[Pupsvette76]

i took the car for a shakedown drive on the road for the first time in a long time and i noticed it has no power with my foot to the floor the acceleration is pitiful especially for a sbc with a turbo... anyways basically to give the best desrciption i have had issues with this motor before...with my foot to the floor it sounds like a cylinder is dropping out and its hard to start
have tried adding time retarding timing with no change i have not done a comp or leak down test yet but i will soon...for specs its a 355sbc with gm stock head 76cc icon forged 9:1 pistons .488 lift cam h beams and forged crank edy intake manifold with pro products TBI on top and single turbo any help is greatly apprecciated thank you

[Bad66]

What's your head casting #? If they are those 462624, these heads are well known for cracking. Not sure if they work with fuel injection so if I'm way off base please disregard lol

[Pupsvette76]

I don't know what the casting # I I took them off a long block I bought for another project that I didn't need them for ... U maybe right about te fuel injection but it feels like I'm running on less that 8 cyl ... At WOT it takes a second for the engine to Rev uP and it doesn't always rev to the full rev limit I have set when it does cooperate it feels rough

[Bad66]

Originally Posted by Pupsvette76

I don't know what the casting # I I took them off a long block I bought for another project that I didn't need them for ... U maybe right about te fuel injection but it feels like I'm running on less that 8 cyl ... At WOT it takes a second for the engine to Rev uP and it doesn't always rev to the full rev limit I have set when it does cooperate it feels rough

If your missing even 1 cyl, you'll know it. The car will barely accelerate. I don't use turbos, so I can't help you there. Maybe check your plugs, or even check the compression of each cylinder to see if it's holding. Other than that, the pro's may know.

[Bad66]

Even better, has the car ever ran right?

[Blazin72]

How long has this engine been together? Has the computer been tuned to work with the turbo?

[Pupsvette76]

I may have a bent valve cuz a few months ago when the car was running last I have two issues one was that a rod let loose and there was evidence that it hit the plug so I'm sure it hit other things... Also a keeper on the same cylinder cam out of the valve on the same cylinder as the rod problem... I have since replaced the rod and piston and put the keeper back in but maybe it did damage to the valve... The car is in the building stage an never been considered road worthy due to unfinished work and running issues

[68NovaSS]

Originally Posted by Pupsvette76

I may have a bent valve cuz a few months ago when the car was running last I have two issues one was that a rod let loose and there was evidence that it hit the plug so I'm sure it hit other things...

What do you mean, the rod hit the spark plug???

[Pupsvette76]

lol just like it sounds the rod lket loose ... when i tore the motor down i saw an indentation on the piston and the electrode on the plug was crushed

[Pupsvette76]

i guess i really should do a compression test and leak down test but i believe i di one once before and came up with nothing conclusive

[grandpa01]

My guess is that the keeper came out when your piston hit the valve. How did you get by with just replacing the piston and rod, what about the crank?

[Pupsvette76]

No damage to the crank or block I shut the engine down really quick when I recognized a noise but ur prob right the piston threw the valve back up before the spring came up and a keeper feel out well I will do a comp/leak down test asap

[eloc431962]

Originally Posted by Pupsvette76

lol just like it sounds the rod lket loose ... when i tore the motor down i saw an indentation on the piston and the electrode on the plug was crushed

The rod didn't hit the spark plug, when the rod let go the piston hit the valve and got the plug in the process, be willing to bet it is in fact a bent valve. JMO you should have checked it out better especially after you found the dent in the top of the piston and the plug damage and the keepers missing from the valve. IMHO



Cole

[Pupsvette76]

Ur absolutely right I got anxious and made a mistake

[Pupsvette76]

ok i finally got in there to do a comp test i tested all cyl and didnt find anything really out of the ordinary the difference between the lowest and the highest was about 15 psi approx but all cyl produced over 135 psi cranking...i then pulled both valve covers and found the intake rocker on #5 very loose i put my inspection cam down through the galley and cranked the motor to see if the cam was flat and it wasnt ...i also found one other rocker arm on #3 somewhat loose not too bad though... but could this cause the symptoms im getting???