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Old 18-01-2011   #1
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Big valve head

When I amass the parts, finances willing, I am going to build a 695cc engine for my 500F.

What I'd like to know is what size valves can I safely fit to a standard single port 650 head?

I intend to get them professionally fitted by one of the local machine shops close to where I live and I guess I could ask them, but I thought I'd first ask those that have experience with these little cars.

Chris
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Old 20-01-2011   #2
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Re: Big valve head

I assume the silence on this thread means "if you don't know Chris, nobody does"

Hope you are keeping dry.
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Old 21-01-2011   #3
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Re: Big valve head

Quote Originally Posted by oopsadaisy View Post
I assume the silence on this thread means "if you don't know Chris, nobody does"

Hope you are keeping dry.
Yeah, yeah, yeah ..... such flattery is unwarranted.

Someone out there must have an opinion.

Today I took the old cracked head down to the local machine shop and they told me that I can safely go up about 1mm on the exhaust and 2-3mm on the inlet valves. The engine will breathe better through the larger inlet valves and by not increasing the exhaust valves proportionately, I also get an increase in compression ratio. They will also bore out and polish the inlet tract to accommodate the slightly larger Dellorto carby. So I'll clean up the good head and ask them to fit 35mm inlets and 29mm exhausts (I think the standard valves are 32mm and 28mm).

As to the floods - we are OK because we are on a hill, but some of my mates in Brisbane didn't fare so well. We've been helping where we can, but it's a huge, heartbreaking job. To add insult to injury, we are still getting the usual late afternoon thunderstorms that characterize our summer.

And as to the cricket ...... best not mention it. The latest joke I heard doing the rounds was when Andrew Strauss won the toss for the last test at the SCG, he turned to Ricky Ponting and said, "You guys can bat". Ricky Ponting replied, "Er, no we can't .."

I'll post some photos of this engine rebuild as I go.

Chris
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Old 21-01-2011   #4
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Re: Big valve head

Quote Originally Posted by Bambino View Post
And as to the cricket ...... best not mention it. The latest joke I heard doing the rounds was when Andrew Strauss won the toss for the last test at the SCG, he turned to Ricky Ponting and said, "You guys can bat". Ricky Ponting replied, "Er, no we can't .."
Now if I was a decent mod, I'd be screaming


but........

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Old 27-01-2011   #5
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Re: Big valve head

So, is anyone out there using a Panda 30 head? And is there much advantage with those if you're lucky to find one?

Ken
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Old 29-01-2011   #6
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Re: Big valve head

The twin port heads are available and don't seem to be overly expensive. I was considering this but was put off by quite a few who've done it and subsequently regretted it. Not only do you need the head, but the tinware has to be panelbeaten to fit and the twinthroat carbies used (usually DCOE Webers) are mongrels to tune, difficult to fit and secure and offer no real advantage over a bigger valve single port head with an appropriately jetted carby (28IMB, 30DIC or 32/28FZD).

Having said that, I'd still be interested in hearing other opinions.

I delivered my head to the machinists yesterday. They were a bit amused as they usually do racing tuning work on 4 cylinder motor bikes and V8 cars, not 2 cylinder putt-putts. Hopefully I'll pick it up Monday on my way home from work.

Chris
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Old 05-02-2011   #7
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Re: Big valve head

Hello all...its been some time since i visited , but back on. Up-date on my car: I finally got it timed properly keeping the Marelli electronic ignition in place, having the advance redone and fine tuning the Weber 40 DCOM . Have a little to go but need to have less ice /snow and freezing weather.

With respect to Bambinos query, I know that my engine has been worked over...Weber , cam , oil cooler, ignition, re-curved dist., extractor exhaust, bored/worked to 750 cc. I cannot tell you what the valves are like (just adjusted ) or the cylinders/bores. I purchased the car from the previous owner knowing only that the builder, Franco Elettrauto Autocarrozzeria ( Italy)did the suspension/engine /5 speed trans work. I have not been able to communicate with Franco or the painter " max air brush". If there is anyway that I can measure something or take a photo to help, I certainly will. I can not wait for this miserable winter weather to leave.......take a ride!
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Last edited by doc18015; 05-02-2011 at 22:34. Reason: spelling errors
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Old 06-02-2011   #8
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Re: Big valve head

Quote Originally Posted by doc18015 View Post
Hello all...its been some time since i visited , but back on. Up-date on my car: I finally got it timed properly keeping the Marelli electronic ignition in place, having the advance redone and fine tuning the Weber 40 DCOM . Have a little to go but need to have less ice /snow and freezing weather.
Glad to hear that your car is now running well again.

I picked up my 'big valve' head last week and would have posted earlier except for some major computer glitches.

I've attached a photo I took when I picked it up and before my computer died. It has been cleaned, checked and fitted with 35mm intake and 29mm exhaust valves on hardened seats. I guess I could have fitted larger valves, but these are a good compromise between better breathing and the structural integrity of the head. I've seen photos of heads where the valves virtually touch. The inlet valve area is up 20% and exhaust valve area by 7%. The inlet port has also been enlarged and polished to take the bigger carburettor.

The head has had a little bit shaved off and once it's mounted with a thin copper head gasket should give a compression ratio of about 9:1 - more than enough for what I want.

Once some more parts arrive, I'll start a rebuild thread.

Chris
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Old 06-02-2011   #9
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Re: Big valve head

Hi Chris, it would be fantastic to see and read how to rebuild one of these engines. I have a 850 Fiat engine on the garage floor which I would love to rebuild. I hope that your rebuild will be in simplistic terms and guys like the writer can have some confidence instilled into doing a rebuild. Can not wait! Good Luck!
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Old 07-02-2011   #10
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Re: Big valve head

Quote Originally Posted by doc18015 View Post
Hi Chris, it would be fantastic to see and read how to rebuild one of these engines. I have a 850 Fiat engine on the garage floor which I would love to rebuild. I hope that your rebuild will be in simplistic terms and guys like the writer can have some confidence instilled into doing a rebuild. Can not wait! Good Luck!
I'll try to take as many photos as I can as I go along. Some of the work will be farmed out - for example, the head and boring out the crankcase to take the larger cylinders. The rest I'll do myself.

Thanks for your interest,
Chris
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