BSiegPaint

Well, after driving my '71 post-rebuild, I knew it didn't have the "ummph" I was looking for. After getting it up on the dyno a few weeks ago, I confimed the awful truth - 205 rwhp and 200 lbs./ft. torque. Hmmm. I've had go-carts with higher numbers... Anyway, I'm no engine guru, and I chose my aftermarket parts based on catalog information and after talking with the parts manufacturers. Everything seemed OK on paper, but the proof is in the pudding, and I ain't got no tapioca. I also did all my choosing before I joined this Forum, so now I look to this group to help me out of this mess and see what I can do to realize my simple goal of 300 rwhp and 300 lbs./ft torque. Not unreasonable for a 350.

So here's what I have: 1971 350, "882" heads (1.94/1.50) with 3-angle valve job, CompCams 270H Magnum cam installed straight up, Weiand Stealth dual plane manifold topped with a Holley 650 DP square bore, mech. secondaries carb. I have a Mallory dual points mechanical advance distributor at 32 degrees advance. I am running 2-1/2" factory exhaust manifolds and '69 side pipes through stock side pipe mufflers. I chose the cam as it was rated best for 1800-5800 rpm with 224@.050"/ 270 adv., .501" lift. I chose the manifold for the same wide torque band and operating range, and the 650 Holley was selected during a visit to Summit where they walked me through all the parts I had selected and "matched" this carb for my intended use and other parts chosen. My engine does not have '71 pistons, rather it has the '70 pistons with the 4 valve reliefs in the top (instead of the dish normally found in '71). I have a very early car - did they just use up old parts? The heads are 76cc's. All cylinders measured within 10 lbs. of each other on a compression check. All other accessories on the car work perfectly - lights, brakes, etc. I have plenty of vacuum and no leaks anywhere. My air/fuel ratio is right around 13.0:1. So what did I do wrong? Too much cam? I'm thinking that I am not getting enough compression. Do I need headers? I have a set I can install. Do I have the wrong heads (chamber cc's too high)? I'm open to any and all suggestions here. It seems there would be no reason that this motor wouldn't give me more power than the stock configuration, but I lost 50 hp somewhere Now I have a brand new motor that runs worse than the 60,000-mile filthy mess it used to be. Anyone with a similar configuration get different results?

Fevre

No expert but I would confirm your balancer is dead on with a TDC locator.

zwede

Verify TDC.

Total timing without vacuum advance should be 36 degrees above 2500 rpm.

13:1 AFR is ok, but you might want to try going up one or 2 sizes to get 12.5.

Flattop pistons + 76 cc chambers usually only give you about 8.5:1 compression or so. Good time to upgrade to some nice aluminum heads with smaller chambers!

You also need headers.

With better heads, more compression and headers it will make 300 rwhp and rwtq, or atleast close to it.

jaggeedfire

I have something very similar in regards to heads, cam, and exhaust setup. When you did your dyno time do you do any tuning or just a test run? Timing and carb setup can mean a world of difference. When I first built mine it wouldnt run right and couldnt figure why....It ran hot and had no power. I checked timing 10 times retuned the carb, you name it I did it. Turned out to be the balancer was thrown 30 degrees!

I would definitely look at the timing issue.

TedH

Your power numbers are low. As others have posted, your advance curve/timing may be off. Also, the '882' heads are decent as smog heads go but are no comparison to a good set of 64cc Vortech's or the AFRs or DART PRO 1 or Iron Eagle. I'd recommend either the excellent flowing Vortech's and matching intake or a good set of 190cc-200cc intake runner heads from AFR or DART. Something with a 67-68cc or smaller combustion chamber in either aluminum or cast iron.

Also, is this a 4-speed car or Auto? If auto, what is your stall speed? Stall should be right at your lower end of your torque curve in neighborhood of 1800-2000rpm.

