[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. Not a big budget either, most parts will be stock or not super costly upgrades. Car should have the # 11 heads which are 1.96/1.66 & a whopping 8.8 c.r - which is probably why it still runs fine on todays pump gas & never been rebuilt. It has the original 3 spd manual but we will convert it to a 4 spd (M20, M21, T-10 or ST-10 depending on what we can find at a good price). The car has the original 12 bolt peg leg rear end that we will put a posi unit in & probably a 3.08 gear set so highway cruising won’t be so bad. Will also be adding rear disc brakes too. For the engine we will be taking off the original 2bbl carb & intake then replacing them with a stock iron 4bbl intake (67-70 non egr) & a q-jet. Going to get a set of repo RA exhaust manifolds & a pypes 2.5” exhaust to finish it off.

My big questions are the following:

#1 is what cam… I was thinking the Summit 2800 (204 int./214 exh.- 0.421 int./0.444 exh.) would be a good one to start. Great price & should give a great little boost of power over the stock cam without being crazy. Not sure what other options are out there but also thought about the 2801 (214 int./224 exh.- 0.444 int./0.466 exh.). Just not sure if it would be tooooooo big & we would lose drivability & low end power.

#2 How much, if any, should we mill the heads to bump the CR up a tiny bit?

#3 What springs, lifters & rockers do you all also recommend?

#4 Any other recommendations you all have for me?

Thanks!

[b-man]

I’d be looking for a 4-speed with the most favorable first gear to get the car moving with that 3.08 rear, at least a 2.64 or even lower. I’m not sure any of the ones you listed would be ideal.

Bore it +.030 and surface the heads enough to get a good sealing surface and you’ll likely end up with an actual compression ratio that matches the factory rating.

Run the 2800 cam, that tall rear gear kind of decides that for you.

Honestly I wouldn’t bother with the RA exhaust manifolds, just run the 2-1/2” head pipes and save the cash for other things. You’ll be spending $400 on manifolds to add maybe 5 to 8 horsepower.

[Dragncar]

I ran the 2801 with 48 heads and it sounded sweet. Ran well but it did not come on until right at 3500RPM. Then it really took off.
2800 with your heads. And the Edelbrock Performer intake works very well on 350s. Its smaller than the stock Q jet intake.
OK, if you want to spice things up you could run a cast 4" crank. Ken at PPR made some fantastic 350-383s doing that. Pistons would cost a little bit though. The cast cranks are pretty cheap and will handle the power you are making.
Mill the heads to get 9.25-9.5 CR.
Good luck with it.

[Formulas]

I have a 1970 Esprit 2bbl 350 wide ratio 4-speed it was original with a 3.36 10 bolt... not to many stick 350 birds in 70 only about 2800-2900 4 speeds built
one of the first things i did was put a qjet on it woke it up alot
second it had a few worn cam lobes replaced the 254 cam with a erson 204 dur .411 lift on 110cl woke it up even more later went with a 2800 cam after rebuild, 2800 will give you typical 4bbl muscle car power band good low end with strong midrange
i went with 1969 #47 heads which have a slightly smaller chamber and i milled them .020 cleaned up the ports some good valve job tapped for screw in studs
i ran headers but dual exhaust with cleaned up logs will be fine for the smaller cubes and lower RPMs

if its NOT a commuter car and extended highway isnt an issue to have a bit more fun the wide ratio trans and 3.55-3.73 gear wouldnt be to bad
i always got a smile dumping the clutch near 5000 rpms and didnt have to worry so much about torque ripping up the trans

[i82much]

2800.

[Shiny]

Just FYI, the advertised 8.8 CR was over-stated. Or just plain misrepresented.

The actual is 8.0 or under as the #11 heads had large combustion chambers (87-89cc) per this and other forum threads:

https://forums.maxperformanceinc.com...errerid=160974

Others can comment on what that means for cam selection.

I did close to what you are proposing ('70 350, #11 heads, Summit 2800, 71 intake w/Qjet, stock exh manifolds, dual 2-1/4" exhaust) but unfortunately haven't driven it.

I suspect I'll be happy enough when I do but I know a CR increase would enable added umph.

[77 TRASHCAN]

X2 on post 6!!!
I suspect the “real” compression ratio is less than 8:1.
Yes, mill the heads, say .030, zero deck the block,if possible, this helps ANYengine, and will help raise the comp ratio a fuzz more.
The 2800 would likely be best, especially with some more comp.

I currently have the same engine in my TA.
I performed a simple rebuilt on it. No machine work. New rings, bearings, cam, lifters, pushrods.
Has a 78 Q-jet intake, same year carb. Cam is Sealed Power CS-641, which is the 066 grind.
It runs OK, but I still have the 2.41 gears. I can tell the comp ratio is woefully low,I’ve had as much as 44 degrees total timing in it, and couldn’t make it ping!!!

