DodgeTalk Forum banner
Status
Not open for further replies.

1977 W200 B block 400

4K views 23 replies 3 participants last post by  key99 
#1 · (Edited)
I'm having trouble finding out what is normal psi reading for compression check on the ol 400 B block. showing 110-120 on 7 but only 30 on 1 , argh :nono
 
#4 ·
OP may be trying to decide if both heads need to come off; the 117 is good news.
... Which cyl is bad, hope it's not #7 !
 
#6 ·
Your right, 7 cyls all tested good, only 1 bad; but OP did not mention "which" cyl is bad (cyl #7 is the one cyl always at risk of "crossfire", and if failed warrants extra attn).
 
#8 ·
Shmut, my old puter won't hook up to the link; glad you probably found someone who could word it better than me (I didn't think the seriousness/consequences was getting thru).
... GOOD public service cribbs!!
 
#9 ·
whats OP? I don't think cross fire is the issue unless it happened earlier in life. everything checks out. Its the number 1 cylinder only getting about 30psi. I haven't done the oil test yet. also i didn't do it with the engine warm or with all the plugs out. I knew about the 8:1 but don't know how to figure the 117psi. getting over my head. I sure appreciate all the interest! keep it coming. thanks
 
#10 ·
Well, glad it's #1 , but the bad news is the head is probably going to have to come off. If the oil test increases the compression then the engine is coming out.... Lets hope it's not that!

Unless someone can think of something else that is. You could pull the valve cover off and see of a valve has dropped I suppose.

OP is the Original Poster.
 
#11 ·
Might be time to put air to that cyl, and "listen" at carb, exhaust, and oil fill cap (tie throttle open, and remove oil fill cap BEFORE putting air to cyl).

Shmut, link still won't load
 
#12 ·
at 100k if the heads come off engine needs redone anyway probably huh. whats the chance of having good cylinders and just need honing and re-ring and valve job? wishful thinking? if it has to come out then might as well do the tranny too. heck, might as well just stroke it, where does it all end? haha
 
#15 ·
Yup; although a bad valve will lessen pressure on the rings, and could "possibly" hide bad rings.

... With the 400s "slow cyl speeds" due to long ish rods (high rod ratio), bores a likely good.

#1 chamber is the last one to get coolant, and likely runs the hottest (wild guess, lol, exhaust valve); but you will know soon
 
#14 · (Edited)
Sorry, not to jack,

cribbs: saw the link, good, but they're a bit too kind (can also destroy/loosen main caps in their registers, and cyl "bores" can split or stretch/deform).

... They were kinda foggy about the two critical cyls involved, the "advanced 90* cyl (LA #7 ), and the wire that can fire it way too early (LA #5 ), all V8s have them, they are always (rule of thumb)---

--- "the two cyls that "are physically beside each other in the block, AND follow each other in the firing order"
(if plug wires are routed normal and "pretty looking", they would run parallel because they are physically beside each other, both at the block and the cap)

... IMO, for LA: if wire set has 90* boots at the cap, #7 wire should be different (straight or angled boot) and longer, so it's up and away from #5 .
 
#17 ·
Ya, springs around the corner; hopefully no going underneath; if the air shows a valve, do as cribbs74 said and pull the cover (could be stuck valve, or broken spring, who knows).
... It was never mentioned how it ran etc; spitting out carb, exhaust, blowby pulses etc
 
#19 ·
finally did a new compression test, still only 30 on no. 1 cylinder. drove it up on ramps (just the driver side so the cylinder would be more plum), put some oil in the cylinder and did another test, this time getting a little over 60. oops.
Also i drained the oil and filled the cylinder full of tranny fluid (hoping for the stuck ring syndrome) for about 5 hours. not much ran out of the drain plug, but some did). then refilled with 10w40, ran it without plug in no.1 cylinder for a bit to blow most of the tranny fluid out, then replaced the plug. when i fired it up it blew smoke out of the left side for a while til it got good and warm and finally cleared up. it seems to sound better but im sure it just likes the new oil. haven't re tested it yet but i'm guessing it will be about 30 haha.
the good news is that after adjusting the ol 727 tranny it is running and shifting (i hate to say it) perfectly!
 
#20 ·
Bump: hows the 400?
 
#21 ·
haven't got it in yet. but its coming.
changed over the alternator to delco internal voltage reg
got rid of the dimming lights at an idle.
got a new(used) speedometer in from mopartruckparts today. the old one bounced around so much it finally quit
this one has 60,000, hopefully and not 160,000 haha
got a different radio too, am fm, same old style out of a car i think
mine only worked at about 7 volume level and is now only an annoying buz
i'll keep all that stuff though, one of these days i'll be fully retired and fix it!
exhaust manifold is cracked
had to get some headers, and of course, to make it easier to hook up to the 2 1/2" flow master exhaust that was recently upgraded, i'll have to get some dumps to avoid welding ;-)
anywho, hail season is about over and i need to get it in to my main dodge mechanic ( no hurry since he just had prostate surgery) I want everything else just right so when we get that motor up to about 350- 400 horse it'll light up all fours! just incase i ever need to of course
always love chattin about the ol truck
thanks key
 
#22 ·
Sounds like you been busy chippen away at the ole girl; good luck to you and the healing mech!

A month or two ago was a thread about speedo cables/lubing; but, by the sounds of the surgery, your mech would likely know issues/cures from that era well. ... Again, good luck man/men lol.
 
#23 ·
the ol girl came with cruise control which is now removed. nasty contraption i don't see ever utilizing. put it in the archives though. never throw anything away.
purchased a new 100" cable. installed it with no lube, assuming it was factory lubed. not much help cuz the speedometer still jumped all over any speed under 40. up around 55 or 60 it would level out fairly well. then if finally quit.
when i put in the radio and speedometer i plan on examining the cable carefully. i see wd40 has white lithium now. do you think it would be good for the cable? I just figured the manufactured had some high tech lube on it from the start. maybe not in this new world.
i know not to get the lube within an inch or so from the speedometer head and to lube the speedometer head with some 3 in one oil. couple of drops in the hole, about like an air tool huh? whaddya think?
I've wondered if the old antenna is going to work with an am/fm radio. probably not the fm i bet. if i can get the ball games and George Noory on am i'll be happy.
anyway i drive it 8 miles a day, 4to and 4from our little bar and grill. 3 of it can be 65mph interstate or we can go 6 miles on gravel. i prefer the gravel but am usually running late
my wife has followed me on the hiway and said i never get it quit to 60 haha. that's wrapping it pretty tight haha, it rides pretty dang good considering the wore out 33x12.50 kumho's
im really loving it, especially since the new alternator fab. bright dash lights and headlights and no dimming!
 
#24 ·
Yeh, hopefully the 100" had some fancy lube on it, butttt

Thousand veiwpoints on speedo cable lubes nowadays; I'm thinking your clime will restrict choices, and specific speedo cable lubes don't really exist anymore.
... Your mech is probably from an era when cables were in widespread use (type of surgery kinda a giveway); he may have far more "hands on" knowledge.

IIRC, consensus is to keep lube farther from the speedo head (6-8-12"??).

Don't recall antennas ever being changed for FM, buttttt
 
Status
Not open for further replies.
You have insufficient privileges to reply here.
Top