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Fel-Pro B20 Head Gasket Crushed Height

vintagewrench

vintagewrench

Active member
Joined
May 9, 2016
Location
Paradise
I am in the process of rebuilding a B18 and will bore and hone it here in the shop to a B20 standard bore size, use B18 rods, an "F" head.

Have rebuilt many engines and have always used Fel-Pro gasket sets whenever possible because to their quality and sealing ability.

The head gasket is .045 thick and I am wondering if anyone might know the crushed height of one of these gaskets?

What would be the ideal squish band height for this combo assuming that the pistons I have not gotten yet are even with the deck height?

Thanks in advance for any help you can give me.
 
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From what I've gathered, .030-.035 is the tight squish band you're looking for for an N/A motor.
If you want to play the tight tolerance game, get a cometic HG - they make them in a few KNOWN crush thicknesses and are ~100 each from Summitracing.
 
Thanks, I have learned about the same things that you have, and am in the process of ordering a set of JE forged pistons in low-expansion alloy with coated skirts with an extra .040 added to the top; that way I can face them to the right height in my lathe or milling machine. This is the reason for asking if anyone knows the crushed height of one of these gaskets.

The crankshaft to head deck distance front and rear will also be measured and corrected if necessary.
 
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runslikeapenguin said:
Crushed standard head gaskets are approximately .040"

This is the subject of much debate BTW
Some say .042, some say .032.
Click to expand...

There are many different head gaskets. You'll want one for the higher compression engines (E specifically or the B...but measure that one). The 0.045 is not enough squish unless you're coming out of the bores by over 0.010.
 
If you're planning on using an F head, you'll need to use the appropriate gasket and I don't think Fel-Pro makes them any more. The larger intake valve and subsequent larger combustion chamber to un-shroud the valve requires the head gasket to have a bump in the fire ring.

I've always used Elring gaskets, so I can't say what the compressed thickness of a Fel-Pro is. The 2 Elring head gaskets for FI cars are 1.2mm & .8mm uncompressed and 1.0mm & .7mm compressed.
 
If you do go the Cometic route, keep in mind they make everything to order. It took 10 days to get a Ford FE HG for a client last month.
 
Canuck said:
There are many different head gaskets. You'll want one for the higher compression engines (E specifically or the B...but measure that one). The 0.045 is not enough squish unless you're coming out of the bores by over 0.010.
Click to expand...

Thanks Craig for your input - my thought is the .045 gasket may compress .005-.010? Since the plan is to have new pistons made to suit the combo and they will likely end up being even with the deck height and it will end up with a squish band of somewhere around .035?

Fel-Pro has a great tech line and I am going to try to find out the compressed thickness of the gaskets today and go from there.

hiperfauto said:
If you're planning on using an F head, you'll need to use the appropriate gasket and I don't think Fel-Pro makes them any more. The larger intake valve and subsequent larger combustion chamber to un-shroud the valve requires the head gasket to have a bump in the fire ring.

I've always used Elring gaskets, so I can't say what the compressed thickness of a Fel-Pro is. The 2 Elring head gaskets for FI cars are 1.2mm & .8mm uncompressed and 1.0mm & .7mm compressed.
Click to expand...

Thanks Ian for the Elring info - the gasket does not have the bump you mention, but there is enough room to un-shroud the valves somewhat on either side of the spark plug. I will check out the Elring gaskets also, both you and Cameron at Volvorelix have recommended them.
 
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Another happy Cometic user here. I have an over-bored B20 block, using B21 pistons, and a reshaped cylinder head (scavenging some CC's back from an overzealously shaved R-Sport head), and I use 93mm bore B20 gaskets. The pistons are even with the deck, and a .036 MLS gasket doesn't compress at all, so you get a very precise placement of the head vs. the pistons at TDC.
 
vintagewrench said:
Thanks Craig for your input - my thought is the .045 gasket may compress .005-.010?
Click to expand...

how squishy you think they are??

Never done a B20 but the b230 Elring gaskets are 1.2mm compressed. Same as this everyone said "no one really knows for sure" so I called Elring and the head of engineering there seemed to know pretty well...

I targeted .035" squish on my engine build.
 
You can contact Fel-Pro directly either on line or thru their tech line (you can Google for the number). I've found them to be really helpful and I'm pretty sure that the compressed thickness is a standard measurement that they can provide.

Dan
 
Dan, Thanks, I called them earlier in the morning and the tech stated that this type of gasket only crushes .003" to .004" max and that leaves the squish band too wide at .042"-.041. They also no longer make "E" and "F" gaskets.

Ian and Craig and Cameron were all correct about using a Elring B20E head gasket which crushes to 7MM or 0.0275 and I have one on the way from my wholesale engine parts jobber.

Now all I need to do is figure out is where and at what angle to un-shrould the valves, and at the same time also lower the CR from 8.7 to 8.5 due to the supercharger.

This engine needs to produce good low end torque, not high RPM peak horsepower.

Thanks to all for your help!!!
 
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Based on my Diesel turbo experience with Mutt the Race Truck I'd guess that the 0.2 points of compression wouldn't make much difference (though I'm running a ton more CR that you Otto-cycle guys are). I would, however, be sure to make sure you have NO sharp points or edges in the chamber as that will definitely cause preignition with boost.

Dan
 
Dan, Thanks, with a SCR of 8.5:1 and a boost of only 6 psi the effective CR at ignition is 12.0:1, which for most street applications using 93 octane pump gas, the effective compression ratio needs to be kept below about 12.0:1 as a blower boost cart recently published by Hot Rod magazine shows.

Since this is a retro project using only period performance parts at least initially, it will have no electronic means of retarding the spark when needed, so this is why the drop will be beneficial. A two point drop in the SCR ends up being a five point drop at ignition.

Rounding off all of the edges in the chamber is a part of the plan.
 
I ran my b18 with unknown mileage, .040 overbore, c cam, and a b20 f head at 54cc to 8 psi on pump gas using the stock advance curve, no pinging or signs of it when I pulled it. I'd say that as long as the chamber is sorted out well around the spark plugs and blended at the squish pad you should be fine.
 
cwdodson88 said:
I ran my b18 with unknown mileage, .040 overbore, c cam, and a b20 f head at 54cc to 8 psi on pump gas using the stock advance curve, no pinging or signs of it when I pulled it. I'd say that as long as the chamber is sorted out well around the spark plugs and blended at the squish pad you should be fine.
Click to expand...

Thanks, good to hear!

Can you direct me to a source of information to learn more about un-shrouding the valves a bit and what to do around the spark plug?

How is your car coming along?
 
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^^^ That was the shape I used, not the same tool, but they ended up the same volume as each other and looked pretty good. And that build thread was the guide I used... Thanks again for that Canuck. lots of good info from him.
 
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