[OE Espo]

Helping someone work on a 70 Lemans Originally equipped with 350 2Bbl. Have build-sheet and under 40k original miles.
Doing some research probably (guessing here) has a 254 camshaft .375 int .410 exh. Has No11 heads. Believe its a 2.78 open rear.

Want to wake it up some this winter but probably in stages.
1. Winter plan replace 11 heads with 13 (have them). getting them cleaned up. they dont have springs OR rockets in them. considering keeping cam now and using 1.65 rockers. no port mods. hoping block is chamfered for larger valves and just increasing ratio that we wont have any valve interference.
2. Add 68-72 iron intake (have)
3) Add quadrajet

Thinking these mods alone should get better seat of the pants feel.
Future considering 068 cam, 3.23 rear posi Want something for highway trips

Should i get heads milled to more like 350 HO #48 heads. had one in my car it ran great. if so to what cc?
other camshaft recommendations?
rear gear recommendations?

thanks

[77 TRASHCAN]

Yo, Steve!!!

[242177P]

I'd suggest not tearing into the motor. Dual exhaust
and the 4bbl will make a big difference. 1.65 rockers
may result in pushrod contact, elongate those holes
if you're set on going that route

[steve25]

You should have great so called “seat of the pants feel “ now up to 4000 or so rpm if the motor is in good shape and tuned well!

Great seat of the pants feel from a car with a auto trans and a 1800 stall factory converter comes from torque production up to 3000 rpm, not the hp being made above 4500 rpm.

With the 2bbl cam I would not just slap on 1.65 rockers with out checking your geometry and push rod clearance needs.

Being that it’s a 2bbl motor you only have the lesser grade GM Moraine 200 series grocery getter bearings in there, not the better 400 series bearings as was used in all of the 4 bbl and tripower motors from 1959 on up.

You also only have a small diameter pick up tube 40 psi oil pump.

These two down sides mean you should not beat on the motor a lot once you swap over to the 4 bbl set up.

In terms of the heads, here once again you have the lesser pressure 2 bbl valve springs that are 40 years old now, so this is yet another reason to not use 1.65 rockers as you will stand a good chance of breaking some valve springs.

I would first put in the 3.23 gears before stuffing in a bigger cam.

Big valve heads can get you some much needed compression, but even if your block has intake valve notches using them will not buy you much added power from just air flow gains.

If it where me I would go with something like the Comp cams 252H, then down the road if you decide you want to trade off some low speed power for more top above 4500, ( and get a 60 psi pump in the motor ) then slap on the 1.65 rockers.

[OE Espo]

Much appreciated input so far, thank you. The car is low mile car that the driver will probably never race, not do i think he will beat on very much. don't really want to change the converter at this point. agree with steve25, probably just going to do intake, carb and head swap first. Upgrading rear gear makes sense to me as next for more getup and go. he may be happy and may not put a cam it but #13 heads have valves but no springs or rockers, so new springs are in the plan.
probably should elongate the prod holes for future. with the heads going to machine shop for clean/mag wondering if i should have them mill down to reduce cc to more comparable to the 350HO which i believe is less than the 72cc #13. dual exhaust is going to be an upgrade as well. should i put. looking at Wallace oem cam charts, the 254 has pretty low intake lift (don't know anything about cam selection) but the chart is nice that shows both 068/254 lifts at different rations. what about putting 1.65 on the intake valves? need rockers anyway. not sure if they still sell stamped steel 1.65 or maybe prw to keep cost down.

[OE Espo]

Well i have another. before we spend money on the number 13's i found a set of 67 140's. not sure what cc they are but seems like compresssion need bumped on the 350. not sure if valve angle is different on the 67'140's they have already been tapped and have 7/16" studs. does anyone know if the 140 would be a better avenue than the 13's?

[srmmmm]

Originally Posted by OE Espo

Helping someone work on a 70 Lemans Originally equipped with 350 2Bbl. Have build-sheet and under 40k original miles.
Doing some research probably (guessing here) has a 254 camshaft .375 int .410 exh. Has No11 heads. Believe its a 2.78 open rear.

Want to wake it up some this winter but probably in stages.
1. Winter plan replace 11 heads with 13 (have them). getting them cleaned up. they dont have springs OR rockets in them. considering keeping cam now and using 1.65 rockers. no port mods. hoping block is chamfered for larger valves and just increasing ratio that we wont have any valve interference.
2. Add 68-72 iron intake (have)
3) Add quadrajet

Thinking these mods alone should get better seat of the pants feel.
Future considering 068 cam, 3.23 rear posi Want something for highway trips

Should i get heads milled to more like 350 HO #48 heads. had one in my car it ran great. if so to what cc?
other camshaft recommendations?
rear gear recommendations?

thanks

You are correct on your current camshaft. On my 1970 Esprit, while in college I converted the 350 from a 2 barrel to 4 barrel by installing a Torker I intake manifold, Quadrajet, Borg-Warner electronic ignition, dual snorkel air cleaner and dual exhaust. Rear wheel horsepower went from 182@4400 RPM to 212@4400RPM on our chassis dyno at General Motors Institute.

