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My idea of replacing the steel nozzle retainer bolts with nylon bolts has gained a lot of traction. Two units here now to receive all of my anti-perc modifications showed up with the nylon bolts already present.
They definitely let the nozzles and nozzle lines cool back down more rapidly after a hot re-start but, by themselves, do they help enough to effectively mitigate the perc problem? I've never tried the nylon bolts by themselves so I don't know.
Well, over on the NCRS forum, one brave soul has tried just the nylon bolts and he was kind enough to broadcast his results:
Hi Jim, finally installed the nylon fuel block bolts, total improvement in keeping the nozzles cool, bolt, nozzles and retainer run about 120 degrees, plenum about 135+ degrees. Restart was easy, still a little edgy until driven to get cooler gas flowing through. Notice no gas smell after shutting off in garage, nozzles felt cool. Still running junk 91 octane California winter blend, less heat tolerance, so bring on the summer good stuff!!!! Thanks again, works fine.
So based on this data point, they do help enough to be noticeable. If anyone else has tried them and only them, please post your impressions.
BTW, calibrating one of the units to which I've just applied my anti-perc mods today in 90 degree heat, I experienced no fuel perc. FYI....
It appears Jim is going to be a little busier in retirement than he anticipated. Super thread, Jim. This has been a great work in progress re: the fuel perc issue. Best discussion in ten years on this Forum.
It appears Jim is going to be a little busier in retirement than he anticipated. Super thread, Jim. This has been a great work in progress re: the fuel perc issue. Best discussion in ten years on this Forum.
I just wish all of this had come to light 5 years ago befor I bought my 65. I passed on a NICE 65 fuelie because I was scared off by this and the octane problem otherwise I would have liked to have bought that car.
Jim, the Nylon bolts help, it's difficult to quantify how much though. I've had several occasions to drive the car on 90 degree plus days and I can say it performed better with the bolts in and the fan off, however at low driving speeds especially in reverse with low air intake it began to percolate within seconds. Turning on the fan blower reduced the percolation significantly (minutes not seconds) but doesn't eliminate it. Of course then I have to tolerate all the cruise night questions, like "Is that stock", "is it a supercharger" or "how does it work". Your modified fuel return solution (and Nylon bolts) sounds like the way to go.
Jim, the Nylon bolts help, it's difficult to quantify how much though. I've had several occasions to drive the car on 90 degree plus days and I can say it performed better with the bolts in and the fan off, however at low driving speeds especially in reverse with low air intake it began to percolate within seconds. Turning on the fan blower reduced the percolation significantly (minutes not seconds) but doesn't eliminate it. Of course then I have to tolerate all the cruise night questions, like "Is that stock", "is it a supercharger" or "how does it work". Your modified fuel return solution (and Nylon bolts) sounds like the way to go.
I appreciate this feedback! It's particularly helpful because I never tried just the nylon bolts by themselves. In the time period I was experimenting with them, they were in addition to the fuel re-circulation modification. So, although my thermocouples told me they helped measurably, I never knew if it was enough to warrant using them by themselves.
I appreciate this feedback! It's particularly helpful because I never tried just the nylon bolts by themselves. In the time period I was experimenting with them, they were in addition to the fuel re-circulation modification. So, although my thermocouples told me they helped measurably, I never knew if it was enough to warrant using them by themselves.
Jim, it appears that you made appreciable improvement in your quest with the simple appication of nylon bolts (which reduced the heat transfer conduction previously enabled through the factory metal bolts). As you mention earlier, there is still an issue of ambient air heat transfer conduction via the metal spider itself.
Building on this approach of "blocking" heat transfer to the spider and thus the fuel it contains (or at least slowing it appreciable), have you thought about coating the entire spider with a TIC (thermo insulating coating)? These coatings are applied in a liquid form (conforming to the shape of the spider) and dry to a hard finish. Studies indicate that they can have beifit with application thickness as little as 1/8". This might futher reduce ambient heat transfer rate to the spider.
Just a crazy thought building on your earlier success.....
Jim, it appears that you made appreciable improvement in your quest with the simple appication of nylon bolts (which reduced the heat transfer conduction previously enabled through the factory metal bolts). As you mention earlier, there is still an issue of ambient air heat transfer conduction via the metal spider itself.
Building on this approach of "blocking" heat transfer to the spider and thus the fuel it contains (or at least slowing it appreciable), have you thought about coating the entire spider with a TIC (thermo insulating coating)? These coatings are applied in a liquid form (conforming to the shape of the spider) and dry to a hard finish. Studies indicate that they can have beifit with application thickness as little as 1/8". This might futher reduce ambient heat transfer rate to the spider.
Just a crazy thought building on your earlier success.....
Just to be clear, the Big Improvement I measured came from developing a way to recirculate fuel to/from the spider on a C1 FI in a manner similar to what's done on C2 FI units.
The thermal isolation provided by the nylon nozzle block retainer bolts helped incrementally and meaningfully as did the conversion to steel fuel lines.
One of my conclusions, based on many measurements, is that radiated heat is not the dominant mechanism by which FI fuel is provoked to begin premature vaporization. Conducted heat is.
A simple experiment confirms this: Hold your hand near a woodstove and make your own assessment of how much heat you feel. Got that? OK, now put your hand in direct contact with the same woodstove. Do you feel more heat or less heat? My hunch is that you feel more heat, bordering on or probably exceeding your threshold of pain. That's conducted heat and it seems to be orders of magnitude more significant than radiated heat.
That said, anything which reduces the amount of heat reaching the fuel in the spider and/or the nozzle lines is a Real Good Thing. So, I'm very interested in learning more about TIC coatings. I've never heard of them before now. Can you provide a link or multiple links to specific TIC products so I can learn more?
