66 C10 sbc 400 compression issue.

['63GENIII]

Originally Posted by travz500

See sometimes you get over worried when its something so simple Its probably just the gaskets but while you got the heads off run them to a machine shop and have them checked and cleaned up just some food for thought

This is a good idea. Cheap insurance if you ask me. If you do take them in, have them make sure that they are for a 400 block. I think there are small differences between the 400 and the rest of the small block heads. Hang in there. You'll get it done.

[sweetlil66]

Update........ Iv got the new head gaskets installed. I was a lil confused on the torque specs for the head- I got some ppl saying 65 and 85 so i torqued her down to 80.

One thing I noticed- the edelbrock torker 3 intake has surface wear the gasket goes has issues around the front two water ports. ( not smooth ) Should I use Sealacone ? (RTV BLACK)? Should I use it on the whole gasket???? Iv got sealed power felpro gaskets.

Man woulden you know I snapped the front drive side intake bolt (Water port)
Theres enf room so I could screw a nut down on it with JB weld (Once it hardens ill try backing her out) I dont have a welder so this will have to work...
If it doesnt work Im going to trying sealing the crap out of the whole area -


I had a f150 with a 5.0 that broke like this before (Both front bolts) I was able to seal the intake with sealacon and never had a issue-I kept a 160 thermostat to keep her cooler and keep the pressure lower. - So Im praying this works again. drove her from 130k to 310k and then traded for this truck....


Im one of those ppl who believes in doing a job right -ITS A HAVE TO WITH ME.
So if i end up driving it with the broken bolt - Ill probably end of pulling the head my first pay check and getting the bolt fixed. until then ill take it easy on her.


I drained the oil today = Yep anti freeze in the oil - Ok so my worries are - did I damage the engine running her like this??? She NEVER Knocked or banged - She had oil pressure at first and then when I noticed she had almost none I shut her down.
Im pulling the pan tomorrow and installing a new oil pump = Milling high volume-
Guess I could pop a cap and take a look......


Thanks guys will keep yall posted.

[Captainfab]

There's no need tor a high volume oil pump, a stock volume will be just fine. If you have just a stock capacity oil pan (4 qts) you can suck the pan dry with a high volume oil pump at higher rpm's. And that's not a good thing.

[Captainfab]

Double post........

[sweetlil66]

Thanks Captainfab. Actually the truck has a 7 gallon oil pan on her. I believe its this one here. Any car or truck I buy used NOT KNOWING EVERYTHING ABOUT IT - I alway replace the oil pump with a high volume oil pump.
Anyway Iv installed the intake - I sealiconed the intake side of the gasket around the water ports.... Tomorrow Ill proceed with installing the oil pump its self and cleaning the pan. I will try to get her all back together and let yall know what happens.



I get irate when people talk about HV oil pumps being bad because there is too much flow and it will pump too much oil to the top end starving the sump.

Pressure and engine clearances determine the flow. So for a brand new engine with both oil pumps putting out 80psi the flow is exactly the same.

In an engine with worn bearings or higher clearances the standard pump will not be able to maintain 80psi because it doesn't have the size to flow more at that pressure. The HV can keep up and will maintain the 80psi even though more oil is escaping past the bearings ie higher flow.

A high volume pump will be able to maintain more pressure on a higher mileage or higher clearance engine than a standard pump. That's a good thing. A damn good thing. ''


