1986 F150 with 4.9L engine [Duraspark 2 conversion w/o EGR, but still have catalytic converters] and the carburetor is from a 1970 F350.

Which PCV valve... 1986 or 1970?

Thanks for your input!

 

I would go with the 1970 PCV if it will fit. I would try to copy the 1970 setup in every way possible.

 

Thank you for your response, Franklin2!

Perhaps if he is not too busy, NumberDummy can share his knowledge with us. That would be great!

I looked on the website of a couple of parts suppliers and found the following:

Rock Auto: 1970 F350 with 300 engine shows Motorcraft EV49B and there were (3) possibilities for the 1986 F150 with 4.9L engine - Motorcraft EV118 [4 WD u/8500 GVW; Motorcraft EV49B and finally, Motorcraft EV111 [RWD].

Advance Auto [does not list Motorcraft]: 1970 F350 calls for Purolator PV736 and for the 1986 F150, Puralator PV118.

Interesting!

 

Realistically, does it even matter that much? Over the years at the auto parts store I work at , customers with custom applications have selected PCV valves based on physical configuration alone, and I can't remember one that had an issue. I know that runs counter to good judgement, but that's what I've seen.

 

I believe they have different flow rates. Afterall, they are controlled vacuum leaks if you want to think of it like that. So it can affect your carb adjustments and fuel metering to some extent.

 

I am always trying to learn more to gain a better understanding of how things work, so last Friday, I obtained a way to contact the Engineering Dept. @ Purolator. They replied very quickly... I was impressed.

I explained that I had substituted a 1970 Carter YF from a 1970 F350 with 300 inline six engine for the original feedback carburetor on my 1986 F150 with 4.9L. Purolator part numbers are PV736 for the 1970 application and PV118C for the 1986 application.

The Engineer supplied me with two charts which show the flow rates. I will attemp to copy and paste the two charts. The 1970 test data is in cubic feet per minute where as the 1986 data is in cubic feet per hour. You will see that the curves are quite different. To equate the data, I assume that one simply multiplies the flow per minute by 60 [minutes] to equal the flow per hour or simply divide the flow per hour by 60 [minutes] to equal the flow per minute. The absolute flow rates range from ~0.75 to 5.0 cubic feet per minute, so yes, Franklin2, it is, indeed, a controlled vacuum leak.

The flow of the PV118 [1986] is flat from 9-18" Hg, where as the PV736 [1970] is never flat. At my truck's normal cruise range [~10-12" Hg], the PV736 [1970] flows approximately 1.6 feet per minute compared to the PV118C [1986] which flows approximately 1.2" Hg. That would represent a flow difference of approximately 25% less for the PV118C.

The relationship seems to make sense since the carburetor calibration for the original 1986 feedback system is more on the lean side due to the EGR system. That partially explains why if one removes the EGR and replaces the feedback carburetor with a non-feedback carburetor which is calibrated for EGR, under light throttle cruise, pinging becomes a problem and timing must be retarded [better yet, recurved]. The carburetor from the 1970 F350 was not calibrated with emmissions in mind.

Look over the charts and I look forward to everyone's input. Well, it shows my stupidity, but I cannot attach what was emailed to me. I have tried multiple ways, but have not been successful. I have been able to print the charts and will PM Chris and ask for his assistance, since I believe this data might have an impact on other's projects. I apologize for the delay.

 

Here are David's diagrams, my apologies for the delay (pretty busy with Taurus stuff at the moment)....

 

I'm kinda surprised Gary hasn't taken part in this thread, if only to analyze?

 

I have been looking at these charts and decided to convert the PV118C flow rate from (Cu. Ft/Hr) to (Cu. Ft/Min) which makes it clearer when comparing.

Starting at the top of the PV118C chart:

Cu. Ft/Hr / Cu. Ft./Min

300 / 5.0
250 / 4.2
200 / 3.3
150 / 2.5
100 / 1.7
50 / 0.8