LT4 HOT CAM vs CA Smog, the results are in
11-20-2009, 03:28 AM
#1
Melting Slicks
Thread Starter
LT4 HOT CAM vs CA Smog, the results are in
96 Lt4 with 140,000 miles, retro fitted with LT4 "Hot Cam"; new Opti II, new plugs and plug wires, Corsa cat back exhaust; rest stock. First California smog test since getting engine running a couple of weeks ago.
@ 1293 rpm, HC, max allowed = 52 ppm, measured = 33 ppm ;
@ 1293 rpm, CO, max allowed = 0.43%, measured = 0.19% ;
@ 1293 rpm, NO, max allowed = 424 ppm, measured = 78 ppm ;
@ 2039 rpm, HC, max allowed = 36 ppm, measured = 25 ppm ;
@ 2039 rpm, CO, max allowed = 0.46%, measured = 0.02% ;
@ 2039 rpm, NO, max allowed = 711 ppm, measured = 218 ppm .
In a word: PASS !!!!
now if someone could tell me where my oil pressure went ?
@ 1293 rpm, HC, max allowed = 52 ppm, measured = 33 ppm ;
@ 1293 rpm, CO, max allowed = 0.43%, measured = 0.19% ;
@ 1293 rpm, NO, max allowed = 424 ppm, measured = 78 ppm ;
@ 2039 rpm, HC, max allowed = 36 ppm, measured = 25 ppm ;
@ 2039 rpm, CO, max allowed = 0.46%, measured = 0.02% ;
@ 2039 rpm, NO, max allowed = 711 ppm, measured = 218 ppm .
In a word: PASS !!!!
now if someone could tell me where my oil pressure went ?
11-20-2009, 03:38 AM
#2
Drifting
Member Since: Jun 2007
Location: Prather, California -1990 ZR-1 White/Flame Red- -SOLD!!-
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I put the LT4 hotcam, 1.6RR and LT4 valve springs in the '93 LT1 I had (everything else stock). With a PCMforless tune in the ECM, it also passed California smog no problem. I never had a problem with oil pressure, though.
11-20-2009, 08:33 AM
#3
Melting Slicks
96 Lt4 with 140,000 miles, retro fitted with LT4 "Hot Cam"; new Opti II, new plugs and plug wires, Corsa cat back exhaust; rest stock. First California smog test since getting engine running a couple of weeks ago.
@ 1293 rpm, HC, max allowed = 52 ppm, measured = 33 ppm ;
@ 1293 rpm, CO, max allowed = 0.43%, measured = 0.19% ;
@ 1293 rpm, NO, max allowed = 424 ppm, measured = 78 ppm ;
@ 2039 rpm, HC, max allowed = 36 ppm, measured = 25 ppm ;
@ 2039 rpm, CO, max allowed = 0.46%, measured = 0.02% ;
@ 2039 rpm, NO, max allowed = 711 ppm, measured = 218 ppm .
In a word: PASS !!!!
now if someone could tell me where my oil pressure went ?
@ 1293 rpm, HC, max allowed = 52 ppm, measured = 33 ppm ;
@ 1293 rpm, CO, max allowed = 0.43%, measured = 0.19% ;
@ 1293 rpm, NO, max allowed = 424 ppm, measured = 78 ppm ;
@ 2039 rpm, HC, max allowed = 36 ppm, measured = 25 ppm ;
@ 2039 rpm, CO, max allowed = 0.46%, measured = 0.02% ;
@ 2039 rpm, NO, max allowed = 711 ppm, measured = 218 ppm .
In a word: PASS !!!!
now if someone could tell me where my oil pressure went ?
11-20-2009, 02:09 PM
#6
Melting Slicks
Thread Starter
bone stock tune; only change not mentioned was a new set of Bosch III injectors.
Only smog related questions "anything aftermarket on it?"
answer: "yes, Corsa cat back exhaust"; reply: "Cat back, no problem".
Since I got (or anyone could get) an LT4 Hot Cam, which is a factory GM piece, from a Chevrolet dealer, it isn't, by definition, an aftermarket part. That's my story and I'm sticking to it.
And no, the idle quality isn't much different from the stock LT4 cam, especially when you factor in an aftermarket exhaust advertised to flow 47% over stock. Then again, I suspect this particular smog test shop doesn't see too many Vettes, LT4s or otherwise.
As to my oil issues, I have a Canton road race pan with matching pickup to install (smog test/registration first) and will investigate it further then. I did hook up a (quality) auto meter mechanical gage to verify that the electrical gage (always suspect in my mind) was telling the truth. I will report further on this later, I don't want to invite too much speculation or raise too many red herrings until I know more.
I want to thank everyone who has shown their concern in responding to this issue.
Only smog related questions "anything aftermarket on it?"
answer: "yes, Corsa cat back exhaust"; reply: "Cat back, no problem".
Since I got (or anyone could get) an LT4 Hot Cam, which is a factory GM piece, from a Chevrolet dealer, it isn't, by definition, an aftermarket part. That's my story and I'm sticking to it.
