Mystery solved, stopped crying.

[78SilvAnniv]

Thank you Paul (drags1998) for suggesting we look at the intake manifold. The intake manifold gasket was torn between #2 and #4 allowing blow-by.

We still took the engine out and entirely apart. The decision was made to build it completely and the block was taken to the machine shop today, with the crank and pistons/rods to be thoroughly checked out.
Because we had sucked the oil out of the pan so quickly, and didn't get it replaced soon enough (in our opinion), we decided it would be best to do a thorough job. The cylinders will be honed, the crank polished, the pistons/rods checked and new bearings installed.
I believe we will also be choosing a new cam (mild/rv) and rebuilding the carb.

Anyhow, not really crying...just anxiously waiting until it's all back together and ready for me to drive again.
Thank you to everyone who gave advice in the first thread; "Go ahead, make me cry".
Heidi

 

[78SilvAnniv]

Thanks go to Jeff and Bob!

JRMaroon and BobChad and his family came over on Sunday to assist. We had a nice outdoor lunch, a great afternoon visiting and discussing engine building plans.
CAC has the greatest members!
Heidi

 

[wishuwerehere82]

:L You have made the right decision.

You'll be glad you did.

 

[Bob Chadwick]

The company was good and they had beer. :L

 

[wishuwerehere82]

It makes the job go faster !!!!

 

[DkBG]

Sounds like you all had a good time and are making the best of a bad situation . I'm glad it's going well now . I've never seen an intake gasket tear between two cylinders like that . I can sure see how that would make it run bad , but can that make it suck oil ? Just asking . Cliff

 

[wishuwerehere82]

Cliff,

The tear in the gasket in between the intakes causes the intake vacuum to pull oil from the valley pan into the intake ports of the cylinders.
What causes the tear? Anyone's guess. Heat, age, improper torqueing, warped surfaces, manufacturing defects.

 

[DkBG]

Thanks for the answer but wouldn't the tear have to be at the bottom instead of between two cylinders ? Ok , having just written that , maybe I misunderstood Heidi and the tear IS at the bottom and located between those two cylinders . Cliff

 

[78SilvAnniv]

The tear is between the #2 and #4 intakes, but Kenny thinks it wasn't torn until he removed the manifold from the block/heads. We peeled off the gasket and placed it on the heads...perfect fit. When he placed it back on the intake, the #2 and #4 holes did not align with the gasket holes...so that entire section of gasket was not performing properly.

As a note: torque was correct, gaskets were new and the engine had less than 400 miles and no over-heating.

When Kenny set the top peices, I think he placed the gaskets on the heads and set the manifold on top. All bolt holes aligned with no need for shifting the gasket so we think the gasket was either improperly made or we may need to double check that our intake holes match our head holes.
Heidi

 

[GerryLP]

One sure sign to verify the gasket tear cause would also be the carbon coke build-up behind the intake valves (the bell-shaped side).

 

[wishuwerehere82]

The tear is between the #2 and #4 intakes, but Kenny thinks it wasn't torn until he removed the manifold from the block/heads. We peeled off the gasket and placed it on the heads...perfect fit. When he placed it back on the intake, the #2 and #4 holes did not align with the gasket holes...so that entire section of gasket was not performing properly.

As a note: torque was correct, gaskets were new and the engine had less than 400 miles and no over-heating.

When Kenny set the top peices, I think he placed the gaskets on the heads and set the manifold on top. All bolt holes aligned with no need for shifting the gasket so we think the gasket was either improperly made or we may need to double check that our intake holes match our head holes.
Heidi

Heidi,

There are two pins on the block that align the heads when assembling. Kenny can place the gasket on those first to check gasket alignment. I hope it goes fast!

 

[78SilvAnniv]

Out of curiosity last night, I went into the garage with a tape measure and measured the hole distances on the manifold and the heads, they match perfectly so that wasn't the problem.
My next measurement was of the gasket and I found our problem:

It appears that the gasket was shifted or stretched when the manifold/head were placed together. I inspected the manifold gasket at the #2 and #4 holes and the hole shapes looked fine, but when I looked to the side, toward the front of the block, I could see two holes (for bolts) that had been stretched, allowing the gasket holes that mate with the intake holes of the manifold and head connection to slip sideways.

I don't know how we did this during the initial install and how do we avoid doing it again?
Heidi

 

[cruzer99]

78 SilvAnniv,

I would think twice about the "RV" cam. GM motors have always been designed to perform best with RPM's, not torque. Several friends have tried RV cams and threw them away after a few months and went back to a cam with some lift and duration. All SBC's love rev's and like to run at 3K or above so unless you are pulling a boat or camp trailer at low rev's, get something that runs.
Good luck.........

 

[78SilvAnniv]

Thanks for the info Cruzer. My usual hwy cruising speed is around 3k rpms.
I'll make some inquiries.
Heidi

 

[vette-dude]

Out of curiosity last night, I went into the garage with a tape measure and measured the hole distances on the manifold and the heads, they match perfectly so that wasn't the problem.
My next measurement was of the gasket and I found our problem:

It appears that the gasket was shifted or stretched when the manifold/head were placed together. I inspected the manifold gasket at the #2 and #4 holes and the hole shapes looked fine, but when I looked to the side, toward the front of the block, I could see two holes (for bolts) that had been stretched, allowing the gasket holes that mate with the intake holes of the manifold and head connection to slip sideways.

I don't know how we did this during the initial install and how do we avoid doing it again?
Heidi

Submitted for your consideration from somewhere in the twilight zone !!

