Bo Thanks bro, Im going to call and see who has these
Kurt, Dude, where ya been my friend?
I want holley's dont get me wrong but I need to finish out the season this year with no more big money
I can get holley's over the winter and bolt them up in the spring.
Im just beyond tapped at this point
Are those marine carbs or car carbs?
I was thinking about holley 750's and someone had said go bigger and adjust back is easier than going small and not having enough so 830-850's would be better and adjust them back a little bit
Rather have too much carb and turn it back than not enough and blow her up
so If I am going to spend the money , im going bigger no question
Who has good prices on marine holley's anyway?
Jason

"Rather have too much carb and turn it back than not enough and blow her up "

dude doesn't matter if you had a 500cfm carb,,,that would not cause it to blow up! if your card is too big then your drivablity will suck....hummm 510ci 730cfm carb kinda sound like a race class of some sort???
:rolleyes:

so i'll say again...it has to do with cid, rpm and the volumetric eff. of the engine...NOT HP!!!

Jayl13.....As to the carbs...Q-jets do indeed flow 750cfm.
and as the name says....Bo Knows !!!! You can drop $600
plus each for Hollys or follow Bo's advice,they will work fine on
you're motors,just tske a little more knowladge to set up.
BUT.....first...you need to adress the oil press. problem !!!
did you Mechanical guage yet ? DO IT NOW !!!! Also Oil Temps
they tell you {And us} alot more about what is going on !!!

Just trying to save ya a bunch of pain dude !!!!:eek:

Hey BO,
That is good for the secondaries but what about the primaries?
The fuel flow at 1200-1600 ish is poofing out the carb and it quiets down running around 3100-3200 rpm's and then it poofs around 4000
I can see the metering rod change helping out at 4000 rpm range but what about the low end when only the primaries are open and the secondaries are closed on the carbs?
Do I need to change the metering rods for the primaries too?
If so you got that part # handy bro?
thanks, cause I got the parts dude on the line (RCM255 here on OSO is PARTS KING!!!!!)
Thanks man
Jason

Yo Jay.....

One more post and you will hit 1000......

You are one troubled post whore!!! :D ;)

Does anyone have the answer to this?
Can anyone help me out here?

Hey Mark, NONE of my posts EVER were whorish!!!
EVER got me buddy boy? LOL
that 1000 posts just means My shiz nizzle be broke more than most is all!

You still going to burlington?
Im going to try but cant do it with a busted ship
Im trying to, Russ can get me the metering rods but need the answer to the primary metering rods question first
Hell why does no one know rochester?
Jason

Jay sounds like Bo Knows. Call him, email him, talk to him and walk your way through all this SLOWLY and watch your oil preasures

Question for you guys. Is there any reason that you can not read the oil temps accuratly with one of those Infra Red Temp guages that you aim at the part and it tells ya what your temps are? like aim it at the pan and the oil filter?

Jon

:D :D True Dat. :D :D

Yea, i'm still going. You and your wife can come out with me if your ship is still broke.

Call the Bowen's place...they do Rochesters all day. they will probably be able to tell you what you need, and sell you the parts. I'll look for the number.

jay,,,what would logic tell ya???

Is there any reason that you can not read the oil temps accuratly with one of those Infra Red Temp guages that you aim at the part and it tells ya what your temps are? like aim it at the pan and the oil filter?

yes there is..... you get the surface tmp of what you are measuring.....heat transfer...what is the delta between the inside and out side of wha you are measuring???...

there are SO many other factors that this dude (engine assembler man) can't give ya....if this bone haed didn't even check for coil bind....now how the **** did he measure install hieight, seat pressure, pressure at 50 and max??? how about checking the damper spring clearance....did he use 3 springs? or 2 w/a damper?? ALL could lead to ASS LOADS of HEAT...what about pushrod alignment??

THanks Audacity. You are such a wordsmith ;) ;) :p :p :D :D

U make'n fun of me again....quit pick'n on the small guys:D

Seems to me this thread is going all over the place beating up his builder, solving heat/lean condition he is not sure does or doesn't exist etc,,, instead of where it should which is to give jay advice on a logical step by step to see if and what his problems are with the min chance of damageing his ride.

to me his problem is low oil pres, this is the big red flag


to solve it

Get a mech oil presure guage and an oil temp guage to verify if indeed the presure is actually low or if it was a guage problem and to see if the oil temp is getting too high and also shut down quick if it is while in the testing process. Get the builder to sign off on the test approach so he doesn't blame jay for the problems.

we can speculate what problem might be, heat from lean carbs, springs, cam gone south, bad guage, or just bad bearings but we got Jay running around looking for carb rods here when he doesn't really know if he even has a heat problem yet of which lean is only one of many possible causes.

