[fiesta62]

hi, I have a 400 HO, mild cam, 2.5 inch pypes, nothing too serious just street driver, I had a performer manifold on car but wanted to go back to stock as car is mostly factory in show condition, so I re-installed the factory cast manifold and no noticeable power loss so that's good,
but now i have re-installed the cast manifold I have pinging under light load and the car got up to 200 pretty fast, though I have only driven twice and both times were very hot days,
but it looks like the cast manifold has caused the engine to run hotter and ping under light load, the exhaust crossover on the edlebrock performer was blocked off so no heat getting up to carby, the cast manifold exhaust crossover is not blocked so that's causing some extra heat under carb , i can block it but not sure that's going to make all the difference
I am finding it hard to believe the cast manifold would increase temp by 15 degree and cause pinging but it looks like it has....i need to test drive some more but just wondering if others have noticed any difference in temp between the cast manifold and the performer.....thanks

[67GTONUT]

I would recheck your timing.... maybe something got moved with intake swap...

[fiesta62]

well anything is possible but I really doubt it, I did the swap and my car is so show ready it was a very slow and very careful swap....it does seem odd that the cast would cause engine to run hotter and ping, I forgot to mention I did also have a half inch aluminium spacer on the performer, but no spacer on the cast, so the cast has no spacer and exhaust crossover is not blocked and I know both these things help to keep engine cooler, but really I cant imagine it would keep it that much cooler it was only half inch spacer

[Satyr1966]

It's been a long time since I had a '67 but I believe the '67 intake was a one year piece that had weird exposed heat passages under the carb & you had to use a special metal spacer between the intake & the carb. Just wondering if your car has this setup or not. Jerry.

[fiesta62]

yes it has the heat passages that run up to carby and I have not blocked off, I might try that before I possibly re install the performer manifold, but I really don't think it will make that much difference, but maybe worth a try.... I am really seeing a good 10 plus degree rise in temp and can hear the pinging under light load

[Goatracer1]

The manifold MUST have the stainless steel plate between the carb and the manifold.

[fiesta62]

yes I have the stainless plate under carb

[GT182]

Originally Posted by fiesta62

yes I have the stainless plate under carb

Under the carb, or do you meant the exhaust passages under the carb to block the heat from the heads?

[fiesta62]

I have the thin metal plate gasket under carb.....but I do not have the plates blocking of the heat coming up the runners in manifold from the heads.....but after lots of research I decided I will install the performer manifold, not for power but I am pretty confident it will keep car cooler,

[GT182]

I just use the stock Felpro gasket under the carb. Metal will conduct heat from the manifold to the carb and that's not a good idea IMO. You want a cooler carb so the gas doesn't get hot. Cooler gas and air give better performance.

As for blocking the heat from the heads thru the intake runners under the carb, an engine builder told me that the stainless steel plates aren't necessary and a waste of money. The "block-offs" in the Felpro intake gasket kit are all that's needed and work just fine. If you run a stock or electric choke don't use them so the choke works. If you use a manual choke blocked them off as it keeps the carb cooler.

[fiesta62]

no choke....I will install the performer and block off the intake runners under carb, that should make a difference, its been explained to me that the performer gives a much better and equal fuel and air to each cylinder , and the old cast did not so this should help with the heat and pinging issue , you would think and hope edlebrock would not design a manifold that performed worse than the stock cast so I'm betting on the edlebrock performer being better in power and heat reduction.....not to mention its 24 pounds lighter than the stock manifold....fingers crossed

[b-man]

The Performer is equal at best to the stock intake on a near-stock 400, it is in no way superior in performance to a factory iron intake and especially so on a more heavily modified or larger-cube engine.

There are a few aluminum aftermarket 4-barrel intakes that quite simply don't perform as well as the factory Q-jet intakes. The Weiand intakes and the original Edelbrock Torker just don't cut it either and the prices for used units reflect their lack of performance value and unpopularity. Just because a well-known company designs and produces an intake to get their piece of the pie doesn't necessarily mean they've produced a winner, there are plenty of flops out there.

The factory '67 intake with the exhaust passage directly under the carb baseplate was one year deal, they made a mistake that year and corrected it for 1968. The best course of action is to disable the two hot exhaust passages leading up to the carb by tapping them for 1/8 NPT pipe threads plugging them with 1/8 NPT pipe plugs.

[GT182]

Here's the intake gasket set that will block off the heat runner under the carb.... Mr Gasket #502G. Cost is under 20.00. It has the SS plate with it as you can see the SS button in the gasket. I just bought the Mr. G set at my local mom and pop parts store I hang out at.

Link to Summit.... https://www.summitracing.com/parts/mrg-502g
Enlarge the photo and it shows the SS plate.

[goatjunkie]

Thought I would chime in here since I am running a stock '67 manifold with stock Q-Jet, I did block the heat ports at the heads and no problems whatsoever. Engine temp 185- 190 sometimes touches on 200 when it's hot. No pinging either.
However, I am now thinking of pulling manifold back off and opening up the heat passages but blocking the passage under the carb as b-man talks of. I don't have a choke and would like to put the factory choke back on because it's a hassle starting when cold. If I leave the ports open at the head but block the under carb ports, will I still get some heat to get choke to work half way proper? Looks like there will still be plenty of heat under the choke thermostat.
I know it sounds crazy to add heat but I did not want to run a manual choke because I restored engine compartment back to original and thought original choke would look better than manual, if you guys think it's a bad move for sure let me know, then I guess I'll go back to the manual choke cable I had before I restored this goat.

[b-man]

The choke will work as intended after plugging the two small ports leading to the carb baseplate. Every '67 GTO intake needs this easy mod in my opinion, exhaust gasses directly under the carb was a bad idea.

[GT182]

Originally Posted by b-man

Every '67 GTO intake needs this easy mod in my opinion, exhaust gasses directly under the carb was a bad idea.

What about the 389s? And was this only for 67s, or includes the years that followed too?

[67GTONUT]

Originally Posted by GT182

What about the 389s? And was this only for 67s, or includes the years that followed too?

67 only manifold......

I removed mine and installed a 68 intake....

[b-man]

Only 1967 Q-jet intakes.

[Frank R]

The thermostat might be the difference between the two. Try installing an 160 degree one.

[GT182]

Thanks Troy and Bart.