Sometimes if the head is surfaced the machinist has to remove alot of material. If the heads have been serviced before and then it was surfaced again when you had it apart the angle of the intake manifold where it attached to the heads is changed. This will cause the intake manifold gasket to not seat properly and the vacuum from the engine will pull it out of shape thus causing the oil to enter the intake valve. To correct you have to have the base side of the intake surfaced to match the new head angle or use a thicker gasket ( not recommended but will work in a pinch). We chased a problem just like this a 406 we built and I think you have the same deal here. If you use another set of heads (with only 1 rebuild and minor surfacing work done on them) you will resolve the problem.

Randy

 

[cruzer99]

One more thing reguarding the RV cam, they typ. die at around 4500 rpm's which is where a SBC is really starting to make some HP. Which ever way you go, check the HP-Torque-RPM curves to make sure you get what you want.

 

[78SilvAnniv]

Submitted for your consideration from somewhere in the twilight zone !!

Sometimes if the head is surfaced the machinist has to remove alot of material. If the heads have been serviced before and then it was surfaced again when you had it apart the angle of the intake manifold where it attached to the heads is changed.

Thank you Randy, but the heads were brand-spanking new (built just for me) only 400 miles ago, so I'm sure this isn't the problem.
It looks like we shifted the head/manifold gasket as the manifold was set onto the top of the block. It also appears that we should have gently poked a slender screwdriver down the bolt holes to check for gasket hole alignment before we just torqued the bolts through the misplaced gasket...which appears to be what we did.
Heidi

 

[78SilvAnniv]

...check the HP-Torque-RPM curves to make sure you get what you want.

Last year, when we first tore the engine apart...I remember reading the various paragraphs about different cams and I recall one explaining where the power bands were at what rpms the vehicle is usually driven at. My driving range is between 1500 and 3300 most of the time, and I recall thinking that is the one most suitable for my application.
Was my thinking correct and is that what you meant?

I'll stop back by the speed shop if it doesn't rain tomorrow and Kenny needs the truck. He won't drive his m'cycle in the rain, and I don't blame him!
Heidi

 

[brusso]

It appears that the gasket was shifted or stretched when the manifold/head were placed together. I inspected the manifold gasket at the #2 and #4 holes and the hole shapes looked fine, but when I looked to the side, toward the front of the block, I could see two holes (for bolts) that had been stretched, allowing the gasket holes that mate with the intake holes of the manifold and head connection to slip sideways.

I don't know how we did this during the initial install and how do we avoid doing it again?
Heidi

I think that there are holes in the gasket that line up with pins in heads. Or is it the other way around. I forget, but I thought that ther was some way that the gaskets were keyed so that you could insure propper placement, before the manifold goes on.

 

[Jack]

Thank you Paul (drags1998) for suggesting we look at the intake manifold. The intake manifold gasket was torn between #2 and #4 allowing blow-by.

We still took the engine out and entirely apart. The decision was made to build it completely and the block was taken to the machine shop today, with the crank and pistons/rods to be thoroughly checked out.
Because we had sucked the oil out of the pan so quickly, and didn't get it replaced soon enough (in our opinion), we decided it would be best to do a thorough job. The cylinders will be honed, the crank polished, the pistons/rods checked and new bearings installed.
I believe we will also be choosing a new cam (mild/rv) and rebuilding the carb.

Anyhow, not really crying...just anxiously waiting until it's all back together and ready for me to drive again.
Thank you to everyone who gave advice in the first thread; "Go ahead, make me cry".
Heidi

Heidi & Kenny:

First, I've been away for a couple days and just now catching up ... I just now read your email & view pics from Tuesday ... and the subsequent CAC posts.



The pics of plug group had all indications of oil-sucking intake. But Cyl #4 seems a bit down. Do reconsider what Randy/vettedude suggests about the head mismatching intake. If I recall, you acquired a set of used heads that were REbuilt for you to "like new condition." If so, it is VERY likely those heads have been surfaced/machined as Randy said ... thus may not mate well to your intake. As Randy said ... this is quite common with reconditioned heads. If you truly got brand new GM castings then it should not matter ... but if not ... then you should reconsider Randy's advice. Also, there's alotta "brand new" AFTERMARKET castings about these days ... and there's been a lotta "seconds" floated onto the market ... beware.



Clearly, you have an intake problem ... but don't discount a ring problem in addition to the intake. Kinda moot since you're gonna freshen the whole motor ... but it might be good to know any/all failure modes.



In accordance with your stated driving habit, desire and rest of motor ... I'm sticking to suggestion I made for RV cam and agree the others' suggestions for similar mild profiles.



The pic of the bearing looks OK ... the one shell shows wear but not any sign of failure. I cannot resolve the other shell's backside well enough to read if standard “STD” size or not.



I'm unsure which piston is pictured ... but assume it's #4. If so, there's abnormal amount of oil-scorching on sides of skirt for a new piston with only 400 miles. This is tattletale for either upside down and/or weak compression ring ... combustion gases blow past compression ring and scorch oil onto skirts. I can't resolve the rings so I can't see if upside down or not. Similarly, it appears as though oil scorched on piston's lands. I see a large "B" on pin boss ... looks like it may be a "Badger brand" piston ... Badgers are pretty good OE replacement type piston.

As I've indicated previously ... I can help you two with getting a good package deal price on rings, bearings, mild/RVcam, lifters, op, gaskets etc. Your machine shop probably can offer good parts prices also. Again, do consider having your machinist check angle/fit of intake to heads. And … have a Q&A w/ speed shop where heads came from … regarding any surfacing/milling/mismatch/ new v. rebuilt v. “seconds”?
JACK:gap