P.S. and the infared is a great idea if you can borrow one, the heat transfer delta accross .050 of steel of the oil filter will be very low, less than the accuracy tolerence of a guage/sender and will tell you if your oil is 240 or 300 degrees which is what you need to know not whether it is 237 or 241

hear, hear. well said. Find the problem before you start fixing things.

i just used a Raytek RayngerST gun...if anyone has a more expensive unit please speak up...i just used it on a 5.8l marine engine running like an m f'er...ADACS data is 247 and holding as well as ALL other parameters...the reading from the gun were taken at 18"....reading were as much as 40deg in various parts of the FL-1A filter...highest reading was 218....

would you like any other data???

so to close...the gun...bad idea...they work better in a pass fail enviornment... any ???"'s

no ideas...just data:D

thanks for the insight about the guns, that was pretty much my point tho, jay needs data about oil P and temp. not ideas about carb brands holley vs Qjet, carb size, carb setup, pushrod alignment, springs, bearings, or hoe great/terrible his engine builder is /was etc etc etc.

Hell he could just have a bad oil P guage, needs to know what if anything is broke before he breaks,, er,, I mean fixes it :)

Ursus.....Thats what i was trying to say this AM !!!!!
Oil Press & Oil Temp !!!!! need those #s first !!!!!!
Then there are people on this board that can help
but if that is a true oil press. reading all the Holly carbs
in the world aint gonna help !!!!!!MUCH more serious
Problems.

Well I think we all can agree on the poofing out the carb is from lean or fuel starvation status
Tonight I am going to change the oil to straight 40 weight as recommended by quite a few people and get the 10 W 40 out of there.
If I have to, Ill order the metering rods (secondaries) but im still 100% lost on how that is going to help the poofs out of the carb at 1200-1600 rpm's when the secondaries are NOT even open at that point.
The 2 set screws on the front of the carb I would have swore that they would ADD more fuel to the setup.
IE Idle air/fuel mixture set screws.
If that dumps more fuel in at idle it would seem to me that when you open the throttle a little before the secondaries open, that would have an increase in the fuel delivery curve present since it is allowing more to flow at idle, when pressure increases will allow more fuel to get out that way correct?

Put it this way, if you take those screws and run them all the way in, right, you cut off the fuel completley?
so by turning them out would you not start dumping more fuel IN then through the primaries?

so it would seem to me that by turning the screws out on the 2 primary venturies, you can dump more fuel in when only the 2 primaries are open and with the addition of the new metering rods for the secondaries, you then can pump more fuel in through the secondaires at higher RPM's to prevent high end fuel starvation or lean condition
(am I just babbling on or smoking crack or am I making any sense to any of you yet?)
God this sucks
Jason

Jay. FYI,
I just copied this comment from Tomcat to Sean.......from another post


Sean

Since you mentioned the low oil pressure problem, there is another possibility that has been discussed on OSO before. If these are GenV/VI blocks you need the high pressure oil bypass valves in the filter pad on the block. I had low oil pressure after a WOT run, but the oil temperature sender after the cooler hardly moved. I would have to fast idle for a few minutes to keep 20-25 psi otherwise it would drop to 5-10 psi like yours. After this cooling off period the pressure would come back. Pressure on cold start and at higher RPM was good.

What I found were 11 psi oil bypass valves instead of the 30 psi valves. This is okay in a car with the filter on the pad on the block, but when you use a remote filter, oil cooler, lines and fittings the extra restriction creates too much pressure at the bypass valve and it opens. The result is at WOT a lot of your oil bypasses both the filter and the cooler, temperatures go who knows how high and viscosity goes down. Come back to idle with this hot oil and you have no pressure. After the oil cools down, you have the pressure back. Sound familiar? This little vlave problem has ruined a lot of marine engines. It seems that when the GenV/VI blocks come down the production line, they all get 11 psi valves, and even the engine marinizers didn't pick up on it right away.