And no, the idle quality isn't much different from the stock LT4 cam, especially when you factor in an aftermarket exhaust advertised to flow 47% over stock. Then again, I suspect this particular smog test shop doesn't see too many Vettes, LT4s or otherwise.
As to my oil issues, I have a Canton road race pan with matching pickup to install (smog test/registration first) and will investigate it further then. I did hook up a (quality) auto meter mechanical gage to verify that the electrical gage (always suspect in my mind) was telling the truth. I will report further on this later, I don't want to invite too much speculation or raise too many red herrings until I know more.
I want to thank everyone who has shown their concern in responding to this issue.
11-20-2009, 03:47 PM
#7
Team Owner
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It means a bigger cam can be installed
11-20-2009, 04:52 PM
#8
Le Mans Master
congratulations on passing!! 
But, if I were you, id drop the oilpan and check the bearings. Is it possible you scraped the cam bearing sliding it in? At any rate, it has to be bearings, or oil pump, and I would not go too long before droping the pan to check.
But, if I were you, id drop the oilpan and check the bearings. Is it possible you scraped the cam bearing sliding it in? At any rate, it has to be bearings, or oil pump, and I would not go too long before droping the pan to check.
11-20-2009, 09:27 PM
#9
Melting Slicks
Thread Starter
I'm not driving the car until oil issues resolved; will try the simple stuff first, like a heavier weight oil; but of course once the stock pan is off will check everything further; then new pan, matching pickup, and recommended oil pump.
No, I don't think there was any bearing damage during cam install...that part of the project went very smoothly and I have installed cams (not in a Chevy) where it was a very difficult (as in a 460 big block Ford).
When I installed the cam, I replaced the main and rod bearings. I plastigaged each bearing and all seemed okay.
I also installed a high volume oil pump with a high pressure relief spring. I am aware that there is some contraversy involving high volume oil pumps, specifically that they can suck the sump dry before the oil is able to drain back into the sump. However in the past I've used high volume oil pumps in other applications with no problems; in fact I've used big block oil pumps in small block Chevy's with complete success.
What I do know is that the stock Corvette is very shallow, 7 inch, which in reality is closer to 6&7/8th inch and pump pickup placement is very critical with little or no room for error. By way of contrast, most (all?) other stock pans are at least 8&1/2 inch in depth and aftermarket pans, where the chassis allow, can be as deep as 9&1/2 inch or greater.
I would like to think that the oil pump pickup is a little too high and the pump isn't getting good suction. The stock style chevy pump and pickup has to be adjusted at the time of installation...maybe I just screwed up.
One of the reasons I'm interested in the Canton pan and pickup is that they are a matched set and more importantly, the Canton pickup bolts to the bottom of the recommended oil pump and in that sense placement of the pump pickup is not adjustable as the depth is already pre-set.
The art and science of windage control has advanced and gotten much more sophisticated in recent years. That said, one of the weaknesses of a stock oil setup is the windage tray; it's the same solid baffle plate as was on my 1961 vette; it may minimize windage in the sump but it bounces the oil back up into the spinning crank and does nothing to promote return of the oil to the sump. Contemporary trays are louvered to promote oil return; my favorite is the Milodon Diamond Stripper tray.
When I poured in a couple extra quarts of oil, the pressure did come up, but not enough to inspire confidence (I like to see something in the neighborhood of 40 psi at idle and 60 to 70 psi at speed...or more).
Before I tear everything apart for the pan upgrade, I will change out the 5w-30w oil for a heavier grade and see how that affects thing. Even with new bearings, normal wear on a 140,000 mile crank could loosen up the oil clearances; possibly to the point that the oil recommended for a new engine / new crank may not be thick enough in my application?
Before I changed out anything, with the original bearings and stock pump oil pressure was okay, but I felt it was low, 20psi idle, 40 psi plus at speed.
New bearings, pump, oil pressure at first was good, 40 psi idle, 60 psi at speed, slightly less after oil heated up. Then the pressure started to go away. 10 psi at idle, 30 psi at speed, sometimes less. With extra oil in pan, 20 psi at idle, 40 psi at speed.
So I'll go from here...hopefully it's something simple.
Thanks again to all who weighed in on this issue.
No, I don't think there was any bearing damage during cam install...that part of the project went very smoothly and I have installed cams (not in a Chevy) where it was a very difficult (as in a 460 big block Ford).
When I installed the cam, I replaced the main and rod bearings. I plastigaged each bearing and all seemed okay.
I also installed a high volume oil pump with a high pressure relief spring. I am aware that there is some contraversy involving high volume oil pumps, specifically that they can suck the sump dry before the oil is able to drain back into the sump. However in the past I've used high volume oil pumps in other applications with no problems; in fact I've used big block oil pumps in small block Chevy's with complete success.
