I took my heads in to a place called cylinder head exchange. They were from a 1990 Iroc Z LB9 (305) TPI. I was under the impression that those heads were smaller valved than the 350's. I got some heads back that have 1.94" Intake and 1.50" Exhust valves. That is what I wanted done to my heads, but didn't have the money for. They wanted $359 for new valves and stuff. I told them I just wanted a simple valve job, got these heads back for $124. So I think I came out ahead on the deal, but I just want ot know if the compression is going to be the same. There's a casting on the sides that I think says 018-5 and 018-8 on the other. Is that right?

 

You may have been taken. I don't know of a machine shop that is going to do the work of installing larger valves, and the machine work if you are not wanting to pay for it. My guess would be that they exchanged yours for some other ones off another engine. I would definetly check the combustion chamber size. I'm sorry I can't help with the numbers you provided.



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Joshua Johnston
1991 Z-28
Flowmaster
K&N
305 / 5spd. (Temporary)

 

Get the casting number off the heads, which is cast right in the middle of the head (valve spring area) and go to http://www.mortec.com and look it up. It should tell you what kinda of heads they are, and what the chamber size is along with what valves came installed on them.

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92 Z28 5.7
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Trick Flow 23° heads, Comp Cams XR270HR-10 cam, Accel intake base + ported TPI,
TES headers, Flowmaster catback, MSD ignition, #24 SVO injectors, 1LE aluminum driveshaft.

Click here to see pics of my car !

 

there is another way the distance between each combustion chamber for each cylinder is a little over 2 in. for a 350 head on a 305 head its less than 2 1 7/8 or so i dont know the exact measurements but even if they did do the work the distance between the chambers wont change if all they did was a valve job and bigger valves

 

You need to get the head casting numbers to identify what you have. The CC on a 305 head should be 58, the 350 head will be 64cc or larger.

The distance between combustion chambers on a 305 or 350 is the same. All small blocks have the same cylinder spacing.

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1988 Formula 5L/5sp 3.45 gears, SLP cold air kit, MAS gutted, TPIS air foil, TPIS AFPR, MAC headers, Mac under drive pulleys, MAC cat back, Relocated MAT.
Best ET street tires 13.85
Best 60 FT street tires 1.930
Best MPH street tires 99.29

 

Stock heads for all small blocks come with 1.94/1.50 valves. The centerline from bore to bore is the same, the bolt patterns are the same, and they can easily be transplanted from 305 to 327 to 350 to 400 and any other older small block configuration. The only ways for you to tell is to measure the volume of the chamber like said above, or look up the casting numbers. The larger, more desirable valve size is 2.02/1.60, they will fit in a large bore small block, 4" or larger.

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'86 TA, T-tops, T-5, 3.73, 4 wheel disks 350, compucam 2040, performer intake,SLP Headers, 3" race magnum muffler, 1.6 Comp rockers, Ripper shifter, perf. friction pads, Hypertech ignition, Earls brake hoses, Hotchkis springs, Tokico Illumina 5 adjustable shocks and struts, Lakewood panhard and trailing arms
14.73 @ 95... traction still a problem

 

Not all small blocks came with 1.94/1.50 valves. Back in the 60's, early 70's some came with 2.02/1.60 valves. A lot of 305 engines (don't recall what years) came with 1.72/1.50 valves.