Technical New Engine lacks power SBC in the Studebaker-RESOLVED

I am sorry to hear that.

 

If my eye's could see the small things it'll be like purple is grape to a child until corrected.

 

The correct manifold is pretty cheap.

Intake Manifold Fit Chevrolet 1987-1995 350 For TBI Stock Heads 52001
Item price USD 123.58
Quantity 1
Item number 143537242428
Shipping service UPS Ground

 

have you checked what your total timing is at 3000 rpm ??

 

How about a distributor dropped in a tooth off? Pretty easy to check and drop back in. I had one on a 327 that was like that, ran better with the old flat lobed cam before I took it apart.

 

Not sure if this has already been mentioned. Are the rockers adjusted properly? I installed a customer supplied 302 once that ran horrible. Ticking sound under the valve covers. He told me it’s a nasty solid lifter cam and he adjusted the lash. Turned out it was a hydraulic cam! But it ran like you described.

 

Don't laugh. I had a 305 performing similar stunts. Timing changes tried forward and backward. Got a tank of non-ethanol fuel...you would have thought it was a different engine. I also believe your Petronix ignitions have a rev-limiter built in, yes?

 

V, sorry to see you going through so much to diagnose your problem.

Couple of things...

If your any of your cam lobes were worn very much at all, you would have been popping and spitting through the carburetor on acceleration, probably right from take off.
31V mentioned that your dial indicator didn't look exactly in line with the lifters and pushrods. If that's the case, your readings will be short... as yours were.

And I see now that you've found no metal shavings. Good deal.

Actually, if I had pulled the valve covers and hadn't detected any loose rocker arms, I might have moved on to other possible issues. But I understand the concern with a newly assembled engine.

The intake manifold...
I've heard about the wedges to adapt an intake manifold. But I would never feel good about using them.
I kind of doubt this is the problem, but have you checked for intake leaks? Spray around any questionable areas with carb cleaner or starting fluid... take note of any rpm change. Does your idle speed tend to hover when you goose the throttle before it finally settles down to the correct idle speed? That's another good indicator of an intake leak.

Okay, the problem itself...
You said the carburetor is full when you check. Okay, let's say it's ignition then. But you've been round and round with that too. Could still be ignition. I have a hunch that it is. Maybe something simple like the spark plugs.
Was your carburetor running rich at some point? If it was, you may have partly fouled your spark plugs which would affect good spark at higher rpms. If spark plugs get fouled even more, it would of course be worse or not run at all.
Check your spark plugs. Just a little bit black? Doesn't take much. Maybe replace them just to be sure. And remember, if any of them are white, you're of course running too lean.

Good luck.
Let us know.

 

Guess I'm way late to this party and someone may have already mentioned this but have you tried running it till it misfires and cutting off the fuel pump just before you shut it down? Then checking the bowls for fuel. Possible clogged vent or pinhole in pickup tube?

 

Small hole made by a rodent sounds feasible...has suction but not enough under load.

 

Dealt with the air in the line deal on my buddies Chevy powered F100. Cracked hose at top of tank pulled air and basically vapor locked at speed.

 

Today my neighbor came over and we did a check to see how the cam timing was. It appears to be OK. The best guess now is weak valve springs. I cheaped out and used the original valve springs that came on the heads when I built the motor.

I have new valve springs on order.

@karl share & @bobss396 I've set timing multiple times with two distributors with 34 degrees at about 3000 RPM or so. I am getting pretty good at swapping distributors As well as distributor wires What a PITA!!

 

Note fuel bowls have always been full. two fuel pumps have been used both electric. all new line/rubber etc.

 

@1946caddy The manifold was just gathering dust, now it is one less item my wife has to take care of after I go to room temperature

 

I still think your problem is that you have the wrong camshaft for your TBI heads. Your mild cam at .450 lift is not Mild for your TBI heads which were the worst head design from Chevy. Your stock TBI valve spring are good for 4500 rpm.
This kit uses a camshaft specifically for a TBI to carburetor modification.
Also noted that the camshaft in this kit has a warning ;
Do not use late model timing sets. They are machined in a retarded position and are not recommended for this camshaft installation.
What timing timing set is recommended for the cam you're using.
https://www.jegs.com/i/Edelbrock/350/2104PK/10002/-1

Your cheapest route is to get a TBI rated camshaft or follow the recommendations in this article.
https://harristuning.com/Tbi/recommended-350-tbi-mods/

 

Save them old ones for cam break in springs!

 

Weak valve springs are not going to give a low power condition, but they will allow valve float at high rpm's, which doesn't sound like what you are experiencing. You've also not mentioned any kind of a mis-fire, rough running or stumbling, surging which would be expected if it was a fuel delivery issue. What you've described sounds like an air or exhaust flow restriction, cam timing or ignition timing. Did you try setting the ignition timing by vacuum gauge yet?

 

I have to put my 3.5 cents in to the Pot.
Most Chevy like the Timing set at 38 even my BBC ran at 38 Total
Did you ever think that the Problem was your Rear end Ratio!

Just my 3.5 cents

Live Learn & Die a Fool

 

I'm starting to think the main problem is too many cooks in the soup.

 

Dave............I think your right

I was thinking that the Rear Muffler bearing's are not Teflon..!
which would cause a Problem..??

Just my 3.5 cents


Live Learn & Die a Fool

 

Had a chevy pickup with a 700r4, truck was a dog, one day the torque converter bolts loosened up and wrecked the pads on the converter. Put in a new converter and flywheel and it really woke up, could peel out and pass on the highway. If the engine looks good maybe the trans is holding it back

 

Back in the day, my 56 Chevy BelAir had a ragged out 265. The block was bored and stock Chevy 283 pistons and parts were used for a rebuild. It had 3 Rochester 2 barrels. I have no idea what cam was used but this car could not get out of its own way. It had to be the slowest SBC powered Chevy ever. It was a complete embarassment. The cam was replaced with an 097 and solids and it woke the engine right up. It then ran just the way it should have.

 

Don’t mean to beat a dead horse but have you tried to stall test the converter yet? I’m telling you a broken or inop one way clutch in the converter will definitely cause this. Will run like you threw an anchor out when in gear. Run fine in neutral. I really doubt the engine is that much of a dog unless the cam timing is way off and you said you checked that.


Sent from my iPhone using The H.A.M.B. mobile app

 

He stated that the engine will hardly run over 2000 RPM. How can this be a torque converter, transmission or rear end problem?

Warren

 

I believe he meant "in gear" when he said that, not in neutral.

 

OP stated it revs to 4500rpm then cuts out, wet rag when driving...

 

I think we are talking load or no load. Still has nothing to do with trany etc.
Warren

 

Following along, interested in the outcome, offering moral support...."go get em tiger"

You have about 53 action items already, I wont add to that list. Looks like spring swap is next on the agenda.

 

As I read it it revs up fine in neutral. Driving it it won’t go ove 2000 rpm


Sent from my iPhone using The H.A.M.B. mobile app

 

@Blues4U Yes I have tried setting the timing by vacuum gauge, no real improvement. I've endoscoped the intake manifold and could find no obstruction as well as the exhaust headers. The rest of the pipes are straight pipes to glass packs. All New.
@a50merc 3.31 gears with a 700 R 4, don't think that is an issue.
@31Vicky with a hemi when I built the motor I wondered about using lighter springs Guess I will have them for any future builds (highly unlikely at this stage of my life)
@1946caddy These are not TBI heads, they came off of an OMC boat motor with a four barrel manifold. This from the Mortec Site
14096217...55-86...350..........Crate motor, 285hp/300hp, 64cc chambers,
72' or 90' center intake manifold bolt angles