Angle plug 492 heads

[383Nova]

I have a virgin set of 492 angle plug castings that I am working on. No previous porting/oversize valve job.

This is going to be used in a 70's styled "day 2" type of build, so no "modern" performance parts are going on this engine.

I am looking for any short comings to using a 2.055"/1.60" valve package in the head.

Will the short turn be a problem with the 2.055" valve & the bowl sized @ 90% (1.850")?

While I am not trying to set the heads on "kill", I do want to produce a fair amount of airflow (250+ cfm).

Thanks in advance.

[F-BIRD'88]

Increased chance of a crack between the seats if beyond 2.02". Less meat. Not nessessary to get 250+ cfm.

[Carnut1]

I have a virgin set of 492 angle plug castings that I am working on. No previous porting/oversize valve job.

This is going to be used in a 70's styled "day 2" type of build, so no "modern" performance parts are going on this engine.

I am looking for any short comings to using a 2.055"/1.60" valve package in the head.

Will the short turn be a problem with the 2.055" valve & the bowl sized @ 90% (1.850")?

While I am not trying to set the heads on "kill", I do want to produce a fair amount of airflow (250+ cfm).

Thanks in advance.

I have a set of 492 angle plug "Crane Fireball" castings. They are quite a bit heavier than my 041x heads I was recently working on. I never had an issue going to a 2.055 i fuelies but supposedly they have a cracking issue . Bowls can get thin so sonic them.

[maxracesoftware]

I have a virgin set of 492 angle plug castings that I am working on. No previous porting/oversize valve job.

This is going to be used in a 70's styled "day 2" type of build, so no "modern" performance parts are going on this engine.

I am looking for any short comings to using a 2.055"/1.60" valve package in the head.

Will the short turn be a problem with the 2.055" valve & the bowl sized @ 90% (1.850")?

While I am not trying to set the heads on "kill", I do want to produce a fair amount of airflow (250+ cfm).

Thanks in advance.

i Ported a pretty good flowing pair of those #492 angle plug castings
from memory , 2.055/1.600 valve combo
a few potential problems is you cannot enlarge the Valve Spring seat's diameters more than 1.460 or 1.480" all the way down to factory OEM level
otherwise you will break thru to waterjacket !
to go larger on Spring Seats i modified 1.560" Cutter w/custom corner radius on the blade + a 0.060" thick spring shim used as a stop,
then you use a 0.060" shim when you assemble the Heads

the next real potential bad problem is you need to be very careful when doing a Valve Job on the Intakes at 2.055
just do a 37/45seat/60 degree cuts .. then rest by Hand so that you are very careful to leave enough material
on the Intake Bowl wall between the exhaust bowl ( the Bridge between the two )
otherwise you can end up breaking thru to waterjacket

recommend 37/45/60 or 38/45/60 or 39/45/60 but don't do any 70 or 75 deg or bowl hog cuts
when intalling 2.055" int valve , i would do same things for even a 2.020" int valve
theres waterjacket waiting for you if you are not careful enough !


i'll Post Port pics + Flow Sheet as soon as i find them .

i just noticed this old Post here
viewtopic.php?p=16852#p16852

Fri Jan 20, 2006 2:17 pm

on the ones Pictured on my site

4.000 Bore Flow Fixture @28" (No-Pipe on Exh)
Lift---Intake--Exhaust
.200-139.9--102.9
.300-201.0--140.9
.400-234.2--185.7
.500-242.4--207.1
.550-246.4
.600-250.3--215.6
.650-252.3
.700-253.1-219.8
.750-255.5
.800-256.4

all out will go 283+ CFM
about the same as above on exhaust side


slightly more Flow on 4.030/4.060/or 4.125 Bore Fixtures
and with Pipe on exh side

[mag2555]

Is the throat already at 90%?

On a set of 487x castings with a 1.75” throat ( 2.02” valve)
I hit 254 cfm @.650” .

I had previously reworked a mule 487x head up to 261 cfm @750”, but I did not have the warm and fuzzy’s about it surviving on the street, no less a race motor!

[maxracesoftware]

SBC_492_rare_Angle-Plug_Port_Job_7.jpg

SBC_492_rare_Angle-Plug_Port_Job_6.jpg

SBC_492_rare_Angle-Plug_Port_Job_5.jpg

SBC_492_rare_Angle-Plug_Port_Job_4.jpg

SBC_492_rare_Angle-Plug_Port_Job_3.jpg

SBC_492_rare_Angle-Plug_Port_Job_2.jpg

SBC_492_rare_Angle-Plug_Port_Job_1.jpg

Fri Jan 20, 2006 2:17 pm

on the ones Pictured on my site

4.000 Bore Flow Fixture @28" (No-Pipe on Exh)
Lift---Intake--Exhaust
.200-139.9--102.9
.300-201.0--140.9
.400-234.2--185.7
.500-242.4--207.1
.550-246.4
.600-250.3--215.6
.650-252.3
.700-253.1-219.8
.750-255.5
.800-256.4

all out will go 283+ CFM
about the same as above on exhaust side


slightly more Flow on 4.030/4.060/or 4.125 Bore Fixtures
and with Pipe on exh side

[1980RS]

I have a virgin set of 492 angle plug castings that I am working on. No previous porting/oversize valve job.

This is going to be used in a 70's styled "day 2" type of build, so no "modern" performance parts are going on this engine.

I am looking for any short comings to using a 2.055"/1.60" valve package in the head.

Will the short turn be a problem with the 2.055" valve & the bowl sized @ 90% (1.850")?

While I am not trying to set the heads on "kill", I do want to produce a fair amount of airflow (250+ cfm).

Thanks in advance.

If you are not going to use a real big cam I would stick with the 2.02 valve.

[rustbucket79]

Another vote for sticking with the stock valve sizes on those heads, also make sure your headers work with the angle plug heads.

[383Nova]

Since this is not going to be an aggressive build (less than .550" lift), I am going to stay safe, dial it back and keep the 2.02"/1.60" valve sizes.

Thank you all for your insight I really appreciate it!