My oil temp sender is after the cooler, and the reason it hardly moves is only a small amount of the oil is actually taking that pathway and it is well cooled by a big oil cooler. Only the temporary oil pressure problem led me to look into the bypass valve. Scoggin-Dickey have a tech sheet that explains what you need to do. (806-798-4000).

While you're at it look at your oil lines and fittings and eliminate unnecessary elbows especially drilled 90s. I got rid of 3 drilled 90s with one sweeping line. If you follow the tech sheet you will remove the second bypass valve in the block (it's there for plumbing an oil cooler directly from the block, where you likely have your oil cooler in line with the remote filter). When you do this you eliminate another 3 drilled 90's. This will increase oil flow through the remote line and reduce the pressure at the bypass valve, so the 30 psi valve should never open. Some guys don't use the 30 psi valve, they just plug the hole, but hot dirty oil is better than no oil at all if the remote line should get plugged for some reason.

The bad news is, it's very difficult to change these valves without pulling the engines. Good luck!

Well that SUCKS
but I have a Gen 4 (Mark IV or whatever you want to term it)
It is a 1990 set of blocks
does that make a difference on this or no?
Jason

Mk IV's don't have the bypass in the bloack and in any case your engines are previously running marine 330's that didn't have oil P problems in there previous life so don't have incorrect bypass valves in them.

Jay,

I'm not sure if the q-jet works anything like the holley, but with the Holley, it has 4 different jets....One of each corner. These control the fuel flow above idle speed, and into the secondaries.

The screws on the sides are for the "idle circut", from which i have been told has nothing to do with mass fuel flow when throttle is applied.

So whether or not the q-jet has primary metering rods...i don't know...but i would make sence that it does if it works like a holley. Unless the metering rods supply both sides?

Any q-jeters out there?

http://www.geocities.com/gtopercy/Pi...rajetTech.html

a decent description of how quads work there altho its for auto's so the metering size info is not applicable

What about an intake valve sticking open at those rpms? Jay, did you try swaping carbs? It was just one engine doing it right? Swap the carbs and you will find out in a hurry if it is the carb or not.

Man o man and I am glad you guys said it Ursus, Birdog and Form31.... I was about ready to jump out my frikin skin. The proper method for problem solving goes.

You have a "fussy" situation... You fact find..... you establish problem definition... you generate solution, then and only then... you take action. Talk about jumping from a fuzzy situation to solution... with minimal facts. Maybe if Jay could list all the facts as known to him, relevant or not, then maybe we could move towards problem definition. Right now the guy definately needs to do more fact finding. Don't spend penny one on a carb until you at least have problem definition!!!!

One additional fact I am curious about is if your spark plugs were loose after your last run? Of course I am still waiting on my windage tray question, but I guess that fact will never be known.

Infrared guns work great. I use one almost every day. The trick is having a proper baseline and knowing what affects its accuracy. Reading the directions that come with the unit with usually suffice. Surface temps are greatly affected by airflow over the surface, so you need to account for that accordingly. There are other variables as well. Any facts are good facts.

BT :cool:

Jay,


Certainly your #1 problem is oil pressure. As was mentioned before I would let the engine builder know about this and ask for some recommendations from him. As far as the popping at low RPM's are both engines popping? If so it's possible they are both lean on the bottom end as well as the top. If only one engines popping it's got to be another problem. If you want to richen up the engine at lower RPM's start here. The primary circuit on these carbs has removable jets & metering rods. Don't replace the jets unless you can't fine tune any further with the metering rods. The stock primary metering rod is a .042. I would start with a .038 part # 7034838. Again this may not be the exact one you need but it should get you in the ball park. These are a little more difficult to change than the secondaries. You will have to remove the top of the carb, not a big deal and it can be done with the carb still on the boat. Take a good look at it and you will see all the screws & linkages that have to come off. You also may need a new upper gasket as sometimes they get stuck & tear when taking the top of the carb off. I like to coat the new gasket with never seize so it comes apart easy the next time & doesn't have to be replaced. Once you get the top of the carb off you'll see the primary metering rods in the front and how easy the are to be changed. Don't be intimidated by carb work. If you can remove & install the engines you are mechanically inclined enough to do carb work !! Once you've done one your an expert !! Good luck & let me know if I can help any more.

