LOW budget engine not working well....HELP!

[Mudsport96]

Are you saying you reused to old timimg chain and gears?

[Cliff Ruggles]

One reply says they replaced it, another reply says they used it over again.

I'm confused here for sure.  We're getting "spoon fed" information a little at a time and it's conflicting.

The most important information given is that the engine only makes 10" vacuum at 650-700rpm's, and that would be with "normal" timing in it.  It should be nearly double to that reading. 

The timing is advanced some and it's got low vacuum, something is fundamentally wrong someplace for sure.

Has anyone done a cranking compression test?.......

[jberenyi]

it has been asked twice if timing set was replaced and if so what TYPE. single roller, double roller, link belt (oem), non-adjustable, adjustable, etc. probably would be a good idea to include if the cam was degreed/checked.

I keep saying everything is bone stock except for bored cylinders .030 over and then honed.  Everything else is OEM stock stock stock!

[Mudsport96]

I keep saying everything is bone stock except for bored cylinders .030 over and then honed.  Everything else is OEM stock stock stock!

Ok i realize you are getting frustrated,  but to the guys that build engines this doesnt make sense man.

You had heads machined correct? This is a change from the original engine, so there could be a problem here.

You reused the old cam... did you keep track of which lifters went in which holes? If not you will wipe the cam lobes fairly soon stop running the engine and buy a new cam and lifters. This could also be your problem.

Reused the old timing set... looks slack or not this is not a good plan. Was it a single keyway sprocket or multiple keyway?

Did you use the thick felpro style head gaskets or the very thin sheet metal gaskets? Thick ones will change compression which will dictate different base timing needed. .. and can lead to similar issues.

You stated that the carb ran fine before the engine was rebuilt.  This leads me to believe it is not the carb but an engine issue


Some guys here are probably just unsure of where to go with all the old parts reusing. Ive done it myself out of several buckets of worn parts.... BUT never expected the engine to idle perfect, just run enough to move the vehicle around.

[Mudsport96]

Fast forward, one month ago my friend let the oil get low and spun a bearing so we had the block cylinders honed and replaced the rings, crank, crank bearings and one connecting rod.

Replaced the crank and one rod? Guys that are in the know are there more than one keyway? Pretty sure one is 2 degrees right of tdc and one is 10 degrees right. And the 86 and newer cranks are like 30 degrees. If this is the case and the new crank keyway doesnt match your balancer and timing cover your timing will LOOK right but be wrong.
Also if it is the original balancer the outer ring may have slipped in the process of removal and installation. So get a piston stop and find tdc with that.

Were the rod ends resized? If the crank was damaged enough to warrant replacement, one would think the large end of the rods would be damaged too.

[Kenth]

Chevy 350 crankshafts has the keyways at the same spot.
What differs are the dampers and timing scale that needs matching.

[Cliff Ruggles]

"I keep saying everything is bone stock except for bored cylinders .030 over and then honed.  Everything else is OEM stock stock stock!

That's BS right there and I'm calling it."

I asked about head gaskets, got no info.

Did you even take the time to measure how thick they were?  I went into detail about it earlier on this thread. 

"Stock" head gaskets were .020" thick.  Even with .020" thick head gaskets the compression ratio with dished pistons and 882 heads is a dismal 8 to 1.  Doing the actual "math" on some of those mid-1970's engines I've actually calculated less than 8 to 1 BEFORE you throw on a Detroit .060" thick head gasket!

IF you installed a "builder" gasket it will be .040-.060" thick so you knocked at least 1/2 a point of compression right out of this build from where "stock" would have been.

It's still unclear what you did for a timing set but likely a cheap POS double roller set was installed since this build appears to have been done with the absolute MINIMUM amount of investment.

No one ever puts a used cam back into one of these engines, that's a recipe for disaster and we never got an answer as to whether you put all the old lifters back on it or bought new ones?

It also appears that you sold this vehicle at some point and are having tuning issues with the engine.  Not sure what dog you have in the new owners fight, but coming on here bellyaching about how my you paid for the work back in 2017 then having issues on this low-end half-ass attempt at a rebuild isn't working to well with me.

I pride myself in doing things right and don't get all caught up in those sort of things.  If someone wants me to re-install a used cam and pick the lifters I pushed out onto the dirty shop floor back into their engine I would very quickly hook the cherry picker to it and drop it in the back of their truck and send them to a local "guru" who deals with that sort of thing.

Engines are EXPENSIVE, time consuming and require great attention to detail and the best parts you can find for them.  Honing one with a rock and stuffing it back together with a bunch of used parts is a poor plan, and likely you'll end up on a Forum bellyaching about how it's not working well. 

That's where this thread came from and has gone to.  I'm renaming the thread and will let it run a little longer.  I should have canned it from the start, but I don't get my panties all wadded up when someone starts busting my balls and trying to insinuate that something I did isn't making the grade. 

