When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Food for thought - flaps = ck valve esque function
DW SD - thank you for making time to interject your experience for my consideration! I’ve not stumbled across a statement enlightening the reader about a reverse air flow mgmt - it seems apparent and obvious now that you tell me... hmm yep that’s the good perspective mod I needed! Gracias —->Tonight I must drain $111 worth of 2 gallons of fancy coolant and then pull radiator.The next time my radiator goes in, my serpentine belt will naturally locate On damper ribs properly and my ‘neat’ coolant reservoir won’t be drip leaking at lower outlet fitting. Then, 2 gallons of my coolant goes back in - and I bought 2 gallons more (another $111). 4 gallons sure seems like it should be enough for just a motor and radiator and small coolant reservoir for max capacity (I can’t find any solid capacity volume numbers to guide me - so I’ll learn myself up to speed).
Originally Posted by DW SD
I'm sure you thought this through based on the rest of your build. If not... some will hang (via rivets) neoprene or other rubber flaps over the holes in the radiator shroud to function as a check valve so air doesn't come in from the engine bay side and out the fan. (path of least resistance)
And some other info:
I built a similar shroud to yours on an $180 2 row Speedway radiator for my '51 truck build. But out of aluminum and welded the shroud in place. I don't have the holes you added on the side, but figured I'd just start with the big hole for the 16" SPAL fan.
I've had sufficient cooling with just that in ambients up to about 100F, including running AC. I think I saw 195F on the freeway @ speed in high ambient temps (100F ish). I'm sure it'd work better with auxiliary holes in that condition.
If you look closely at the pic I posted above, you'll see that SPAL (also a big OEM supplier) puts flaps over the openings for precisely that reason. Under cruise with the fans off, the flaps open to allow natural airflow over a larger percentage of the core. When the fans are on they create a lower pressure inside the shroud than on the backside of the fan essentially "sucking" the flaps shut so that all fan-induced air flow comes from air on the front side of the rad.
As for temps -- with or without holes in the shroud, the other consideration is what is the t'stat doing? Clearly even with reduced flow across the core (because of shroud shielding) at high ambients, you're generating enough heat transfer to keep the truck at normal operating temp. However -- is the t'stat just barely cycling open/closed, or is it wide open allowing max coolant flow to make up for reduced air flow? You have to have the answer to that to know just how much excess thermal capacity you've got in the system. I think that's worth considering because for the OP -- the thermal load he's going to put on the system on the track is way, way more than the minimal load we see when cruising down the road, even in high ambients. For my dedicated track cars (road course) I always ran no fan at all to minimize obstructions to airflow across the rad. Obviously, it takes some discipline during cool down laps and in the pits. And for a car that might see street time, autocross or drag strip -- you need a fan to keep things cool.
To the OP - do you need any sort of aero device (often referred to as a 'splash pan') to help create low pressure behind and below the rad to help high speed airflow across it?
Hi Michael,
good points and 100% agree! My truck doesn't see track time.
I've watched my temps closely. The T-stat for me in steady state operation with more than sufficient thermal capacity available sticks around 185F on my gauge - which I've loosely calibrated with an IR temp gun. I'd guess my gauge reads 10F low in fact as I run the stock L92 / LS3 T-stat. I think the cycling happens within 5F, maybe less.
(Note, my gauge sensor is threaded in to the head it is an autometer classic electric gauge). The temp gauge is analog, but about 1" in diameter. Not exactly high resolution.
As mentioned, my thermal capacity seemed tapped (no extra as evidenced by temp moving from its normal position) running at higher speed (90mph) with AC on full with T-stat obviously wide open (gauge at 195F, maybe even 205F) and 100F ambients. Again, I'd guess because flow through the radiator was limited by flow through the 16" spal fan. I probably have at least 1 square foot of radiator outside of the fan.
This one scenario didn't motivate me to drill holes and add flaps, though I considered. I live in coastal San Diego and don't go to the desert with the truck. We just had a heat wave and I ran up to orange county on the freeway.
But, for a track car or something that'd see a lot more frequent throttle in higher ambient temps, I'd definitely do those mods.
Maybe some cool flaps would be made of the same acrylic as the shroud mounted on hinges. Or even powder coated aluminum to add some color. Or carbon fiber.
Obviously, the attention to detail on your build is great! Hope the info helps.