Bo

Bo Knows
 

Hay Jay put Bo's telephone number in #1 speed dial on your cell phone he is good (god):D Charlie

Oil pressure-
I would definitely change the filter, and pour the contents out into a pan and sweep a magnet through it to check for cam glitter.

I always change the oil and filter after the cam break-in period. I use the moly cam lube that Isky recommends, and the moly particles will plug up a filter.

Temperature-
The overall engine temp in an engine running lean may be 5 or 10 degrees hotter, but the piston top may be 100 or 200 degrees hotter.

The leaner a mixture is, the hotter it burns, also faster. Always start off fat/rich, and work your way down- eliminates concerns about melted pistons. Also, I would be very careful about running year-old gas.

"Infrared guns work great. I use one almost every day"....what brand is it????

....like i stated and supplied data for in my previous post.....they only work good in a past/fail...yes i'll use them too shoot all the headers to find a dead hole...but i will not use them for accurate temp readings...i will account for the down time and have a tech put a TC in it...or do it myself!....they are used a lot more in an electrical diagnostic situations.

J, i wish i knew the Q-J stuff...i would help ya....funny all this talk about carbs....and last night i spent 5 hours on a mill making chips form a holly(s):D ....then i had to do another set of props:( ....i'm tired!....KAMMA....do you want a set of 32's after the race season????

Okay if you want to know all the data that I do have here we go

First general engine data
9.5:1 compression
Large oval heads
edelbrock performer manifolds spread bore dual plane intakes
No choke on Rochester carb
Gen 4 blocks (stock 1990 blocks that came with boat new)
Oil pan DOES have a tray inside it yes
Cam is as follows
Comp grind # xe-268H12 PN 11-242-3 Intake Dur 224 Exhaust Dur 230 Intake lift 515 Exhaust lift 521 LSA 110
Put in 10W 40 and had engine trouble starting and leaked a little water in engine
took all oil and oil filter off, changed, dumped a few quarts of oil in engine while pumping it all out to clean out water
put in more oil 10W40 ran it one time in driveway and developed a snap out of the carb on port side engine
bent pushrods
took to engine builder
changed all springs and seat shims ect.
Put back together, Changed oil again after both engines ran at engine builders for about 10 minutes a piece and oil filters were changed again
Took it out on the river for about 15 minutes on a quickie test drive to see how she was
brought back, changed oil and filter again
I took boat out for about hour and a half and oil psi on this run dropped to 20 on port engine stayed around 40 or so on Starboard engine
I am NOW going to change the oil AGAIN (not filters this time) to straight 40 weight
none of this car **** anymore
I have 16 qts of HD 40 straight syrup from aunt Jemimah!!!!
I ordered the secondary metering rods for the carb as a JUST IN CASE type of thing

When on start up engine produces just under 60 psi on BOTH ENGINES
After running 10- minutes or there abouts a glance at the gauges tells the tale
The starboard engine runs fine, No oil pressure problems, I dont think that is the engine that is POOFING out of the carb (that one has run solid since before I took engines out to begin with that one never had any problems but if your going to do one engine you better do both!!!)
the port, that is the one with the bent pushrods, had problems when I first pulled the engines out to begin with it had ingested water, and the oil pan tray broke and was slamming into the crank shaft under load. (weld broke in oil pan and the tray would lift up some how and hit crank dont ask I have never heard of that one before)
I set both engines timing to 8 Degrees on the MONEY!
both idle in and around 700 ish when warmed up
little high but cams chug a little too much any lower than that.
Friend of mine (RCM255 here on OSO) he turned in the set screws on both of the carbs and turned them back out one and a half turns for the fuel on the left and the air on the right
He said that was a good place to start and should be close to what you need

NOW as far as volumetric efficiency NO CLUE joe my friend, I have no damn idea.
I AM running 2.19- 1.90 vavles I THINK
I WILL have to check with engine builder on that
they are Large Oval heads
one is off a 1970 something and other is a 1969 set
there were new guides seals (big deal seals whoopeee doo) springs, retainers ect all installed
the douche bag that put the seats too high
(4 shims and the rotater on top of 4 shims) was FIRED
he was a junkie and an old douche bag
If I go messing around with all of this and get a mechanical oil pressure gauge and slap it on there and an oil temp gauge and it reads high, I THINK im going to yank out this engine and take it back to engine builder and say well here is your warranty case, pull it apart again and FIX it!!!
So Ill be in the dog house with the wife so if any of you are truly friends you can put me up for a few days?????
She is going to flip if I yank this back out but if I cant get it to stop poofing and low oil pressure ect what else can I do?
Jason

Change oil filter too!
 

