[just501]

I've searched and could still use a little help. I have been working on a 1973 350P and am trying to identify the shortcomings of my setup (besides cid). I would like to see performance on the 350HO level.

The engine is in a 68 firebird, m-21, 3.36 blown posi, log manifolds to 2.25" dual exhaust. I plan to go to long branch manifolds as this car will eventually go back to a 400 when time/funds permit.

The 350 was stock except performer intake and over-carbed with Edelbrock 850 cfm (burning pretty rich @ 11.8:1 AFR WOT). Stock 555 cam. Stock bottom end (flat top pistons). Points distributor.


Present Setup
Cam: Edelbrock performer 204/214 .420/.440 110 LSA.
Heads: 1970 #16 (not ported) small valve milled to 68 cc raise scr to appx 9.9:1
Compression test showed appx 190 psi on all cylinders.
Timing: 6* ini and 32*total to prevent detonation on 91
Carb: Edelbrock 650 cfm - running close to stoic afr at WOT. Have not tuned it.

The increase in compression and cam swap yielded about 16% increase in peak HP on the dyno from
Before: 196 RWHP @ 4200 and 274 RWTQ @ 3100
After: 228 RWHP @ 4750 and 293 RWTQ @ 3300

I would appreciate opinions on what could make this setup perform a little better. Thinking of going with 068 cam or similar profile with possibly a little more lift. How much improvement could a carb tune yield?

Thanks,
Justin

[shotgun]

http://216.178.81.108/forums/showthr...&highlight=350

Read this post, pay attention to
Jagtecs combo.

The engine was mine for a short period and lives on in a Firebird now.

[just501]

Thanks, I've actually through that tread a few times, (as well as a quite a few others) and that one in particular is a great discussion. Jagtec1's combo was impressive and I have been considering that cam along with the 068. I have a question of the effect of each cam in raising or lowering cylinder pressure as well as expected change/shift in torque curve from my current.

Current: Lift .420/.440, Duration 204/214, 110 LSA
Crane 272: Lift .454/.480, Duration 216/228, 112 LSA
068 cam: Lift .410/.410, Duration 212/225, 116 LSA

One thing I have noticed though is that several 350 builds have been discussed, but not many have reported results of changes they made. (I realize some may not have been performed to date.) I have seen a few end results, such as Jagtec, bman, PMDRACER, and tom s. I am very interested in hearing about results from some of those who have posted their questions on the 350 as well as what they learned in their approaches.

Thanks

[AdamHoud]

I will dyno mine when I finally figure out the throttle bracket issue and put a few miles on it. It has 40K original miles on the bottom end, and tested 155-160 psi on all cylinders.

I am running the following:
73 block stock with flattop pistons
69' 46 heads 72cc
crower 60240 210/221 422/446
71' stock iron 4bbl manifold
77ish jeff walker rebuilt qjet
RA manifold repros
pypes x-pipe setup

I wonder if you could get some extra power somewhere in your exhaust?

[Overkillphil]

I have had good experiences with the Pontiac 350's over the years. These days we really don't bother with them anymore. But back in the 80's they were commonplace as most older Pontiacs we bought had one of them in place. The darn things are nearly impossible to kill!

We found that doing the minimal made them work best all around. Nothing fancy needed. The stock heads were plenty, and the 350 likes both the small and large valve heads, just pick the cam accordingly. Compression isn't critical either, as we had 7.6:1 screamers as well as a couple of 9:1 varieties.

The performer intake or good stock iron with either a decent Qjet or 600 (650 max) Holley carb works well.

The most surprising combo we had was a 79 T/A we bought with a blown (that's blown apart, not supercharged) 301. We swapped in a 73 350 with fresh 6X-4 heads from a 76 350, an 067 cam (broomstick!), performer intake, elcheapo Cassler 4 tube headers, 2.25 dual exh. w/turbo mufflers, Holley 600 w/vac. sec., turbo 350 w/shift kit, and of all things the stock 3.08 posi out back.

That car ran consistent 14 flat with good traction. While that sounds boring to most of us today, it was quite a surprise to us back then with the low compression and semi-tall gears.

Imagine if someone put some effort into it?

Another one of our old thrown together combos was a 76 Bird that ran a Pontiac 350 with the stock 6X-4 heads, but ran a 650 mech. sec. holley on a 68 iron intake, 3.42 gears, as well as a Crower 280 Monarch cam. That one went high 13's but idled rough and was not any quicker out of the hole than the 79, undoubtedly due to the more aggressive cam which nullified the advantage of the steeper gears.

The 350 Pontiac is a much maligned engine. Nowadays it doesn't make any sense to build one for performance reasons, but not because it is a bad engine. Rather it doesn't make good financial sense when it costs the same or less to build a 400 or 455. And since none of them are really common anymore to stumble across, even the good running stockers have all but dried up. FWIW.

