24 replies to this topic

[Lloydguy]

New gaskets are the only "must" IMO...but what parts you want to change while its open is up to you.You dont know how many total KMS or miles are on the complete engine?
If you dont,then changing the crank seals wouldnt be a bad idea,but that would require a complete tear down.It's up to you as to how deep do you wana go into this thing.
If you ring end gaps and cylinder clearances check out good,then you could get a quick hone done and your only out some time and a small amount for the hone job and a set of gaskets.
I'm NOT trying to tell you what to do,just throwing idea's at you.

[670blues]

Hmmmm. I'm leaning towards re-using what I can since the ring end gap was so close to spec and the finishes all look good. So at minimum I'd want to run a hone over the cylinders to de-glaze and prep the surface?

[BillInIowa]

Ah well, next time I do a top end it will be that much easier! Looks like I'll have to slap it back together and run the electrical diagnostics. Thanks for the help!

Looks like you can even see the hone marks in the cylinders. My 98 583 GT has 120 lbs compression and starts fine.

[sledsrockcolorado]

At this point here is what I would do, using a new base gasket (same thickness) put the top end back together. Just for giggles I would do a squish test (using the simple solder method). I would then pull another compression test on it, IF it seems low - add a little oil to the cylinders for better ring seal. Repeat the compression test and compare numbers. If all is well there, I would move onto the carb/HAC/electrical.

I just went back and re-read this thread, your low psi compression number could be nothing more than a low reading gauge. Do the compression test again and then add some oil and repeat. If the numbers don't change much you have good ring seal and it's time to move on to the HAC. You are running the 40mm carbs with HAC correct?

[Lloydguy]

Sled rock,do you think he should give the jugs a quick hone with maybe
a fine stone before he put's the topend back together?I personally would
check the piston to cylinder clearances for sure before re-assembly,just
to make sure the last time the topend was done,it was done to decent tollerences.

[sledsrockcolorado]

Sled rock,do you think he should give the jugs a quick hone with maybe
a fine stone before he put's the topend back together?I personally would
check the piston to cylinder clearances for sure before re-assembly,just
to make sure the last time the topend was done,it was done to decent tollerences.

Good point! Wouldn't hurt to measure out the cylinder and piston to see what the clearance is. To be totally honest, I would run a hone through it and new rings as a minimum (because I'm kinda anal). Is it needed, good question?

[thumbdoctor]

You have some problems there. First and obviously you have HO flat top pistons with a Standard 670 head. Second, those cylinders aren't HO either as the HOs have a half round cut away in the rear under the boost port Casting number 6923194. Probably a good idea to remove the R/V cover and check to see if the bottom end is HO. A correct HO (Summit X) with have isometric crankcase inlet ports with a matching R/C cover. Lastly, if the bottom end is genuine HO parts then the crankshaft keyway is in the wrong timing index for a standard 670 top end. The power output won't ever be correct until either the top end is restored to an HO providing the bottom end and calibration module is high output. The other option is if the bottom end is standard 670, rebore the cylinders 1st oversize and install standard 670 pop up dome pistons.
 HO cylinder.jpg   55.17K   0 downloads

HO oil pump placement is on the top of the R/V cover.
 HO oil pump location.jpg   83.98K   0 downloads

[sledsrockcolorado]

You have some problems there. First and obviously you have HO flat top pistons with a Standard 670 head. Second, those cylinders aren't HO either as the HOs have a half round cut away in the rear under the boost port Casting number 6923194. Probably a good idea to remove the R/V cover and check to see if the bottom end is HO. A correct HO (Summit X) with have isometric crankcase inlet ports with a matching R/C cover. Lastly, if the bottom end is genuine HO parts then the crankshaft keyway is in the wrong timing index for a standard 670 top end. The power output won't ever be correct until either the top end is restored to an HO providing the bottom end and calibration module is high output. The other option is if the bottom end is standard 670, rebore the cylinders 1st oversize and install standard 670 pop up dome pistons.

Whoa, whoa.....he already stated it was NOT the HO motor. No need to confuse the issue. He has a std 670. The only thing I was not able to verify was the pistons. The dome on the std piston isn't like a pop-up dome on a race car motor.

[BillInIowa]

Whoa, whoa.....he already stated it was NOT the HO motor. No need to confuse the issue. He has a std 670. The only thing I was not able to verify was the pistons. The dome on the std piston isn't like a pop-up dome on a race car motor.

Yeah, all the guy was trying to do was solve a hard starting problem?

[Lloydguy]

Bump.anything new with your situation?