As Bart mentioned, there’s not enough air flow through the engine to warrant using anything better than the stock exhaust manifolds.

[dataway]

I drove a 69 Lemans for a while with a 350 and TH350 .. with a 3:23 it had a satisfying level of acceleration.

The RA manifolds will add about 14 lbs in weight too ( I think).

[25stevem]

Within a tight budget here’s the way I would go, but first in terms of the 350 motor being so close to being square in terms of bore and stroke keep this in mind especially since you want to stay with 3.08 gears.

The air flow in and out of the motor determines the level of hp, but the air flow rate ( velocity ) thru the complete intake side determines the torque output to a large extent.

To maximize the production of both with your motors CID and not loose drivability, but pick up on drivability you need to run as much lift as possible.

Moving more intake air thru the same size intake tract will provide higher torque numbers for any given rpm.

The ago old hot rodder’s rule of Thumb that states duration makes hp and lift makes torque is still very true.

To this end then the added expense in this build of going to 1.65 rockers is well justified..

Looking at your first stated cam pick the 1.65 rockers will make for .463” lift on the intake and .488” on the exh side .this will make for moving a good amount more air out of what those heads can ultimately flow.

There is also a side benefit of the 1.65 rockers adding some 4 more degrees of duration over the nose of the cam without effecting cylinder pressure nor the idle.

In effect it’s like your where running the second cam that you rightfully questioned as being too big!
You can have your cake and eat it too!

In terms of the head itself and the block. decking either can get expensive real fast, especially if your total reduction calls for having to mill the intake flange to get things to bolt up and seal.

In light of this and the need to increase compression your better off taking careful measurements and getting a custom piston made with only the needed 2 valve notches, but one that comes up out of the deck by .005” to .008”.

The pistons should also have a high top ring placement and use 1/16” compression rings.

This will get your compression up without all the machine work, but the heads at least should have a .002” clean up cut done to them even if they check straight.

The heads will also need to be set up to run springs to handle .500” lift .
The valve guides tops will need to cut to accept positive type seals , and most important of all the heads need new valves even if the fit in the guides is acceptable.

The stock valves have been known to lose there heads which can take out a whole motor at times , no less that cylinder , piston and
connecting rod!

Any valve that shows more then ,001” of stem ware should be considered scrap metal anyway.

If you run the stock log type exh manifolds then clean the hell out of them and get in side them as far as possible to polish them.

Rusty bumpy inside surfaces eat up exh flow numbers like you can’t believe.

On a flow test that I posted up here some years ago on a head pulled off a good used running motor ( 6X casting) all I did was to remove all the carbon build up and rust with a 80 grit sanding roll and I was rewarded with 8 more cfm.
This work per port took less then 10 minutes, and no I did not polish anything to a shinny surface.

Also in terms of torque and transmissions to use, don’t discount the 2.52 first gear ratio of a TB 350 and then on top of that the 2 to 1 torque multiplication of the converter!

Once you get into being able to drop the clutch at 4500 rpm then money wise your into a bunch more needs drivetrain mod’s to get things to hook up no less live!

Oh, and since new pistons will require the motor to be balanced , please get the stock rods out of the motor.

Lighter aftermarket pistons and rods will allow the motor to spin up faster and this in and of itself provides a nice performance gain.

[Shiny]

Having read a lot on this forum and owning/driven a 70 Tempest 350 for several years, I think a stock 70 350 will have enough power to enjoy driving and I think it would be easy to cause trouble chasing performance. By trouble I mean reduce reliability or low-end torque/driveability.

25stevem makes great suggestions and they make sense. But the cost of new valves, custom pistons, rods, rockers, and machining is higher than zero. The #11 heads also have pressed-in studs so may not hold up to higher valve-train stress.

IMO it really comes down to budget vs goal. If low budget dominates, I think it comes down to what shape the engine and heads are in. If you have to bore and refurb the heads anyway, I suspect the budget is already expanding and then it is not an easy decision space.

[BDH79TA]

While I can't suggest anything directly related to the 350, I can weigh in on the overall project. I've changed directions, each with their own "cost" on the same drivetrain in the last couple of years. First was a decent rebuild. Stock rods, decent cam, Q-jet, TH350. Then decided a 4 speed conversion. That went to a TKX 5 speed, E heads, ProFlo4, so on and so forth. The latter meant tearing the engine down and using forged rods, which I probably should have done in the first place.

The point is, stop and consider what you truly want out of the car. While budget dictates a lot of decisions, many times it's our desire to have it done as quick as possible. Decide the end goal and direction you want to take and try to stick to it. Even if that means it takes an extra year or two to complete. If you settle for something less you'll be disappointed and only end up going back and redoing what's already been done.