[shotgun]

"One thing I have noticed though is that several 350 builds have been discussed, but not many have reported results of changes they made. (I realize some may not have been performed to date.) "

Most likely will not find much either.I have nothing against the 350 or 301 for that matter.
A 350 is kinda a stepping stone engine.
Most comments start with
" it came with a good running 350 so...."
" I needed something to hold me over 'til my 400 or 455 or .... is done"
" can't afford a 455 now so....."
You get the idea.
They get built,run forever and get forgotten.

[69Customs]

I think you aren't running it rich enough at WOT. 10:1 to 12:1 WOT AFR is normal you don't want to run stoic at WOT (14.7) unless you are looking for MPG. I set mine up to run 11.5:1-12:1 at wot and 16:1-17:1 at 2000 rpm cruise. and it works great. When its at WOT I want the gas pouring in for power. Stoic is just for ideal air emissions.

[just501]

Thanks for the responses.

Originally Posted by shotgun

They get built,run forever and get forgotten.

Kinda the reason I started this thread. The other threads end without results and "get forgotten." Makes it a little difficult to see if suggestions in those threads were beneficial.

Originally Posted by 69Customs

I think you aren't running it rich enough at WOT. 10:1 to 12:1 WOT AFR is normal you don't want to run stoic at WOT (14.7) unless you are looking for MPG. I set mine up to run 11.5:1-12:1 at wot and 16:1-17:1 at 2000 rpm cruise. and it works great. When its at WOT I want the gas pouring in for power. Stoic is just for ideal air emissions.

Thanks, I intend to get that resolved. I have not tuned the carb and plan to be at about 12.5:1 or close at WOT. Question though, how much power (percentage) increase could I realize by getting the carb dialed in. I should be able to run a little more timing when I get a little richer??

Originally Posted by Overkillphil

The 350 Pontiac is a much maligned engine. Nowadays it doesn't make any sense to build one for performance reasons, but not because it is a bad engine. Rather it doesn't make good financial sense when it costs the same or less to build a 400 or 455. And since none of them are really common anymore to stumble across, even the good running stockers have all but dried up. FWIW.

Thanks for your comment, I agree. I enjoy working with what I have to get as much as I can; what little I have done to this point has been done using old parts laying around the garage. Of course, the next cam swap will be out of pocket. Good experience.

[Will]

Carb tuning will help. How much %-wise? Dunno. I just know it will help. Try it and report back, then we'll all know how much it helped your specific combination.

My initial thoughts are that you have plenty of compression but a small cam. You also have a very restrictive exhaust. Exhaust improvements should almost always be one of the first things you do. They help even a stock engine make more power and allow modified engines to perform to their potential. Also, freeing up the exhaust may require retuning the carb, so why not do the exhaust first so you don't have to mess with the carb twice?

Next up, you're already limiting your timing due to your high compression. Of the cams you've listed the 068 is the only one designed to work specifically in high compression engines. Without doing a more detailed analysis though I can't tell whether it or the Crane will build less lower RPM cylinder pressure. My experience tells me the 068 would probably make less cylinder pressure down low, allowing you to run more initial timing, and produce a broader torque band than the Crane cam but probably less power at RPMs above about 4000-4500. That's just my semi-educated guess on how those cams would react.

In any case, freeing up the exhaust would be my first step, followed by carb tuning, followed by a bigger cam, followed by more carb and distributor tuning to match the bigger cam. I'm betting that those modifications will net you significant power, possibly as much as 50 HP or more.

[455Darren]

Just wanted to chime in on my 350 experience as many folks don't mess with them. I had a '72 LeMans GT (Endura front end) with the 350 2 bbl, 3 spd manual, 3:23 open axle that I drove set up like that for a few years. Performance not too exciting. Later on I thought of installing some '69 #62 heads, 068 cam, and '69 4bbl intake. Pretty much like a '69 350 HO set up. Wish I had done it earlier. What a sweet combo! Unfortunatly the car rotted out around the drive train. My favorite daily driver car.

[rad400]

Just501 Ken the Ace Brewer From PPR build a Strocker 383 from a P350, and it will run. Contact him he is on this board.

[just501]

Originally Posted by rad400

Just501 Ken the Ace Brewer From PPR build a Strocker 383 from a P350, and it will run. Contact him he is on this board.

Thanks, but the 350 is in the car, and I have no intention of pulling it to rebuild the bottom end. That being said, I have read a lot about his 383, and I am quite impressed by his results. Will keep that in mind if I do another 350. I plan to use his 4" stroker and rotating assembly on my 400 when I build it.

Will, thanks for the suggestions. I have a set of repro long branch manifolds that will be put on in the near future. Not really wanting to go with headers, although I know that would really wake it up.

[Jagtec1]

There is a lot of info on those threads...not sure what more you want. You need to dump that carb and get a good Q-jet or maybe a 600 or so CFM Holley. More cam will help. You should also consider headers...gotta get it out to make power. I ran a 3.55 gear with a T-350. I removed the choke on my carb...it was hanging open at one point, and I gained around .2-.3 by wiring it open. See my cam specs (in above linked thread) for ideas on cams that work. Tuning the proper carb will give you better "seat of the pants" performance. HTH.

