I have bolt-on L98 (stock bottom) with auto tranny behind it. Going to be running the AS&M siamesed runners, and ported plenum shortly.

I am going to be using the XR269HR from comp cams. The AFR 68cc heads stock would bring me to the upper 8's for the compression, which is good for the supercharger, but bad for current performance. I asked him if he could port a set of aluminum L98 heads, which I already own, and he said that I would be spending around the same amount to have them ported and setup compared to just purchasing the AFR heads. He basically said that I'm the spending the same amount of money and it's just personal choice.

I will be bolting on a procharger kit later, but I would still like some power now, and noticable too. My questions are below:

1) What would the supercharger work with better? Aluminum L98 hogged out or AFR 180cc heads?

2) Would I see a great amount of power with the AFR heads and comp cam to play with now? I'm not made of money, so the sc would have to wait.

3) If I do get the AFR heads, would I still get a good power increase to not have them milled down? The charger would like a lowe compression anyway.


Cam:
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@.050: 218/224
Lift @ 1.6: .528/.535

Heads:
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Part Numer: 918
http://www.airflowresearch.com/pages/180sbc_sh.htm

 

High compression isn't the be-all end-all of making power. You might make about 15HP less than the same motor at 10:1 (and probably lose about 20-25 ft/lbs in the extreme lower RPMs) but it's not like compression alone is going to make it a pig off-boost. Plus it'll run on the cheap stuff with no problem, saving you precious pennies to be applied to your future blower purchase.

I'd go with AFRs over ported L-98s any day of the week unless you're going to be given guarantees (and proof) on the final flow numbers of the ported L-98s.

 

I think I am going to go with the AFRs, just wanted to get some other opinions. He said that he would flow test them and that he could gaurentee them to flow better than the hutter corvette heads. Here is the hutter:

 

Hutter compared to the AFR 180cc:

 

why not do the supercharger first and just run lower boost numbers until you can lower the compression with better heads. You'll run faster with the procharger on the stock setup than NA with better heads...granted its a bit more time before you can put it together.

just another perspective....

 

Great, now another thing I have to think about.

Good point, I am thinking that one of the gaskets is bad, so when I changed the heads, I was just going to change those.

I can use the stock aluminum L98s a couple more horsepower now, and low boost...and then go nuts!

Yeah, I just need to weight everything.

 

keep in mind aluminum L98s have 58cc combustion chambers...so they'll raise your compression if you don't change your pistons.

 

Yes but due to them being alum, it might be a trade off.

a 10:1 alum head motor is like a 9:1 iron head motor.

-- Joe

 

Looking forward to pics.

 

stock L98 with factory 64cc iron L98 heads = 9.3:1

stock L98 with factory 58cc alum L98 heads = 10.26:1

 

Thanks for the numbers, I was just thinking about that today.

Questions, questions...I have some thinking todo appearently.

 

its not that big a trade off when you're talking about running large amounts of boost. low compression is your friend...10.25 ain't low lol

 

10.25 isnt low, not really.

But you dont want to go too low either. ANd how much boost are we refering to?

An S-trim for example (6-8psi) is made for a stock 9.3:1 iron motor.

-- Joe

 

that's what i said lol...its not low at all.

true, i don't know how much boost he'd like to run...but low 9s is about where you want to be for just about everything save crazy high levels... Don't need to worry too much about detonation and you don't have to worry about "sluggishness" either.

 

It's going to be on the stock bottom end for a while. I am going to get the AFRs first and then have them mill down the heads to run about 9.5:1. Does anyone see any problems with this?

My final plan is to run an intercooled 15-18lbs with these heads and a four bolt forged bottom. I think I am going to get the heads and cam first and just start building on the bottom.