(1)pressure is the resistance to oil flow
(2) the high voluum pump can push about 25% more oil
(3) the oil pump bye-pass circuit limits the max pressure in either size pump to about 65lbs-75 lbs MAXIMUM before it BYE-PASSES all additional oil voluum
(4) the engine can accept and use only the max flow voluum that the engine passages can flow at the max pressure the pump provides , at any point less than max pressure the passages can flow only what the pressure and voluum provided by the pump supplies
(5)if the bearing clearances can flow more than the pump provides in voluum and pressure at any rpm level the film of cooling oil that provides a cushion between the bearing surfaces are at risk of not being supported and seperated by that cushion of oil
(6) now since the sweep voluum is greater with the high voluum pump it will reach that bye-pass circuits max pressure at about 25% lower rpms and supply a POTENTIALLY higher voluum of oil to the supply passages/bearings
(7)SO... all a high voluum pump does is provide the maximum oil flow the engine can use up to the max pressure allowed by the bye-pass circuit at a 25% lower rpm level if the system can reach max pressure, but it also supplies 25% more oil at every rpm level below that point to provide additional cooling and protection for the engine. and if the engine can flow more than the stock pump can provide the high voluum pump helps fill the need faster
(8)oil flow through the bearing clearances INCREASES at a faster rate as the rpms increase
(9) in most engines the oil flow can be provided by the stock pump IF the clearances are close to stock AND THE RPM LEVELS ARE KEPT IN ABOUT THE idle-6000rpm range but if rpm levels exceed ABOUT 6000rpm,or if bearing loads greatly exceed the stock hp levels, or the clearances are greater than stock, the high volume pump is a good idea , simply because it potentially provides that extra volume of oil.

[luvbowties]

...sounds like somebody's been reading a post from 9-27-'07 by a guy with screen name "grumpyvette", post#14...

>> http://www.corvetteactioncenter.com/...-question.html <<

[sweetlil66]

double post srru

[sweetlil66]

Thanks Captainfab. Actually the truck has a 7 gallon oil pan on her. I believe its this one here. Any car or truck I buy used NOT KNOWING EVERYTHING ABOUT IT - I alway replace the oil pump with a high volume oil pump.
Anyway Iv installed the intake - I sealiconed the intake side of the gasket around the water ports.... Tomorrow Ill proceed with installing the oil pump its self and cleaning the pan. I will try to get her all back together and let yall know what happens.



I get irate when people talk about HV oil pumps being bad because there is too much flow and it will pump too much oil to the top end starving the sump.

Pressure and engine clearances determine the flow. So for a brand new engine with both oil pumps putting out 80psi the flow is exactly the same.

In an engine with worn bearings or higher clearances the standard pump will not be able to maintain 80psi because it doesn't have the size to flow more at that pressure. The HV can keep up and will maintain the 80psi even though more oil is escaping past the bearings ie higher flow.

A high volume pump will be able to maintain more pressure on a higher mileage or higher clearance engine than a standard pump. That's a good thing. A damn good thing. ''


(1)pressure is the resistance to oil flow
(2) the high voluum pump can push about 25% more oil
(3) the oil pump bye-pass circuit limits the max pressure in either size pump to about 65lbs-75 lbs MAXIMUM before it BYE-PASSES all additional oil voluum
(4) the engine can accept and use only the max flow voluum that the engine passages can flow at the max pressure the pump provides , at any point less than max pressure the passages can flow only what the pressure and voluum provided by the pump supplies
(5)if the bearing clearances can flow more than the pump provides in voluum and pressure at any rpm level the film of cooling oil that provides a cushion between the bearing surfaces are at risk of not being supported and seperated by that cushion of oil
(6) now since the sweep voluum is greater with the high voluum pump it will reach that bye-pass circuits max pressure at about 25% lower rpms and supply a POTENTIALLY higher voluum of oil to the supply passages/bearings
(7)SO... all a high voluum pump does is provide the maximum oil flow the engine can use up to the max pressure allowed by the bye-pass circuit at a 25% lower rpm level if the system can reach max pressure, but it also supplies 25% more oil at every rpm level below that point to provide additional cooling and protection for the engine. and if the engine can flow more than the stock pump can provide the high voluum pump helps fill the need faster
(8)oil flow through the bearing clearances INCREASES at a faster rate as the rpms increase
(9) in most engines the oil flow can be provided by the stock pump IF the clearances are close to stock AND THE RPM LEVELS ARE KEPT IN ABOUT THE idle-6000rpm range but if rpm levels exceed ABOUT 6000rpm,or if bearing loads greatly exceed the stock hp levels, or the clearances are greater than stock, the high volume pump is a good idea , simply because it potentially provides that extra volume of oil.[/QUOTE][url][url]http://http://www.digitalcorvettes.com/foru...?t=85963Thanks

[sweetlil66]

ops ok theres the link but idk why it came out like that in a double post- the link should have came out in the first post - maybe it had something to do with fire fox and google chorme running multi tabs or something srry. Grumps a smart man when it comes to just about anything.

