[Ronj1969]

Just replaced my head gasket completely reassembled my engine with new gaskets and started it up it appears the I have a massive air leak coming from the exhaust crossover. The Intake gaskets came with what looked like 2 exhaust crossover block offs. When installing decided to not use them as I didn’t use them on the last time a pulled the intake Here are the pics. Should I have left these block offs in there even thought they were thicker than the actual gasket which is why I chose to not use them ?

[Sirrotica]

What year heads, and what year intake?

You appear to have a early intake on late heads. There is a mismatch that will show up as an exhaust leak at the junction.

[Formulas]

See where i drew the blue line? The crossover hole in your intake is bridging over this divide and leaking, The top hole above the blue line is a dead area, Most people fill in the head or use a block off plate / shim.. Something like the second pic is going on if you hear noise

[PontiacHO]

Sure wished I would have used block off plates. Now I’m boiling fuel in my Quadrajet.

[Ronj1969]

So I’m using a 1977 intake on a set of 1969 number 62 heads the original gasket set came with two pieces that were used to block off that port however, those two pieces were a little thicker than the actual gasket so I thought it might cause an issue when I torque the gasket down there’d be a leak there. The engine hasLess than a minute of runtime is it too late to add the shims and keep the gasket that’s on there or do I just start over if I need to start over? What year of gaskets do I need to get to correct the issue?

[Sirrotica]

You can use a 65-71 intake on the #62 heads without a mismatch problem, or the aftermarket aluminum intakes will fit both early or late heads without a problem.

Then of course you can block the heat crossover with plates, but that renders the choke inoperative. To handle that problem there are electric choke stats that can be adapted. The supplied block offs will eventually burn through and you'll be back to square one. On race cars I have cut my own plates from sheet stainless steel, but driving a car on the street without the crossover heat can be miserable in cold weather.

Personally I prefer to keep the heat crossover operative with a hot air choke, but you can handle the mismatch which ever way you'd like to.

In your situation I have linked to an article that states if you have a late intake on early heads you can use a late gasket set to seal it without resorting to block off plates.

Link to Wallace Racing explaining the mismatch problem, and how to solve it with iron factory intakes:

http://www.wallaceracing.com/intake-crossover.html

I believe this article will answer your questions.

[Formulas]

Take a pic of you head numbers on the center ex ports and please post it

[Kenth]

1977 intakes will fit any 1965-79 heads using 1972 and later intake gaskets.

[b-man]

Originally Posted by PontiacHO

Sure wished I would have used block off plates. Now I’m boiling fuel in my Quadrajet.

I would try the carb insulator gasket first.

I’m having no fuel boiling issues with my 421 with a fully operational exhaust crossover and hot air choke. I’m using .280” thick phenolic insulators with gaskets on both sides between the 3 carbs and the intake.

[Formulas]

One picture is an early head such as a #62 the actual crossover goes up to a little over mid point of the intake port and lower than the crankcase passage holes

then look at OPs pics the top of his intake at crossover is a tad below top of port IE should cover crossover in head also as i have marked up with blue arrow way above top of ports seems to be a void not associated with early heads but is there on 6X and variants... Either i am out to lunch or something is amiss because OPs pic seems the opposite stated used parts... I do like to eat so i am not worried either way

Or is what appears to be a void a blown out gasket piece?

[unruhjonny]

Originally Posted by Ronj1969

So I’m using a 1977 intake on a set of 1969 number 62...

My knee-jerk reaction is that you should use the later intake gasket;
The only difference is the crossover area;
I have seen some aftermarket generic intake gaskets (maybe they were old stock) that had a small circular hole for the crossover - which appeared to allow mixing and matching of intake vs heads...

I think I had this scenario when I owned my brother's '73 Formula - I had a '77 (W72) 400 shortblock, with '69-62 heads, and a '72 intake manifold.

I will look into this - because I want to know...

[Singleton]

Some gasket sets come with a block-off and one that is open. If you don’t have the open plate, you could cut-out the area needed. But you must use one or the other with that type gasket set.. Or use the 72-79 gasket that has been mentioned.

[Sirrotica]

The link I posted to John Wallace's site show pictures of all the variants of exhaust crossovers, pictures of the gaskets needed, and what is needed to interchange iron intakes early and late, with early and late iron heads. If you look at that link it should all become clear how to make the interchange work...........

Here's the link again:

http://www.wallaceracing.com/intake-crossover.html