350 doesn't come alive at, and never reaches the top

[77Astre455]

Distributor vacuum is plugge/disconnected. Heading out to get a camera. If it has domed pistons along with the unidentifiable cam, I'll probably replace the engine with a 383 crate. Any recommendations?

If vacuum advance is disconnected and you have 34 etc by 2700 the previous owner probably set it up that way. That is NP and is most likely not holding you back, except for a little worse MPG on the street. I wouldn't go spring for a 383 till you have that one running correctly. You could have the same issue with any hi-po engine if fuel psi is dropping off at RPM. But on other hand if your expecting to run well into the 11 second ET range your gonna need more than you have now. As in better flowing heads, stall convertor, more gear, bigger better tire, etc.

RC

Another thing to check is make sure gas is not trickling inside carb at idle. You shouldn't see any gas at idle. You could possibly have trash in needle and seat for float in front carb bowl/(s). That will make it run rougher and appear to have bigger cam/ or seem too rich on jets. I doubt its jetting on secondaries because that carb you have probably has a rear metering plate instead of rear metering block with jets. (I'll look at pic again) Also check float level with side screw on carb bowls while not running. Should be right under screw hole. If trickling gas your sooty exhaust and brown plugs can be fooling you thinking your too rich. Typically when too rich... at part throttle cruising it will kind spit/sputter/miss(not run clean and smooth). I recommend one day changing carb to a 750 dual feed or a double pumper so you can tune/ change rear jets like the fronts. An 750 dual feed vac sec is cheap and you can add a rear metering block with jets but you will need a double pumper longer dual feed line. You can change vac diaphr. spring for secondaries or you can make it mechanical secondaries by using the small screw on linkage on drivers side. I doubt your engine is too lean in secondaries from what I've heard but that will hold you back too. If in doubt take carb apart and clean and blow out with air especially on secondaries with the metering plate. It will tend to mess up gasket when you pull it apart.

RC

Just looked at your pic and your carb does have a rear metering plate not rear metering block with jets. You have calibrated holes on secondaries acting like jets which could have trash or old gas residue. If all else fails take carb apart and clean and blow out with air. Also on a long shot, take air filter off on a test drive and make sure your air isn't getting choked off. Good luck, don't give up, and keep wrenching.....hehe.

RC

[pcguy]

Well, the secondaries were not opening (hard to make it on a two barrel) - got that fixed and now it’s semi-mechanical and semi-vacuum. Unfortunately I ran out of time last November and never got to run it again. Planning to get back out there in a week or so, but I need to have a more accurate tach – ordered a Auto Meter 3690 Sport-Comp II Tachometer 3 3/4 in and it will be here tomorrow.

The plan is to find out what the rpm is when crossing the line – that will tell me what the converter is doing (probably .9), all of which will let me know whether my 373’s are the right ones or not depending on how hard it’s pulling at the end. After I change the gears, I can determine what I need to do in the way of tires – really hoping to not have to cut the fender wells.

More to follow...........

[crawfw]

Any progress on the lack of power on your motor? Just curious what you found. Ever find what lift cam was in the motor? I saw you listed 280 on the cam. I assumed thats the duration. If the duration is that high I assume from the idle you described it has >.500 lift. The car I purchased in feb of 2013 also had a low performance issue compared to what I thought it should run in the h body. Smaller (.460 lift cam) but felt like < 200 hp motor when the build suggests 290 to 310 hp. It was as simple as the primaries only opening 1/3 the way with the pedal. Just had to replace the throttle bracket with an adjustable bracket. Now Im trying to find traction for the thing.

[pcguy]

Ran the Vega last Wed. evening with the basic intent of verifying the RPM when crossing the line, but I was totally surprised by the difference in the performance with the secondaries and the power valve fixed. So much so that I nearly burned the right rear tire off - 3.8 secs. @ 60’ decided it wouldn’t be worth running again so I left. Granted, the tires and rear end are going to be changed, but the goal was to find out about the torque converter loss, and that never happened.

So I guess I’ll just run it on the street accelerating at 55mph and multiply by 2 to get a theoretical RPM that I can use as a gauge for new tires with the new 3.73 gears that I’m about to install. My guess is that I should be shooting for a combination that requires 6K rpm at 115+- rpm. Based on a seat of the pants assessment, this 350 has a lot left at 6K.

The ulitmate goal is 11’s......

[pcguy]

Ran the Vega last Wed. evening with the basic intent of verifying the RPM when crossing the line, but I was totally surprised by the difference in the performance with the secondaries and the power valve fixed. So much so that I nearly burned the right rear tire off - 3.8 secs. @ 60’ decided it wouldn’t be worth running again so I left. Granted, the tires and rear end are going to be changed, but the goal was to find out about the torque converter loss, and that never happened.

So I guess I’ll just run it on the street accelerating at 55mph and multiply by 2 to get a theoretical RPM that I can use as a gauge for new tires with the new 3.73 gears that I’m about to install. My guess is that I should be shooting for a combination that requires 6K rpm at 115+- rpm. Based on a seat of the pants assessment, this 350 has a lot left at 6K.

The ulitmate goal is 11’s......

[beakerztoyz]

Replacing the cam and carb is my limit as long as I don't have to deal with clearances on domed pistons. My guess is that if I run it much more the way it is, the rich AF is going to wash the cylinder walls it'll start smoking.

Trying to develop a plan and if the plan comes down to pulling the heads and the pistons are really domed, I'll probably be better off just replacing it with a dyno'd crate engine like something from Smeding Performance, or.....

I realized that you've found the problem was in the carb.... But I am still puzzled as to why you would think it would be better to use a crate motor than bolt on better heads if the motor has domed pistons. The original lt1 back in like 70 used domed piston's and 64 cc head's. I know numerous people who have bolted aftermarket heads on top of domed piston's. I suppose maybe if the dome was too big then it might have issue's but i would think there would be some way of measuring the dome with the heads off.

Honestly if whoever bolted the motor together used domed piston's any bigger than the ones they used to put in the old lt'1 s with a set of steel 75cc heads he really had no idea what he was doing.

bolt on some AFR, Holley, or edelbrock alluminum heads and you'll be makin power for a lot less than buyin a new motor

[pcguy]

Will be finding out soon if this thing really comes alive at the top. Getting ready for the first real run - Eaton posi with 373's big DOT drag radial, CAI, carb fixed and waiting to test the "running hot" issue that I believe is fixed. Compared to my ZR1, this is feeling like it's running right.