[carbking]

A word of caution:

I don't have a 1970 Firebird, so don't know.

I have a 1974 GTO.

I was told by several on this forum that the RA repro manifolds would fit.

And they will fit, IF you have manual steering ONLY!

So found a manual steering box, and found the pitman arm is different!

I don't remember ALL the modifications required (the repros are on the car); BUT THE MODIFICATIONS NECESSARY TO INSTALL THE REPROS COST DOUBLE THE COST OF THE MANIFOLDS!

And I replaced the original transmission, again after I was told it would work, with one of the really wide ratio Borg-Warners. The shift linkage, when installed on a Pontiac, was right in front of the speedometer gear. Result: electronic sensor to a converter so I could use the original speedometer.

All this was 20 years ago, and hopefully opinions are better founded today.

And not throwing rocks at anyone; just stating reality.

So the point here being is that one modification often begats 6 more; do your homework on modifications. Two of my friends had the repro exhausts on a 1974 GTO, but they had a manual box. When something is said to interchange, make certain you are compare oranges to oranges, not oranges to tangelos (which look like oranges).

Jon

[BDH79TA]

For what you're goals are, stock type replacements should be fine. Get a Melling 60 psi oil pump. Pretty much any name brand double roller timing chain. Don't worry about the 3 keyway type for your build. Stock rockers, pushrods, etc will be fine. The more "exotic" you get the more likely it is you'll bring in other issues like rocker arm geometry. No matter what the claims are, you really don't gain much from rockers, especially the roller tip only style on a mild performance street engine.

[cdoggy81]

Good first hand info bman & thank you! 2.64 or better, roger that 👍🏻

—-

Yes, keeping the #11 heads.

The carb setup will be whatever Cliff builds for us 😎

Yes we have the original distributor.

——

No RA manifolds, that was already removed but thanks for the heads up.

——

Melling 60psi & Double roller, roger that. Stock stuff for the rest. Only exotic parts would be a quality set of 1.5 roller rockers but only if we somehow find a crazy good deal.

Thanks again guys!

[BDH79TA]

I'm not authority, and can't say for certain but I believe the only roller rockers for a Pontiac are 7/16. Which would require a change of the rocker studs. Easy to do if your studs are factory screw in. Much more difficult with press in studs.

[cdoggy81]

Thanks BDH & good point. I believe those non performance #11 heads probably have press in studs so looks like no roller rockers for us.


Side note - I called Bullet Cams & they did have a nice option for the Pontiac 350. Specs are 207*/211* .432"/.441" on a 112. Cost is $300 with a 10 week grind time. They had the lifters ($140) & springs ($100) in stock though.

[b-man]

I’d do the 066 cam and just use all the stock rockers and pushrods. There’s nothing wrong with using your stock parts as long as they’ve been inspected carefully for excessive wear.

The press in studs will thank you.

It will be plenty peppy, the 066 was used in the 350 HO automatic cars in 1968 with about 10:1 compression. With your low compression 350 and a stick shift it will run very well.

Super budget-friendly and reliable.

Roller rockers will definitely work, only the top portion of the studs are 3/8”, the bottom where the rocker pivots sit are 7/16”. However they’re going to buy you next to nothing in the power department so they really don’t make sense to use.

[Shiny]

Just curious... what are the durations at .050" for the 254 cam used in the 70 2bbl? Were they significantly lower than the 066 or does the 254 just have lower lift?

[b-man]

9777254 {U)# cam:

269* advertised, .374” intake / 277* advertised, .406” exhaust / 47* overlap

9779066 (N)# cam:

273* advertised, 197* @ .050”, .406” intake / 282* advertised, 206* @ .050”, .406” exhaust / 55* overlap

I could only find advertised duration numbers for the 254 cam, draw your own conclusions for @ .050”.

[carbking]

Originally Posted by cdoggy81

Hey guys,
I'm looking to help my brother rebuild our dads firebird. He got it new in 1970 & has had it ever sense. It is a base 1970 Firebird 350 (255HP model I believe) & has PS & PB but NO AC. We are not looking to go crazy with the rebuild, just a nice street cruiser.