I also recommend headers over exhaust manifolds if you are going for more flow. The side pipes may be hurting power/torque (too open). If you were pushing for 350-400hp, I'd say use the sidepipes. If in the neighborhood of 300, I'd say, headers, duals, x or h-pipe and low restriction turbo mufflers (such as Dynomax Super Turbos).

zwede

Almost forgot: Verify that pedal to the floor = full throttle. If the linkage is adjusted wrong you may not be getting full throttle.

redc3

good point! i would guesstimate no less than 100 hp from head and header swap, depending on the heads chosen. and find an old dude or a bubba to tune the carb fer ya. with all these mods ya gotta get it right. its a combination of all your parts, but the secrets in the heads.

redc3

oh yea! you mentioned stock exhaust manifolds? are the heat exchangers working? the metal valves in some manifolds that open with heat? these things NEVER work! toss em'! if their not working, its the same as sealing off your exhaust, and trying to run it.

bobs77vet

something is not right....the torque numbers are way low.....205 RWHP does seem low but the 200 ftlbs of torque is the dead give away something is not tuned right.....my L 48 with 126K pulled 230 ft lbs...

JDRez42

I agree with bob my 1980 L 48 with 105k pulled 180 HP and 270 FT LBS. That with air injection removed, headers, true duals and an underdrive pulley. 200 seems real low

BigBlockk

This engine is in need of headers and a street port job on the heads. You're loosing a lot of power on the exhaust side of the equation. I would say you're giving up a good 70 hp here.

You also need to find your engines limit as far as timing goes. You won't need a timing light for this. Warm the engine to operating temp. Then advance the distributer very slightly. Now take the car out and stand all over it. IF it doesn't rattle, put a little more timing in it. Repeat this until you hear detonation then back the advance off a little. When you get to this point shut the motor off for 5 to 10 minutes then try to restart. If the starter bucks or drags you'll need to back the timing off some more. This is the maximum timing your engine will tolerate. Doing it this way you don't need to worry about a slipped timing ring on the damper.

Hope this helps.

MYBAD79

I'm not that much of an engine expert but here's what my problem was (similar to yours):

Hot cam in combination with insufficient compression. Your CR is about 8.5:1 ? That's low, mine did not run good with 9.2 CR and the Edelbrock Performer RPM camshaft.... I installed a milder cam and have a lot more power than before...
I was told I need at least 9.5CR, better 10:1 for a cam like the Perf. RPM (234/244 duration @.050)

BSiegPaint

Great advice from everyone - thanks. First, I did forget, this is an auto with stock convertor. BigBlockk, I did the timing as you stated - I NEVER got the car to detonate. I advanced it so far that it finally wouldn't start when cold, then backed it off. That's how I ended up where I am. The tuning was done on the dyno - this was as good as we got. I'm thinking I should see if the balancer is off. It is the original one. I'm also wondering if those old side pipe mufflers are really free flowing or if they are clogged up inside somehow. I'm not sure of their makeup internally. It SOUNDS loud, I'll give you that. The heat exchangers are new and working. I think you might be right, RedBad - I might have too much cam with low compression. I've got a few things to think about! I can get the heaaders installed without too much trouble in the next few weeks and see if that does anything after I verify the balancer is on the money. That may be the root of my problem...

JCL

Hey Bob. I can tell you how to pick up some of the HP your losing. It's the sidepipe covers that would be the problem, though. You know what I'm talking about...............

E-mail me sometime.

You really missed ALL the snow this year.......

vetteaddic

seems your engine should rocknroll with that combo,except for the heads, get some 64cc heads.

tsw71

You'll never get there with those heads. I tried with S/R Torquers and my best was 240rwhp/296rwtq. Better heads (in my case Trick Flows) got me to 308rwhp/316rwtq. As everyone else has said, you'll need 10:1 and a bit more cam too.

BSiegPaint

Oh, Jim - I was going to call you anyways I think that if I do a little finagling with the side covers, I can get a 3" pipe under there. The driver's side cover is shot to hell anyway after collecting all the Ohio salt - peeled the chrome right off... Once I get the headers popped on, I can take a trip to a local muffler shop who will do a couple custom bends and drop a straight 3" pipe under the covers with a store-bought turndown at the end - should look great and sound better. I was also thinking I could do the same with a 2-1/2" pipe, and use 2-1/2" baffles??? How short can we go??? Couldn't be any louder than it already is...

BSiegPaint

I'd love to stay with a stock configuration. Does anyone know what heads have the 64cc (or smaller) chamber? I think there are 62 and 58cc heads out there too, right?

stingr69

Get a 268H cam OR get the small chamber heads. The cam does not match the heads. If it was mine, I would go with some better heads.

-Mark.

JCL

Bob. We can surely get 3.0" under those shields. Huge power move from what's there. Call me and we'll get SOMETHING going............

New car for the garage.........I'll e-mail you a picture. Really neat TLB "55.".