Thread: Too much crankcase pressure, novice engine builder

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Originally Posted by 34_40

My other thought is your selection for the ring end gap is excessive.
And another thought, drop some of the bearing caps.. the ring materials went somewhere! Find it before you close the motor up.

Fair points. I am reducing the gap this time around. Every piece will be removed from the block and cleaned well before placed back. As for the oil pump, it's an brand new OEM style pump. I still think excessive blow by was the main culprit here.

Originally Posted by 34_40

My last thought.. a "guy" with a dyno, who can't handle a carb.?.? He is NO tuner! But that's my opinion I guess. You know a carb has like 2 moving parts right?? 36Sedan has a couple of great write-ups posted around here.. The link above from him is a keeper! Hint /Hint... PRINT IT! LOL.

As for my tuner, I'm sure he's fully capable of messing with carbs, he just gets enough business with fuel injection he doesn't have to mess with carbs. It's not worth his time and I understand

Originally Posted by 34_40

Mr. Spears. At the bottom of your linked page it says this ...
quote;
"UPDATE: Looks like they’re out of business.

Link: King Electronics out of business

King Electronics has them for sale on eBay No longer available

Posted on October 12, 2011
Filed Under: Garage workshop, Made in America, Shop tools"

I wasn't pushing to look for that specific machine, but more to look for a good shop that has a distributor machine, like a Sun. I was more intrigued by the headline, touting that Distributor machines are making a comeback, and that guys are seeing the value in customizing their timing curve, old school.

which two cylinders had the low pressure??????? Please post a list of all 8 cylinders--------

Originally Posted by jerry clayton

which two cylinders had the low pressure??????? Please post a list of all 8 cylinders--------

WOW Jerry, I totally misread two cylinders! If they are adjacent each other you are correct, it would most likely be a blown head gasket, GREAT CATCH!! It would explain everything, and SBC are especially prone to the center two cylinders with their exhaust ports so close.

Might be an easy fix after all..

Originally Posted by jerry clayton

which two cylinders had the low pressure??????? Please post a list of all 8 cylinders--------

cyl.....1st test......2nd test
1.......135............didnt test
2.......130............100
3.......139............70
4.......132............133
5.......133............didnt test
6.......137............didnt test
7.......125............didnt test
8.......144............134

Once I saw 2 of the 8 cylinders as low as they were, I was cracking this open and didn't even bother with the rest of the cylinders. The engine bay has already been torn down, I just have to lift it out of the car tomorrow.

oil was completely clean when I drained it, and smoke was oil smoke. I'd be surprised of a bad gasket

you need to do a cylinder leakage test!!!!!!!!!!!!!!!!!!!!
why did you just check #3 on the left side and when it was 70 didn't check the others????????

Originally Posted by NegativeZero

oil was completely clean when I drained it, and smoke was oil smoke. I'd be surprised of a bad gasket

You can blow a head gasket between cylinders but not compromise the coolant passages. What 36 sedan and Jerry are telling you is that by not checking all cylinders and also doing the leakdown test you may be overlooking an easy fix that saves you money. Remember 36's second rule?

Originally Posted by 36 sedan

TROUBLESHOOTING - Test, test, test, SPEND less, less, less

Of course you may have already pulled the engine by now..... Hope you find your problem, and that you share what you find.

400 sbc have siameze cylinder walls--with very small space between cylinders they use special head gaskets

Cylinders crack often to the coolant holes---

oil smoke mostly will be from bad seal between cylinder head and intake manifold allowing oil to being sucked into intake port

with extra vents on valve covers he has killed possibility of any vacume in the crankcase

seals and gaskets leaking are most likely from poor installation

what head and manifold gaskets did you use?

what sealant/adhesive ?

Here's some advice I can offer on boost and rings from the school of hard knocks. Most of my boost experience is from diesels. But the same principles apply when it comes to the ring gap. First of all, don't use cheap rings when you want to run larger gaps. The cheap rings aren't "round" anymore when you gap them wide and then they don't seal properly. Also when the cheaper rings get heat soaked they loose their tension. Not really cool in a diesel. Haha. In my case the cheaper brand was perfect circle/sealed power and in the gas world those seem to be a good choice. But in my scenario they were the wrong choice. 2nd, have you checked your piston to wall clearance? I don't remember if you did or not. But if your PTW is excessive and your piston isn't growing when boost/heat is added then your bigger ring gap hurts you. Years ago I didn't realize how much a piston would grow under boost and higher cylinder temps. 3rd On any high boosted engine you're going to have to have some sort of crankcase breather evac or catch can system. It's just the nature of the beast.


