Hey Carl, does your hood have any understructure in the area of the vent like a factory cowl?
Quote:
Originally Posted by rallystyle
good to see some pictures of the testing. and the reason i want a flat hood now that the carb is gone. cowl hood is really only good for a carb setup or if you need room in the bay. some like the looks also. looks like what chevy found when the did the areo for the 2014 camaros with the hood vent . http://mixmotor.eu/wp-content/upload...Camaro-016.jpg
I like the styling of the cowl hood but the flat is probably easier to build large venting in ala OLAC.
Quote:
Originally Posted by z28cp
Remember, the purpose of the cowl hood was to pull fresh air in for the carb.
Yup.
Quote:
Originally Posted by Payton King
I would be curious about the pressure difference if you vented the side of the fender instead of the top of the hood...like a second gen Trans Am. Seems to me you would be pulling the air that is packing up against the fire wall.
Great work, by the way, thanks for taking the time!
Yeah I did some staring at the the side fenders and may do a pressure differential test in that spot for fun though for style purposes I'm not sure I would add any venting. I'm also thinking about doing some tuft or pressure testing around the inner fender openings. My TCI subframe kit came with block off plates to seal the opening from the inner fender to subframe which I never installed. I'm wondering if that section allows high pressure air from the wheel well to enter the engine compartment too.
No structure in that area. It a fiberglass part made by JCG.
I too toyed with the idea of fender vents. On a new build perhaps it would be worth it. On some of the Chrysler hemi cars there were top fender vents installed. When tested recently for functionality via the oil drop method, there was zero movement in the drop even at 100+ mph.
Time for an update including an important fundamental understanding of how the factory thermostat works in LS motors.
So I've been chasing an electrolysis issue which wiped out my AFCO radiator. It was still functional but had a pinhole leak that would show up after a track day or other high heat event.
Since I haven't fully cured my electrolysis but wanted a new radiator before this weekend's Optima event I bought the cheapest one I could find. The Griffin 8-00009-LS from Summit.
A couple of notes about the radiator.
Has the 23" core but very narrow tanks so the driver's side mounts in the SBC location
core isn't as centered in the core support openeing as the AFCO was
Claims to use the correct sized inlets & outlets but the lower hose uses a 1.5" outlet where the AFCO used 1.25" I think factory on a lot of LS cars is actually 1.25"
Core is about .5" taller than my old AFCO
The narrower side tanks also caused the outlets to move slightly and required new hoses. After several trips to the auto parts stores I finally found hoses I could cut and make fit without resorting to the universal hoses. I used the following:
Lower - Gates 21585
Upper - Dayco 71576 (length code D)
I also took this opportunity to install the 75-79 Chevy Nova coolant recovery tank in the passenger fender. Learned about this from Vince on this site. The older I get the more I appreciate function over form. I was tired of my billet tank which I could never accurately tell how full it was and it was catch can style rather than recovery. I wanted something I could see the level at a glance. Here is the pic Vince shared. I haven't taken one of my own set up yet but it looks pretty much the same.
So once I got everything mounted I thought I was chasing an air bubble due to low coolant flow at idle. This had happened to me before where at low engine speed the car would run warmer. This is regardless of vehicle speed or the fan being on/off. Rev up the engine and it would cool right down.
Well after lots of research online I stumbled on a bunch of threads at LS1tech.com talking about the need to have coolant flow through the heater hoses because that is how the thermostat senses when to open. Because the LS thermostat is on the lower radiator hose but has the sensing component on the back side of the thermostat it won't open based on the temp of the coolant coming from the radiator. The Factory Thermostat has a "bypass valve" on the back side of it that will allow hot engine coolant to hit the backside of the thermostat when it opens but the reading I've done online says this only opens with 5+ PSI of pressure. This would explain why at idle my car hits 210* and stays there but as soon as I blip the throttle it would drop below 200* fairly quickly. That blip of the throttle is likely opening the bypass valve which allows hot coolant to wash across the back of the thermostat and triggers the thermostat to open more fully.
The bypass valve on the back of the t-stat looks like this:
To test this I got the car nice and hot and then switched my heater valve open and within in a few minutes I could notice a huge difference in the behavior of the thermostat. Watching the coolant flow from the upper radiator hose I could see the Thermostat opening at a lower ECT and opening much farther (saw a lot more flow). I could actually see the temps cycle consistently.
Here is a video of the the behavior of temps with the valve open and then the valve closed all at idle with a fully warmed up engine (oil temps over 200* too).
Final note. This issue runs 50/50 on LS1tech.com between those who claim you can't block the heater ports and those who have blocked off the heater ports and notice no problems. But if you are ever fighting low engine speed/idle temps this might be one to check out.
Whew what a weekend at the Fontana Auto Club Speedway with the Optima USCA. Man was that ever a hot weekend and car event!!!!!! I drank over 350 liquid ounces of water and Gatorade Sat & Sun and I still lost 7 lbs in those two days and had dehydration related cramping.
However, it was still a fun weekend. No other event that I've been to besides Optima USCA do you see such a wide variety of cars and while it gets increasingly competitive every year its great seeing the camaraderie continue and getting to see some of my fellow competitors and friends.
This was the last Optima USCA event before the invitational at SEMA and the competition in the GTV class was off the hook compared to my previous experience in April in Vegas. I was very happy that in all three driving events I managed my best times in my last runs. Regardless of how I stack up on the scoreboard I always feel much better when I see consistent improvement throughout the day at a driving event. Overall I came in 9th out of 33 GTV competitors which considering the competition is something I pretty happy with.
Getting after it on the autocross (thanks Tim for the pic)!
And video of my best lap on the road course. I did 5 sessions and it took me many tries to get to this time lol.
Edited to add: I feel like I'm finally starting to get the car and most importantly the driver sorted on the road course. I still have a lot left to learn but this past weekend I probably did more throttle induced oversteer than the rest of my track driving combined and it felt good to predict it, control it, and even prevent it.
Also, great job to Jimi Day and the whole Optima USCA team for another really well run event. I was especially appreciative of the ability to wear shorts on Saturday for the autocross and speed stop and the extension of judging to Sunday.
Also, thanks to TCI Engineering and Wilwood for great hospitality over the weekend.
Electrolysis can be caused by a blown head gasket. I chased electrolysis on a car for months and it dissolved 5 heater cores. GM had me doing all kinds of stuff from flushing the cooling system with baking soda to soldering grounds onto the heater core and radiator and adding new grounds to the block. What it came down to was a blown head gasket that would let exhaust gas into the system but wasn't bad enough to burn coolant.
Electrolysis can be caused by a blown head gasket. I chased electrolysis on a car for months and it dissolved 5 heater cores. GM had me doing all kinds of stuff from flushing the cooling system with baking soda to soldering grounds onto the heater core and radiator and adding new grounds to the block. What it came down to was a blown head gasket that would let exhaust gas into the system but wasn't bad enough to burn coolant.
I hope it isn't that and don't think it is based on the testing I've already done. Will keep it in mind though.
Quote:
Originally Posted by Panteracer
I saw your results the other day... very good in the company
you are running.. and some have brand new tires etc
thanks for the update... glad you did well
Bob
Thanks Bob. I was one of them running new tires but am still happy to get into that company!
Brian Hobaugh SCCA National Tour June 2014
First Hemi 'Cuda Convertible Ever Built
Short clips: Goodguys Pleasanton autocross and pit videos
but am still happy to get into that company!
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