BC GTA

I came across this good reference source on cylinder heads and flow rates for Chevy engines. http://www.chevyhiperformance.com/techarticles/41598/ It explains a lot about cylinder heads and gives the flow rates for various heads in the articles at the bottom of this article. The reason this interests me is I am about to go to my mechanic to discuss rocker arms for my 1989 GTA. I am considering 1.6 ratio rocker arms. This will increase my gross valve lift from about .48 for intake and exhaust to about .51 for intake and exhaust with the comp cam I have in it now. I have been looking at the cylinder head flow rates to determine if there is much of an advantage from this increased valve lift from 1.6 ratio rocker arms. The 882 head barely flowed any more air above .500” of valve lift, the 441 head and L 98 aluminum head were a little bit better. What heads were used on a 1989 GTA 5.0 liter TPI engine?

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smithtc

081 Castings...

I'm not aware of any head flow postings from anyone on these. Will guess they flow about 180/130 +/- at about 0.400 before stalling out. In a few months I'm going to lay the hammer down on my 5-speed car...Will get some flow numbers for stock 081 castings when I take them off. Plan to mildly port them using stock valves sizes, change intakes and cam, and increase compression to see what I can do with this 305 cheap... before ripping it out and donating to "Replenish the Earth".

__________________
'89 GTA 305/T-5/3.45
'69 Camaro X55/M20/3.31
"In theory, there's no difference between theory and practice. In practice, there is."

BC GTA

I did some net research and found that these engine's heads were either 081 or 187. Then I took my valve covers off about an hour ago and found my casting number. It is 14102187, so I guess mine is 187. I also have not found any flow head flow data yet, but I will keep looking.

gmgod

I don't think thats right, 187's are swirl ports iirc.

305RSlc

Yes, 187 casting were for the L03 engines or the 305 TBI, they should not be on your car if you have a GTA since it should be Lb9 heads.

Grim Reaper

Yes, but he has a "Canadian Car" (i.e. Export). There are a number of inconsistencies between Canadian F-bodies (especially pre-1990) and US F-bodies. In fact, a number of LG4 (carb) 305s don't even have an ECM.

BC GTA, you can verify whether those are the original heads. They should have the Sequence# from the VIN# somewhere on the heads.

BC GTA

Well I have done some research to hopefully solve this head casting number problem. First, I am the original owner of the car, which I factory ordered and bought in Vancouver, B.C. in 1989. Two years ago a replacement rebuilt engine was bought from my local Chevy dealership. This engine came from the USA I was told. This morning I went down to this dealership and they checked their casting number book and found either head casting number 14102187 or 14101081 are correct for this engine. Casting numbers are the last three numbers ie. 187 or 081. The technician explained head casting numbers change over the years. Next I did some web research and found this article which tends to support this theory. The article states” The casting number is the one on the top. The last three digits, 081, tell us that these are the good heads. There are too many casting numbers to list, but Mortec.com has quite an extensive list and a brief explanation of each one. Many TBI-equipped cars use a swirl port head, which has a large obstruction in the intake passage. Stay away from those if possible.”

See article: http://www.gmhightechperformance.com...311htp_frugal/

Then I found the following site which indicates the TBI head casting number is 12509859 or 859.

See site: http://www.cylinderhead.com/gm-pricelist.htm

Finally I consulted Mortec, which seems to be the reference source for GM casting numbers. They list all three head casting numbers ie. 14102187, 14101081 and 12509859. The 14102187 or 187 on my car the site lists as “14102187...87-91...305..........1.84"/1.5" valves”.

See site: www.mortec.com

Well the conclusions I draw from this research is the TBI engines should have 859 heads on them while our TPI engines should have 187 or 081 heads on them. I would be interested to hear others views on this subject.