New headers, lower top end

1strodeo

Well-known member
Supporter 2019
Installed CI headers and thrush turbo mufflers, ran dual exhaust out in front of rear tires, sounds great!! But took it on 2 mile stretch of highway and ALL she had was 65mph on level ground!! Stock manifold and single exhaust I could hit 75 if I wanted to, always held her below 70 for safety reasons. Also I keep blowing exhaust manifold gaskets between 3-4 exhaust ports, will the Clifford wedge help with that? Or is it a matter of manifold vs header mating surface? Thanks
 
1strodeo":3mdx7zcd said:
...Also I keep blowing exhaust manifold gaskets between 3-4 exhaust ports, will the Clifford wedge help with that? Or is it a matter of manifold vs header mating surface? Thanks
Yes, I believe so. That's the only (proven?) advantage in my mind (no 1 has been able to document a power increase frm the port divider it'self). It DOES get the hole down to match the others ~ 1 inch sq design & direct the hot gasses tho. I'm finding (this wkend) that there's more hand work to fitting the thing than I understood. I've been using a straight sided burr on both the head and the 'wedge' as U call it. Cleaning up the groves in the exhaust to slide in the divider & grinding down the shape & sides of the divider to slide into the port…

I thought it would fit easier and the most work would be on bringing the "T" surface down to match the port's surface to-mate the-header flange. Ol arthritic hands gave out but I am gettin close to that final step.
 
I put in studs with long bronze nuts when I rebuilt my engine and I've tightened them three times now in 600 miles. I just did it and each time the middle turned the most and easy. I'm tying to avoid blowing the gasket out by keeping an eye or wrench on it. I haven't had leaks yet. I was surprised they still needed snugged the last time after 500 miles. Always the middle needs the most and the very outsides need next to none. Stock manifold. With any exhaust gasket on any engine they need to be heat cycled and tightened cold a couple of times. Cast iron is more forgiving b/c it mimic's the block's thermal characteristics. When we would replace cast wet manifolds on mercruisers we would retorque them at least once and it worked. But I always felt like they would like another. But it wasn't a problem. Headers on any engine are notorious for needing re-torqued forever. The 3-4 hole with 3 bolts and narrow faying surfaces, in general, across all of the ports on these heads makes it harder to get a good seal. It should hold if they're both flat and it isn't loose. That's the story and I'm sticking to it.
 
1strodeo":1kldkja6 said:
Installed CI headers and thrush turbo mufflers, ran dual exhaust out in front of rear tires, sounds great!! But took it on 2 mile stretch of highway and ALL she had was 65mph on level ground!! Stock manifold and single exhaust I could hit 75 if I wanted to, always held her below 70 for safety reasons. Also I keep blowing exhaust manifold gaskets between 3-4 exhaust ports, will the Clifford wedge help with that? Or is it a matter of manifold vs header mating surface? Thanks

You will probally need to do some retuning as the headers are more efficient and usally require a jetting change. Good luck :nod:
 
The exhaust manifold surface of the head may have needed surfaced.

Yes tweaking the carb most likely needed but too large of an exhaust is another issue. Dual 2" can easily be to large especially on a rather mild build. Running close to 200 HP in a 200 found equal length dual outlet headers ran best making my own very long smooth Y pipe merged into a RH exhaust from a Boss 302 worked best.
 
Hi, good advice so far. Just put a heat cycle in it and snug them down. Check timing. Run it without the air cleaner. A plenum spacer under the carb can make the engine act as though there is a bigger carb. Now you may be running lean so be careful at wide open throttle. Check a couple plugs after your test flight. Good luck
 
HOwdy Back 1st rodeo and all:

I'm trying to recall, is this on the original, tired 170 engine or ????. What carb are you using on this road test? Any other changes along with the header/exhaust install? You do your plugs look? What is your initial timining set at on the DS II ignition?

Yes, both truing the mating surface of the exhaust manifold and using the port divider will help with sealing. Retightening after heat cycling will likely be necessary. Also tighten the manifold/header from the inside/ middle bolts to the outside/ends will help too.

