Mustang II V6 conversion to V8 HO and T5 problems and solutions

GOvert · Dec 27, 2025

I'm glad that you got the exhaust manifolds figured out. The mid late '60s Mustang manifolds appear to work well.

greenflash79 · Dec 28, 2025

Yes, and you can get them new, without rust or cracks, and they fit really well.

welder4956 · Dec 28, 2025

greenflash79 said:
Hey everyone,

Does anyone have timing cover plates from the 5.0 HO and older 5.0 V8 engines for comparison?

I've heard the 5.0 HO has a different water pump rotation direction, and the timing cover has different water flow directions.

For my Mustang II conversion, I was specifically recommended an older timing cover because of the oil dipstick, The older ones have a precisely cut hole for the dipstick.

I'm not entirely sure if my cooling system is working correctly and would like to confirm that the control caps for the water channels inside are identical.

Does anyone happen to have pictures or experience with these different caps?

This is the timing cover I used with a late model roller lifter engine going into our Cobra II with front dipstick hole and mechanical fuel pump - https://www.amazon.com/dp/B0B58Q37Z6. I also had to install a press-in plug in the block for the side dipstick hole. I don't recall the size of the plug (maybe 3/8"), but think I got it at NAPA.

greenflash79 · Dec 28, 2025

Pit Stop: Ford Small-Block V8 Front Cover and Water Pump Interchange

What fits what: The scoop on mixing and matching small-block Ford water standard- and reverse-rotation pumps and front timing covers.

www.hotrod.com

greenflash79 · Jan 28, 2026

The control unit cover and the corresponding water pump are installed.

Can you see water flowing with the radiator cap open? I can't see anything. The radiator might not be completely hot yet, but the top was already quite warm, while the bottom was still fairly cool. Unfortunately, I couldn't detect any water flow.

LILCBRA · Jan 28, 2026

You should see water flowing if the thermostat is open. I'd suggest an infrared thermometer to check the temperature at the thermostat housing. I would suspect that it should be open by time it reaches 190 degrees Fahrenheit. If it gets much warmer than that and you don't see movement, you'll most likely want to replace the thermostat.

greenflash79 · Jan 28, 2026

I'll take some measurements after work and let you know how it went. Thanks for the tip!

LILCBRA · Jan 28, 2026

No problem - hope you get it!

One thing I thought of that may have an impact - you mentioned timing covers and an electric pump earlier in this thread. I would also like to mention, even though I'm sure you have already done so, is to make sure your pump is flowing in the right direction.

It may sound simple, but I think we've all been fooled into thinking that we had something right which proved to not be.

greenflash79 · Jan 28, 2026

I completely agree with you.

I replaced the ECU cover and initially left my old pump installed.

After that, my lower radiator hose started bulging.

I have to admit, I wasn't sure if my original pump would fit the ECU cover.

I got the correct pump and installed it.

The old pump wasn't the problem, though; I had routed the serpentine belt incorrectly, so the pump was running backward (stupid of me!).

I have an '85 HO engine, which has a counter-rotating pump.

The radiator is new, the pump is a more powerful one and also new, and the channels are aligned.

Perhaps the thermostat isn't opening properly; I'll check it and then replace it. I already have two new ones.

greenflash79 · Jan 28, 2026

Mein Riemen ist jetzt richtig montiert.

Noobz347 · Jan 28, 2026

Just a reminder:

We post in English. Please review the Terms of Service and PM me with any questions.

greenflash79 · Jan 28, 2026

Please excuse me, I had actually posted in English, but an automatic program must have translated it beforehand; I didn't notice because I see everything in German.

LILCBRA · Jan 29, 2026

greenflash79 said:
Please excuse me, I had actually posted in English, but an automatic program must have translated it beforehand; I didn't notice because I see everything in German.

I copied and pasted your posts into Google Translate. I don't know enough German to understand everything you were asking but have used Translate enough at work that I didn't hesitate to use it here. But English is easier since it's the native language of most everyone here.

greenflash79 · Jan 29, 2026

No problem, it's the other way around for me ;-)It was just a mistake; my translation program usually switches off, and I can actually reply in English.We also have a good Mustang forum in Germany, but they don't know everything either, so I like to ask here sometimes.I usually reply in the language where I'm asking my question; it's a matter of respect.Things get really chaotic on YouTube ;-)

greenflash79 · Jan 29, 2026

My thermostat opened yesterday shortly after 89°C, and the new pump did a great job. ;-)
Now I can build the electric fan.

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