My goals are to help and get a good end result with these things.  If this thread goes any other direction I'm going to can it.......Cliff

[jberenyi]

I can't believe how far off base this thread has gone and it's all my fault.  I never meant to offend anyone.  I was only looking for help.  I offered what I knew and looks like it wasn't enough or done correctly. I should have let my friend who did the assembly after it left the shop do all the typing and info sharing since he could have answered all your questions accurately and in a timely fashion.  I was only involved in the timing and carb adjustment after it was completed and installed.  I honestly didn't know there were so many variables in an engine build that can cause issues later.  So sorry for everything everyone.  I promise to do better next time.  Clifford, if you want, just delete the thread and again I want apologize to you and everyone else involved   Stay healthy and be safe everyone. 

[Mudsport96]

I can't believe how far off base this thread has gone and it's all my fault.  I never meant to offend anyone.  I was only looking for help.  I offered what I knew and looks like it wasn't enough or done correctly. I should have let my friend who did the assembly after it left the shop do all the typing and info sharing since he could have answered all your questions accurately and in a timely fashion.  I was only involved in the timing and carb adjustment after it was completed and installed.  I honestly didn't know there were so many variables in an engine build that can cause issues later.  So sorry for everything everyone.  I promise to do better next time.  Clifford, if you want, just delete the thread and again I want apologize to you and everyone else involved   Stay healthy and be safe everyone. 

Hey, it happens man.

I see where this got all wonky now.

So you didnt do the assembly, you just got called at the end of the deal to be "the tune guy".
This is like when i show up for night shift at work after day shift had been fiddlefudging with a machine all day and have to take over with half the info on what was done.

Yeah, if you sisnt personally assemble the engine and ( IF YOU ARE CONFIDENT IN YOUR TUNING CAPABILITIES)  you can not get the tune right.... assume someone assembled something wrong. Especially, if it idled fine before... something mechanical changed to make the old settjngs of the carb inadequate. Simple disassembly and reassembly with " the same stock parts" wouldnt change that. So if you didnt assemble it, just maybe something isnt as "stock" as you were told.

[Cliff Ruggles]

In only delete threads and ban users when we don't follow the rules for posting.

There are a few things you need to be aware of with engine "rebuilds".

The SBC engine is a perfect example.

99 percent of the "builder" pistons supplied for them in oversizes have a REDUCED pin height.  This is some lame attempt to put the pistons lower in the holes at TDC and not raise the compression proportionally with the overbore.

Few if anyone out there knows this, not even machine shops, engine builders and local "guru's".

Most SBC builds also get a "double roller" timing chain, recommended by every "guru" on every Forum out there as some sort of "upgrade".  90 percent of them are JUNK, and even the top end varieties aren't as strong as a factory Morse type chain nor to they provide constant tooth contact and "smooth" drive for the camshaft, distributor and oil pump.  Speaking oil pumps it will also get a "high volume/high pressure pump" that does nothing more than rob 10hp or so from the assembly and put a LOT of additional load on the distributor gear and oil pump drive.  I don't even use the HP pumps on full race stuff as the SBC has an EXCELLENT oiling system and if you know how to clearance things its fine with stock pressure and stock pump volume.

Continued.....

[Cliff Ruggles]

Moving on here, the factory had the pistons pretty close to the top of the block at TDC and used .020" thick head gaskets.  This was done to keep quench pretty tight for higher compression, improved combustion efficiency, cooler running temps etc.

ALL replacement gaskets showing up in "builder" kits will be much thicker, typically in the .040-.060" range.

So between your pistons being .030 or deeper in the holes at TDC and your thick head gaskets quench is no longer in the ideal .030-.39" range and up in the .055-.095" range someplace.  SBC engines with that much quench run hotter, overheat, don't make chit for power, take more timing and more fuel, etc, etc.  To add insult to injury folks doing these things think their compression ratio is nearly a point higher than it actually is.

Then most poorly informed enthusiasts bolt on the common 882 castings which don't flow for chit and have a very restrictive exhaust port to help provide some natural EGR and make the EPA happy.  Doesn't matter at this point what else you do, fancy cam, intake, headers, exhaust, etc, you just built a "turd" and you're stuck with it.

It's easy to spot one of these engines, they don't sound "clean", "deep/heavy" exhaust note at idle (low vacuum), poor throttle response, LOUD exhaust when they aren't pulling a load, lackluster power everyplace, REQUIRE a lot of timing to be happy, and they consume huge amounts of fuel for "normal" driving.

Sadly many of the owners don't know all this because they haven't had a professionally built SBC with all the right things done to it and correct parts used in it to compare it to.

As all of this applies to this thread there are many unknowns as to exactly what was used and the parameters, but what we do know is that the engine is only make about half the vacuum it should at idle speed.

Could be as simple as the lifters adjusted too deep, some worn cam lobes, retarded cam timing, LOW compression, retarded ignition timing, etc.  I can tell anyone reading this for certain, IF you have a correctly rebuilt stone stock 1974 350 engine it will make great vacuum at idle without a lot of timing in it.  You will not need to back the idle mixture screws way out on the stock carb either, and the throttle plates will be nearly closed at idle speed.........Cliff

[lightning boy]

Based on your knowledge of engines, this guy must be desperate if he needs you to "tune" it.