Oldster65

Last weekend, the 425 Super Rocket in my survivor 17k mile 1965 Delta 88 ignited again after 30 years. It runs amazingly well - except for the "pfft pfft pfft pfft" exhaust leak from the missing inner bushings in the heat riser valve.



The "65 has the heat riser valve integrated into the manifold. I was pleased when I saw the valve in what I thought was operational condition, but when I heard the leak, I removed the manifold to inspect and see what was needed to repair. What really surprises me is that while the (brass?) part of the bushing is intact. the inner part on both sides is completely gone after just 17k miles (is it ceramic/asbestos?). This proves (as we all know) that these things just do not last and are almost always removed or wired open.

The white part shown here on these new bushing is just gone in mine (picture from web search)

This has me in a bit of a conundrum. I really wanted this car to be 100% original. I also want to drive it (to shows, on Sundays, etc.). So here are my apparent options:

1. Buy a NOS bushing and heat riser valve kit -- for $100 to $200 if can find -- and somewhat painstakingly R&R the heat riser valve to make it work as new...and expect failure of the valve relatively soon down the road.
or
2. Remove and cap (braze) the old valve in a way that "could" be restored in the future. And drive the car without a second thought about the heat riser or exhaust leaks.

I live in California as the car has forever, so cold start and quicker warm up is not an issue.

I am 95% leaning on option 2. Any advice, or reasons to talk me into option 1?
(Also adding pics for future reference.)


1965 Olds Delta 88 425ci - LH manifold w/ heat riser valve

1965 Olds Delta 88 425ci - LH manifold heat riser valve

v8al

I am going to suggest option 1 and 2 which is option 3 and do some self promoting

3. Put original manifold on shelf and look for kit to repair at your leisure. Purchase my manifold and perform option 2 on it.

Seriously though pick up a spare manifold and do option 2.

droldsmorland

Agreed...gut it weld the holes. Then weld in crossover block-off plugs into the intake. Manifold paint will never burn off and hot start boil-offs are eliminated.
Painted this intake around 20 years ago.

Olds64

I moved the posts to a new thread. Hopefully you'll get more traffic this way.

I think you should delete the valve. I had one in the exhaust manifold of my 64 98. I just knocked out the valve plate and left the shaft in the manifold.

oldcutlass

Those goofy valves have been a headache for decades and the car will run fine without it. If you want the car to look stock just weld the arm in the open position.

joe_padavano

If you don't ever plan to drive the car in freezing weather, you can eliminate the heat riser valve. Blocking the crossover in the intake is worthless unless you are drag racing the car and need every tenth of a second ET reduction.

Sugar Bear

On a 58 year old car with 17K miles I'd do my best to keep it original and regularly maintain the valve. If it wasn't for the preservation aspect I'd disable the valve.

Good luck!!!

droldsmorland

I modified the divorced choke to lighten the spring tension. It takes a minute or two longer to open, but it works just fine.
It takes a few more revolutions to start but IMO I like to see the oil pressure before it fires off.
I haven't had a single negative problem eliminating all this crap and blocking off the crossover. I am searching to extract every last ounce of torque.
Sure it's cold-blooded but it's a summer car.
+ Plugs are nice and tan
+ Colder denser AF charge
+ Can run more timing
+ It effortlessly hot starts on the hottest most humid days
+ Solved 100% of hot start boil-over bs
+ Runs sooo much better in 90* heat
+ No more burnt intake paint
+ Unseen modification
- Not a good winter car.... bummer :^(

joe_padavano

Other than the burnt paint, I can say all of that about my cars without the crossover blocked. The change in density likely can't be measured. A/F won't change if the carb is jetted correctly. I don't have hot start or percolation problems, and my cars run perfectly fine in mid-atlantic 90 deg/90% summer weather. Oh, and they DO run well in the cold. But I'm sure your butt dyno registers a huge improvement.

Oldster65

What great input.