[Will]

Originally Posted by just501

Thanks, but the 350 is in the car, and I have no intention of pulling it to rebuild the bottom end. That being said, I have read a lot about his 383, and I am quite impressed by his results. Will keep that in mind if I do another 350. I plan to use his 4" stroker and rotating assembly on my 400 when I build it.

Will, thanks for the suggestions. I have a set of repro long branch manifolds that will be put on in the near future. Not really wanting to go with headers, although I know that would really wake it up.

The repro long branches are a good design and will really help, especially if you put a good, free flowing system behind them. 2.5" minimum diameter, mandrel bent, with an X-crossover and free flowing mufflers. No, they're not as good as a 4-tube header but in your combination the headers might be worth an additional 15 horses or so. You can make that power up elsewhere.

Oh, have to agree on the carb comments above. The E-brock carbs, in my opinion, are garbage. Get a well-tuned Q-jet or a Holley on there. If an 800 cfm Holley isn't too big for a healthy 400 then a 750 should be fine for a 350. I wouldn't go smaller than a 650 in any case. The Holley "universal" 600 cfm carbs aren't bad units, but aren't enough carb for a healthy 350 either. I'd rather have a 650 DP or a 700 vacuum secondaries on there.

Oh, and another thought on cams - give the Crower 60241 some serious consideration. That should be a very powerful cam in your combo.

Good luck!

[TheLastNorell]

The Pontiac 350 is indestructible . Ive had one in My 71 lemans for 4 years of daily driving and track time almost every week with no problems. I drive it about 50 miles to and from school with the engine turning 3k at 70mph. Then on friday nights i go to midnight madness at budds creek and thrash on it there. Best run so far is 14.3 @94 , not a bad little motor.

[Donovan]

I was looking through some old boxes today (just finished moving)

Back in October of 2003 I was changing the thermostat when the intake cracked at the bolt hole. I had to keep it on the road so I threw an old P4B Qjet intake on it. A few days later I dropped in on a Dyno session and put my car on the rollers. I didn't realize it until it was over but the secondary lockout was engaged the whole time since I had the choke wired open at the flap.

I dynoed 180HP and 260 lbft to the rear wheels on primaries ALONE hahahaha

Stock 68 350HO except intake
with longbranch Manifolds and crosspipe
TH350

Anyone have any idea how much I left on thetable without opening the secondaries? Same car with a stock intake, Performer cam and 1.65 rockers later ran 14.1 at 99mph

[Widetracker]

Those of you that have done the 068 with 72cc heads, what is the ideal cruising rpm? I'm looking at building my 350 into an ho with the addition of Rhoades lifters and four tubes. Fuel economy is a priority so that I can cruise some miles in my 69 bird. I'm deciding on gearing right now and trying to base it off the rpm.

Thanks!

[69Customs]

350, summit 2800, 71 cc heads (47 milled) edelbrock 650, P4B, 1-1/2 Carb Spacer, malory ignition , Summit headers, 2-1/2 exhaust w/homemade cross over, cherry bomb mufflers, Overdrive .81 standard transmission, 2.80 posi rear out of 72 lemans station wagon, P255R60-15 rear tires (26-1/2 dia.) 3760 lbs w/full tank gas, no driver. (This fat girl needs to lose some weight! But she is a convertible)
87 octane gas, 2000 rpm @70mph, A/f 16:1 to 17:1 at cruise, 20-25 mpg highway.
$4.00/Gal gas don't scare me! Even though she's got a 22 gal. tank.
Thats just what I did.

[Ken -Ace- Brewer]

We are almost done with a 350 Pontiac Oval Track motor! Thats right. The rules say the motor cannot be over 360 ci. With a .030 overbore we are at 359.3 PERFECT. This is an interesting build up. So many rules. And if I miss something it is a $1000 fine for EACH infraction PLUS a suspension for 1 year. So I have to be on my toes. The head has to be stock. And the cam CANNOT be over 510 lift. So we opted to use #62 heads with a Superstock valve job from SD Performance. The heads flow 200 cfm at 500 lift. Pretty good! We have to use stock type rods. Lucky my Tomahawk 5140's will work :-). And my Forged SRS pistons. We went for a no hole balance as well. Cam CANNOT be a roller of any kind. So a solid custom grind Comp cam that has been Nitrided is going in it. Specs at .050 are in the 240/250 range. With 502 lift on a 108 to be installed in at 102. We can only use roller tip rockers as well(with a stud girdle). And you can only use a Performer intake with a 2 barrel carb.

I will let you all know what this very mighty 350 does on the dyno in about 2 weeks! Stay tuned!!

Be Cool,
Ace

Oh yeah it is going to a 64 GTO. There no other Pontiacs of any kind at this track! Just Chevy's and Fords.

[wrenchmen]

Hey Ken...how is the 383 with aluminum heads coming along?....when should I start looking for an article on it in ...what was it..Hot Rod mag?