400 rebuild opinions wanted
 

Ok Mopar gearheads need serious opinions. My 72 400 is at the rebuild shop. The man in charge tells me he'll do whatever I want him to do to my engine however his recommendation is to bore it out 30 over with new pistons. He says the cylinders are tapered but won't say by how much. The cylinders are not scored just tapered. The engine has 102k miles on it. 130lbs compression in all cylinders except #3 @ 126lbs. (This cylinder was subjected to a partially collapsed header pipe at the time of the compression test) minimum compression is 100lbs. The engine ran fine,did not use any oil and only smoked a bit on startup -- probably valve seals. All cylinders have somewhat of a ridge. He says just honing it and installing new rings I'd be asking for future trouble- burn oil because the new rings won't fit the old pistons properly. If I do not have it bored out, since everything is worn collectively together I should not hone the cylinders and should leave the rings in the old pistons. The main bearings appear to be in good shape. Is he just trying to squeeze me for more money??? He will not stand behind his work if the engine starts to burn oil down the road. The history on this engine is it has never been abused or raced. It's out of a 72 Charger that has been a trip vehicle for the original owners, alot of long distance driving . It originally has a 2 barrel, now has a 4 barrel with headers. A new cam kit will be installed. A general rebuild costs about $1600 to $1800, double that if it needs boring and new pistons. It will get at least a valve job. Should I take the block back and disasemble it myself to prove the cylinders are tapered and need boring??? Max cylinder bore taper is .010 according to my spec sheet. Should I pay up to $4000 for this work??? Speak freely and often I need to make a decision by Monday the 25th. Thanks dudes!:yikes:

My 2 cent's in a nut shell.... Dont 1/2 azz a rebuild. It will only come back and bit you in the azz for sure.....
Sheesh... Even decent rebuilds come back on us now'a days....
However... If the guy is not familiar with Mopar Engines. I would not have him do it anyway!!!! Specially if he is not going to stand behind his work....
I'd be outta their.....
You should get some kind of warranty....

Here is my serious opinion.

If it was just to get by and save a buck, I have honed rering with new bearings and a head freshen up. This type of thing many will do themselves to save more.

I would do this to a family vehicle but not my baby, I would possibly do it to get by until I could afford a proper full rebuild.

If you truly love your '72 do a full proper rebuild with a good step piston for some quench with compression increase.

hi neighbor

Time to load everything in the pickup and find another shop

I did a re ring in my father in laws 400 motor/ PU truck. S$#%. It was an oil burner. Ended up re boring it. DO IT right the first time..

The compression is not too bad for a low compression engine. Also, how much are you going to drive the car in the future? Will you really depend on it? If the pistons have not been removed from the block yet, and especially if the engine has not been removed from the car ... and if saving $ is important, I would consider leaving the bottom end undisturbed. It will deteriorate over time, but not very quickly. And since it was not burning oil before ... Its always a bit of a gamble, of course.

about the cylinder wall usable specs. i am getting this info from a 1967 factory service manual. but specs should the same. for a 383 with a nominal bore of 3.375". std 4.2495"--4.2515". a diff of .002". out of round max before reconditioning .005". max taper.010". reconditioning working limits for taper and out of round ,001". max over bore .040". max variation between cyl 125--155psi, std engine, 9.2 cr 130--165 psi HP engine, 10.1 cr. now for my ideas. the 9.2 cr had a 2 bbl, the 10.1 cr had a 4 bbl, in 1967. i have seen more out of round, and taper, work good enough. and have seen compression as low as 110 psi in high mileage engines work good enough. i dont know the 400 bore dia. but the 413 -426-440 are .060" apart. hope this helps.

I think the later 70's blocks are not as hard as the older motors

I second 440's response, load it all up and find a better place that will tell you information and stand behind their work.

ADDED info... Now is a great time to add a stroker kit !!!!!

If you are looking for a budget deal, have someone "you trust" mike the bores and see if you can just re-ring it. At 100K this is a big possibility. I've got two late 70's 360's out there that have nearly no taper at all, and a minimal ridge.

Engine rebuild reply
 

Hey Mopar madmen, thanks for all the replies ad advice. Since the engine-400 has enough ridge on all cylinders and the rebuild shop gave me a good price on a complete job - valves, boring & pistons etc, I'm letting him do it right. I've known him since H.S. I gave some thought to creating a stroker but the extra expense and the fact the car is a boat and is not being raced on the strip I'll forgo it, tempting though. Need to save some mula for the future gear change at the rear. If the engine dynos out to be at least 330hp I'll be happy. It's getting a new cam kit and already has a 750 Edlbrock, Edlbrock Performa RPM intake and Hooker headers with dual Flowmasters. Just need lower gearing, has an embarrassing 2.45 rear. What ratio should I change to? 3.23, 3.55, 3.71????? What will fit in an 8 1/4 hsy??

reply
 

sent you an email months ago, got no reply, should I try again??

It doesn't cost that much more !! When you figure the crank re build & bearings & pistons & rings cost ...

yes, drchallenger at Hotmail.com