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  #1  
Old July 15th, 2013, 04:25 PM
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Clark Bowen
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ACR headers

I discovered by emailing Turner Manufacturing (very fast, helpful response BTW) that the motor in my 1970 has a gas flowed head with a 2.5 litre cam. Thought it felt much better than a stock motor.
It has a Zenith carb and the stock exhaust which I'm considering changing to the ACR 4 into 1 tubular header.
Has anyone made this change and did you notice any improvement in gas mileage and/or performance?
What about cold start and warmup.
Looking at the stock intake/exhaust setup it appears that heat from the exhaust manifold will always be heating the intake manifold and the incoming air. That would seem to be a disadvantage in the warmer months or when the engine is warm. Any thoughts on this?

Thanks
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  #2  
Old July 18th, 2013, 06:52 PM
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Rob Wollschlager
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There is no way to get around the exhaust manifold from heating the air in the intake manifold, in the summer months this is not really a problem unless it gets super hot and you could experience vapor lock (where the fuel in the carb bowl boils and cannot be mixed with air to make combustion and it won't run until its cool and condensed again). To prevent that there is a cheesy heat shield one can install, but it often gets in the way and does not do all that good so I run my trucks with out them. In the winter months, the exhaust helps heat up the intake manifold which helps with the cold start and reduces warmup time.

As for the header, I have no personal experience with them, but they increase performance at the expense of fuel mileage. I would ditch the zenith in favor of the weber (increase in reliability) or if you're looking for the best performance look into the Rochester B carb conversion (increase in power at expense of mileage, and parts/rebuild kits are available through any good auto parts store).

The best performing set up is the Rochester b, K&N filter, headers, and a 2" diameter exhaust, but expect mileage in the low teens.
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Old July 18th, 2013, 08:34 PM
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Teriann Wakeman
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Quote:
Originally Posted by cdb View Post
Has anyone made this change and did you notice any improvement in gas mileage and/or performance?
I ran a 4 tube header for five or six years. Never noticed a performance boost nor improved fuel mileage.

One thing that I think does help is to replace the exhaust system with one that has the next larger diameter tubing and a free flow muffler. The exhaust system is too restrictive.



Quote:
Originally Posted by cdb View Post
Looking at the stock intake/exhaust setup it appears that heat from the exhaust manifold will always be heating the intake manifold and the incoming air.
Yep. It improves vaporization of the air fuel mixture. If you live in an area with hot summers you might want to use a stack of under carb gaskets to better insulate the carb from the intake manifold. Just a thought.
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  #4  
Old July 18th, 2013, 09:11 PM
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Clark Bowen
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Hello Teriann....

It has been a long time. Mendo Recce in the mid 1990s, I think.
Thanks for the ideas and saving me time and money..

Rob......

Thanks for your thoughts too.
I already have a K & N, along with a Weber and Rochester carbs from the prior owner.
The Weber, I understand, is difficult to get to run right on these motors, so I've avoided using that, but the Rochester might be interesting, especially if it has a solenoid fuel shutoff (stop the dieseling).

The larger exhaust sounds (pun) good along with a free flowing muffler.

Clark
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Old July 19th, 2013, 10:50 AM
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With the gas flowed head and 2.5 cam your engine would be a good candidate for the 2 barrel Weber. Advance the timing a little bit and set everything up properly and you will have a rocketship! (Comparatively)
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Old July 19th, 2013, 11:02 AM
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Quote:
Originally Posted by rwollschlager View Post
The best performing set up is the Rochester b, K&N filter, headers, and a 2" diameter exhaust, but expect mileage in the low teens.
One opinion. Rochester with the wrong jet will cause some serious problems.

Like TaW said, headers are marginal. Local truck always had cold start problems. He ditched them along with the other ACR crap.

If you want more, re-power and stop wasting time and money on the 2.25
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Old July 19th, 2013, 05:41 PM
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Quote:
Originally Posted by EricWS View Post
One opinion. Rochester with the wrong jet will cause some serious problems.

Like TaW said, headers are marginal. Local truck always had cold start problems. He ditched them along with the other ACR crap.

