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My dad and I just built a 350 sbc for a 88 Chevy truck. It is not our first engine to build. I am 66 and he is 85. I’m mostly have Ford experience and he was known as a dirt track car builder. This engine is pretty standard. Left overs from his dirt track days Flat top pistons over 30. TBI heads ( I know not the best) proformer intake. Rodchester carb. Stage 3 cam )from a shop supplier) long headers, super 10’s. Inline fuel pump.
Just had no power! Less power than the TBI motor that was in the truck before. Timed at about 12 at idle. HEI distributor. We need to figure out why no power. Looking for ideas on what to look at. Thanks in advance $
 

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The distributor is a what? You can’t use the original TBI.

People use this term as like your Stage 3 cam, this has no meaning. For a cam it’s specifications that count when trying to figure compatibility.

There are two TBI Swirl Port heads used on the 350 one ends with 191 in the casting number the other 193. The 191 is a 74 cc low compression head the 193 is the 64 cc higher compression head, you need to know which is there.

Both heads require self guiding rockers as there is no cast in guide. The exception would be if you installed sheet metal guides and screw in studs.

12 degrees may not be enough advance for the cam especially if compression is low. I find these heads like a lot of advance in the base like maybe 14 to 16 degrees with 7 or more vacuum off a full time port.

What Rochester carb and exactly who’s intake? These heads use a different bolt angle alongside the plenum the best carb intake I found with these is the Professional Products Typhoon if you have the vertical space.

What did you do for a fuel pump and system?

Bogie
 

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Discussion Starter #3
The distributor is a what? You can’t use the original TBI.

People use this term as like your Stage 3 cam, this has no meaning. For a cam it’s specifications that count when trying to figure compatibility.

There are two TBI Swirl Port heads used on the 350 one ends with 191 in the casting number the other 193. The 191 is a 74 cc low compression head the 193 is the 64 cc higher compression head, you need to know which is there.

Both heads require self guiding rockers as there is no cast in guide. The exception would be if you installed sheet metal guides and screw in studs.

12 degrees may not be enough advance for the cam especially if compression is low. I find these heads like a lot of advance in the base like maybe 14 to 16 degrees with 7 or more vacuum off a full time port.

What Rochester carb and exactly who’s intake? These heads use a different bolt angle alongside the plenum the best carb intake I found with these is the Professional Products Typhoon if you have the vertical space.

What did you do for a fuel pump and system?

Bogie
 

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Thank you for your reply. I learned several things from it all ready. I will gather some info to answer your questions and get back. Soon as I can.
 

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Start with the basics. Do a compression check. This will tell you if the engine is internally healthy (ring seal, cam broke in, not to big of miss match of parts, and etc). If the compression is decent above 125 psi and around 15% of each other, then work on the tune. Ignition timing, carb tuning, etc. You will never get any power out of an engine that isn't healthy.
 

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Thank you for your reply. I learned several things from it all ready. I will gather some info to answer your questions and get back. Soon as I can.
 

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Also has already said, camshaft specs would help a lot. "Stage 3" camshaft sounds like a pretty big camshaft.
 

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Discussion Starter #8
Good evening.

If you guys are still there I have a few answers to questions you asked. The fuel pump is a inline electric. It’s from Auto Zone. Nothing special. Supposed to be psi for a carburetor. It’s direct at the time. About to run it through a gauged regulator to see what the pump is actually doing. Thats one of my concerns.
Carb is a Quadra Jet that has been rebuilt.
Intake is a Edelbrock Proformer. Distributer is a HEI (internal coil). Sealed Power over 30 flat tops. The cam is a Engine Pro. 465 in and out 224 duration. The 193 stamped heads, reworked. Roller tipped rockets from Summit Long headers with Super 10’s.

The engine and heads are rebuilt by a local machine shop as a short block. We put it together with what we had around. Except of course critical parts.
Trying to find time to check to fuel supply and if the carburetor is working properly. Also timing. Is the advance working.
Could a bad coil be a problem?
Thanks in advance for your help.
 

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I’m presuming the intake is the 2104 for TBI heads.

The cam is pretty big it will want a lot of base advance.

The Flat tops will push the compression high, with cast iron heads detonation and preignition can be problems.

Spark plugs should be gapped pretty tight on these heads .030 to .035 is about right.

Aftermarket HEI is a crap shoot, faulty modules then coils are common. I presume the original computer and it’s wiring are removed. This means you needed to retire for the distributor and the fuel pump. When doing this type swap I usually leave the existing in tank pump and use a bypassing regulator with original bypass system to drop the pressure to carb friendly and protect the pump from dead heading.

What did you do for fuel tank venting?

Bogie
 

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I know you're working with what you have laying around, but it sounds like a whopper of a mismatched combo. Cam specs are an absolute must here.

Bigger cam, modest compression (probably about 9:1) and the single worst-flowing heads chevy ever produced, including old-school 265 heads from the 50s.

You have heads that completely stall flow at 4500 rpms, but a cam that probably doesn't even wake up until 3500.

As has been mentioned, you need to use a traditional HEI, not the one from a TBI. The one from a TBI is controlled by the computer, and without the sensors and things from the TBI, it won't work.

It's slower than the original TBI because you've added a larger cam. You have tanked cylinder pressures at the low RPMs where the heads shine. Cam, compression, flow. All of those need to match the application. If you mismatch one of them, you have a wheezer :)
 
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