ok here is my problem i just rebuilt the motor (new pistons, rings,cam etc)the problem is that i am pushing oil out the dipstick tube .and onto my newly jethot coated headers .I did a compresion test and all the 8 cylinders fall between 145 and 150 the motor has less then 150 to 200 miles on it .some more details are 377 stroker trw cast pistons comp ratio is about 9.5-1 brodix t1 heads lunati roller cam ATI supercharger mighty demon bc carb will doing a leak down test tell me more .what else could be causing this problem

 

improper PCV or venting

 

cast pistons, blow thru supercharger, 9.5:1 comp.
Did it happen from first start or did you lean on it?

 

I have been having various problems since I started the project .but the first time that I leaned on it it started to leak oil.but i only have seen about 3 lbs of boost (in other words I didn't lean that hard) the supercharger should boost about 5-6 lbs

 

exactly...


what are you doing for crankcase ventilation?

 

I was just using a regular pcv when the problem started and I even tried it with the pcv disconnected but still have the problem any suggestions?

 

sounds like u have massive blowby.make sure your pcv is working(valve,vent etc) since u just rebuilt this motor id drive the car for about 500 miles(break in the motor).if its still there after that ,its probably due to the cylinder walls not machined and/or deglazed right.do a cylinder leakdown test to isolate the problem. forced induction can make it worse(too much boost) i know cause on my beater (eagle talon turbo) the dipstick never stays seated.

 

not to sound totally off subject, but isn't a 377 a destroker not a stroker?

 

 

9.5:1 (what does it actually measure?), cast pistons, blower and low cylinder pressure… either:
1 – you broke it already
2 – you assembled it incorrectly

there is no way a 9.5:1 engine without something wrong with it is going to show a cranking pressure of 145… with a reasonable cam you should be in the 185-195 range. Pull the oil filler and start the car, is it doing a choo-choo impression (puffs of smoke out the filler?)

90% chance you’re pulling it and taking it apart to figure out what’s wrong.

 

the heads are alum 68 cc chamber with a 4.25 bore and a 88cc dish piston and a 0 deck block 5.7 x rods the cam is a custom grind fron lunati solid roller 555 intake 568 exhaust. I can't see how it could screw up all eight pistons at once. and YES a 377 is a destroked 400 block with a 350 crank. won't pulling off the oil filter make a really big mess???

 

A standard bore 350 with a 3.75" stroke is a 377 stroker too .

 

Isnt proper breakin on a blower motor to break it in 500 miles without the blower?

 

A 377 is a 400 block, bored .030” over with a 350 crank resulting in a 4.150” bore x 3.48” stroke. You will not get a 4.25” bore out of any stock small block, and it’s doubtful if you’ll do it in any aftermarket block.

An 88cc dish would be roughly ½-3/4” deep, not leaving any room for the piston pin with any normal length rod. I don’t know of any small block pistons with over a 31cc dish, and most are under 21cc’s

If you want to pull the oil filter off and run the engine you’ll screw it up worse then it already is. I suggested you pull the oil filler, ie, the cap on the valve cover.

 

Chevrolet: 400/377 stroker, .030 in. overbore, 3.75 in. stroke, 5.565 in. connecting rod, and 3.48 in. stroke, 5.70 in. connecting rod, .083 in. dish, forged, piston

Thanks to a special aluminum alloy that doesn't expand as much as other alloys, this forged piston is designed to fit tight, providing the stability and ring control you need, plus the strength you want. It even has a ribbed skirt for better oil retention. Compression ratio may vary depending on cc of cylinder head. Some oversizes priced higher.

MY BAD this is the specs on the pistons in my motor if u would like to look it up your self it is on summit racing page part# trw-l2352f30 if there is any thing else you would like to bust my ***** about just ask






:hail:

 

after further searching into my reciepts the heads are a 64cc not a 68cc and the bore is a 4.155 not a 4.25 the next time i will where my glasses when i type a responce .that is probaly why i thought it said filter when it said FILLER

 

OK, good, so you’ve got decent forged slugs in there with 12.5cc dishes… Doing some quick math it looks like you’ve probably got between 9.7 and 10.1:1 compression (actual, it’s not lower then 9.7 assuming all the numbers are exact and you used a typical .038-.040” thick, 4.16” bore gasket… but since the chambers in those heads tend to be a little tighter then advertised it’s probably closer to 10:1). Basically, way on the high side for something that you want to run boost with, but good NA.

I’d either find a way to lower your compression without hurting quench: deeper dishes, have someone open up the chambers (if you get them up to 76cc you’ll be in the 8.9-9:1 range which would be much better) chamfer the pistons… or run it on race gas.

If I were to guess you’ve probably cracked some rings. Take it appart now or later, but you will be taking it appart to get it running right.

 

.555 lift cam eh? Whats you .050 duration and LSA?

 

duration @.50 is 248 intake 256 exhaust advertised duration is 290 intake 289 exhaust lift at valve is .555 intake .564 exhaust that is with 1.5 rockers I am useing 1.6 roller rockers those # are strait off the cam card

 

Side queston: What you plan on revving this motor to? 377 should be a screamer ... build alot of boost at higher RPM's too ...

 

my machine shop said i can rev to 8000 no problem but before i rebuilt the motor i was shifting at 6500 and it pulled up until then

 

I don't have any experience with big cams like that one but I've read that large cams bleed off low rpm cylinder pressure... It stands to reason that this could affect your compression test and cause a lower than normal reading. There has to be other people here that have cams about that big you can ask. If not, I bet if you dig through some old car mags you might find them quoting similar numbers.

You are running aluminum heads... that usually allows about .5-1 additional point of compression before detonation sets in. Your big cam also gives you the ability to run more compression because it is bleeding off that low RPM cylinder pressure. You have a centrifical compressor that probably doesnt start making more than 1 or 2 psi of boost untill it gets over 4000 rpm... this is on the far side of the place an engine is most likely to detonate. There are lots of otherwise stock combos running aluminum heads with 10:1 or higher compression ratios running 5-6# of boost. Add this all up and I'd bet you're ok as long as you keep your a/f ratio safe and dont get too crazy with the timing.

I'm not quite convinced youve broken something because your compression test gave similar numbers for all cylinders. If those pressures are not normal then I think its more likely to be something assembled wrong like rings upside down or something but I doubt someone would mess up and flip them all upside down... could also be something unrelated to your oil spew like cam timing or lash incorrect.

...So whats causing your problem then?
What exactly is going on with all the holes in your valve covers? Did you disconnect the PCV from its vacuum source or pull it out out of the valve cover? Do you have a breather in the other valve cover or just a plug in the hole? A picture would be worth 1000 words here.

I'm kind of wondering what the point of running a PCV on a motor like this would be... seems to me it would do a bit more harm than good. Its creating a pretty big vacuum leak on a motor where every 1/2 inch of vacuum is a big deal. I'm assuming you change your oil regularly.

 

here is a pic of the motor out of the car ( before installed )driver side is a breather pass side is a pcv i tried it also with the pcv pluged as for oil change it was changed after about the first 15 min of run time with a new filter and the oil and filter has been change twice since then about 150 miles and in a time period of 4 months

 

Try a breather in both valve covers

 

wow that looks like my engine, i have the same valve covers.i have a question what kind of ignition u runnin?

 

lets start from the beginning stock hei distributer w/ diffrent springs,weights,brass gear,and bushings. MSD coil in the cap, CROSSFIRE cap, and TAYLOR 10 mm wires w/ braided stainless heat shields .Also have the MSD 6AL with a MSD btm

 

what i would do in your place is get rid of the hei.HEI dont work good in high rpms.your just aggravating the situation with a supercharger.when i installed my motor i was runnin hei ,if the car idle long it would develop a miss and start smoking.i also had a problem of it not goin pass about 5500 rpms(it smoked alot at that range).so i threw out the hei ,than i bought msd distributor,coil,wires and the 6al.problem solved.

 

What kind of piston rings are u using? I would disconnect the blower for a while and let the piston rings a chance to seat in. I always break in my motors without putting any boost for at least 500 miles. The boost sort of fights with the seating of the rings. It most likely set in with it on but might take longer. This is only a suggestion though. it seems like your problem might be something else though.

I would definatly check to see if your intake manifold is sealing properly(bottom of ports). That would account for a drop in psi.(going to the block instead) and also why you would have some much presure there too.