My son's 1968 Chevy

[dbrannon79]

Well as you guys have head, my son bought him a 1968 chevy C10 with a 250 straight 6 and 3 speed manual trans (floor shift) that has TBI installed from a company called Dynamic EFI. the company has since gone out of business with the owner passing on. There is not much info out there on this setup other than finding resources on their old website through the way back machine and a couple of forums where the owner was active in before his passing. I'v listed his truck in my signature for others to see.

Here are some pics of it when he bought it.

 

[dbrannon79]

I have been helping him work on the truck trying to get it to the point where it's mechanical safe and good for an every day driver. have already done lots of tuning on the ECM along with repairing several odds and ends that it needed to run and get closer to that goal.

some of my posts are on other threads but I figured I would start off with a new thread here on furthering that work.

Just yesterday I took him out in the truck so he could start learning how the shift it since he has no experience with a stick, but after a good while of putting around in an open parking lot and trying to drive across town, it broke down on us. we got it home and I figured out that the ignition module in the HEI dist had failed.

Now proir to this, I have been driving it here and there and noticed that it seems not to have much power, it can't really take off from a light very fast nor does it have hardly any acceleration. it will build speed just seem down on power.

runs smooth without any missing so I stupidly dismissed the simple things like spark plugs and whatnots.

Well this changed today.

 

[dbrannon79]

with knowing the ignition module will cut out after it get hot, it still runs fine. today I decided to pull it around to the back driveway and do some simple things like have a look at the spark plugs and even do a compression test to see the overall health of the engine. mind you this engine was fully rebuild at the local machine and engine shop here in town years ago and only has about 7600 miles on it since that rebuild.

the first three plugs looked good but had some carbon on the tips. the back three were completely gummed up and fouled with oil and carbon.

Hmmm.... I pulled out my compression tester and got this...

#1 = 170
#2 = 170
#3 = 170
#4 = 60
#5 = 0 zero
#6 = 70

Now I'm getting concerned and thinking bad rings and a blown piston or burnt valve. I wanted to have a look at the cylinders but could not find my bore camera anywhere so I pulled the valve cover to see if something was up under there...

do yall see anything wrong with these photos?

 

[dbrannon79]

Yes this thing has been running on three cylinders for a while from the looks of the plugs. funny thing is it doesn't miss and runs smooth even trying to goose the throttle while sitting still.

from what I can tell, three of the studs on the head holding the rockers have pulled up, I can easily see the three studs are higher than the others.

I really hope there is a fix for this without having to pull the head. the push rods on these three are also very slightly bent. wiping them off and rolling them on a flat surface I can see a slight bend, also the push rod on #4 has a indentation on the ball end where it was slapped a time or two. hope a valve is not also bent, this cylinder had no compression at all.

you guys know if there is a repair for the studs pulling out of the head? I assume a thread repair kit would be needed not unless there is a longer stud and maybe some extra threads further in the hole that can be used. IDK. both my son and I are bummed to find this.

 

[dbrannon79]

Just reading online trying to find a repair, I am finding out that the studs may not be threaded into the head. I always thought they were threads in there. I can't specifically find that info on a 250 L6 engine though.

 

[dbrannon79]

Here is a pic of the plugs for reference. starts #1 through #6 right to left.

 

[dbrannon79]

Trying to ID the block and came up with this.. block casting number is 3921968 date code is H157, other code is CON2

From what I found the casting number can be a GM 250 or 230,

Date code H157 shows the 8th month, 15th day, 7th year of the decade. Meaning August, 15th 1967

Code CON2 is conveyor #2 in the GM plant

I cant see the vin code stamp that should be on the dist boss, doesn't look like anything is stamped there so I cannot verify if this is the original engine to this truck.

 

[dbrannon79]

Rockauto shows press-in rocker studs for this engine. both standard and oversize. Not sure if this is a repair that can be done on the truck or even on the bench. may have to be done at a machine shop. I saw where the studs can be pulled with a nut and stack of flat washers and might be able to be re-installed by freezing the new stud and heating the boss on the head, but not all that sure it would hold.