My big questions are the following:

#1
#2
#3

#4 Any other recommendations you all have for me?

Thanks!

#4: One of the nice things about building Pontiacs for a "street cruiser" is the fact that Pontiac offered their engines in several stages of performance. The 350 was offered in variations from a single two-barrel low-compression engine to the 350 HO.

This is the "street forum" and you asked about a "street cruiser".

Lots of good suggestions, however remember that an engine is a "system".

Pontiac engineered their builds. You really cannot go wrong in duplicating a factory build; simply choose the one that fits your requirements.

I am one of the ones that went totally overboard on a "street" 350 engine build (the only members of my family that can drive it on the street are myself and my son!). I had a reason for building it as I did, and I am not sorry I did it; but a street cruiser it is NOT. And it cost a LOT of money!

There are lots of "tricks" on (maybe) increasing performance for race engines that get thrown into the street forum threads.

Some have been discussed in this thread, and disputed by others as having little benefit for a "street cruiser".

So bottom line on your question #4: pick the factory build that most closely matches your desires, and build it. Above all, have a plan BEFORE you start acquiring parts. And enjoy the build!

Jon

[Formulabruce]

Look at what you have, I have one as well.
1. Small valve heads NOT designed for high rpms.
2. 2bbl carb MORE THAN ADEQUATE for 255 hp AND
375 Torque @ cruising speeds of 2400- 2900 rpm. The specs YOUR engine has.
This engine will Gain Nothing from RA manifolds , and 4bbl carb and intake and cam, EXCEPT more Hp Higher in the rpm range, shorten your Torque curve
AND cost you about twice as much on gas.
Most peoples opinions in this thread are NEVER based on cruising, and have their roots in drag racing and or bragging rights.
You Can, or he can Enjoy it by leaving it alone ( gasp a money saving comment)
The 12 bolt probably has a 3.07 gear in it ( chevy ratios in 1970 12 bolts) that ratio is fine for cruising.
Don't Discount Pontiac Engineers, they DID the homework!

[cdoggy81]

So leave it alone & keep the 2bbl carb on there.....
Where’s the fun in that?

[tom s]

I would put a 4bbl QJ on it anyway.Smaller primarys than the 2bbl.Tom

[77 TRASHCAN]

Originally Posted by tom s

I would put a 4bbl QJ on it anyway.Smaller primarys than the 2bbl.Tom

And it will breathe better at higher RPM’s.

[b-man]

Originally Posted by cdoggy81

So leave it alone & keep the 2bbl carb on there.....
Where’s the fun in that?

Exactly.

Upgrading the cam one step above the 254 to the 066 (used in many 4-barrel medium performance 400s and all 2-barrel 455s) should be enough to see a noticeable performance increase. It don’t see it being be a big enough change to greatly degrade low end or mid range power. Of course the original 254 cam will have a couple of heavily worn lobes so that’s out and good luck finding a new one so the 066 used in just about every regular stock rebuilt engine is pretty much your only choice if you’re wanting a mild factory cam.

The small primary Q-jet carb on a factory intake gives you excellent low speed running and throttle response along with being more fuel efficient than the 2GC 2-barrel carb. It’s pretty well known here on the forums that a professionally calibrated Q-jet can run almost like fuel injection.

A free flowing 2-1/2” exhaust using the stock manifolds will give the engine enough breathing to make use of the big Q-jet secondaries when you need the power. The stock manifolds lend themselves well to low speed running and response but are designed well enough for decent breathing ability.

The 3.07 rear really necessitates the pairing of the right 4-speed, it won’t be the least bit fun to drive around town with a tall first gear. Even the 2.64 low is marginal, one of the Saginaw boxes with the common 2.85 low or even a Vega unit with a 3.11 first would work very well.

Putting the right transmission in it will be the key to fun and spirited driving in the city, choosing the wrong one might make the project a failure.