Yes Luv you wear right i got it from him and turtlevette a friend of mine but the write up was on a different site a different site and he got it from ericthecarguy.com https://www.ericthecarguy.com/

[sweetlil66]

Update. Iv got the engine back together.... Havent had a chance to start her yet but the compression issue remains. Cylender 3 has right around 75 ish and 5 has 80 ish.
So now what do I do??? I starting to think the block is cracked.
I guess I could pull the heads back off and run them down to a shop.

[Captainfab]

While you had the heads off, you didn't have them checked out?

Originally Posted by sweetlil66

Update. Iv got the engine back together.... Havent had a chance to start her yet but the compression issue remains. Cylender 3 has right around 75 ish and 5 has 80 ish.
So now what do I do??? I starting to think the block is cracked.
I guess I could pull the heads back off and run them down to a shop.

[sweetlil66]

No sir srry. Me and the wife got in a fight about speeding money. They wanted 150 alone just to test the heads. then 750 to fix them if something was wrong.
250 to resurface.

I feel like balling. Everything was riding on this.
I just know the blocks cracked.

[sweetlil66]

If the head was cracked woulden I have noticed more - milky oil when i pulled the valve cover??? I would think if i was the head it would have been everywear

[Captainfab]

Sounds like you need to find a different machine shop. Around here I can get a quality valve job done, including surfacing the heads for about $275.00. Of course that does not include valves, seats or springs if needed.

Now you're also going to need another set of head gaskets and intake gaskets.

Have you considered finding a good running small block just to get you up and running?

Originally Posted by sweetlil66

No sir srry. Me and the wife got in a fight about speeding money. They wanted 150 alone just to test the heads. then 750 to fix them if something was wrong.
250 to resurface.

I feel like balling. Everything was riding on this.
I just know the blocks cracked.

[sweetlil66]

Iv been looking around and I see engines going for 500 or so but I really dont have anymore money to mess with. Im not sure what to do.
This is probably a bad block isnt it?

[tincan1966]

All along I'd have been extremely concerned on how long the PO drove this with water/antifreeze in the oil. My guess is that is why it got parked. Head gaskets don't normally go bad while sitting. If you've already changed them and compression didn't improve, you've got other issues.
I didn't understand why you changed the oil pump? GM specs say that 25-40 psi is normal oil pressure.

Not to be a bearer of bad news, but I personally think you're wasting money on this engine at this point , if not going to rebuild it. Since you don't have any history about it, you may be chasing gremlins for along time and invest more money trying to patch it than you would fixing it.
SBC 400 heads are notorious for cracking. Also they require a special head gasket-due to bore size and the steam holes between the cylinders.
Anytime you are mixing fluids in the oil pan, it's not a good thing. Even an intake gasket can leak coolant around the crossover passages, and enter antifreeze into the lifter galley, which will drain into the oil pan. Sever bearing wear occurs when antifreeze and oil mix.
As CaptFab said- I'd find another machine shop- around here I can get heads crack checked for about $40. You can also buy ready to run, rebuilt heads for about $200/ea for most mail order places,if needed. $750 to do a pair of stock SBC heads is a bit pricey.

Good luck and hope to can get it fixed up!

[Irishbleueyes]

Originally Posted by sweetlil66

Update. Iv got the engine back together.... Havent had a chance to start her yet but the compression issue remains. Cylender 3 has right around 75 ish and 5 has 80 ish.
So now what do I do??? I starting to think the block is cracked.
I guess I could pull the heads back off and run them down to a shop.

Remember my posting about getting a leak down tester to find the original problem first? I guess you skipped right over it.....