If you want more, re-power and stop wasting time and money on the 2.25
Thanks Eric, but I've been that way with RRCs (supercharged, 4.6, flowed heads, cam etc.), Series 1 (with a Scotty's adapter and an Iron Duke), Defender (300TDI, port matched, raised turbo pop-off, injection pump work) and now I just want some light fiddling and I'm happy with the 2.25.
We just took our Porsche C4 911 to take our grandkids home and it was surprising how the performance euphoria wore off after 200 miles. So, move to a turbo 911? GT3? Ruf? Problem is that it is never enough and I'm tired of that road. I'm too damn old for the craziness you can get into also. That's why I no longer have the built-up RRC, but I do have a crushed left hand,.
So, I like tinkering with the 2.25 - but just tinkering. No 9.1 CR, no ACR cam, etc (although I did consider both until I spoke with Turner). Just grandfatherly fiddling.
It is interesting to hear you describe ACR stuff as crap. There was a long debate on one of the forums between Richard Turner and the owner of ACR about 9.1 heads. I listened to Turner because he stresses reliability and answering to his customers. ACR and RPI remind me of each other; too much hype.
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Old July 19th, 2013, 05:43 PM
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Quote:
Originally Posted by transientmechanic View Post
With the gas flowed head and 2.5 cam your engine would be a good candidate for the 2 barrel Weber. Advance the timing a little bit and set everything up properly and you will have a rocketship! (Comparatively)
Maybe, if you had the intake manifold and the SAME 2 barrel Weber that came with the 2.5L. Maybe. But the 2 venturi Weber commonly offered for the LR four has a flow that is WAY too high for the engine. The stock Weber 32/34 DMTL has 24/25 mm venturis

The aftermarket Weber 3236 DGV has 27/27mm venturis. I still reccomend the smallest of the B series Rochesters as the best performance upgrade from a Zeinth.

Rocket ship? I suspect a 2CV might be faster.



Quote:
Originally Posted by EricWS View Post
One opinion. Rochester with the wrong jet will cause some serious problems.
ANY carb with the wrong jet will cause serious problems if the jet is off enough. Any carb with too low or too high a CFM flow can cause problems as well. The trick is finding one that flows in the range that will most effectively work with your engine.
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  #9  
Old July 19th, 2013, 06:23 PM
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Clark Bowen
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How would I select the right jet?
Never done that before and my guess is that it is trial and error.

Found the Rochester article on your website. Guess I'll give it a go.
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Old July 21st, 2013, 10:19 AM
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Quote:
Originally Posted by cdb View Post
How would I select the right jet?
Never done that before and my guess is that it is trial and error.
Not necessarily. You can always get a sniffer put up your tail pipe and come up with the air to fuel ratio and use that to go up or down a jet size. The correct jet will depend a lot on which venturi size carb you end up with (smallest is best) and what altitude you are driving at (higher the altitude the smaller the jet).

When I did it by trial and error, I progressively dropped down 2 jet sizes until I reached the point where the engine started cutting out being driven ho the cruise circuit then went up two sizes. Then I had the CO2 level checked. It was a good ball park for my carb at sea level (where I lived).
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  #11  
Old July 23rd, 2013, 05:14 PM
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I had a Weber 32/36, Pierce inlet and Clifford headers on my lightweight and was quite happy with them. When I moved from Cleveland to Madison WI it cruised quite happily 65-70 the whole way with 750R16's.
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  #12  
Old July 23rd, 2013, 06:35 PM
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Quote:
Originally Posted by transientmechanic View Post
With the gas flowed head and 2.5 cam your engine would be a good candidate for the 2 barrel Weber. Advance the timing a little bit and set everything up properly and you will have a rocketship! (Comparatively)
Yes you might get over 90 HP if you're lucky.
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Old July 24th, 2013, 12:43 AM
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Quote:
Originally Posted by TeriAnn View Post
Not necessarily. You can always get a sniffer put up your tail pipe and come up with the air to fuel ratio and use that to go up or down a jet size. The correct jet will depend a lot on which venturi size carb you end up with (smallest is best) and what altitude you are driving at (higher the altitude the smaller the jet).

