Compression Numbers
#1
Compression Numbers
so on my 331 stroker that is fairly fresh I measured the compressions to average around 151 with the highest being 154 and the lowest being 143
Those in my opinion are very good.
question is...
Why is my motor smokin like a diesel when i get on it?
Smokes more so after i have been cruisin at 65 mph in 5th gear and get on it vs. after i've gotten on it several times in a row. almost like there i
is a build up ofoil then a little crank case pressure blows it by the seals or guides.
my thoughts are:
[ul][*]Valve seals[*]Valve guides[*]Combo of above 2[*]Running Rich and blowing a bunch of fuel by[*]Combo of all three[/ul]
Some background:
[ul][*]I bought it built up and in my opinion the person that did it wasn't very good (sucked!!!!).[*]when i pull the valve covers the cap nuts on the roller rockers are only holding onto rocker studs with 4 threads ( so locking hex is way deep inside) either too long of studs or too long of push rod[*]I have heard that it's pretty common that if the machinest doesnt' know what they are doing they will measure pushrod lenth incorrectly and cause a lateral torque on valves causing guides to prematurely wear?[*]Plugs - when pulled plugs to do compression test they were discusting, completely packed with an oily residue, there were a couple that you could not see the gap between porcelin and threads.[*]AFR 185 heads are as new as motor, around 5500 miles or so[/ul]
Thanks for your responses
Matt K.
Those in my opinion are very good.
question is...
Why is my motor smokin like a diesel when i get on it?
Smokes more so after i have been cruisin at 65 mph in 5th gear and get on it vs. after i've gotten on it several times in a row. almost like there i
is a build up ofoil then a little crank case pressure blows it by the seals or guides.
my thoughts are:
[ul][*]Valve seals[*]Valve guides[*]Combo of above 2[*]Running Rich and blowing a bunch of fuel by[*]Combo of all three[/ul]
Some background:
[ul][*]I bought it built up and in my opinion the person that did it wasn't very good (sucked!!!!).[*]when i pull the valve covers the cap nuts on the roller rockers are only holding onto rocker studs with 4 threads ( so locking hex is way deep inside) either too long of studs or too long of push rod[*]I have heard that it's pretty common that if the machinest doesnt' know what they are doing they will measure pushrod lenth incorrectly and cause a lateral torque on valves causing guides to prematurely wear?[*]Plugs - when pulled plugs to do compression test they were discusting, completely packed with an oily residue, there were a couple that you could not see the gap between porcelin and threads.[*]AFR 185 heads are as new as motor, around 5500 miles or so[/ul]
Thanks for your responses
Matt K.
#3
RE: Compression Numbers
as far as the blow by maybe pcv, valve seals or rings need to seat..... now for the roller rocker issue ......could be too long of push rods but I doubt it .....mine did the same thing but I didn't have time to address issue until one of the tips of the studs broke off, so I called afr cause i got 185 heads and the first question they asked me was "what kind of roller rockers are you running??" I said comp magnum 1.6 3/8 stud mount and he said there's the problem!!! the way the trunion is on some roller rockers it is taller and requires use of longer studs. arp sells the slightly longer studs. I knew it wasn't push rod length on mine because I set it up my self and had it so the travel of the roller tip stayed in the center of the valve stem replaced them with slightly longer studs and that was 2 years ago and today it's still fine!!!
#4
RE: Compression Numbers
my 331 has around 180 on all cylinders except the one that got messed up and it has nothing, im tearing it apart tonight to find out what went wrong. i had around 250 miles and after the first 75 i wasnt loosing any oil at all, i broke it in hard, maby a tad to hard, but i detonated that thing from messing the timing up, damn advancement gun!
#5
RE: Compression Numbers
ORIGINAL: 94StinkinLincoln
my 331 has around 180 on all cylinders except the one that got messed up and it has nothing, im tearing it apart tonight to find out what went wrong. i had around 250 miles and after the first 75 i wasnt loosing any oil at all, i broke it in hard, maby a tad to hard, but i detonated that thing from messing the timing up, damn advancement gun!
my 331 has around 180 on all cylinders except the one that got messed up and it has nothing, im tearing it apart tonight to find out what went wrong. i had around 250 miles and after the first 75 i wasnt loosing any oil at all, i broke it in hard, maby a tad to hard, but i detonated that thing from messing the timing up, damn advancement gun!
cool, your 180 psi could differ from my 150 for a number of reasons. if that's what you are referring to. I believe that in the case with a fairly fresh motor, when doing compresssion test you are looking for large variances like you are experiencing
I think, please anybody correct me if i'm wrong but compression will differ because of a number of reasons, a couple of which could be compression ratio and the 6500 feet of altitude i was at when testing.
Good luck with motor rebuild
Thank you for reply
#6
RE: Compression Numbers
ORIGINAL: mjr46
as far as the blow by maybe pcv, valve seals or rings need to seat..... now for the roller rocker issue ......could be too long of push rods but I doubt it .....mine did the same thing but I didn't have time to address issue until one of the tips of the studs broke off, so I called afr cause i got 185 heads and the first question they asked me was "what kind of roller rockers are you running??" I said comp magnum 1.6 3/8 stud mount and he said there's the problem!!! the way the trunion is on some roller rockers it is taller and requires use of longer studs. arp sells the slightly longer studs. I knew it wasn't push rod length on mine because I set it up my self and had it so the travel of the roller tip stayed in the center of the valve stem replaced them with slightly longer studs and that was 2 years ago and today it's still fine!!!
as far as the blow by maybe pcv, valve seals or rings need to seat..... now for the roller rocker issue ......could be too long of push rods but I doubt it .....mine did the same thing but I didn't have time to address issue until one of the tips of the studs broke off, so I called afr cause i got 185 heads and the first question they asked me was "what kind of roller rockers are you running??" I said comp magnum 1.6 3/8 stud mount and he said there's the problem!!! the way the trunion is on some roller rockers it is taller and requires use of longer studs. arp sells the slightly longer studs. I knew it wasn't push rod length on mine because I set it up my self and had it so the travel of the roller tip stayed in the center of the valve stem replaced them with slightly longer studs and that was 2 years ago and today it's still fine!!!
do you happen to know what the product number and sizes for the new studs you bought are?
Thank you for your reply
Matt K.
#7
RE: Compression Numbers
ORIGINAL: r.barn
You running PCV set-up?
bet your sucking a lot of oil thru PCV valve.
You running PCV set-up?
bet your sucking a lot of oil thru PCV valve.
anybody please feel free to weigh in on this...
#10
RE: Compression Numbers
oh man as far as the part number goes???? I called afr at the time and told them my dilema and they gave me an arp part number and I got them from summit racing when they came they said something like small block chevy 3/8 studs I'll see if I can find the part number give me a few minutes I keep all reciepts so I'll check