Also, is your crankshaft end play within specs? Did you plastigauge any of the bearings when you assembled it? If you don't have all the measuring tools, plastigauge is a great way to check clearances.
.

Alright, it's been a long week. On the plus side, I found the problem. On the downside, the problem is a few cracked pistons.


Got the motor out and torn apart Monday. Tapped out piston number 5 and a chunk fell off. At that point, I gave everything to a machine shop I trust to look over and make sure I didn't destroy anything else. I noticed a few of the rod bearings had some spots and sure enough, those are no good. Soooo, machine shop got back to me the following day and thankfully, I didn't destroy my crank or camshaft and the block is okay too. I've asked if they will reassemble the complete bottom end, since that's what I botched the first time. This way I'll know everything to the exact thousandth. This is the same place that conditioned my block in the first place. Talked with him for some time about my plans for the motor and he's selected a new piston head and we're moving forward. I've asked if I could be there as the block is assembled just so I get a chance to see how these are professionally put together and he's agreed.

Now, I've been doing a ton of reading since throughout the week, and either my type of piston damage is a result of either hydro locking or detonation. Detonation being the most likely since a few of my rods are bent as well. Luckily, it appears the only thing I've completely done in are the pushrods and bearings and pistons heads. However, I now know that you're not supposed to use a liquid based assembly lube when putting in pistons, which I did. And because I am a certified moron, I installed the distributer in backwards my first time I tried firing it. So I'm sure that didn't help either.

Now, how to avoid this happening again. I wasn't aware detonation was so destructive as it was or I would've taken more precautions. I've double checked my compression ratio calculations and it is definitely 10:1, so I don't think my gas is the problem. This is likely a result of my lack of experience with timing, but I just don't ever remember hearing much detonation. Not sure what it sounds like at high rpm however, but I am familiar with the knocking sound at lower rpms and idle. I'm debating on bringing my engine to a place with an engine dyno to have the break in done out of the car by someone who knows what they're doing, but finding someone who will work with carburetors and edelbrocks at that are few and far between here. I've heard of machines that you can put your distributor on and get a resulting timing curve per rpm back. Currently looking for a place that can do that so I can use this distributor. I'm trying to avoid buying a new fancy one just because I'm planning on switching to fuel injection in a year or hopefully less.

So that's basically where I'm at. Thanks for the help here and encouraging me to crack it open lol.
Honestly, I'm not even that mad just because I know what the problem is and I didn't ruin too much it seems. Only way is forward from here. Will continue to update and answer questions.

EDIT: also to answer a few of the other questions, head gaskets are fel pro steel core laminates and were fine. I may end up buying new ones that have a higher compressed thickness just because these new piston heads raised static compression just a hair, and I want to remain as close to 10:1 as I can.

Ring gapped will be reduced with better quality rings this time around and I've also got some dry powder lubricant for ring break in.

Good to hear your on the road to repair.. pun intended!
Discuss the ring break in with the engine builder. In the event you ask him to warranty it, be up front and honest with what you're thinking of doing. I'd agree with your thought on the thicker head gaskets, and I'm curious as to how much boost you intend to apply, starting with 10 to 1 just seems steep to me.

With you having a 400 block it is vital that you have gaskets for the 400 cast iron block and aluminum heads-----If I was doing it I also would o-ring the cylinders----

are those cast pistons??????? for your desires you need a good forged piston

I suppose I should give the full roadmap for the engine. I want to switch to fuel injection and be running e85 before adding boost to help keep things cool. I'm doing this all one step at a time however. Adding fuel injection is the next step, then switching to running on e85, then adding a supercharger with intercooler setup. I'm hoping that will keep things cool enough since 10:1 is a tad high for boost. Planning on running around 7lbs of boost, no more then 10 for sure. Goal is just to reach 700 hp. What I'll probably do is have a <600ish hp setup for street driving with a 700hp set up for the track. My builder knows my plans for the engine. I'll have to ask about a warranty, but given my track record with breaking in engines, he may not want that lol

I do have 400 specific gaskets, they include the stream holes. My heads have the holes in them as well. I've read about o-ring style gaskets but I never found any for gen 1 small block chevys, only LSs

Here are the pistons I'm going with this time around. They are forged.
https://www.summitracing.com/nv/parts/wis-pts510a4