Jay,

I would suggest that you change the oil filter too while you are going to the trouble of changing the oil. It will only cost a few bucks, and they are easy to get to. If you perform a search on oil filters, you will find some good recommendations. I recall someone having problems with oil filters that contain organic filter media swelling and clogging up when a small amount of water got mixed with the oil. It caused the bypass to kick in, which meant that the oil cooler was also bypassed, leading to high oil temps and low pressure. I know you didn't see any evidence of water in the oil, but sometimes it does not show up that easily. I think the board member who posted the thread was GregP, and he found that running the Wix racing filters (available at any NAPA) corrected his problems because they use a synthetic filter media that is not affected by water. Give it a try - couldn't hurt!

Good luck! Believe me, I've been in your situation. Did virtually the same rebuild as you last year. Spent half the summer without the boat because the engine builder broke his ankle before he finished the engine. Then the flunkee who he recruited to help him out didn't use thread sealer on the head bolts! So I know all about the frustration level you are dealing with. Hang in there.

"changed all springs and seat shims ect."....if shims were installed (to adjust install height)....how the **** did you have coil bind???...all the cam info u gave was from a cam card...those are the #'s that it sould be...even the cam manufacture will tell you to dial it in and double check it!....so what is your seat psi,,,50 and max...these ARE VERY important #'s in a boat!!!..one pass in a car will not make a **** differance to oil tmps.

FIRST!!!...what are your leak down #'s???...

SECOND!!!!check ingnition system...what are the #'s on all the componets??

THIRD!!!!Investigate the carb.

hummmm,,,,fuel, air, heat....sounds like the making of (actually you can't make anything, but that's another story.LOL)......start with basics....sometimes they suck so people SKIP them. generally people with the MOST experience do it because they...."this one time i had...." you are all over the place in diagnostics here,,,yes, we the people here that lurk on the OSO board are not helping...LOL....but the best thing to do is let Mr.I-Can-Put-Engine-Parts-Together-Man take it from here!...tell him MAKE MY BOAT WORK!!!...bill me for anything that is NOT engine related....

I had coil bind from too MANY shims under the rotaters
then the springs sat on top of the rotaters and they compressed the spring down, slapped the retainer and keepers on it
uncompressed the spring
boom done
now when the cam lobe comes up
pushes the lifter
pushes up on push rod
pushes up on rocker arm
pushes DOWN on valve compressing spring
BLAM bent pushrod cause spring was sitting up too high to begin with
coil bind happened cause spring would not compress enough
the cam lobe was still pushing UP on the lifter when the spring was 100% compressed and could not go any further
what gives?
the pushrods gave out and bent
(some were bent to **** too)

Leak down tester was used when changing pushrods on engine to hold up valves and change valve springs and readjust seats and rotaters
I dont know what the numbers on the leak down tester were but when we pumped air into each cyl it moved the crank around until that particular piston hit BDC and held up the valves, the gauge was off the scale saying there was no leaks
we popped the valves when new springs were on and made sure the thing worked okay and the needle would jump but then come back and rest when it was full of air
I dont know what you mean on #'s on all components of Ignition system
I have ac delco plugs in it, gapped to .035 Taylor wires brand new, new dist cap, new dist rotor and thunder chicken bolt #4 with timing set at idle (700 rpm) to 8 degrees advanced
The carb, HA the carb, well I have never been a rochester fan much and I would LOVE it more than lift to have 2 deamons or 2 holleys staring at me in the face no doubt but that is not going to happen right now.
Maybe over the winter I can get 2 holleys and drop them on in the spring, all of a 20 minute job there but for now I just want to run this god damn thing for the piss ant summer that is left (not much left either)
I cant believe that this bull**** is happening to me
and now wife wants me to sell this thing and get Bumpnuglies fountain she loves that thing
I might think about that but still does not change the fact I cant sell this thing the way it is right now anyway.
I WILL NOT BE BEAT by this
No freakin way

J, i understand engines...it really was not a question..i was just pointing out this dude is a DUFASS..

diagnostics should be done w/in 2 hours MAX if this guy knows anything???!

