Hot Rods SBC won't rev - are rebuilder pistons the problem?

No wonder it's gutless.

 

Wow, seems like a decked block a a 3.25 crank?

 

Yep, I agree with Budget36, if that is for sure a good measurement of true TDC, you need to check the crank stroke before blaming pistons.
No rebuilder's 350 piston is ever that low. The difference between 350 and 327 is .115" of piston compression height....so .120" down is darn close to ballpark area for a good 1.560" 350 piston stuck on a 3.25" stroke large journal 327/307 crankshaft by mistake.

I had one of these anomaly's once, from a local shop....put three cams, two intakes, two carbs and two different sets of heads on it before I discovered the .140"-ish down at TDC flat tops....still had toilet low compression with the flat tops and 76cc heads. I was 19 and didn't know to check it beforehand.
It ran like a dog, sounded like it was pulling a boat trailer down the track as one friend described it, you couldn't overadvance it and get detonation no matter how hard you tried, would hardly spin the tires,

 

Those look like L-2304 TRW pistons.... Or maybe speed-pro replacements.....

 

Another possibility is 400 rods @ 5.565".

 

Sounds dumb but make sure you’re throttle linkage set up is allowing full throttle at the carb. I’ve seen this problem many times while performing tune ups and fixing it obviously wakes up the response tremendously

 

Extremely low compression, an anemic camshaft, and so so heads. It's no surprise it's not a good performer. The fix is a set of heads with extremely small chambers, like the older SBC 59-62cc chamber heads. A much better cam also, and it will likely come to life and run much better.

 

Wonder what the OP found out/did?

 

Waiting for covid to clear up before I go around my parents again (motor is in dad's shop). After losing two family members, dad is now taking this stuff super seriously. I work around too many people to say I'm not contaminated on any given day.

 

Turns out the thrust surface for the cam(behind top timing gear) was badly worn which allowed the cam to have crazy end play. God only knows what that did to the timing curve. The block is probably worn .035

Time for a new block.

 

That combination of dished pistons, 76cc chambers, and the lower performance camshaft all sell a low performance engine build. I'm not surprised at all that it's all in at 4,000 rpm's. A switch to a smaller combustion chamber head, and a better camshaft will likely wake it up. Or since it's likely 8:1 compression, maybe time for a blower on top and a better cam?

 

Wrong pistons for the crank used ? Saw this exact situation many years ago when a friend used a mixture of 350 & 327 parts which resulted in the pistons being way down in the hole at TDC. His response ? "I thought all 4" bore pistons were the same"

 

They are ....... just needed the right length rods.

 

I found the tick in my old motor.

 

Wow! Was it stuck like that?

 

I thought the thrust was forward on a SBC,,,,?
It looks like it was wearing at an angle,,,,,,isn’t the lower section there in the pic,,,,,showing a lip worn into edge on the bottom ?

Also,,,,,that block can be repaired .

Tommy

 

Don't forget the advance in the hei. Make sure the weights aren't stuck.

 

The bad block has horrible core shift or the cam was machined off center. I'm going to rebuild my old engine. The broken piston is a TRW forged piston that was installed in 1994.

 

The skirt broke. It was still sitting where it came from when it slid out of the bore. I drove it for 1,000 miles tring to find the tick. Bearings looked good and wrist pins were all tight....I stopped short of pulling pistons out.

 

Crazy!

 

I guess this means that the 25 year old high stall converter was still good too. I swapped all kinds of stuff chasing that damn tick.

 

2 valve relief flat tops, race prepped pink rods, Sportsman 2 heads and summit 1105 cam are all being swapped over to my old block and crank.

With any luck it will be back in the truck today making sweet sounds.

 

It is almost back together. I should be able to crank it in the morning. I couldn't resist mocking up my swap meet scores from the hot rod reunion. Not the really cool old finned valve covers, but ones that work for me. ....yes I run a PCV valve. Can't decide if I am going to keep the turquoise script....it is growing on me.

Oh yeah, the 3,000 stall converter went back in..

 

Years ago I bought an El Camino with SBC. It was very low on power and rpms. I finally pulled the engine to find the oil pump pickup was layin in the pan. The cam bearings were toast. It did not have an oil gauge and the idiot light had never come on. I always run a gauge now!

 

By golly, this son of a bitch revs now!

I did a 20 minute break in with no issues a took it out for a spin.

I did about a 20 punch and laid about 200 ft of black marks, just barely hazing the tires. It sheets and gets now!

Cracking the throttle in park, it gets to 7,500 rpm in an instant. I'm very happy with theway it runs now.

 

Check your crank for the proper stroke!!! could have a 283 crank??

 

Sounds like your out having fun now !

 

Yep! The Summit 1105 isn't a huge cam by today's standards, but it runs good. I don't know what it would run in a quarter, but is has enough power to be fun.

 

Here's what it sounds like. Dad took the truck to a cruise night and somebody took a video.

https://m.facebook.com/story.php?story_fbid=1338972643184213&id=1219840291