[sweetlil66]

Ok- I got the motor back down again.
I can look at 3 and 5 and there smooth as could be.
I took a straight edge to the head and ether the head is warped or my straight edge is....
Im not sure but I found a guy who said he will check the head for 15 and if there is a issue - if i have him fix it he will drop the 15 and charge 35$. Soo I off to the shop will update asap.

Thanks.

Ps. Irish I posted before that I do not have a air compressor or leak down tester.... Our autozone or orailys do not rent the leak down tester...
I wanted to get a radiator pressure test but they wanted a 109$ just to rent. I would get my money back once I returned it but I dont have a 109$s.
I was trying to ignore your post.

I did start the engine and the oil psi with 10/30 held for over 20 mins at 60 psi.

[tincan1966]

Make sure you get the right gaskets when reassembling. This is not one of those "a small block chevy is a small block chevy" instances. I'd also consult a Motor or Chilton maunal to get the correct torque sequence and amount.

[contagious102]

I would not worry to much about a 5 psi differance,valve wear,valve adjustment, piston rings,many things will affect that. Your motor will not care about 5 psi.It will all change cold to hot.Me ,i would run it ,and keep an eye on things for a while,see how it does over time.!!! Just me.

Didn't read the whole thread,are 3 and 5 a lot lower than the others? If so i'll shut up.!!LOL

[Irishbleueyes]

Originally Posted by sweetlil66

Ok- I got the motor back down again.
I can look at 3 and 5 and there smooth as could be.
I took a straight edge to the head and ether the head is warped or my straight edge is....
Im not sure but I found a guy who said he will check the head for 15 and if there is a issue - if i have him fix it he will drop the 15 and charge 35$. Soo I off to the shop will update asap.

Thanks.

Ps. Irish I posted before that I do not have a air compressor or leak down tester.... Our autozone or orailys do not rent the leak down tester...
I wanted to get a radiator pressure test but they wanted a 109$ just to rent. I would get my money back once I returned it but I dont have a 109$s.
I was trying to ignore your post.

I did start the engine and the oil psi with 10/30 held for over 20 mins at 60 psi.

Ok, in the future try and borrow a compressor. Still be cheaper to buy a leak down tester than spend money in the dark. You can also get radiator hand pressure tester for as low as 50 on Ebay.. Good luck man, we're with you..

[sweetlil66]

Originally Posted by Irishbleueyes

Ok, in the future try and borrow a compressor. Still be cheaper to buy a leak down tester than spend money in the dark. You can also get radiator hand pressure tester for as low as 50 on Ebay.. Good luck man, we're with you..

Thanks and I agree with your advice...

Ok update time. The head had a 1/2 crack in it going from the exhost valve down to the lower part of the head on cylinder 3(The tech this is wear the water was coming from!!!) - cylinder 5 had warped valves and caused the lower compression.

To have the head checked it was 15$ but he waved it bc I paid for a new head.
A complete new head with a 5k warranty cost me 200$ - all new parts installed.

He said more then likely the other head is fine since the compression is 175 on every cylinder.

Guys Thank you so much. I owe every poster a beer or two = pm me your address and I mail it.

Thanks!

[sweetlil66]

Originally Posted by contagious102

I would not worry to much about a 5 psi differance,valve wear,valve adjustment, piston rings,many things will affect that. Your motor will not care about 5 psi.It will all change cold to hot.Me ,i would run it ,and keep an eye on things for a while,see how it does over time.!!! Just me.

Didn't read the whole thread,are 3 and 5 a lot lower than the others? If so i'll shut up.!!LOL

3 and 5 was 75 psi -- the other wear 175.

Iv got the new head soo Im going to fallow your advice and drive it once I get it back together and keep an eye on things!!!

[contagious102]

Good deal ,glad you found the problem.Put her back together and drive the wheels off it.!!!!

[Captainfab]

As long as you got a head with the steam holes for a SB400, and you use head gaskets for a SB400, you should be fine.