The difference in HP and Torque could be attributed to flow as well as compression ratio. What flow numbers are you using for each type of head in the desktop dyno program? Also, what size valves do you have programmed in for each head type? I am implying that the number may not be accurate in comparison depending on how accurate your flow numbers are.

Another explanation may be that the increased flow of the new heads is just able to compensate for the loss of CR in the lower rpm range, but at higher rpms, it runs away with it.

 

head flow data i used was for afr: 1.9/1.6 valves with the flow data published on their website (measured with 1.9/1.67) and compression ratio of 8.75
for the stock i used CR of 9.5 with 1.78/1.45 valves and the flow data i have for the C5AE measured with 1.78/1.45 (0.200 96/64 03.00 124/88 0.400 155/98 0.500 160/100)

so what you're saying makes kinda sense.

Thanks mdbiag. i was suspecting something like this but i couldn't put my words around it

 

While generally true for cleves, that has no bearing at all on 289/302 motors. There are no differences between 4V and 2V 289 heads. The only significant difference between engines are the pistons (flat top vs dished) and the intake/carb.

 

Ran the numbers too using the new DynoSim5 and got similar, but slightly different numbers. Based on a mythical stock type cam and the stock head flow numbers you gave, it looks like your two options (higher compression vs better flowing heads) is a wash under 2500rpm. Above that the AFRs start to shine. Take that for what it is worth.

 

"paddy the farmer"? LOL

don't you have any decent machine shops over there?

 

Hahahaa, do they machine using a potato peeler!

 

there is actually a decent engine shop in Cork. but I'd say they've probably never seen AFR heads. i know a miller is a miller but bringing brand new heads to a shop who don't hve experience with those types of cars ... i don't know

cowboy: thanks for testing as well. I get the same result. under 3000 nothing happens and then the thing goes insane.
tonight I'll try what mystang77 suggested on my last postings. 1.7 ratio rockers. see what difference that makes ...

Kalli

 

anyways my intake just arrived. this time a edl 2121. wish me luck!
if that solves my problems then i won't need heads ;-)

 

i dunno why you had all these intake problems, the 8124 is supposed to be a great intake

 

only if you're not too stupid to put it in.
I torqued them with hand (my best torque spanner). And never re-checked on them
Bolts got loose, engine overheated. since then I changed gasket twice. So know i'm hoping I have 'bent' the intake as alum goes quicker than cast iron. that's the reason i'm trying replacing. i thought i get a different one just for the sake of it. my first choice would have been the 8124 alright.
the reason why i still have hope it's the intake leaking water and not the heads is that I have true dual exhausts and both are steaming. i changed both head gaskets and can't believe i fried both heads ... so i'm still on the please please please let it be the intake route. it's going in tonight, so i'll see from there