing is to verify it has the proper one. Car was not an HO car, but that was what was in it when the previous owner bought it about 20 years ago. For a second I almost thought of building a "tribute" TA, but so much has been changed from stock, Im just going to make it what I want. I'm having the painter put on the HO stripes from 67,69. We will see how that goes. Interior is getting redone, just back to factory but it will be new.
I'm slowly getting the wife warmed up to the idea of doing the HO motor. Should hit the paint booth this week or next and I'm putting HO stripes on the side, so I kind of HAVE to put the HO in. Not looking to build a race car, but I would like to just do a "to spec" HO 350. I got to thinking, will I have any problem on pump gas with 10 to 1 compression? The gas we have now is way different.
Yes 10:1 will be tough. i have been down this road many times. I would seek out better gasoline if you want to go that route with that compression. You have to be on point with tuning but even then you cant set the timing to where it would be optimal for the engine to run like it should. I would drop it down to 9:1 with custom pistons since there is really no choice with an off the shelf piston.
So what will it do if rebuilt to stock specs with the correct carb? Will I fight pinging and just have to retard the timing a bit? There for not getting everything out of an HO like they were made. Am I just looking at running a higher octane? It's not going to be a daily driver, but I want to take it on a couple of 200 to 300 mile trips and not have to worry about fuel. So for that I'm thinking build it to run on pump gas.
You could try an octane additive or aviation gas if you have a small airport locally. The problem with retarding timing to compensate for the pinging is that it greatly effects engine performance and just adds heat to the exhaust so the engine will run hotter. But you really need to figure out what the actual compression ratio is. you really need to know the exact CC of the combustion chambers of the heads, the piston the deck clearance, the volume of the valve re leafs in the pistons and the thickness of the head gasket. some of these cylinder heads did not have the supposed combustion chamber size. Not all 72 cc heads had a 72 cc chamber. If you have a set of the #48 350 HO heads, those chambers were supposedly 68cc chambers. But you never know. Back many years ago when we had good gasoline we would run Sunoco 93 in these engines without any problems.
Thanks for the tips. Sounds like I'm going to have to really pick the brain of the engine builder and get his thought also. He got the shop from his dad and has a long time following from the Pontiac crowd. When I first approached him about the 350HO and explained that I just wanted to refresh it and keep it stock, he commented I could do that, but I would really have to watch my tune. Didn't ask for clarification at the time. I got really excited when I was doing the research and found that I had a 350HO with #48 heads. Factory 325HP with no build, COOL. Now I'm coming to the conclusion that I can't really run that engine on todays gas. Or I can, with a bunch of modifications. Hardened valve seats, Lower comp pistons, different cam. Then its not really a 350 HO then is it? I got all summer to decide..........
OK, here I go. Bought the proper carb for the engine. Sent the vin to PHS and surprise, it IS an HO car. From what PHS says, it is one of 2455 1969 350 HO with manual transmissions. From Hagerty, it is 1 of 112 convertibles that came with the HO 350. Just going to do a stock rebuild. machine shop is 8 to 10 months out so I'm pulling the heads to get them done first, speed up the process and take a look at cyl walls. Hopefully no cracks, 48 heads don't look to be cheap to replace. Ran all the date codes and the block, heads and intake are all good. HO motor is not numbers matching to the car, but the fact that I got an HO 350 from 1969 is pretty awsum I thought!
Things are looking up. Pulled the heads, dropped them at the machine shop. Saw a couple of cracked exhaust valves but heads look straight. More excited about the lower end. Almost no ridge on the cyl walls and looks to be a virgin 350 HO. Still has the nylon timing gears. Rod and main caps have not been stamped and it had "GM" head gaskets on it. This could turn out really cool.......
Is it too late to change heads? If the car is not 100% correct anyway, why suffer with those heads? Pontiac adjusted compression ratios with the heads. Others like Buick did it with the pistons. I have a 1970 GTO 400 that I used in my DD station wagon. It had very high compression heads and it sucked. I researched and found a set of 1972 big valve 400 heads with much lower compression. I used those and the engine loved them. I could run lots of timing advance on cheap cat piss gas. After 1973 the heads still had low compression, but the valves got smaller. Testing by guys like Jim Hand reported that unless you are racing, the later heads will flow just fine on the street. You could even play around with 455 heads to get what you want. This site has all the heads and cc volumes listed. Head codes and specs The 1971 and 1972 big valve heads sometimes were missing the end bolt holes for the exhaust manifolds. I guess they saved $.05 on every head. They beveled the flanges of the manifolds so the two inner bolts clamped the manifolds to the heads tightly. This can be done to any manifold to work with the heads. I know any Pontiac V-8 heads are going for big bucks these days. But you can still find deals out there. You could probably sell the HO heads and get several sets of low compression heads.
That sure gives me something to think about. Would kind of like to keep it an HO motor and from what I understand, the heads are really the only thing that makes it an HO. Cam, dist, carb all can just be swapped out. The heads are currently at the machine shop waiting for disassembly and evaluation. That will tell me a lot. I'm not building a street racer and the knowledgeable ones I have talked to all say R/R the heads to include hardened seats and if a stay with a stock HO cam grind and keep the timing to factory specs, I should be fine. Just don't get greedy for HP and go for more timing. Like most, I am on a budget and the fact that a 69 350 HO landed in my lap has me excited. Thank you for the advice, I will consider it pending the evaluation.
That's another plus to using later heads. They come with hardened seats already. Many moons go when I still had my 1968 hardtop, I blew an engine and needed one fast. My local junkyard had a 1969 GTO 400 YS motor. I grabbed it and ran that engine for years. It pinged like crazy but otherwise ran well. I used the best gas I could find, retarded the timing, nothing eliminated the pinging. Eventually I spun a bearing so I removed that engine and took it apart. The valves had receded so far into the heads I could not believe it. That was because after 1973 there was no lead in the gas anymore.
