[sixty8coupe]

New to the OHC world with my 68 firebird.

I just rebuilt my stock 1 BBL head and hope to fire the car up soon. Not fun setting a 6 cyl head back on a car by yourself...

I'd like a little more performance than the stock 1bbl can provide.

There's so many little bits and pieces of info out there I'm trying to string together some options.

Due to reading a lot of negative info on wait time and losing manifold jigs, etc, I'd like to avoid clifford at this time.

My questions:

The most important is, is it even worth going to a 4bbl with a stock cam (which if I understand right, I would also need the double valve spring for the 4 barrel, sprint cam, and followers?) I don't wish to do all that work again (wish I had found out about the springs, etc earlier.) Going from a 2V to a 4v on my 65 Mustang's 289 made it an entirely different car, but I don't know much about these motors yet.

I thought I've read the intakes are car specific? Like A vs F body and there might be a difference between the 66-67 230 and 68-69 250 intakes? Is the difference just linkages or is there an actual difference in the intake castings?

Can I buy a sprint intake and use an aftermarket header? Or do I need the sprint exhaust manifold too? I've seen where there is a gasket that's supposed to go between the two?

Any special parts I need to find (like funky linkages) if I find one on ebay, etc?

Thanks for any help, I've spent most of my time in the ford and GM small block world. I did as much as I could with searching this site, another, and google

[Jeff Hamlin]

S8, Welcome aboard always good to see new blood.

Yes 75#+ heads are good times for sure, I always set mine on the core support then have to straddle the engine to get a clean set.
That's the good thing about an inline 6 lots of working room

Anyhow on to your Q&A
I wasn't aware Clifford was still in the game for anything OHC so that would be a long-shot option for sure.

It's not just the springs and the Cam you ideally need the whole '68 4BC top end.

Intakes can swap but you would be better suited to stay on the 250 side of things.

4BC intakes come up for sale often and if you can find an old Clifford Header set it would work with the stock intake,
but they are seldom seen anymore and when they do pop-up they are either way overpriced or beat to hell.
It's my understanding that a set of shorties are what fit best, if I'm wrong I'm sure someone will chime in.

I find more complete engines being offered over parts anymore and most times that's better as it will have all the bolt-on's and "Funky" bits.

I would stay with getting your engine all back together and dialed in so you can drive and hopefully enjoy it,
while you plan out your performance upgrade and accumulate needed parts.

Best of luck and keep us posted.
Cheers

[694.1]

Sixty8 brings up an interesting question, that is: would a 1bbl Cam & Carb be well matched or is the engine under carbed or under camed? Wondering here if the car is an automatic.
If so, it will benefit greatly with a TH350 and/or a rear gear swap.

[Jeff Hamlin]

IMO I think if you throw a 4BC carb/Intake on a 1BC head you gain 0.
The head/valve/flow are what's needed along with the cam and carb.
If you just want the WOW look then no harm but if it's the extra zing, you need the top end.

[66sprint6]

I agree with Jeff: put what you have together if you can, and enjoy the car while you sort out the Sprint stuff. You’ll need the 4barrel head all done with cam and springs, intake/exhaust manifolds, the carb, linkage. Everything.
Good luck and let us know how it’s going.

[sixty8coupe]

Wow, thanks so much for all the info.

I had not realized the actual head was different (which makes sense though). So, I basically need to somehow locate a complete unmolested 1968/69 sprint engine... sounds easy! 1BBL doesn't sound so bad at the moment! lol

I bought the car because I love the Firebirds. My dad had a bunch of first gens when I was a kid and a white 67 400 clone was the first car I ever handed him tools on... that was just over 30 years ago.

I know everyone hates this term, but the car is somewhat "rare" in it's uniqueness. I got all the PHS docs, bill of sale, trade in, original build sheet, and original title from the original owner (A lady!) to confirm the data tag and what I'm seeing on the car. It's a an April Gold TWO TONE car with a Primavera Beige painted roof and gold interior. It also had a deluxe steering wheel, redline tires, hubcaps (long gone) AND a 3 on the tree 3 spd manual trans (still in car). I like the rear axle ratio, it's a 3.55, perfect for a 5spd OD (researching that now.) I've converted my 65 Mustang to a T5 and I love it. The only way it could be cooler is if it were a Sprint.

