 
     |
| V6 iron cylinder head (Page 10/12) |
|
lordfiero
|
APR 19, 03:40 AM
|
|
Easy choice for me, I already have a healthy L32 block waiting for action  Otherwise 3900 would be interesting if there was available cam blanks for that one.
|
|
|
|
lordfiero
|
APR 27, 12:22 PM
|
|
Heads back from machine shop
They got recut valves and seats, I also shaved 0.6mm from the surface to get compression right. The exhaust unshrouding and combustion chamber smoothing set head combustion chamber to 52cc, now its approx 3.5cc lower.
|
|
|
|
lordfiero
|
APR 27, 01:14 PM
|
|
Most performance valve springs need more height than available in this head/valve combo, so this has to be fixed.
I checked the valve length with a flat surface, all valves sits pretty much at the same height.
The valve guides are not level in height, look at the gap. The reason I checked this is with a high lift cam and stock valves combined with viton seals the lower groove in the valve stem will go inte the seal.
According to my service manual the valve spring installed height shall be 1.58". I checked this, and in my heads the intake and exhaust valves are different in spring height, I do not know if this is poor tolerances or intentional but im going for 1.7" at both intake and exhaust.
|
|
|
|
lordfiero
|
APR 29, 04:46 PM
|
|
The top of the valve guide has now been shortened , but I still have 2" valve guide length. The spring seats have been machined down to equal height between valves.
After this mod I can run up to 0.5" lift on both valves without interference with the valve seal and the new seat position allows 1.7" springs to be used.
The intake and exhaust valves have the lock grooves in sligthly different position, this can be adjusted with thin spacers under the spring or even more simple, changing the lock plate.
|
|
|
|
Will
|
APR 29, 05:29 PM
|
|
| quote | Originally posted by lordfiero:
Heads back from machine shop
They got recut valves and seats, I also shaved 0.6mm from the surface to get compression right. The exhaust unshrouding and combustion chamber smoothing set head combustion chamber to 52cc, now its approx 3.5cc lower.
|
|
Did you give them specs for the valve job? That can have a significant effect on low lift flow.
|
|
|
|
La fiera
|
APR 30, 10:33 AM
|
|
|
|
|
lordfiero
|
MAY 27, 03:53 PM
|
|
Started to measure the lower intake manifold. I dont want to handle the finished heads so Im using one of my test intake head ports for this. The flow is slightly less than the finished heads but not that far away.
This is the setup, the intake valve is put upside down to block the valve stem hole and provide max head flow.
I found that the area around the edges of the lower intake manifold intakes are not as sensitive to edge interference as the cylinder head intake ports
so I measured this without any round edges (on bare cylinder heads it is critical to use round edges, often formed by clay).
btw someone asked about the flow bench, this is the U-tube pressure meter. Note the side mounted scale and the high tech device of moving/holding it..
I did notice a restriction of >10CFM when LIM is used on these ported heads. I would not worry about the LIM on stock heads.
|
|
|
|
lordfiero
|
MAY 27, 03:58 PM
|
|
|
I also measured the Fiero 2.8 LIM against the Camaro 3.4 LIM, no difference in flow.
|
|
|
|
lou_dias
|
MAY 27, 09:23 PM
|
|
|
yeah they are identical other than the port for the IAC and perhaps no cold start injector port either...
|
|
|
|
lordfiero
|
MAY 31, 04:32 PM
|
|
I noticed that the LIM port outlet is blocked in two corners, marked with black. The third port that is offset from the two others is only blocked in one corner, but that lump is twice the size.
Removing this and shape a smooth transition of the walls from the injector position to the port did help the flow.
|
|
|