I understand the appeal of a genuine 350 HO, but unless you find a way to reduce compression you will not be happy. What bigchief said about using dished pistons is right on. But that would require a complete engine rebuild costing a lot of money. It is indeed a dilemma. I have a 1968 400 HO engine. I have never used it just because of the compression. I would have to use the low compression heads I have stashed away.
Did you run the engine code? On the front of the block, passenger side, just below the head, is a two letter code. A partial VIN may be there too. The code will tell you exactly what engine that is, what cam, what heads. Use this chart: Engine codes
A 1969 WN- that is SOME engine. It came with the 068 cam, that is a lot of cam for a 350. My buddy used that 'S' cam in a 400. It was a lot even for the 400. What about the 350 that is in it now? What year, code, etc?
I ran the H cam in my pontiac 350 But had 4.10 rear and a 3000-3500 converter Without those it would be a total turd Ran that same exact cam in a 400 with a 3.73 rear and the car ran low 12's
Its a dog. Came from one of about four different years with a two barrel. Apparently the 2 vs 4 barrels used a different throttle cable. The one in there stops just short of starting to open the secondaries. Did a compression check and got everything from 110 to 135. Somethings going on inside but its still a driver.
with cranking compression that low its time for a rebuild But parts are limited for 350's the correct head gaskets are hard to find dished pistons will need to be custom made
Only smokes on start up. Just keeping it going till the HO is done, which is the whole reason I'm doing the HO. I put a lot of money into everything else and if the installed engine was good, I would just run it. But after doing the compression test, things are not great internally.
That is my point. Pontiac made fantastic racing cams. That same cam sitting in Wrong Island traffic gets old fast. You have to make up your mind what you want to do. Go cruising or racing. Hard to do both these days with speed cameras everywhere.
On the other hand, those two barrel 350 heads are probably small valve, low compression jobs. If you are really honest about what you are going to do, getting those heads done up would go a long way to making that 350HO street-able. Maybe just grind off the head codes, claim they rusted away, who would know? Choose a nice street cam, with a bit of grumble, and enjoy the hell out of it. Post the crummy 350 codes if you don't mind. [wink wink- nod nod]
Not a racer, that's why I'm keeping it stock. It's an HO and I'm putting the factory grind cam back in. Same thing for the carb. Got one for an auto and mine is manual but shouldn't make that much difference. I don't think they had much "lope" at an idle from the factory. So if I just stay with OEM, I'm thinking I should be fine. Hell, I'm even staying with points. Used them for years and is you know what your doing and how they work, no big deal. You do you and I'll do me. Thanks a bunch for the discussion. Gives me a lot to think about and more info and input is always a good thing. I'll keep you all informed and let you know how it turns out. At the very least, I kept a "69" convertible Firebird on the road for a while longer.
Points too? You are hard core old school! In that case I can recommend the Mallory Super Condenser. Back in the day it was standard procedure to use the Mallory Volt-Master coil. That was big medicine compared to the stock coil. Nowadays you can get a high voltage coil that is no bigger than the stock unit.
But the best thing ever was the Super Condenser. It was so big you had to attach it to the underside of the distributor. But, wowsers, your points seemed to last forever. It's kind of rare now, but is out there. Here is a pic of the set-up as it would have been installed in 1969. See the condenser mounted on the dizzy. Using the window on the side of the cap all you had to do was re-set the dwell maybe a single degree once a year or so. It made living with points a lot easier.
Myself, I hate points. They are right up there with drum brakes. I switched to the GM HEI as soon as I could score a Pontiac version. Guys that wanted to look like they still ran points would use the Pertronix or Mallory Uni-lite conversion that fit under the stock points distributor cap. I want my engine to start right up, run perfect, and not degrade from point wear. But as you said, I do me- you do you.
The HO that I have already has a Accel super coil. Not sure if it works. Would like to put an OEM back in. I believe it is a #1111965 if anyone knows where I can get one? Otherwise I'll get the specs for the advance curve and make a clone. Only going to put a couple thousand miles a year on it so points should last awhile. Yes, I'm old enough to remember points, cap, rotor condenser and plugs every year. Plug wires every other. With a lot of people going to LS motors, fuel injection, electronic ignition, I think it kinda cool to do it old school. When everything is right, it all works pretty good. To show you how old school I am, I picked this up a couple of weeks ago. Can't wait to hook it up!
Where did you find that relic? The Smithsonian? I should talk. Back when tailpipe sniffers were part of the State inspection, I bought an exhaust analyzer from a co-worker. By the time I got it calibrated and working, the State had moved on to OBD2. Story of my life.
I always stuck with Mallory ignition parts, or Blue Streak. Accel was what the speed shops pushed but they used to crap out unexpectedly. If you can't find a stock coil, I am sure you can get a high output version, same size, and just paint it black to look stock. I have a big coffee can full of the old spark plugs for our Firebirds. I knew someday it would be hard to find them. I don't know if they make an Iridium version of ours. If they did I would use those. I have Iridium in all my other cars and they last forever.
Found it on facebook market place. the guys uncle worked at the local dealership for years and when he retired, they gave it to him. Mainly because no one else new how to use it. Sat in his shop for years, then given to a nephew. Sat in his shop for years. Went to look at it and he made me an offer I couldn't refuse. It will probably sit in my shop for years. Thanks for the advice on coils, that would be one thing I would upgrade. Hotter spark is never a bad thing.