My cars get driven, I've taken the 65 Mustang on 4 long hauls on the hot rod power tour for a total of over 10K miles. From SC the cars been as far north as Wisconsin, as far south as Florida, as far west as Texas/OK, and as far east as the Carolina coastline. I love to drive I'd like to replace the Mustang with the Bird as that car someday (It needs A LOT to get there).


So, the backstory, this car is stupid solid. I'm originally from NY, I HATE rust, and I'm not a fan of repop paneled cars *if it can be helped*. I'm glad those parts exist to save more cars, but I prefer OEM if at all possible. The car was bought by a mom in December 1967. Around 1971 it was transferred to her daughter who drove it until 1981. It was supposedly under a carport all those years. In 1994 some dude bought it and had a TERRIBLE, and I mean TERRIBLE Maaco style paintjob done (to the original colors). That's when I believe the engine was rebuilt. Either the motor had problems, or the project stalled, but the car has sat in one of those metal containers since 1994. The guy I bought it from bought it in 2017. He couldn't get it to run right so he punted it to me. I got a good deal on it. I didn't want a 250 car, but it's what I could afford. It will need ZERO rust repair work done to the floors, trunk floor, doors, front clip, or roof. There are a few quarter sized rust bubble areas in the lower rear quarters on each side, that's it.

What I found when I pulled the head was a ridiculously clean bottom end. Like two of the pistons look like they were never fired. The reason I think that is, is it either sat for many years before someone tried to start it, or it sat for a long time and was then rebuilt, however it happened, the bottom end looked fantastic as well as the cam. However, when I pulled the head, I found that ALL TWELVE of the lifters were stuck solid and all the intake valves were very sticky (maybe from old/bad gas?). So basically 4 of the cylinders had little to no compression (which explains why it looked like a couple cylinders had never fired - they had no compression so they didn't). There was still assembly lube in the top end. So I cleaned everything up, lapped all the valves, have good movement in tall of them, and I replaced all of the lifters with ones from kantor.

I wanted to try to get it to make some noise today but I got out of work really late and my alma mater just won the college football national championship!!!

[Jeff Hamlin]

Sounds like a solid car and a great base to work off.

Hang in there, Research and gather info and plan out an upgrade.

Engines/parts like below pop-up now & then.
You just have to be patient and the right stuff will find you.
https://inlandempire.craigslist.org/...780574764.html

[camerjeff]

It does sound like a great car!

As for the differenced between 1bbl & 4bbl OHC-6 heads, other than the 4bbl heads having smaller combustion chambers to increase the compression Ratio, and different spring pockets to accept the dual valve springs. There is not much difference between the 2, they flow the same numbers on the flow bench both intake & exhaust.
In fact when we built the stroker we used a 69 1bbl head to lower the CR to around 9 to 1. If you are looking for a set of headers I do have a very nice set of old Clifford long tubes that are Jet-Hot coated available. And a 69 Sprint exhaust manifold.

But I agree, get the car running 1st and drive it. See how you like it, and make plans to modify it if that's the way you want to go. I personally think the stock 2 speed automatic transmission really hurts these engines performance. A 3 speed TH-350 is almost a bolt in and makes drivability much better IMO, it won't actually make the car any faster, but it feels better in the midrange. If you car is an Automatic it probably has 3.23 gears that are not a bad road gear.

That 68 Sprint Engine in California is actually a pretty good deal, it has the Large HB, along with the power steering Brackets, and the almost unobtainable 68 only 2 groove water pump pulley. You could probably get it for $500 and when you add up all the individual part prices, that would be a steal.

[ho428]

With reluctance I pulled the base OHC out of my 68 Convertible bird and replaced it with a 350 engine for awhile. The base engine has new issues but never did have enough power to get out of it's own way.
I have 3 complete OHC engines, one being a Sprint I can use parts off of. I plan to try and build up a Sprint over time and re-install it. But after dealing with the base engine ever since I bought the car in the mid 80's, I'll never have another base OHC in my car, they look cool but have severely disappointing performance.