You'll get plenty of opinions on how to spend your money here. Some great. Some skew so far from your original desire you wonder if they even read your opening post.

[AG]

Originally Posted by BDH79TA

While I can't suggest anything directly related to the 350, I can weigh in on the overall project. I've changed directions, each with their own "cost" on the same drivetrain in the last couple of years. First was a decent rebuild. Stock rods, decent cam, Q-jet, TH350. Then decided a 4 speed conversion. That went to a TKX 5 speed, E heads, ProFlo4, so on and so forth. The latter meant tearing the engine down and using forged rods, which I probably should have done in the first place.

The point is, stop and consider what you truly want out of the car. While budget dictates a lot of decisions, many times it's our desire to have it done as quick as possible. Decide the end goal and direction you want to take and try to stick to it. Even if that means it takes an extra year or two to complete. If you settle for something less you'll be disappointed and only end up going back and redoing what's already been done.

You'll get plenty of opinions on how to spend your money here. Some great. Some skew so far from your original desire you wonder if they even read your opening post.

Either go totally budget or do as BDH has suggested.

[25stevem]

It always pays to pump most of the funds into building a strong short block, even if it means running the heads stock for a season or two and not running the Cam that you otherwise would like.

A spun bearing from a stock rod going out of round will end a whole season of driving fun real fast. ( I know this all too well! ) and then even if your lucky to be able to use the block and crank again the cost in the end to get the motor back up and running is close to double from the first rebuild!
A lot of this is due to shop labor rates that have historically never gone down.

[cdoggy81]

Thanks guys & good info.
I think this will be more budget related for sure.
2800 cam
1.5 rockers
Mill the heads .030”
Stock iron intake
Get the q-jet setup for the 350

Looks like a M20 Wide-Ratio from 1966-'74 will work:
First Gear 2.52:1
Second Gear 1.88:1
Third Gear 1.46:1
Fourth Gear 1:01

Now the fun of trying to find all the parts... :-)

[Elarson]

I don't have any connection to this seller other than just generally being a fan of the Super T-10. This one has the really low 1st gear. Not great for racing but nice for a driver.

https://forums.maxperformanceinc.com...67#post6258667

FWIW,
Eric

[Elarson]

If you want to keep costs low and have a minimum of chaos, consider the following approach:

1) don't mill the heads any more than required to get them flat. You won't gain much compression and you start to tinker with valvetrain geometry and intake manifold port match.

2) Q-jet and iron intake is a terrific plan.

3) 2.5" dual exhaust is a must. Mild Pontiacs really respond to a free flowing exhaust. Repro RA manifolds are hard to find and not of a big benefit for a really mild engine.

4) slightly more cam than stock with an eye toward a grind that is intended to maximize cylinder pressure and torque at low rpm. I'm not up on what's currently out there. The Summit cams mentioned might be fine. I always turn to Tim Goolesby at Bullet Racing Cams for advice.

5) keep the rotating assembly mostly stock-type parts as long as you're staying under 5000 rpm. If you're going to thrash it, then better rods would be a smart idea.

JMHO,
Eric

[BDH79TA]

If you consider the T-10, the ones put behind the Pontiac 400 were fitted with a 2.43 first gear. Most of the Chevys used a 2.64 first gear if you're looking to run a higher rear and still have a gear that will get it in motion. It would pair up fairly decent with your 3.08 rear.

[cdoggy81]

Ok so it is looking like:
2800 cam
1.5 rockers
Mill the heads .0XX” to get them flat & not affect the intake mounting.
Stock iron intake
Get the q-jet setup for the 350
Stock exhaust logs, just ground, sanded & cleaned up as best we can.
2.5” dual exhaust
T-10, super t-10 or m20 (whatever we can find for the price) with a low first (2.64 - 2.43) to go with the new 3.08 rear position.

Any recommendation on timing chain, lifters, rockers, pushrods, oil pump & fuel pump? Stock stuff or something else & where to purchase?

Thanks everyone!

[b-man]

I had a completely stock 1969 Firebird 400 4-speed car, standard 330 Hp engine with the 067 cam, by the time I acquired it the cam had been replaced with the 066 by the previous owner who had rebuilt the engine.

Had the original M20 Muncie with the 2.52 first gear and factory issue 3.23 open rear. You did have to slip the clutch a tad more than I liked to move out in first.

I’d be looking for a 2.64 first gear at the very least for your 350 backed by a 3.08 rear.

[Shiny]

Hope it all goes well!

It's fun to see someone on a parallel path, even if mine has stalled for years.

Are you keeping the #11 heads?

I'm interested in your carb setup when you get there.

Do you have the original distributor?

If original, the damper is worth at least a close look.