For my restoration of the car, it has been a full rebuild. The 1970 block does have chamfered cylinder walls. I installed 6X-4 heads milled down .010 inches. The deck was given a cleanup pass at .005 inches. The valve spring seats needed various degrees of milling to get correct and even spring pressures across all cylinders, and with the use of Comp Ultragold 1.5 ratio rockers and Johnson hydraulic roller lifters, custom length push rods were necessary for correct valve train geometry.

Other mods included a 4.25" Eagle crank and Eagle H-Beam rods, Ross flat-top pistons, Comp XE275HR cam and MSD billet distributor. Displacement is now 413 cu in with 9.3 cr. I am replacing the 2.78 open diff with a 3.23 posi, and going from the stock converter to a 2800 RPM stall unit.

I had always thought about dropping in a set of 1.65 ratio rockers back in college and my auto engineering professor, Jim Lyons, who later went to Pontiac to head up the Turbo 301 development, cautioned against it without upgrading the rest of the valve train for the added stress. In his estimation, going from the 2 barrel to the 4 barrel was the best bang for the buck.

[android 211]

I had two 350-2bbl Firebirds. 1968 and a 1969. Both were automatics with tall rear axle ratios. The '68 received headers and duals to replace the single exhaust. Mileage improved from 17 to 21 on trips. It did not seem to make much more power at all however. I installed a 69 GTO Quadrajet and iron intake. At 3000rpm power just flattened out just like before. It flat spotted a cam lobe so I replaced it with a Pontiac 067 cam and a new timing chain. There was a huge improvement in power. I finally saw the power I was looking for. The '69 already had a bad cam and bent pushrods so I replaced it with a Crower RV cam and true duals on stock manifolds. It stayed 2bbl for awhile; it also exceeded 20mpg on trips. Eventually I found a cast iron intake and a Quadrajet for it; power was as good as the '68. Don't install a 4bbl without improving the cam.

[SD455DJ]

Originally Posted by OE Espo

Helping someone work on a 70 Lemans Originally equipped with 350 2Bbl. Have build-sheet and under 40k original miles.
Doing some research probably (guessing here) has a 254 camshaft .375 int .410 exh. Has No11 heads. Believe its a 2.78 open rear.

Want to wake it up some this winter but probably in stages.
1. Winter plan replace 11 heads with 13 (have them). getting them cleaned up. they dont have springs OR rockets in them. considering keeping cam now and using 1.65 rockers. no port mods. hoping block is chamfered for larger valves and just increasing ratio that we wont have any valve interference.
2. Add 68-72 iron intake (have)
3) Add quadrajet

Thinking these mods alone should get better seat of the pants feel.
Future considering 068 cam, 3.23 rear posi Want something for highway trips

Should i get heads milled to more like 350 HO #48 heads. had one in my car it ran great. if so to what cc?
other camshaft recommendations?
rear gear recommendations?

thanks

We have two ’69 350 HO cars, a 4-spd Firebird and a Custom S with a TH400. The Firebird’s 350 HO has the 068 cam and the Custom S (Lemans in 1970) has the 067 cam. They are both strong running cars with easy 14 second quarter mile times (low 14’s for the Bird, mid 14’s for the Custom S - the Firebird has a 300 lb. weight advantage). They both have their original 3.55 rear ends.

I like what you’re planning with the #13 heads (75 – 78 cc’s) with the factory cast iron intake and a Q-jet carb (find a 7040264). Don't cut them more than you have to just ensure they are flat and true. This will keep your compression in the mid-9's and run fine on 93 fuel). The 3.23 (with posi) is a great gear for in-town and highway driving. I would suggest the 067 cam (with decent springs) with the TH350 trans and the stock convertor. I wouldn’t go with the 1.65 rockers arms. Obviously, a good dual exhaust system is part of the power equation. If you can change the oil pump to the 60 lb. version would be great. The bearings will be fine if you keep the revs under 5200 rpm and use a good grade of oil like Brad Penn, Lucas, or Valvoline VR-1. You won’t need to shift any higher with an 067 spec cam anyway (the Summit 2800 is a good choice too). It’ll be quicker than you think.

Dennis

[Goatracer1]

Changing cam, heads etc. is only going to move your power range upward. You will get the biggest bang for the buck by changing the rear end ratio. Steve 25 had the right idea by recommending 3.23 0r 3.55 gears.

[steve25]

It’s amazing that to this day and age with all the info that’s at your fingertips, it’s seems that folks in a way build up a more powerful sounding motor that can’t even match the performance of a high performance stocker that is well tuned and set up.

Is it not more impressive to have a mild sounding motor that performs exceptionally?

