F head hop up debate on exhaust

Following the Weber Carburetor thread which has also discussed Clifford header upgrade, I went to a local exhaust shop and asked him about how much he would charge to build a set of headers for my F head. The guy said that "I wouldn't waste my money" He says unless you are running it at top end all the time, headers won't really get you very much, and he says the 18 -22 percent Clifford claims is probably not going to happen. He also says if I decide to do it, get the Clifford headers because the ones he builds would be at least twice as much and would be basically the same in design and performance.

He says that he would smooth out the inside of the stock exhaust manifold and upgrade to around a 2 inch exhaust system and that would get you as much or more than headers, because the cast iron manifold retains more heat in the metal and doesn't allow the exhaust to cool and stagnate in the system as much, whereas headers are thinner they typically dissipate the heat quicker and can cause exhaust gases to slow down, reducing performance.

I'm pretty sure this will open up a can of worms among my fellow F head owners.

I was really thinking about putting headers on in order to get everything I can out of that little engine, but now I would like to know what forum members think on the subject, and if anyone can vouch personally for the improvement in average road use from the header upgrade.

Are headers really worth it on an F head?
What about grinding the inside of the exhaust manifold for smoother flow?

So what say you?

 

I have no experience with headers or polishing the inside of the exhaust manifold but I do think there is some truth to the stock 1.625 exhaust hampering high end performance. The early models ran the 1.625 pipe all the way out while later models stepped up from 1.625 to 2" pipe from the cross member on out. With the F-Head having larger intake valves than the L-Head and the exhaust system from the L-Head being carried over in production the Manufacturer may have been on to something with the 2" step up at the cross member, Possibly to improve the high end exhaust flow and reduce temperatures due to The F-Head being driven faster and harder on better highways and roads in general.......just a theory.
I plan on replacing my aging and PO butcherd system with the later method of 2" from the cross member on out because I think it will be plenty good for the way I drive with a stock carb.
There is no doubt some performance to be had but it would depend on the way you drive and what other compatible modifications have been done, For a stock rig and average driving I think the later style exhaust system would yeild good all around performance.
I am contemplating insulating the 1.625 inch pipe from the cast iron manifold to the 2" step up at the cross member in and effort to reduce radiated heat on the fuel pump, oil pump, steering box and brake master cylinder..........Even if that experiment only yields moderate results it certainly could not hurt anything.

 

I'm always glad to see more and more FHead performance threads

I had extensive emails with Clifford re: their header and after many specific questions, only got un-substantiated claims, no dyno reference, no user testimonials that installed the header with a stock exhaust, no performance gaurantee.

I, too, have been told, by those I believe to be knowledgable, that the manifold is a pretty good flowing design and that smoothing the inside would be best ... but maybe just marginally better than non-smoothed.
Furthermore, I was also told that the Clifford "shorty" header would only add to very high rpm conditions, if any at all. However, I was told, if I had the money, one fellow would build me one that was a 4-into-2, with a ~20" primary collector then, 2-into-1 with another ~20" collector that should give maybe a 10% increase in low-mid power ... yeh, not worth it.

When upgrading mine, I was torn between going with a 1.75" (OD) or a 2". If you believe that NO "back pressure" is good but, adequate exhaust velocity is mandatory, you'll have the same dilema.
I went with 2" because of the 90° crush bend over the axle and another behind the axle, to maintain the stock config.
I'm satisfied that my new exhaust was a major improvement but 1.75" might have worked just as well.

I also believe that any piping improvement could be negated by a restrictive muffler.

 

The exhaust velocity thing relates to the "extractor effect", IIRC. Each pressure wave of exhaust from the exhaust stroke will leave a wake of low pressure behind it. If the exhaust velocity is matched by the runner length and diameter, the next pressure wave will arrive at about the time of the low pressure from the previous wave, and will tend to flow more easily into the exhaust pipe. I beleive this becomes more like ideal continuous flow (laminar flow) and less energy is required to move the exhaust out.

I know that improving the flow of exhaust will also improve the volumetric efficiency of the engine. Lower exhaust backpressure will mean less exhaust gas in the cylinder on the compression stroke. I don't see how it's physically possible to reduce the exhaust pressure to less than atmospheric, but it is certainly possible to make it higher than atmospheric (back pressure). Ideally I'd expect the exhaust should provide as little restriction as possible, thus porting, polishing and relieving should always help. A less restrictive exhaust should help too.

Note that changing the exhaust efficiency will change how the incoming charge is diluted by the residual exhaust, so a slightly richer mixture may be needed.