So, my opinion is don't waste your time and money putting a stock base OHC-6 back in the car.

[sixty8coupe]

I haven't had a chance to confirm yet, but according to the build sheet and PHS documents my car has a 3.55 rear end.

Depending on which one I choose, most T5's have a nice low 1st gear to get off the line a little quicker. It made my anemic stock 2V
289 feel pretty quick until I started upgrading the motor.

I'm more of a touring/cruiser kind of driver. I don't like drag racing (my stuff) or doing 90 down the interstate. I'm happy rolling 55/60 on a back road.

However, if this motor is a bust, it's so $$$ to build a good 350/400 I would go LS/6spd (complete blasphemy, I know!)

That cali motor is a good deal, but 2000 miles is a LONG ways away!

I have my eye out for one of those elusive W/P pulleys, if this motor works out I'll have to add A/C, my wife won't get in the car without it.

What makes the 2 groove W/P pulley 1968 only? I've read there's short and long shaft W/P... is one 66/67 and the other 68/69?

[sixty8coupe]

I figured out pictures!

The rest of the floor, fender, quarters are this nice. The trunk floor has some light to moderate pitting on the inside, but no holes.

[sixty8coupe]

Few more:

You can see the two tone top better. They used the same trim the vinyl top cars used to separate the colors, the car was slightly disassembled when I got it.

[sixty8coupe]

And a few of the where I'm at now.

[ho428]

Car looks very nice. I'd like to see the OHC stay in it but I stand by my take of the stock base engine in a Firebird.
Even at it's best with the stock 3 speed manual my car was a dud. Yeah it would drive ok once up to speed but just getting it there was painfully slow.
If you wind it out with the 1 Barrel carb it doesn't even sound good. More like a Pffftttt, reminds me of the old 6 cylinders in early Ford Falcons. Given the weight difference they pulled about the same. Meant to get ma to the old grocery store, that's about it.

[66sprint6]

Originally Posted by sixty8coupe

And a few of the where I'm at now.

Ha ha. Been there, done that. You've got to be a dedicated cammer to love these engines.

[sixty8coupe]

lol, I don't know about dedicated, I just want to get it running/driving. Brakes are good. It *ran* well enough to get it up to about 30 around the block. That was before I knew the compression was crap. Clutch and trans feel good. It's just the motor and some wiring fixes away from being drivable again. Then I can go system by system and make it better. That's how I did my mustang. I did it all in phases so the car was never down for more than a couple months at a time. Keeps you more motivated. This car will need a full repaint at some point though, so I'm going to concentrate on under the car, trunk, interior, and under the hood until I can swing that big paint check. This one is a keeper for me, I won't ever find a more solid original car in this area. I've had my 67 C10 for 23 years and the mustang for 7 now.

My other toys:

[sprintbird]

Very nice project! I am going to take a guess as to why this car sat: I believe that either the valve seats were possibly cut too deep, causing the valve to sit up too tall, or the oil pressure is cranked up. Either of these conditions will cause the valves to stay open and lose compression in the cylinder(s). If you did not confirm the valve heights when you had the head off, you may have the same condition when you reassemble and try to run it. I am not trying to be negative, just trying to avoid another disappointed Cammer. Can someone confirm the valve height? I think it is .875” +/- .020. Also the oil pressure is designed to be low overall. I believe it is 28 psi at 2800rpm? Can someone also confirm? Good luck!

[sixty8coupe]

The car sat from 1981 to 1994 and then again from 1994 until now, so who knows what happened.

I'll check the oil pressure when it's running.

As far as the valves being hung open, I had read that could be an issue. On the bench, I reassembled the head/cam cover with the old gasket (same as the new one) and slowly went valve by valve making sure they were full seated/closed on their circle.

[sprintbird]

Good to check it assembled, but oil pressure wasn’t present and influencing the lash adjuster. So it still may be an issue. Did you confirm that the metering tube is installed and the correct size? That is something else that could cause problems.

[sixty8coupe]

I can't locate any reference to a metering tube within the service manual... where is it located?

If it blows or isn't good, in goes an LS. I'm not going to spend repeat efforts on it