[Formulabruce]

Originally Posted by cdoggy81

So leave it alone & keep the 2bbl carb on there.....
Where’s the fun in that?

400 -428 ft lbs of Torque at 2400 rpms you have NEVER felt.....

[SD455DJ]

The base Firebird in 1970 with the 350, 3-spd manual with, or without AC, would come with the 3.36 10-bolt rear end standard. With an M-20 trans it would have fairly decent 1st gear multiplication of 8.47 to 1. I think adding the Summit 2800 cam (or similar) would allow you to keep your heads stock with the pressed studs and give you a little more mid-range power. Any larger cam with more lift and you'll need to convert to screw-in studs. I would definitely swap on the factory 4-bbl intake and Q-jet too. As others have mentioned previously, I would retain the factory exhaust (log) manifolds and go with 2.5" mandrel headpipes into a true dual, or Pypes crossover, exhaust system. You don't need an H or X pipe for a mild 350. This would be a budget build I would do. I would add a posi unit too...

My brother has a '69 350HO/M-20/3.55 rear Firebird, so has the large valve #48 heads, 068 cam, std. exhaust log manifolds, of course the cast iron 4-bbl intake and Q-jet and it is torquey off idle and will easily melt the tires in first gear (I acknowledge it is lighter than a '70 Firebird by 200 lbs at least, and has a lower 8.95 1st gear multiplication), but it doesn't seem to be hampered by the 068 cam (has an actual 9.9 SCR) at all. The 068 cam would be OK if you had at least 9.5 compression in your 350, but you'll never get there with the #11 heads without lots of shaving (not good) and domed pistons (expensive).

Good luck with the build! It'll be a fun street runner.

Dennis

[cdoggy81]

Thanks everyone for the replies. Pretty clear which way to go with this:
066, Summit 2800 or Bullet 207 cam
4bbl qjet
Stock Iron intake
Stock internals
Stock exhaust manifolds
2.5 dual exhaust
3.08 rear posi
4spd 2.64 or higher first gear

[25stevem]

You also want to in the least since the car will likely be driven briskly install a factory style late model baffled oil pan and 3/4 or even better full length windage tray.
If not the tray then get a crank scraper.

Also don’t forget a 60 psi oil pump and a HD driveshaft for that.

[Cliff R]

WAY back in my High School days a local guy here had a GT-37. Not sure what year, 71 maybe? It was a really quick street car and he won a lot of street races with it. We always thought it was a 400 or 455 powered car till one night he opened the hood in the High School parking lot and low and behold it was a 350! It was backed by a 3 speed manual transmission and 3.55 gears nearly as I can remember.

Pretty impressive non-the-less, at least for the combination of parts.......

[SD455DJ]

Originally Posted by Cliff R

WAY back in my High School days a local guy here had a GT-37. Not sure what year, 71 maybe? It was a really quick street car and he won a lot of street races with it. We always thought it was a 400 or 455 powered car till one night he opened the hood in the High School parking lot and low and behold it was a 350! It was backed by a 3 speed manual transmission and 3.55 gears nearly as I can remember.

Pretty impressive non-the-less, at least for the combination of parts.......

That's a great point Cliff, good gearing and dual exhaust in a 350 A or F car is huge to how they perform, especially off idle up to 3500 rpm. Way back in 1973/74, we were always cruising the local used car lots and found a really nice '72 Lemans GT (T-41 Sundance Orange with black top & interior) similarly equipped as the GT-37 you recall...350 2-bbl, 3-spd (M-13), 3.55 std. rear gears, factory dual exhaust, etc. that was a pretty peppy car for what it was. We passed on it because it was just a 350 2-bbl...lol!

Back to the OP's question, since you are rebuilding the engine, now's a good time to upgrade the heads to #13's, 62's, or '68 #16's that would give you 9.+ compression. Cost the same as rebuilding the #11's and come with screw-in studs already...just a thought.

Dennis