I'd suggest you get some vintage hop-up books - I have one about the flathead Ford that likely has some good advice. I know that Dick Datson's books also have some info about PP&R, though the info is kind of sparse. His Studebaker book might be a good source.

 

It may be necessary to fractionalize the Fhead hopup thing ... among those, like me, that just wanted to see if an antique tractor motor could perform in a similar fashion to any old or new bone stock, run-of-the-mill 4 banger car or not, I'm done, it does, every day, with the mods I and several others have done. No old tricks or machine work necessary. Job done. Amazingly happy

 

I have a 64 cj5 5.38 gears 32x9.50x15 swampers. I have installed a modified Clifford header, Solex carb with jetting modifications and my Jeep runs down the road 3000-3500 with ease. Will pull a steep grade and only loose a few hundred rpm. I do not know how a stock F head would perform with 32 inch tires and Carter carb. I can tell you my Jeep runs out real good. I have found best power with timing at 10 initial, but I can not remember the total.My exhaust is 2 inch from the collector back to a flowmaster muffler and dual 2 inch tailpipes. I love duals!

 

I will be staying with the original exhaust manifold - might smooth it out, might not...
However, I am getting Clifford to re-grind a spare camshaft, and my spare cylinder head is at the machine shop getting a shave (0.060")
Once those are done, we'll see what is next.

 

http://www.jpmagazine.com/techarticles/engine/154_0603_jeep_engine_performance/photo_06.html

This article makes sense to me.....

 

After the 0.060", is there anything left for one more maintenance surfacing?

 

I don't think so, the guys at the machine shop wanted to make sure I actually wanted to shave it 0.060".

 

any further updates on this old topic? Has anyone encountered evident gains with the clifford headers and decking the heads .060 I too seem perplexed by what clifford claims. Any thoughts and revelations to add to this thread please ? thank you

 

Wow!? this site is back up?
I dunno, i'm still not taking a running motor apart for a cam and not buying a header without guaranteed performance. 2" exhaust, weeber carb, msd fire is working for me ... withing the parameters of an "old tractor motor"
I'm just driving mine, not messing with it anymore

 

oh man this is good to know. I got a stroked, ported and decked f-head i'm getting ready to put back together. I am going to switch to TBI and coil over plug set-up. (maybe) I will eventually turbocharge my engine and exhaust is very important touchy subject. The size of the exhaust valves limit everything to around a 88 VE. Still, thats a big gain over 76 VE stock.

 

As a follow up to my earlier post on this thread, where i was contemplating using 2 inch pipe from the cross member on out I had a local shop put a new exhaust system on my 55 with f-Head, I opted at his recommendation to run 1 3/4 inch pipe all the way out as opposed to the original 1 5/8.

With the .080 over pistons and the head and block both cleaned up .020 worth each the engine now displaces just shy of 141 cubic inches and has a resulting compression ratio increase from stock 6.9:1 to between 7.3:1 and 7.4:1.

The 1 3/4 pipe performs very well, does not seem to get as hot between the manifold and cross member as it used to even with a standard 1 3/4 pipe oval muffler. Low end torque is still strong and judging from hard second gear running and near full throttle third gear mountain driving flow is more than adequate as engine is very willing at the higher rpms with right now throttle response even when close to wide open.

Personally at this point I think 1 3/4 all the way is plenty good for a stock rig with carburetor and mild improvements. I am very happy with it.

 

best way to make power is compression. Making it breath better is only part of the equation. I would not be susprised that you can get a 45% increase in power just from doing some other internal changes. As I recall, for every .010 over a increase of roughly 4 HP can be archived? not sure thats the exact # but boring it .080 over? is their any meat left between the cylinders still?

2 inch would have been best. Smaller pipe was only on their to help it start easier, with the lower compression ratio stock, lots of back pressure helped it.

 

The only reason I tried the .080 option was that the top end had been re-ringed several times and the machine shop ( based on bore measurements ) was not confident that going .050 over would clean it up and get rid of the ring ridge proper . the custom .080 over pistons were more economical than sleeving back to standard, if I remember right the pistons ran about $90.00 each.

There is plenty of beef in the F-Head block for the .080 over, They said that going more would definitely require sleeves. There have been no issues with running hot, It runs right on T-Stat and in fact when not under load a little under.

 

The previous owner of my Jeep put a header on it and I'm looking to replace it with a stock exhaust manifold and then install a new exhaust system. The darn thing came with 72hp when it was new and I can't see how 5 or 10 hp if that much is going to make a major change in the performance.