When I did it by trial and error, I progressively dropped down 2 jet sizes until I reached the point where the engine started cutting out being driven ho the cruise circuit then went up two sizes. Then I had the CO2 level checked. It was a good ball park for my carb at sea level (where I lived).
Any reason that I couldn't install a wideband O2 sensor and gauge to monitor the ratio. I think I still have one around from my Megasquirt/EDIS disaster.
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  #14  
Old July 24th, 2013, 08:33 AM
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I adjusted my Rochester the old school way once I got it close by installing a new set of plugs and checking them now and then. Too light a burn with hesitation and it's running too lean. Dark or sooted up plugs and it's running too rich. The Rochester is a great carb - very dependable and easy to work on if you ever need to.
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Old July 24th, 2013, 09:31 AM
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Quote:
Originally Posted by cdb View Post
Thanks Eric, but I've been that way with RRCs (supercharged, 4.6, flowed heads, cam etc.), Series 1 (with a Scotty's adapter and an Iron Duke), Defender (300TDI, port matched, raised turbo pop-off, injection pump work) and now I just want some light fiddling and I'm happy with the 2.25.
We just took our Porsche C4 911 to take our grandkids home and it was surprising how the performance euphoria wore off after 200 miles. So, move to a turbo 911? GT3? Ruf? Problem is that it is never enough and I'm tired of that road. I'm too damn old for the craziness you can get into also. That's why I no longer have the built-up RRC, but I do have a crushed left hand,.
So, I like tinkering with the 2.25 - but just tinkering. No 9.1 CR, no ACR cam, etc (although I did consider both until I spoke with Turner). Just grandfatherly fiddling.
It is interesting to hear you describe ACR stuff as crap. There was a long debate on one of the forums between Richard Turner and the owner of ACR about 9.1 heads. I listened to Turner because he stresses reliability and answering to his customers. ACR and RPI remind me of each other; too much hype.
If you are happy fiddling with the 2.25, why all the talk about upgrading it? Your polishing a turd. I really don't follow your logic. You seem to be one of those folks that is never truly happy with what they have.

Regardless, yes Turner had it out years ago with ACR. Turner is just better at shilling his product. He kept his improvements to a minimum and goes on reliability. ACR had issues years ago, but seem to have overcome them. Turner just copied what the hot rod guys were doing here and kept his quality in check. ANy good machinist or race shop can do just as good work at half the price.

Buy a book on blueprinting the engine, rebuild it, throw a solex on it and done. Want more than that than repower.

------ Follow up post added July 24th, 2013 08:35 AM ------

Quote:
Originally Posted by TeriAnn View Post
Maybe, if you had the intake manifold and the SAME 2 barrel Weber that came with the 2.5L. Maybe. But the 2 venturi Weber commonly offered for the LR four has a flow that is WAY too high for the engine. The stock Weber 32/34 DMTL has 24/25 mm venturis

The aftermarket Weber 3236 DGV has 27/27mm venturis. I still reccomend the smallest of the B series Rochesters as the best performance upgrade from a Zeinth.

Rocket ship? I suspect a 2CV might be faster.





ANY carb with the wrong jet will cause serious problems if the jet is off enough. Any carb with too low or too high a CFM flow can cause problems as well. The trick is finding one that flows in the range that will most effectively work with your engine.
Uh huh. And the first time they started to put Rochesters on series trucks everyone burned their valves. BP eventually figured it out in regards to the jet but it still is not a better carb IMO.

Ultimate solution is still the OM617 kit from RD. Add ROAM discs and axles, maybe a HD shafts and for most you are pretty much done and down to tire size preference...
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Old July 24th, 2013, 11:29 AM
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Eric.....

Look at all the other posts on this topic and then look at yours.
They are helpful, yours are just spouting off.
Maybe it is time to reconsider your approach if you want respect for your opinions.
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  #17  
Old July 24th, 2013, 11:33 AM
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Mike, fixed the chart for you...
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Old July 24th, 2013, 11:55 AM
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Old July 24th, 2013, 12:53 PM
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Old July 24th, 2013, 02:35 PM
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I can't take all the credit. You set me up for the slam. Thanks buddy.
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