It is fun playing with the available data re: temps. Mine runs the stock 187F t'stat, on the water inlet of course. My factory temp sender is in the front of the driver's side head -- sensing temp after heat transfer in the head has occurred. So far, regardless of ambient, when I have enough road speed to turn the fans off (20-35 mph depending on ambient), I see 194-195F on the phone app reading from the diagnostic port. My gauge sender is in the radiator tank adjacent to the return hose. Not enough detail on the gauge to distinguish 190F from 205F - but it appears to be in the same range. With fans on, A/C cranked up and ambients in the 90's (with lots of humi-dittys) I see consistent 198-199F on the ecu data. That's with the fans set to a 202F operating temp. I run a variable speed controller that varies fan speed to maintain a set operating temp. So, pretty pleased with what appears to be about a 5F band of operating temps regardless of conditions. And -- not enough hard track time on mine to tax it and see what happens to temps.
So... a total of about 7min of total run time - and on ‘the’ start that was going to lead to driving the car out of the garage, I heard; *****-Cling-Donk... and motor immediately came to a screeching halt... on its own.
And now.... the costs are now way over as I had just told My Wife about 1hr prior they were not :-(
Last edited by MUL8NO1; 06-11-2018 at 03:14 PM.
Reason: Words
Awful news. This stuff happens all too often.
I had that happen on a 911 engine I bought from a third party. The rebuild was about $9k. Sucked big time.
Sorry. Good luck!
i am awaiting a full build from Texas Speed and Performance in Georgetown, Tx.
i took my locked-up/broken LS2/3 to TSP 2.5 dats after it broke.
Without full funds in hand to put money where mouth (wants) is, I committed to a full-on ‘N/A motor build.
There facility, tools, equipment, staff, etc are exactly the effort I’d put together if standing up a biz in this engine building game.
After a thorough and sufficient facility/staff tour, it was decision time.
TSP will:
Fully Tear Dow/Diagnose LS2.
fully disassemble everything.
use LS2 Block for Darton Sleeves (if Block good).
4.125” bore in Darton Sleeves.
4.0” Crank throw with TSP Forged crank.
TSP Forged rods.
Certain pistons for my n/a mostly road race / some C&C... try to stay around 11:1 Comp ratio on 91 octane.
LS3 heads torn down inspect etc.
If poss, reuse my new upgraded Spring/retainers, my tsp steele roller rockers etc.
Full CNC effort on 821 heads.
Upgrade valves, guides, et al to pair with above.
Flow at needed lift should be 360-375.
Design TSP cam for 427ci W/above heads using my FiTech Sheetmetal intake/102mm Tb seen in other posts.
Johnson Lifters etc.
Reuse my Cloyes Hex Adj Cam/Crank sprockets.
Reuse my C5R timing Chain.
Reuse my 2-piece timing cover.
Install another new upgraded oil pump.
Reuse my Improve Racing oil baffle assy.
Upgrade oil pick-up support.
ARP everywhere.
Use new appropriate bearings, rings, gaskets, etc.
$5k down to start.
$5k due here in next 2wks (I’m ready)
The Only Build concession from a full ‘max effort deal’ here will be the reasonable compression ratio and the need for ability to drive very selectively to street-based events... so a Stage 3.5 of 4 type cam.
TSP has a $1M dollar cam creating machine - we plan to derive an appropriate cam that considers all of the above... and uses TSP experiences in LS3 cam design and cam design for 427ci... and my intake - and vehicle rpm use/duty.... you know —>
My LS2/3 combo could have netted very near 500rwhp with what all I had.
This next combo can do 700hp... but dumbed down compression and cam may only due 650hp/550tq.
Ill have to make due with that in my 2400-2600lb car.
Luckily, vehicle is fully built to support and thrive with this power.
My new Spec Stage 3+ clutch kit and associated lighter flywheel is supposed to work.
My Stock and only 2,000mi GTO Transmission MN-12 with the built 3.73 Diff (clutches/ramped), custom axles, blah will have to work together to get the job done.
Until then, I do my best to prepare a meal for the kids who are out of school on this Ice Ice baby Central Okla Day A Racecar for each of them... because, like Guns, Racecars dont kill people, People kill people - I’ll teach ‘em how to smartly use both - from there, well... u know This dude will press out my LS2 sleeves and install the Darton Sleeve action This... I think :-) I sure would liked to have a weekday meal like this when a kid... nourish mind / body / spirit - my fortune cookie knowledge at work.
Excited to see the build come together. I really want to know what the cause of the failure was!
Doug
TSP fully tore down my Thread-Stated Motor.
I received email report from my contact on Monday of this week.
Apparent cause for motor lock up:
#2 piston stuck Kak-eyed in upper portion of cylinder.
#2 rod ripped in half (Arp bolts are strong eh).
