69 340 heat riser repair

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nutz

nutz

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found 340 hp manifolds ,missing the heat riser dose anyone make a repair kit for them
thanks
 
I don't know if its the correct kit. Your best bet is to look for the part number in the 69 Parts book available for free at mymopar.com then google the part number

Heat Riser Kit 1968-70 340, Exhaust Manifolds/Components, 199-DR085 Reproduction, NOS and Used Mopar Muscle Car Parts

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There is a kit I believe manufactured by a mopar enthusiast in the greater Detroit area. His name is Neil Jenks if I recall correctly and his company is called dynamic revolution. Should come up on a Google search.
 
There were different kits available. The correct application is dependent on the inner diameter of the manifold matching up with the valve.

Here's links to a couple NOS ones to compare to the repops. There's some good info on the Brad's site. Some good pictures on the Ebay listing.

If you're still in doubt, give Mega Parts a call. Every time I've called, they've answered the phone and been helpful.

I only saw B/RB engine valves on Dynamic Revolution's site.

NOS MoPar 1968-70 340 Exhaust Manifold Heat Riser Package 3004574

NOS Mopar 1968 Thru 1970 Hi Perf 340 Exhuast Manifold Heat Riser Kit 3004574 OEM for sale online | eBay
 
I repair them by taking them completely out, then pressing in 2 plugs that I get made at a machine shop! No more stuck flaps, no more rattle, rattle, no more phhht phhht phhht exhaust leaks. :)
 
Its a stock build so keeping it
Helps warm up the choke coil faster
 
I delete them on all my cars, I tap them and screw in stainless button head cap screws. No stuck flappers diverting all the passenger side exhaust through the intake manifold and exhaust leaks at the shaft. With a good valve job and carb, you will never notice the valve is missing.
 
66fs said:
I delete them on all my cars, I tap them and screw in stainless button head cap screws. No stuck flappers diverting all the passenger side exhaust through the intake manifold and exhaust leaks at the shaft. With a good valve job and carb, you will never notice the valve is missing.
Click to expand...
Although the heat riser system is to aid in cold weather warm up and prevent carb icing, that is usually not an issue with our old cars and how we use them. I may start mine once in the winter, but 99% of my driving is in 70-100° weather. My AFB with the electric choke (adjusted properly) and a 10 min warm up works perfectly. I don't start it up and immediately drive away so I don't need any cold drivability systems. Same with the Thermac door in the air cleaner snorkel of the later cars. That is a smarter system than the Heat riser I think.
 
Even on the original AFB choke system you can play/adjust the pull off gap, idle speed, and spring setting on the choke and pretty much warm it up for a couple minutes and drive off. I used to live in South Dakota, and it took a while adjusting but it was that good.
 
Modern fuels percolate and boil over causing hard starts after shut down when hot. By keeping a heat riser in exhaust manifold and keeping heat cross overs open in intake manifold your gonna have excessive fuel percolation and fuel boil overs. You don't need a choke unless your driving in middle of Canada in the winter. Blocking heat cross overs in intake manifold removing or wiring open choke engine will run much better and have a lot less problems too.
 
Last edited:
340sFastback said:
Modern fuels percolate and boil over causing hard starts after shut down when hot. By keeping a heat riser in exhaust manifold and keeping heat cross overs open in intake manifold your gonna have excessive fuel percolation and fuel boil overs. You don't need a choke unless your driving in middle of Canada in the winter. Blocking heat cross overs in intake manifold removing or wiring open choke engine will run much better and have a lot off problems too.
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The next time I have the intake off of mine the passage ways will get blocked.
 
On my 69 273 2 bl
It had a horrible hesitation
It turned out to be the cross over was clogged and on quick acceleration the fuel would puddle and hesitate
I tried everything till I cleaned the passage
Ran great cold when the choke was still on
I know most carbs with a good stream on the accelerator it vaporized in the intake without heat
But this made a big difference
Yes the heat riser isn't critical and not going to make much of a change and will most likely loose some power
Just want it to be as the Mopar gods created it
Makes it easier to tune
Don't want to be hunting ghost performance problems
 

toolmanmike said:
Although the heat riser system is to aid in cold weather warm up and prevent carb icing, that is usually not an issue with our old cars and how we use them. I may start mine once in the winter, but 99% of my driving is in 70-100° weather
Click to expand...
I agree with this!

my heat riser valve spring is MIA but the flapper is free to turn. so it tends to stay in the open position due to the weight. I DRIVE my car 12 months out of the year here in northern Colorado, -10 was my coldest, the garage gets to about 30-35deg 3-4 pumps crank crank, 1-2 pump crank crank and varoom. It stays running no issue while I get fluid back up into the trans in N for a few seconds then put it in reverse. Occasionally I have to feather the gas a bit but once out of the drive way I'm good to go. I'm sure the OEM design is for best driving experience etc. so the little old lady from Pasadena would not have any issues doing her burnouts out the driveway!

Moral to the story, nice to have but not necessary 98% of the time.
 
Don't think it maters on a 69 340 cause it doesn't have the heat riser on the air filter
But carb icing is normally at 40 deg and high humidity
I guess it cause at below freezing no humidity
 
Oh and I haven't even driven my car with the top up yet ........
So it's more of having it all stock and working the way it was built
 
nutz said:
Don't think it maters on a 69 340 cause it doesn't have the heat riser on the air filter
But carb icing is normally at 40 deg and high humidity
I guess it cause at below freezing no humidity
Click to expand...
The Thermac door on the air cleaner snorkel (if it has one) has nothing to do with the heat riser.
 
nutz said:
On my 69 273 2 bl
It had a horrible hesitation
It turned out to be the cross over was clogged and on quick acceleration the fuel would puddle and hesitate
I tried everything till I cleaned the passage
Ran great cold when the choke was still on
I know most carbs with a good stream on the accelerator it vaporized in the intake without heat
But this made a big difference
Yes the heat riser isn't critical and not going to make much of a change and will most likely loose some power
Just want it to be as the Mopar gods created it
Makes it easier to tune
Don't want to be hunting ghost performance problems
Click to expand...

Exhaust will still go through the intake. It just won't be forced to go that way.
 
Yea I get it .....
On my slant 6 shop truck I'm not playing with it
I just wouldn't sleep at night if it wasn't there on my baby.....
 
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