Keep it coming.

Adios, David
 
Thanks to each and all...it is in fact the '66 170 that is most likely original to the vehicle. All I know about the engine for sure is that all cylinders measure 115-120 psi, I think they measure 150+ original/after rebuild?? but I'm thinking 120 is respectable enough to keep running it. Anyway yes I only did the header mod, I like to do things one at a time to see what happens. Everything mentioned thus far makes sense. Next will be the Offy install...maybe I shoulda just included this in that thread...oops
 
The CI headers have a 1 5/8" primary pipes which are too large for a 170 & a 200 with an iron head. A 200 with a CI head with mods can handle that size.
You really need headers with a 1 1/2" primaries, like Hooker Headers full length primaries.
You need to check your A/F ratio for being too lean.
As CZLN6 stated keep checking header bolts from the inside to the end many time during the first week of use till the header gasket seats.
Otherwise you need to use felpro or Hooker header gaskets.
 
wsa111":3iqept29 said:
...Otherwise you need to use felpro or Hooker header gaskets.
What about Mike's "special" gasket.
Matt sent me the original and a 'special' one.
Treat that any different?
Y is it so much better?
 
chad":1bhkqhdm said:
wsa111":1bhkqhdm said:
...Otherwise you need to use felpro or Hooker header gaskets.
What about Mike's "special" gasket.
Matt sent me the original and a 'special' one.
Treat that any different?
Y is it so much better?
You tell me, I have Hooker Headers & their gaskets are excellent.
Mike might have used Corteco or had a special one make.
Post a picture of those 2 gaskets you mentioned.
Either the problem is not tightening many times after installation, header flange not true, or a gasket problem??
 
chad":1xvkb0hn said:
wsa111":1xvkb0hn said:
...Otherwise you need to use felpro or Hooker header gaskets.
What about Mike's "special" gasket.
Matt sent me the original and a 'special' one.
Treat that any different?
Y is it so much better?

I did talk to Matt about the 2 gaskets (I didn't take a pic) he said it was one that Mike found/designed/made in the past that worked better than the one they came with, which was usually damaged in shipment anyway, so he includes one of "Mike's" gaskets in each box. This is the one I used, but I tried to re-use it and that may be part of the problem.

Where can I order the Hooker gaskets?
 
1strodeo":3fghqeoc said:
Where can I order the Hooker gaskets?
summit, jegs, performance parts.
Just make sure it's for the right motor/headers.
 
Do you do much off roading and if so what kind of terrain? If you frequently drive on very steep dirt roads with loose rocks the transition from 1 carb to 3 when pressing on the gas could cause some excitement when you don't want it.
But it would be fun on pavement.
 
bmbm40":1uh6nzwz said:
Do you do much off roading and if so what kind of terrain? If you frequently drive on very steep dirt roads with loose rocks the transition from 1 carb to 3 when pressing on the gas could cause some excitement when you don't want it.
But it would be fun on pavement.

Nope will be pretty much all pavement, but hopefully if I do off road I'll get a reminder to disconnect the linkage before I get into trouble
 
What are the details on your ignition system? In addition to rejetting or new carbs a custom curved DSII might be what you need to get the most out of what you have.
 
I have a DS ignition system out of a combination of 78-79 Fairmonts, 1100 currently on engine is SCV so vacuum lines are all plugged...carbs I'm rebuilding are non-SCV sooo

One guy on the bronco site suggested using vacuum to open the secondary carbs?? Anyone done that?
 
Here are pics of each plug, not purty...thoughts? What causes the oil on (some of) the threads? bad oil ring? that wouldn't make sense because the oil seems to be more on the outer threads vs the combustion chamber end. Pics are in reverse order, starting with #6 thanks

PS for the record I increased the gap to .050" when I installed the duraspark...too much?

Jeff
 

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Oil often comes from a leaky valve cover gasket on plug threads. Looks also like you have too much total timing. The ground strap should turn dark half way through the curve (not past it) indicates proper total timing.

How many miles are on the engine how many on the plugs?
 
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