What I do know is that the stock Corvette is very shallow, 7 inch, which in reality is closer to 6&7/8th inch and pump pickup placement is very critical with little or no room for error. By way of contrast, most (all?) other stock pans are at least 8&1/2 inch in depth and aftermarket pans, where the chassis allow, can be as deep as 9&1/2 inch or greater.
I would like to think that the oil pump pickup is a little too high and the pump isn't getting good suction. The stock style chevy pump and pickup has to be adjusted at the time of installation...maybe I just screwed up.
One of the reasons I'm interested in the Canton pan and pickup is that they are a matched set and more importantly, the Canton pickup bolts to the bottom of the recommended oil pump and in that sense placement of the pump pickup is not adjustable as the depth is already pre-set.
The art and science of windage control has advanced and gotten much more sophisticated in recent years. That said, one of the weaknesses of a stock oil setup is the windage tray; it's the same solid baffle plate as was on my 1961 vette; it may minimize windage in the sump but it bounces the oil back up into the spinning crank and does nothing to promote return of the oil to the sump. Contemporary trays are louvered to promote oil return; my favorite is the Milodon Diamond Stripper tray.
When I poured in a couple extra quarts of oil, the pressure did come up, but not enough to inspire confidence (I like to see something in the neighborhood of 40 psi at idle and 60 to 70 psi at speed...or more).
Before I tear everything apart for the pan upgrade, I will change out the 5w-30w oil for a heavier grade and see how that affects thing. Even with new bearings, normal wear on a 140,000 mile crank could loosen up the oil clearances; possibly to the point that the oil recommended for a new engine / new crank may not be thick enough in my application?
Before I changed out anything, with the original bearings and stock pump oil pressure was okay, but I felt it was low, 20psi idle, 40 psi plus at speed.
New bearings, pump, oil pressure at first was good, 40 psi idle, 60 psi at speed, slightly less after oil heated up. Then the pressure started to go away. 10 psi at idle, 30 psi at speed, sometimes less. With extra oil in pan, 20 psi at idle, 40 psi at speed.
So I'll go from here...hopefully it's something simple.
Thanks again to all who weighed in on this issue.
11-21-2009, 11:19 AM
#10
Le Mans Master
20 psi at idle is acceptable. although my 86 original short block with 150K has 40 at idle and 64 at 1700 RPM hot.
I would guess that the pump is the culprit with either excessive clearances where the lid and the gears interface, or there is something in the pump under the seat of the pressure relief check ball under the spring behind the roll pin, (carbon, gasket material, teflon tape, silicone sealer, etc.)
I would get a regular pressure high volume pump, as the added effort in turning a hi press. high vol. pump can wear the pump drive components in a comparatively short time.
I would guess that the pump is the culprit with either excessive clearances where the lid and the gears interface, or there is something in the pump under the seat of the pressure relief check ball under the spring behind the roll pin, (carbon, gasket material, teflon tape, silicone sealer, etc.)
I would get a regular pressure high volume pump, as the added effort in turning a hi press. high vol. pump can wear the pump drive components in a comparatively short time.
11-21-2009, 12:15 PM
#11
Former Vendor
Luckily the C4 oil pan is easy to remove. Let us know what you find. If you get it done by the 5th, you should join us for the Toy Run. See the Norcal section. Its a chance to meet lots of Norcal Vette owners
11-22-2009, 10:29 PM
#13
Safety Car
I once ran a 400 hp small block in a 69 camaro with a 7 quart Moroso oil pan. That thing used to go down to 5-10 psi at 6000+rpm when it was warmed up. I literally ran it for nearly 2 years before I had the thing out for a look. All I did was buy a windage tray for it and the issue was gone. I always believed that the bottom end was getting enough oil, but the top end was a little frothed and the sending unit tube for the mechanical gauge was just too high on the block and got a head of air in it.
If you changed back to the stock 5 qt pan, I bet it would be fine.
If you changed back to the stock 5 qt pan, I bet it would be fine.
11-22-2009, 11:05 PM
#14
Melting Slicks
Thread Starter
right now I have the stock pan, stock windage tray, and high volume oil pump with a high pressure relief valve spring; my only theory...and its just a theory until further investigation, is that the low oil pressure is a result of one, or a combination of:
high volume pump sucking pan dry before oil can drain back;
aggravated by less than contemporary stock windage tray which has no features designed to promote oil return to sump;
aggravated by an oil pickup inadvertently installed too high off the bottom of the sump ?
Remember that the oil pressure did come up after I added an extra two quarts of oil.
or maybe just a small piece of debris holding the oil pump relief valve off its seat ?
Time will tell; thanks again to everyone.
high volume pump sucking pan dry before oil can drain back;
aggravated by less than contemporary stock windage tray which has no features designed to promote oil return to sump;
aggravated by an oil pickup inadvertently installed too high off the bottom of the sump ?
Remember that the oil pressure did come up after I added an extra two quarts of oil.
or maybe just a small piece of debris holding the oil pump relief valve off its seat ?
Time will tell; thanks again to everyone.