The latest news: At the request of a person who wants me to rebuild and modify his FI unit, I'm going to evaluate the effect of thermally isolating the entire FI Fuel Meter. I'll be reconnecting my thermocouples and measuring the temperatures of the fuel bowl, the fuel lines to/from the spider, and the nozzle lines. I'll be comparing the temperatures with the Fuel Meter thermally isolated from the doghouse to those with it in conventional thermal contact.
Jim, thanks for the info and current thoughts. Your next project to isolate the fuel meter sounds very interesting and should provide further insight in your noble quest.
As you indicate, addressing radiant heat transfer may only be a small piece of the puzzle but, given the daunting challenge of keeping the fuel in the line below 110 degrees untill the engine heat disapates (or at least lenghtening the time period before the fuel is heated to 110+), may require many pieces / layers of solutions.
They have come a long way in the last 16 years. Today, there are many advance products on the market. Here is just one example of a product readily available used in turbo / header applications:
Since they can be easily applied in several coats to acheive the desired thickness, given the irreglar shape of the spider and the tight tollerances, it might be worth further investegation.
A second thought would be to also apply a TIC to the top of the intake manifold itself (under the spider) to thermally isolate / shield the fuel unit from the radiant engine heat acting direclty under it.
Once again, just some thoughts...best of luck all with the quest!
Oh, one last idea. You would have to talk to the material manfactures to confirm the appication, but you may be able to find a TIC that you can apply to coat to the underside of the intake manifold itself. This would have two advantages: 1) stopping / reducing the intake from absorbing the engine heat in the first place (thus not radiating it to the spider and fuel unit) and 2) maintaining the stock look of the intake.
You could take it even one step further. You could coat the top portion if the intake mounting bolts (not the threads) to isolate direct heat transfer from the block through the bolts to the intake.
Oh, one last idea. You would have to talk to the material manfactures to confirm the appication, but you may be able to find a TIC that you can apply to coat to the underside of the intake manifold itself. This would have two advantages: 1) stopping / reducing the intake from absorbing the engine heat in the first place (thus not radiating it to the spider and fuel unit) and 2) maintaining the stock look of the intake.
You could take it even one step further. You could coat the top portion if the intake mounting bolts (not the threads) to isolate direct heat transfer from the block through the bolts to the intake.
Just a further thought.
Interesting product, like the idea of applying it to the bottom portion of the adapter manifold, I am concerned if the hot oil in time will wash any of it away & how that will interact with the engine oil, bearings, etc. & would it promote any sludge to the engine oil ? Cant remember past posts why a splash shield couldn’t be used to prevent oil splash under that intake also?
Time to start reading:-)..
Interesting product, like the idea of applying it to the bottom portion of the adapter manifold, I am concerned if the hot oil in time will wash any of it away & how that will interact with the engine oil, bearings, etc. & would it promote any sludge to the engine oil ? Cant remember past posts why a splash shield couldn’t be used to prevent oil splash under that intake also?
Time to start reading:-)..
Thanks Chalie
These materials are 21st century nono-technology that are quite stable and durable; some rated up to several thousand degrees but YES, I would definitly want to check with the engineering staff for the TIC product to verify if it is suitable and stable in such an environment.
7-15-22 Update:
I was courious and called this company today and spoke to their staff engineer. To my surprise, they said it only requires an application thickness of 2 mils. In addition, they stated:
- It is imparative that you follow the perscribed prep and application process.
- If applied correctly, it has been tested to withstand extreem engine environments up to 1900 F.
- It could be applied to the spider as well as either sides of the intake manifold.
- It is impervious to oil, gas, and all other know combustion gas chemicals.
- It could be applied to other metal components in the fuel unit assembly as long as those componts can withstand the prep process (required in order to purify surface of contaminants prior to application).
- If applied correctly, it can only be removed via sand blasting.
I would highly recommend further evaluation and testing on replaceable / donor "test subject" components prior to appling it to any valuable original components.
I’ve looked through the thread but I can’t find the size or length for the nylon bolts. Could someone post it.
thank you
joe
They are 1/4-20x1.5".
On the units I've modified, I do NOT retain the star washer used with the steel bolts. The nylon bolts have enough natural "stiction" that they won't back out.
Last edited by jim lockwood; 07-17-2022 at 06:15 PM.
Reason: addressed major spelling error
Jim
Pardon my ignorance , but is that a real word ?
HA! Well, I didn't make it up. I've known of the word for many decades but I don't remember where I first heard it. It kinda defines itself, doesn't it?
Jim, It seems that your nice "sting ray like" modification to the spider addresses heat reduction while the motor is running and the fuel is being pumped through the assembly so I am assuming the remaining challenge to address is the heating of the fuel in the fuel system components when the car is first parked thus making the cars difficult to restart. As discussed, a TIC (thermo insulating coating) may be of benifit in shielding these components from absorbing the heat during this period (as the engine cools over 10's of minutes).
To build on your "sting ray like modifications" I was thinking of my 65 365 car. It runs chrome lines between the fuel pump and fuel filter but switches to a rubber line for the last 10" or so. Rubber has a very low heat transfer profile (vs the steel or copper). So this design has the benifit of creating a nice thermo heat propagation barrier between the fuel filter and carb and via versa. I didn't think of it until now but maybe this was the intent of the engineers....
Could such an approach help in your problem? Could these areas of the spider feeds be modified where they are cut and replaced with 1" - 2" of rubber fuel line to create an additional thermo / physical heat propagation barrier between the spider and fuel meter assemply? It would appear to be a very simple & inexpensive modification...
04-30-2022, 11:10 PM
, but is that a real word ?
