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Username Post: compression readings        (Topic#347798)
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
10-21-17 04:32 PM - Post#2711635    

OK Data;
79 P-20 292 I-6
odometer reading 213,000
sat for last 15 years
cold dry comp readings; 1-145 2-140 3-150 4-145
5-150 6-150 With no leak down
after warm up readings; 1-170 2-160 3-160 4-160
5-155 6-150
book specs say 130
upon first rotation on tests compression started at 140-145 then up to recorded reading after 3-4 rotations.
My Question is why are the readings so high with 200k + miles? as far as i know this is all original




Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
LMC Truck
2plus2 
Member
Posts: 1089

Loc: Mission,BC
Reg: 02-03-05
10-21-17 05:06 PM - Post#2711638    
    In response to dbgryche

Hwy miles with regular oil changes would be my vote


69 Canadian Pontiac 2+2
factory L48 350 Chev,TH350,PW,PT
99 Silverado RCLB 4.8 NV4500 14BSF 4.10's locker 6" Procomp 35 bfg m/t's 9k winch cutout flares
07 Town Car Loaded,Tinted,Getting Bagged


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
10-21-17 05:42 PM - Post#2711640    
    In response to 2plus2

it was a service truck for local heating and a/c company and why would it have a higher comp. than fact spec with 200k miles on it

Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
raycow 
Honored Member
Posts: 27084
raycow
Loc: San Francisco, CA
Reg: 11-26-02
10-21-17 06:22 PM - Post#2711650    
    In response to dbgryche

Do you know for certain that the head is original to the engine? A 250 (or smaller) head is a bolt-on swap and will increase the CR.

Ray

Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
10-22-17 01:58 AM - Post#2711655    
    In response to raycow

no not for sure i dont. are there markings that would tell me so?

Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
gchemist 
Senior Chevytalk Moderator
Posts: 24202
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
10-22-17 03:40 AM - Post#2711660    
    In response to dbgryche

Wow. The engine was well taken care of or it had work done to it. Maybe, it's the best one ever built.

Sitting for so long, it's hard to tell if any work has been done to it. Check for new gaskets. Are any bolts missing or look different?



'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
Shepherd 
Frequent Contributor
Posts: 1040

Loc: Lake George, NY
Reg: 11-11-15
10-22-17 05:31 AM - Post#2711670    
    In response to gchemist

Lets not forget gage variations, and carbon build up at that mileage.



 
raycow 
Honored Member
Posts: 27084
raycow
Loc: San Francisco, CA
Reg: 11-26-02
10-22-17 08:17 AM - Post#2711689    
    In response to dbgryche

Sorry, I was wrong. It's only the 194 head which has a smaller combustion chamber.

Ray

Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
10-22-17 03:55 PM - Post#2711729    
    In response to gchemist

from what i can tell its all original it has exhaust manifold leaks so that and intake are coming off to replace gaskets.Those bolts dont look like they are going to come out without a fight. the back side of valve cover is all beat to crap from?? I tried a new gasket on it but still leaking. Im looking for a replacement valve cover. as far as buildup, when i had the valve cover off the top of head/ valvetrain has no sludge buildup at all. ill snap some pics as i break it down, i got a full head gasket set figure might as well replace them all since im leaving that motor in it.

Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
10-27-17 04:35 PM - Post#2712403    
    In response to dbgryche

ok well here is what things look like atm. still undecided as to if i should pull the head and check the chambers for buildup, AKA being the cause for the high compression readings. well i donated subscription and still tring to figure out how to upload a couple pics http://s1302.photobucket.com/user/dgiacchino69/lib ...

Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


Edited by dbgryche on 10-27-17 04:59 PM. Reason for edit: trying to show pics

 
gchemist 
Senior Chevytalk Moderator
Posts: 24202
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
10-28-17 04:22 AM - Post#2712433    
    In response to dbgryche

Hit the reply button. If you type in the box below, you won’t see the option to attach small pics.
Do you have a scope camera available? You can scope down the ports with the manifolds off.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
10-28-17 10:23 AM - Post#2712464    
    In response to gchemist

i do not have a scope but that would only allow me to see above the valve seat unless the valves open far enough to pipe a cam head past it into the cylinder. with the manifolds off the inner more exhaust valve stems have some carbon buildup on them 2,3,4,5 . 1 and 6 are pretty clean and all the intake stems have a light gray buildup on them. the ports themselves are as clean as the valve train shows in the pics.
Code:

  





Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
11-06-17 02:03 PM - Post#2713465    
    In response to dbgryche

well head off and still no obvious reason for the high compression readings unless my gauge is off.. ill clean up, re gasket and assemble and check it again..

Attachment: DSCN8227.JPG (452.38 KB) 4 View(s)


no build up here


Attachment: DSCN8230.JPG (461.01 KB) 3 View(s)


or here


Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
Shepherd 
Frequent Contributor
Posts: 1040

Loc: Lake George, NY
Reg: 11-11-15
11-06-17 02:55 PM - Post#2713473    
    In response to dbgryche

Cylinder on the rt looks wet or oily. Some carbon build up could boost the compression some, cam timing has a lot to do with compression as you know.



 
gchemist 
Senior Chevytalk Moderator
Posts: 24202
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
11-06-17 03:08 PM - Post#2713475    
    In response to Shepherd

What does each cylinder hone look like? Can you see good or worn marks?

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
11-06-17 09:34 PM - Post#2713531    
    In response to gchemist

very little carbon and the cylinders are smooth with no distinguishing marks at all and very little ridge buildup at the top. How would cam timing change the over all compression of the cylinders? i dont understand that.

Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
Shepherd 
Frequent Contributor
Posts: 1040

Loc: Lake George, NY
Reg: 11-11-15
11-07-17 04:58 AM - Post#2713544    
    In response to dbgryche

A stock short duration cam will always build more static compression. A long duration extended over lap performance cam reduces static compression, all other factors being equal. Of course your engine is as manufactured it seems. Again gage accuracy and cranking speed can vary the readings either way.



 
gchemist 
Senior Chevytalk Moderator
Posts: 24202
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
11-07-17 05:59 AM - Post#2713552    
    In response to Shepherd

If honing marks are worn off, I would suspect gunk build up is causing higher compression readings. Piston ring metals are now way better than back then.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
11-07-17 01:45 PM - Post#2713593    
    In response to gchemist

But as u can see there is no build up. the readings i got with comp tester were all taken with 3 revolutions, average 1st was 125 to recorded by 3rd. i guess I'll just replace all the gaskets and put it back together. maybe fixing the exhaust leak and rebuilding the carb will pep it up a little

Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
Shepherd 
Frequent Contributor
Posts: 1040

Loc: Lake George, NY
Reg: 11-11-15
11-07-17 03:56 PM - Post#2713605    
    In response to dbgryche

Agreed, if oil consumption was not an issue.



 
fedupwithchevy 
Forum Newbie
Posts: 52

Reg: 12-21-14
11-07-17 05:33 PM - Post#2713612    
    In response to Shepherd

While the heads were off, I'd take a look at the valve seats and seals. A couple of those jugs look oily.





 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
11-07-17 09:46 PM - Post#2713630    
    In response to fedupwithchevy

the piston tops have .030 stamped on their tops and i think the top end kit i got came with valve seals but i'll have to acquire a spring compressor. as far a oil consumption it leaked out the beat up valve cover and side panels bad.

Attachment: 20171107_183230.jpg (4.76 MB) 4 View(s)




Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
11-17-17 04:20 PM - Post#2714788    
    In response to dbgryche

ok almost done but not sure on vacuum lines there are only 3 lol have the temp switch at top of thermostat housing , 2 lines come from it. 1 goes to hei distributor advance, the other goes to 1 of 2 ports on carb? am i correct?

Attachment: 20171117_161416.jpg (2.89 MB) 3 View(s)




Attachment: 20171117_161458.jpg (3.59 MB) 3 View(s)




Attachment: 20171117_161508.jpg (3.65 MB) 3 View(s)




Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
11-27-17 09:07 PM - Post#2716033    
    In response to dbgryche

ok im about to blow this thing up. I got it all back together and had it running. Wednesday i went to test drive, when i got to the end of my street(down hill) and turned applying throttle it fell on its face . almost like lack of gas, just would not go I gimped it around the block and back to the shop, when i turned the key off it dieseled and blew out a cloud of white gas vapor out of the carb. i checked the oil level, removed the HEI dist. cap and inspected for any damage, Double checked plug wires and firing order. everything looked right. I tried starting it again it fired and idled fine but stumbled when throttled. i shut it down and left it alone for holiday/family time. today i pulled #1 plug brought piston to TDC re checked distributor for proper location and rotor pointed at #1 on cap and in line with #1 spark plug and timing mark was on TDC buttoned it up and started it. it started up let it warm up a few min then throttled and still stumbled. so im thinking a tooth off on timing maybe? when moving dist. a mark in either direction it would not seat completly, 1/8 inch from seat. so put it back where it was and started again it started and idled fine but stumbled with throttle. i pulled dist. all the way out and all of a sudden the lower shaft below gear was milky soaked. crank case oil/ antifreeze mix no oil in coolant WTF

Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
Shepherd 
Frequent Contributor
Posts: 1040

Loc: Lake George, NY
Reg: 11-11-15
11-28-17 07:49 AM - Post#2716084    
    In response to dbgryche

Intermix on the dipstick?



 
gchemist 
Senior Chevytalk Moderator
Posts: 24202
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
11-28-17 08:12 AM - Post#2716085    
    In response to Shepherd

Time for a compression check.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
11-30-17 01:00 AM - Post#2716354    
    In response to Shepherd

oh yes the crankcase was a full oil coolant mix... the question is how/where did it get there. the head was re pulled to try and discover source.

Don't sweat the petty stuff pet the sweaty stuff
1979 Chevy P-20 292/3 spd, 89 Dodge Ram Charger 318 20 over TBI 4 spd w 5"lift with just added 37/13.5/17 ,


 
Shepherd 
Frequent Contributor
Posts: 1040

Loc: Lake George, NY
Reg: 11-11-15
11-30-17 05:22 AM - Post#2716364    
    In response to dbgryche

Hmm, leaking intake, cracked block or head, most common causes.



 
dbgryche 
Silver Supporting Member
Posts: 35
dbgryche
Loc: Shelton WA
Reg: 04-23-15
01-04-18 11:33 AM - Post#2719995    
    In response to Shepherd

ok well took head to machine shop to check and was borderline .005 so had resurfaced. reassembled and now having crank, no spark. i have 12 volts at battery terminal on distributor coil tested .879 ohms pickup tested at .43 both within spec.so assume modual replace it and still no spark to plugs. this it with new cap and rotor tried old rotor and had same no spark result. somebody save my sanity here please.....



 
raycow 
Honored Member
Posts: 27084
raycow
Loc: San Francisco, CA
Reg: 11-26-02
01-04-18 10:02 PM - Post#2720060    
    In response to dbgryche

Did your sanity think to check if you had 12V at the coil terminal WHILE the engine is cranking?

Ray

Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.


 
LMC Truck
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