The stock cap I believe should be 18lb. My walker radiator reccommends a 15lb. - 18lb. cap. So will I be fine getting a 16 lb. cap? Thanks

 

Why would you not get the 18 psi cap the stock system is supposed to have? The pressure rating is an important part of providing the proper cooling capability.

 

Lower lbs. is not usually recommended....


http://www.stewartcomponents.com/tec...ech_Tips_2.htm

In a cooling system, a higher pressure equates to a higher boiling point for the coolant. Higher coolant pressures also transfer heat from the cylinder heads more efficiently. We recommend using a radiator cap with the highest pressure rating that the radiator is designed to accept. In general, performance radiators will accept 22-24 PSI, and professional racing radiators will accept a 29-31 PSI.

The coolant will typically only build to 16-18 PSI, due to expansion up to 200°F. However, if the engine does overheat due to external factors, the pressure inside the cooling system could reach as high as 28 PSI. Once the radiator cap has opened and vented coolant, the engine will not cool down until it has been turned off. The radiator cap is basically a "safety valve", so always use the highest pressure radiator cap that the radiator will tolerate. If you are unsure of the pressure rating for your radiator, check with the manufacturer for the maximum recommended operating pressure.

 

This is on my '35 and I'm looking for a nicer chrome cap.

This is how this catalog lists it:
Please note: 7 lb. radiator caps are designed for use on original radiators and 16 lb. caps are for use on New replacment radiators like Walker, Afco, etc. You will want to use the highest lb. radiator cap that you can as for each lb. of pressure in your radiator, it will increase the boiling point of your antifreeze by 2 degrees.

These places only offer 16lb. yet they say you want the highest rating you can and Walker says 15-18 so they make it seem as if 1 or 2 pounds won't matter, but that is why I'm asking.

If it is critical I use an 18lb. cap I'll use the one on my old camaro's radiator until I find a nice 18lb. cap. Since the LT1 runs a little hotter than a SBC maybe this is a special circumstance that these hot rod catalogs are not accounting for?

 

From my understanding, a pound or two will not hurt... I generally run a 16lb..

If on your '35, and its the original engine, you should run what was original or close to it... Older engines from the 50's and back were generally 7~10 lbs...

 

My '35 has an LT1 (see sig) with a Walker Cobra radiator that's why I'm asking here . A pound or two will not hurt is the answer I was hoping for, but if I need an 18 lb. for the system to work properly I will use an 18lb. cap even if its not a pretty chrome one

 

If you had mentioned that in the beginning, it might have made a difference in the response. You can probably get by with what you want to do. Keep an eye on it for any potential problems.

 

That is exactly why I didn't mention it I figured someone would do what you just did ha (assuming that was sarcasim ). Well I don't want to just get by. I want everything to run properly and that is why I am asking here. I value the opinions here especially yours. I have used your site more than a few times to get me out of a jam. I'll use a stock cap for the time being.

 

I'm running a Billet Specialties #75220 16psi cap in my stroker. But the cooling system is not stock, with a large Griffin aluminum radiator. No problems with cooling.

http://www.injuneer.com/images/photo...ne/Braille.jpg

 

That is the exact cap I was looking at. I may just pull the trigger and see how it works...worst case I spend 20 bucks on it.

 

Is it advisable to get larger or heavier caps? Will that make some difference with the cars performance?

 

im using 18 psi with a red lever on top and that cap works awesum no issues Injuneer recommended that one to me im stickin with the 18

 

Has nothing to do with "performance" if you mean torque or HP. The correct pressure rating (it's higher pressure, not "heavier") allows the cooling system to operate the way it was designed, by elevating the boiling temperature of the water/coolant mix. And there is no "larger" cap - it has to fit the fill neck on the top of the radiator.

I run a lower pressure cap, but I also keep my coolant at about 192*F based on the engine dyno testing that was done on it.