Just swapping over to the 068 cam now would raise your peak torque and Hp rpm by 600, which with your current 2.70s rear gears would be useless to you.
On the other side of the coin going from 2.78 to even just 3.23 would pick you up 18% greater rear wheel torque.

This would at least make up for that 600 rpm change in rpm level from the cam change.

In short make the gear change first .

[4dblnkldude]

Originally Posted by Goatracer1

Changing cam, heads etc. is only going to move your power range upward. You will get the biggest bang for the buck by changing the rear end ratio. Steve 25 had the right idea by recommending 3.23 0r 3.55 gears.

This is exactly what I did with my 70 Esprit. (original car with 120k) I did 3.23 posi, bumped timing up to 10 deg advanced and rebuilt the carb. Literally like driving a different car. I think theres is a tad more in it too.

[OE Espo]

Originally Posted by 4dblnkldude

This is exactly what I did with my 70 Esprit. (original car with 120k) I did 3.23 posi, bumped timing up to 10 deg advanced and rebuilt the carb. Literally like driving a different car. I think theres is a tad more in it too.

So you just rebuilt the 2BBL carb? I was thinking a well tuned quadrajet would improve power and fuel economy both, and while i was that far, upgrade by raising compression with heads. Have 140s or 13s that I currently have. orig heads i believe are 11s on the car now which i believe are like 8:1

[NeighborsComplaint]

Rear gear change, intake and 4 bbl, headers and dual exhaust. Leave the internals of that good running engine alone. I did that to a ‘65 Lemans 2 bbl 326. The rear gear ratio change came last. I did the headers and duals first which were the biggest bang for the buck. Made for a snappy little car up to 4000 rpm.

Everyone complains about header leaks but I never had issues. I’ve used copper, aluminum and Remflex and none have leaked. I always check the header flanges with a straight edge and grind any high spots or weld spatter before mounting. Using 1-5/8” headers, they aren’t that tough to tighten properly and retorque after the first heat-cool down cycle.

[BILL BOWMAN1]

As others have stated… gear, headers or long branch.. duals , iron intake with a suitable 4 bbl.
Add a few degrees timing , plugs, cap, rotor. I wouldn’t crack open the motor.

[b-man]

Two good reasons to crack it open.

Worn cam lobes are pretty common, usually at least a couple have rounded off to the point where there’s a significant power loss.

Stretched timing chain, another power loss.

Once you freshen up these two things it will feel almost like a new engine.

I’d stick a new 066 cam/lifters and timing set in it, while you’re doing that you can check out the timing cover and see if it’s getting corroded and replace the water pump, divider plate and sleeves. Use the 068 cam instead if you really are doing the swap to 3.23 gears in the near future, I would also recommend a 2500 stall converter with the 068 cam.

Keep the log exhaust manifolds. Very little bang for the buck spending $500 to replace them with HO/Ram Air manifolds and head pipes for the 5 to 8 horsepower gain at most at this power level. Just use some PYPES 2-1/2” head pipes and a free flowing exhaust. Keep in mind that the 326, 350, 400, 428 and 455 all share the same log manifolds, so a 350 breathes pretty freely through them compared to their bigger brothers that also do just fine with them.

[4dblnkldude]

Originally Posted by OE Espo

So you just rebuilt the 2BBL carb? I was thinking a well tuned quadrajet would improve power and fuel economy both, and while i was that far, upgrade by raising compression with heads. Have 140s or 13s that I currently have. orig heads i believe are 11s on the car now which i believe are like 8:1

Yes, I ran a 15.1 in a stock in my 81 TA with a 77 400. That car was originally a turbo car with 3.08's. Not a doubt in my mind the 70 esprit would beat it with the two barrel.

[OE Espo]

Looking for parts to complete this. this air cleaner listed as a 70' can anyone confirm? and is that a end or is made to clear something?
Also looking for
4bbl throttle cable bracket.
throttle cable
choke stove (unless 2bbl will work)
vaccum port for back of 4bbl for power brake
primary throttle shaft to and cable hookup to use "other brand" 4bbl

[b-man]

1972 air cleaner.

The 1970 would have a bigger snorkel opening.

You will need a 4-barrel choke stove.

[OE Espo]

Originally Posted by OE Espo

Well i have another. before we spend money on the number 13's i found a set of 67 140's. not sure what cc they are but seems like compresssion need bumped on the 350. not sure if valve angle is different on the 67'140's they have already been tapped and have 7/16" studs. does anyone know if the 140 would be a better avenue than the 13's?

So, i dug the 140's out of the shed. they have all new SS valves, new isky guide plates, didn't measure the valves yet but intake and exhaust are almost touching, new springs, 7/16" studs, no rockers, measure 68cc looks like some cleanup work on both intake and exhaust, guy we got them from was racing them on a 326, low cost install so unless there is a reason not to go this route probably going to install them. from Walace calculator looks like it gets CR up to 9.4 should give more power than what it has now. any thoughts?