#2 wrist pin still through upper part of rod hole
The New Clevite bearings for rods and crank apparently weren’t properly measured/mated (whateve)... soooo they were TIGHT.... after my 4-6 starts - idles - revs - and two oil changes, there was no oil where it needed to be.... blah yuck puke
Soooooo the local machine shop who assembled this ‘fresh’ LS2 bottom end didn’t do things right. The LS2 Block had fresh hone, all arp bolts, Clevite bearings, new rings, etc - but my buddy had opted to keep OE LS2 crank/Rods/pistons otherwise - because that set up was going to meet his budget and Performance goals with the LS3 heads/LS3 intake mani/NW 92mm t/b.
I went another direction with some of that - as noted in my Thread - uhmm... so apparently I’m continuing that theme.
We totally cannot afford this - but moreover, I can’t afford to quit and have Nothing... so in car-guy fashion, we find a way!
i bought chassis and many parts from buddy (Buddy A) that I’d been helping create this car for many years - buying my sweat equity, aaaand Some. Buddy (A) has a Buddy (B) take short block and parts to local machine shop to clean/machine/assemble the LS2 short-block. I guess I’m Buddy (C) in this **** Sammich equation. I end up with the project nearly 2yrs out from the fresh short-block assy...
I do believe i have the receipt from Buddy (A) and that receipt has Buddy (B) info on it... you can “C” how Buddy Me is Fk’d 2 ways from Sunday.
I served our country in uniformed service - I think I remember my programming, err training, was to say, “thank you Sir... May I have another” - or maybe I just heard that in a movie - yeah, so... my “oooh la/la project buy” isn’t any longer the wondrous ‘deal’ I had been selling the Mrs’ on now... buuuuut if we are gonna have ‘real money’ in a “Built Not Bought” Car - and be proud that We-Did-That, well this is the car for me I suppose!!!
Diagnosis of the previous failure? I'd want that nailed before I dropped some $ and went to fire up the next one.....
so...... way up in our post-bio I talk about me putting new oil pump on - without removing the pan etc
I paid that $300 tear down cost to KNOW what happened.
it was told to me that the oil pick-up tube o-ring that secures under the oil pump via that little 10mm bolt (they said this was loose too) was ripped and causing oil pressure loss thus oil not getting up where it needed to be leading to issues that go with dry rotating engine internals.
im sure those guys know how to look at things - that said, man I spent all kinds of time ‘ensuring’ I properly installed that stuff... Uhmm ughh.
gents who tore motor down from TSP also did say the build at a whole looked very promising - and it was a shame to see this happen to a new motor.
i can Woah-is-me all day... but it sure is what it is at this point.
like was said in a Top Gun scene, “who’s butt did you kiss to get in here”.... “the list is long, but distinguished”... “yeah, so’s my Johnson” (lifters)
“ha, I crack myself up”
... and apparent I break o-rings
lastly, we are in final moments to spec a cam that works beat with the colossal parts list I have for this 427.
we are 10 more working days max from motor being crated and ready for me.
ill not be hurrying nor dallying on the re-birth
i got this car back running again - so that’s been good tgerspy
Stunt double Former racecar... with no stickers and fresh Mckeyes37 equals street car Wheel/tire swap - show up out of blue to local SCCA autox = FTD on second run... they didn’t see that coming
Sounds like you're on the right path. I had to fit 2 different aftermarket oil pans to mine to manage the swap/crossmember clearance. It took a lot more time/research than it should have to nail down exactly which O-Ring I needed with the pickup tube/pan I ended up using. Seems a design short coming to have something as fundamental as oil pressure all be subject to a poor-fitting single bolt flange that holds an O-Ring in place -- and one, at that, which comes in several different sizes depending on subtle variations in 2 or 3 pickup tube sizes. I feel your pain.
Edit -- and I put about 30 miles yesterday and today on mine after having it down for almost a month. Put in a GPS/electric drive for my stock cable speedo - and having that process interrupted mid-stream by blocked bile duct/gall bladder attack which required 3 days in the hospital for 2 different surgical procedures. Perfect weather for drives -- I'm so glad I chose a box stock LS3 new crate motor. It just starts, runs, drives perfectly every time. Idles so quiet I can hear the injectors clicking under the hood. 20 mpg around town. And 440HP or so in 2980 lbs. is plenty of fun. Good luck getting yours back on the road....er...track.
Last edited by Michael Yount; 04-02-2018 at 06:46 AM.
01-12-2018, 04:38 PM
Food for thought - flaps = ck valve esque function 