Here's my thought now, Option 4, I guess. I just *really* like the idea of keeping the original external parts in working order, but removing the risk of the flap causing flow issues. I also find myself on a bit of a budget right now. I'm going to start by removing the flapper to get the weight, bi-metal spring and shaft out, with the intent of installing new bushings but leaving the flapper out. There are many sources and sizes of bushings available, so I'll clean up the original shaft which is in fair condition and see about getting solid bushings to press into the manifold. Since it's the flapper valve that holds everything in place, I'll cross that bridge when I get there - maybe just weld a little stop on the shaft or drill a hole thru it for a small roll pin. All pretty basic work and low cost - and no visible alterations - WDYT?

JohnnyBs68S

I think my dad disabled every valve like this on every car he owned that had one. The most simple way to do it is to un-hook the spring from the pin on the manifold to relive its tension and let the weight hold the butterfly open. All parts remain intact in case you want to "re-activate" it. Dad did this on my '68 back in the '70s before I owned it and it remains that way today.

Oldster65

Thanks - and I would be all over this quick solution -- but the only thing wrong with mine is the inner parts of the bushings are completely gone (disintegrated) - so there is an exhaust leak. I need to get to the bushings...so might as well just remove the flap.

Koda

I think the best of all worlds is to repair it to original, then unhook it. It can always be hooked back up in case of planned winter trip.

Koda

When that valve is closed, I'm thinking that 90% or so goes through the crossover. When it opens, I'd think it would be the opposite, if even that much. I would think, assuming a V engine of equal performance on both heads in terms of exhaust outflow, that there would be effectively zero airflow across the crossover once the valve opens. Convection heat transfer would stop and you'd pick up more conductive heat transfer through the iron than up the non-moving air column. I'm not sure how much cooler a blocked off crossover would make an engine, compared to the same engine, same conditions, with open crossover, once engine is fully hot.

Oldster65

I decided to restore the manifold to full functional status so this Olds remains 99% original. I replaced the 3 bushings with NOS and just tack welded the old valve flap back to the original rod in the same place. Works perfectly fine for the time being. Opens when hot and the "cold" start (for CA) is very smooth and seamless. Pump the pedal once, engine starts and runs great until the cold light goes out.

Ground off spot welds

2 new (NOS) bushings tapped in smoothly

Two bushings on this nearest side, one on the far side.

tack welds the original flap back in place

ready to re-install - bi-metal spring works great (still)

VC455

That is possible.

However, think about that sharp exhaust pulse coming out of the center valves on each side. That pulse could flow through the three areas open to it (one through its exhaust manifold, one through its neighbor's exhaust manifold, and one under the carb to the opposite exhaust manifold).

My experience on my first Vista Cruiser was...

I had aluminum poured into the center two exhaust ports before I ported the heads. After porting, I drilled a 1/2" exhaust hole through the aluminum and had enough heat for smooth winter warm up at -20° and no heating problems during 90° summer days.

That's why I suspect there is still significant heat transferred under the intake in spite of an open riser valve.

GCH

Very intresting , wrote a thread in the big block part of CO . Should unhook the spring. Thanks for nice pics of the manifold.

droldsmorland

If the spring is removed so should the valve and its shaft. Weld up the holes. Then block off the crossover in the intake.

joe_padavano

Note that starting with the 1970 model year, Olds no longer used the heat riser valve. Blocking the crossover is a lot of work for no gain on an otherwise stock, street-driven motor. You'll never see the difference (though I'm sure the butt dyno will show a 20 HP improvement...).

On a dedicated drag car where you jet the carb to make the most of the plugged crossover, that's a different story. Stock class cars need every hundredth of a second.

GCH

Your intake manifold looks great after 20 year , i was under the car this morning and unhook the bimetal spring
and secure the weight with a wire. Would like to remove shaft and valve but donīt take the chance of breaking
any bolt now when we have fun with the car. Better to check this in winter when car is parked.

FStanley

further info here:

https://classicoldsmobile.com/forums...e-heat-105434/