Can someone explain heat crossover to me?

Posted By: roe

Can someone explain heat crossover to me? - 04/30/13 02:06 AM

Ive seen it mentioned where its something to block off when doing an intake manifold gasket, IIRC, as it helps to prevent excess heat to the manifold and reduce chances of percolating fuel in the carb. What are the steps to block this off, and where exactly is it located? Im getting ready to do my intake gasket over and if it applies to me, I'd like to block this thing off while im doing this.

roe

Posted By: m88mark

Re: Can someone explain heat crossover to me? - 04/30/13 02:25 AM

Get a gasket with the crossover blocked, Felpro 1215 for BB. Need elec choke if it's cold.

Posted By: scratchnfotraction

Re: Can someone explain heat crossover to me? - 04/30/13 03:10 AM

the function of the cross over is to heat the floor of intake for better atomazation/vaporizing of the airfuel mixture to increase cold weather drivabilty.

yes,it will help with fuel perking in the carb, but it can also make it run ruff/rich while cold untill it gets up to operating temps.

it also does what the old H-pipes in the exhaust did. even out the exhast pulse between the cys and helps with scavaging of the exhaust ports. (this is why the sound of the exhast system will change when you block them giving a deeper more divided sound of the cyls at duel pipe ends.) check that out when you block them, listen close before and after.

IIRC i used the metal shell of a radio

I cut 2 oval shaped pieces and trimed to cover the hole in the head with out covering the 1/2 moon shaped hole you see when intake is inplace.

you do not want them too thick,the intake bolts will keep working loose around the center of intake. but not so thin it will burn thru over time.

i just used copper rtv to glue them to the head and placed the fel-pro 1213 gaskets with the cross over blocked on top of the blockoffs.

the gasket alone will burn thru in short order every time.

MP used to sell a kit with SS plates,I still have them,to me they seem a little thick, bolts kept coming loose,I would have to re-torque the 4 center bolts around the heat cross over every 3-6 months.

IIRC,the radio shell was just the right thickness and ez to trim with metal/tin snips.

when you pull the intake you will see the oval hole and the 1/2 moon shaped hole. just trim them to cover the oval hole.

another trick I did one day R&R the intake was to trim both VC along the edge of intake runners so I could pull the intake without pulling the VC. clearance them just enuff the intake clears the VC lip.

sometimes you have to trim cast alum VC in the same place so they will seal the gasket by not hanging up on the intake runners. same idea for fast R&R of intake.

now is a good time to check/replace the o-ring on dist and check the oil line/ferrel/fitting for the gauge.

Posted By: roe

Re: Can someone explain heat crossover to me? - 04/30/13 04:04 AM

Very nice info. I had already picked up a set of Felpro gaskets part# MS90109, which I believe doesnt have the heat crossover blocked. Right at the center point of the gasket, there is an oval and a half moon shaped openings. The oval opening right there with the half moon shaped opening is the one I need to block if Im traking correctly. Right?

Also, one side of the gasket has a ridge built into it. Does this ridge need to face the head surface or the intake surface when I replace the gasket?

roe

Posted By: RonaldV

Re: Can someone explain heat crossover to me? - 04/30/13 05:39 AM

I blocked mine off cutting a piece from an aluminum pop can.

If you do this, make sure its mountain dew.

Fish

Posted By: scratchnfotraction

Re: Can someone explain heat crossover to me? - 04/30/13 01:17 PM

Quote:

Very nice info. I had already picked up a set of Felpro gaskets part# MS90109, which I believe doesnt have the heat crossover blocked. Right at the center point of the gasket, there is an oval and a half moon shaped openings. The oval opening right there with the half moon shaped opening is the one I need to block if Im traking correctly. Right?

Also, one side of the gasket has a ridge built into it. Does this ridge need to face the head surface or the intake surface when I replace the gasket?

roe

correct, ovel hole under 1/2 moon shaped hole.

I always put the ridge up towards the intake. I put them on dry the first time. I have reused felpro intake gaskets up to 3x with a little rtv around the water ports after first install dry.

Posted By: roe

Re: Can someone explain heat crossover to me? - 04/30/13 04:30 PM

Quote:

I put them on dry the first time. I have reused felpro intake gaskets up to 3x with a little rtv around the water ports after first install dry.

Are you saying that you put the gasket on dry and then torque down and run the motor that way? And then if you ever have to remove the intake at a later date you reuse the gasket and just add a rtv to the water ports? So no rtv around your water on the initial use and you get good sealing results? If so, I'll give that a shot.

roe

Posted By: roe

Re: Can someone explain heat crossover to me? - 04/30/13 06:00 PM

Quote:

I blocked mine off cutting a piece from an aluminum pop can.

If you do this, make sure its mountain dew.

Fish

Is a mountain dew can made of something different than say, a coke can?

Posted By: SomeCarGuy

Re: Can someone explain heat crossover to me? - 04/30/13 06:34 PM

You might look into a shield to block oil coming up and splashing on the bottom of the intake. That would cut some heat down for you much like this project will.

Mountain Dew cans are made of a special alloy that is patented.

Posted By: scratchnfotraction

Re: Can someone explain heat crossover to me? - 04/30/13 08:14 PM

Quote:

Quote:

I put them on dry the first time. I have reused felpro intake gaskets up to 3x with a little rtv around the water ports after first install dry.

Are you saying that you put the gasket on dry and then torque down and run the motor that way? And then if you ever have to remove the intake at a later date you reuse the gasket and just add a rtv to the water ports? So no rtv around your water on the initial use and you get good sealing results? If so, I'll give that a shot.

roe

correct.

I do wipe block end rails/head gasket surface/intake gasket surface down with brake clean on a rag and let air dry.

I do use the rtv in the 4 corners with a very thin coat on the endrail gaskets bottom side only.(so intake does not stick for removal later)

torque the intake in steps feeling with fingers that the end rail gaskets do not slide out of place. you can push them in with fingers if they move outward on you by going slow on the torque/steps.

I like to have the dist re-moved so I can feel the endrail gaskets with my fingers till it is torqued down good. and gives room for throttle brackets/bolts as they need to be in place before torque.

only re-use them if it has not be very long and providing they dont tear any around the ports. I just sometimes spray them with WD-40 and use rtv in the 4 corners only. depends on the condition of the used gaskets.

all the block offs I made from alum soda cans burnt thru before to long.

a lid from a larger bean can will work if it has no ripples/ridges in the center of lid and bigger than the exhaust port.

Posted By: roe

Re: Can someone explain heat crossover to me? - 04/30/13 08:43 PM

Thanks for the tips. In about a month I will have some free time and will be installing headers, recurved dizzy, blocking the heat crossover, and tuning the carb. I think I'll be very happy with the results.

roe