hummmm someone one said...."
you just said it!!...you put this $$$ into a boat...make it less reliable and your wife is going to freak!...the best advice yet...keep it bone stock...make boating a huge great experience for her....get her hooked and then step up to a boat that was build from the core glass work up for more power....a TON of people on this board always look to the engine for more speed....i would love to see for once some one with a stock power boat step up and by full hydrulic steering as the FIRST upgrade. NOT the last or at all!

keep it stock! increase the resale value, not decrease it!"

get the engine guy to make it work....get a lawyer to document it all....cover your ass, mr. engine builder has u bent over....trust me, it looks like it's going to hurt...ever been in a turkish prison???LOL

Well Im going to call engine builder back again and say LOOK THIS IS NOW YOUR PROBLEM
he had me calling all over the place yesterday to local speed shops looking for someone that knows carbs
WTF Why am I doing your job for you
jackass
im really getting freakin pissed off here
this has been nothing but problems and it shoudl be a no brainer here.
if you have been messing with engines for 35 years I would think you would know SOMETHING about ROCHESTER carbs?
gee probably only most popular carb out there for stock applications in the world?
HELLOOOOOOOOOOOOOOOOOOOOOO
you cant tell me everyone in the world is running a freakin holley
that is bull
Im friggin going to blast him if I dont get an answer that I want
Ill do the damn metering rods and adjust the idle set screws to richen up the mixture as per a few websites on rochesters I have found but Who the hell knows if it will be enough and run okay at that point
I will take a wild stab at the fact that the oil pressure will increase a little bit due to the thicker oil that is going to be in there.
BUT still does not mean it wont get hot as hell either.
If I can get some more fuel into the engine that will as a guess stop the poofing out of the carb, that will at least make me feel better about this whole thing.
then if the oil pressure still drops
I think im going to tell engine builder, look something is really wrong, im going to pull it, bring it back you mess with it and fix the damn thing like you said you were going to to begin with and then Ill pick it back up when your done
This is just really getting out of hand and im really getting pissed cause he is more interested in messing around with his dick than anything else
Jason

Jay
 

:D Jay keep up the good work and I love reading your post you get this "TUB" done and you will have to start somethig new for the winter to keep us all intertained:D Charlie

Thanks Rag, Im trying
I think over the winter im going to take up a hobby of airbrushing
I paint almost everything and im not bad at it now, I have sprayed cars, toys and other things with my paint gun but want to do more detail oriented painting.
I think im going to get a few books from the book store and a HVLP gun and a half way decent airbrush to tinker around with.

I dont mean to be that entertaining but you should see me with 3-4 beers in me, I have all my friends in stiches and the wife rolling on the floor when I get on a roll.

Now for the carb
we will figure this out.
it will run this summer with no poofing before im done with it
Now time to take the wife out for her birthday
I will see all of you later and some of you tomorrow night up in Burlington NJ to watch the fireworks on the water
Just look for the arch and swing by.
If your an OSO your cool in my book!!!!
if you cant see the arch, then look harder!
ill be there
If I have to switch to plan B to get home so be it (plan B being big paddles to row my tub back to shore)
Jason

Jason, you won't need the paddles, just don't beat the S@#% out of it till you get all the stuff fixed. Its only a short ride to the fireworks. If you do have problems out there call my cell phone
(Check your E-mail for #) We will be in Burlington also.
Tom 21' Blue Formula (MissMyMoney)

Jay remember 10 pounds per 1000 RPM's!!!! Keep that in mind when you are out there. Going to 40wt oil is only going to buy you some time. Your oil preasure will still drop. I wish I could give you better news then that but that is what happend to me when I was going through the same thing.

Jon

Audacity,.. my IR gun is same as yours, but the ST 30Pro. You are holding the gun too far from the surface for accuracy. 18" is a good distance for a flat surface greater than 6" wide (min). You were shooting a round filter ~ 3-4" in dia. Try again at 1-2" away and I bet your accuracy improves. The spec on accuracy for these units are +/- 1% measured temp, which is much more useful than pass/fail. Again, I use these every day in thermal processing of glue with excellent results. TCs are certainly better for permanent installations, but these IR guns have tons of useful applications when properly used. The only other consideration for accuracy is emissivity, but I don't think that is why yours is inaccurate.

BT :cool: