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vortechtruck
I love my Chevy Chevette!
Posts: 3
Joined: 03/13
Posted: 03/13/13 07:49 PM

Hi everyone. I just joined and started looking through some threads, and lo and behold some of the same things I have done to my truck are up for discussion. amazed at the right on responses and how smart you guy's are.
I have a '79 GMC short step side that I have built from the ground up; 400 sb .040 over, 350 rods, Keith Black hyper.flat top cylinder specific pistons,350 cast iron vortec heads, 64cc 194/150, machined and re sprung for .500 lift or more, but running a single grind .464 ground on 108 centers. Do not recall overlap and lift at off the top of my head. Edelbrock pro/airgap 7516, Edelbrock 850 sq. bore. Backed up with a Muncie M-22 Rock Crusher ( a true R.C. ) with a 9" ford w/3.89 gears, 31 spline, and a Detroit Locker, and 12" rubber on the ground. I built a tilt front clip using the original mounts with a drill shaft and bearings w/helper springs from a '99 Chevy P.U. hood as the steel is heavy.
I also built suicide doors w/poppers just for fun. Turned out to be allot of work and an extra door because the first one got pretty butchered up getting it right.
Any way I am looking for info on my intake mounting. I keep breaking pistons and distributors. It seems that the manifold gets to one side after it has been run a while, and the next time I get on it, Bang there goes a piston. Has been the #2 twice, #1 once and now #6. each time  the rotor is also broken, and I have replaced dist. twice for the bushings being worn to one side or locked up. This has been a torque monster and when everything is right.... HANG ON. Has any one had this problem? What am I missing. Manifold bolts are new ( they recommend to replace them after 3 times of torque un-torque. They are only torqued to 11 ft. lbs.and I follow the order of torque. Also I get very high crankcase pressure and have oil leaks everywhere. I met a guy at the track with a 400 who had this same cc pressure prob. and he install an evacuation system and took care of that problem. Could this high cc pressure be lifting the manifold off and letting it settle back to one side or the other.

Thanks all. Look forward to chatting on here.   Jim  

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waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 03/13/13 09:45 PM

do you have a fuel pump pressure/vacuum gauge around..

Fuelpumpvacuumtester

where if the engine is together and running.. you could push the hose over the dipstick tube with the dip stick removed to monitor crankcase pressure or vacuum..


you should not have much of either...

are you running a PCV valve....  and a breather in the other valve cover.. with either a filter in it or a hose connection to the air cleaner can with a  breather filter on it...

why... the breather filter prevents the PCV valve from creating vacuum in the crankcase when the blowby is low and the vacuum is high... it allows filtered air into the crankcase to make up for what's being pulled out by the PCV... but the trick it does but its not obvious... is during acceleration and heavy loads/high power situations.. where the manifold vacuum is low and there is lots of blowby.. the PCV cannot keep up with this usually..  so the breather filter allows excess crankcase vapors out and feeds them thru the filter to catch any oil particles.. but because of the location in the air filter housing. the vapors are pulled in thru the air filter and burned by the engine..

if you have the crankcase breather blocked off.. you could be creating over 20 inches of vacuum in the crankcase.. then under load.. you could be creating many pounds of pressure..

its going to be almost impossible to seal a motor if the crankcase breather is blocked..

there is a TEST i found to get close to the correct PCV flow rating...

use a digital tachometer.. if you have an automotive digital volt meter with a RPM clamp.. or an advanced TIMING LIGHT with RPM readout along with the advance..   you could pinch off the PCV hose or block the opening.. the engine at idle.. should drop 50 to 70 RPMs if the PCV calibration is correct.   on later computerized engines.. you will have to disconnect the idle speed control valve or motor.. so the computer cannot compensate...


i have seen timing covers pulled in so hard the chain dug into them..  valve covers that were flexed so often that they had fatigue cracks..  oil pans that  pulled upward and blocked the pickup  screen..  i have not experienced manifolds shifting. but with the TINY bolts the vortech heads and the silicone ribbed intake gaskets... that is a possibility of vacuum pulling it down and out of place.. then pressure building and shifting it...


in addition... i have a friend across the street with a drag race honda coupe.. he had the crankcase vents all blocked and kept blowing out the oil seals..  so he decided to use a vacuum sump ... this time.. he sucked the seals into the engine and still oiled the track down..   i ended up finding him some seal part numbers with flanges to prevent the pulling in of the seals..  he uses a electric driven smog pump now for pan evacuation duties..  he also has a dash mounted turbo boost/vacuum gauge to keep an eye on the crankcase pressures..

hope this helps...

you might it seems want to check into a ZERO gap second ring set also...

what's breaking on the pistons.. is the piston skirt breaking.. the ring lands collapsing and crushing the rings then allowing blowby..

you might also be making enough power to step up to forged pistons..

you will want to perhaps.. photograph and post the piston damage.. and don't throw out the broken pistons.. if you order a custom forged set to get away from the HU pistons. you will want to show the broken pistons to the piston manufacturer.. so they can tell just what they have to change to make your life easier..

i would like to know on tear down.. if the broken piston tops are cleaner like they were washed.. as if you are lifting the intake.. perhaps some coolant is flowing across the gasket and being pulled into the intake port where it hydraulics the piston..



which distributer are you running also..    large CAP HEI??? or something else???

do you have wire separators.. so the last 2 cylinders on the drivers side are kept apart to reduce the induction between the number 5 wire and the number 7.. where it will create a ghost spark in the #7 wire 90 degrees early and burn off part of the fuel.. so it will be lean when it gets to the top...

the lifting of the intake could also be leaning out your air fuel ratio..

one last thing until you ask more or answer some of my questions..   are you locked into that intake...  BHJ or goodson has a drilling jig to drill vortech intake surfaces to the either the straight six bolt or the 2 straight, tilted 2 and then 2 more straight pattern.. so you can use a conventional intake on the vortech heads... the jigs were not cheep but some machine shops did buy them..   it should not cost a fortune to have your vortech heads drilled for the 3/8" fasteners on a different intake..  it depends on which jig the shop purchased..

DRILL%20IN%20USE%201%209 19 01%20(Custom)  

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Dave632
I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 03/14/13 08:48 AM

Your heads may have been milled, or the block, causing the manifold not to sit properly. This could account for the manifold moving to one side. That could account for the distributor breaking but taking out pistons is another story.
I ran 400 shots of nitrous without taking out pistons even if I had a misfire.
What kind of pistons are you running, forged I hope.  
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vortechtruck
I love my Chevy Chevette!
Posts: 3
Joined: 03/13
Posted: 03/15/13 06:15 PM

Wayne, Thanks for all the input. I am running a pvc and breather, the big HEI dist. and yes I do have vac.pressure gauge. When I get her back up and running I will perform this test to see where it's at. Never even thought about the hydraulic situation. But you are right on. The broken piston has always been clean, almost to the point of looking new. Also my catch can has been almost full each time this has happened. Seems like I may be blowing by on the water. I check it regularly, so I don't water down the track since the 400's run so hot to begin with. This would also explain why they break in different places, have had them break off about a 1 1/2" section of the top land at the 2 o'clock, 6 o'clock, and this one at the 10 o'clock. the skirts have not been broken on the past ones, but maybe on this round, haven't pulled it out of the hole yet. Have the heads off and pulling the engine out tonight.
I do have the wire separators, lesson learned on a 327 I had years ago, GOD I loved that engine.  Thanks for the input and I will keep you posted here on what I find. I may have to go to the forged plugs as I am making quite a bit of power. Going to dyno when done this time around just to see.
Thanks for "spilling" the brain power for me on this one. Hope I can return the favor, if not to your self, someone else that has a problem that I may have over come in the past. PAY IT FORWARD..

Jim  

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vortechtruck
I love my Chevy Chevette!
Posts: 3
Joined: 03/13
Posted: 03/15/13 06:20 PM

Thanks Dave. I did have the heads milled to make sure they were flat,as I ran them on another engine I killed in a wreck. The guy I take my heads to did his magic to them and assured me I would not have a problem with this.......but who knows? That could be the problem or his magic wand just didn't calculate correctly. Blush  Anyway I will take a better look at this as the Vortec head seem to be pretty sensitive to mod's.
Thanks again.

Jim  

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Dave632
I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 03/15/13 06:40 PM

When the heads are milled some material must also be taken off the intake manifold to allow it to seat properly on the heads.
I had an intake manifold that was meant for a Chevy BB low deck 9.8. I used it on a 10.6 deck Keith Black aluminum BB. I had to have spacers made that were about 3/8ths of an inch thick on each intake side and 1/4" thick where the manifold meets the top of the block. It all worked well though.  
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Dave632
I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 03/15/13 06:41 PM

When the heads are milled some material must also be taken off the intake manifold to allow it to seat properly on the heads.
I had an intake manifold that was meant for a Chevy BB low deck 9.8. I used it on a 10.6 deck Keith Black aluminum BB. I had to have spacers made that were about 3/8ths of an inch thick on each intake side and 1/4" thick where the manifold meets the top of the block. It all worked well though.  
[[SUPPORT AMERICAN CARS, STOMP A RICE CAR TODAY.]]

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