wph351

iTrader: (3)

Hi all,

Stock bore LQ4 with stock dished pistons. Going to be running a set of used AFR 205 heads, 66 cc. This motor is going into a short box square body with a btr stg 3 truck cam. 218/224 .553/.553 113+3 .

The heads are used. I'd feel better about them sealing if I had them milled. Also willing to mill extra to bump the compression.

How much should I mill and what would be the resulting compression ratio?

A.R. Shale Targa

iTrader: (2)

Have a clean up cut done to get them about 65 cc and with 6 cc less volume than the factory heads which produced 9.4:1. I’d guess 10.2:1-ish with factory head gaskets.
Check the Summit racing website calculator. Plenty different versions around

wph351

iTrader: (3)

Worth it with this combo to mill some extra and bump up the compression farther?

A.R. Shale Targa

iTrader: (2)

With such a small camshaft I wouldn’t Mill any more than .020”

wph351

iTrader: (3)

.020 milled would put the compression around 10.5 ish? I've tried those online calculators and I must be doing something wrong. End up getting an odd ball number irrelevant to what I'm seeking.
This motor is getting a gm mls gasket .051 with a 4.02 bore.
What are the benefits of keeping the compression down around 10.5 ish with the small cam? Downside to going higher? Thanks in advance.

A.R. Shale Targa

iTrader: (2)

Small cam and higher compression ratio will up the cylinder pressure to beyond 93 octane use.......If you have E85 available then that number can be raised as the "Corn" fuel has 105 octane rating

wph351

iTrader: (3)

Good info thanks for that.

on a side note, would this mild cam be ok with stock rockers on the AFR's bronze guides? I've read on other threads that guys moved to rollers to keep from prematurely wearing the bronze, buy those guys were running a much higher lift/longer duration cam than myself.

Thoughts?

G Atsma

The bronze guides are too soft to handle ANY side load for any real length of time, hence the roller tip requirement. The amount of lift has little bearing on it. AFR demands roller tips be used on all their bronze-guided heads.

A.R. Shale Targa

iTrader: (2)

With a clean up cut being .004"-.007" and 65 cc chamber volume I got 10.02:1
A .020" cut should land you at 63 cc and 10.25:1
Tony Mamo who used to be an AFR engineer told me that the factory rocker tip does most of it's scrubbing/valve guide damage at lifts approaching .600" lift
Keeping it in the mid fives like your cam "should" last a good twenty thousand miles or so and lets face it; most combos get changed and/or switched out prior to that....however YES....AFR does suggest the rollers for the valve guide wear

wph351

iTrader: (3)

Man so much to consider. Id love to keep the stock rockers, they are stout. With only having .55x lift how much side loading can there really be?

I've seen many pictures of broken after market rockers on this site. Granted, many of them are from 8-10 year old threads, but reliability is king. It almost sounds as if I'm going to take a reliability hit with these heads either way. In the forms of possible rocker arm breakage or probable guide failure?

If a roller is in the works...whats a reliable and economic brand to run. I was just on summits website eyeballing their summit brand 1.8 ratio rollers. Anybody with experience with these.

How about replacing the guides with stock style hardened ones? Is that something that people do and if so is it cost effective?

G Atsma

Stock style is powdered iron, FYI.

wph351

iTrader: (3)

Is swapping out the bronze guides for the powdered iron guides something thats done?

A.R. Shale Targa

iTrader: (2)

Could do that but it's expensive since another valve job would need to be done
You could sell those and replace with the CNC Trick Flows 205 that use stock sized valves flow nearly 300 CFM AND have the powdered metal guides that are stock rocker arm friendly
Else Howards sells a decent roller rocker arm.....heavy but you're not gonna need to be shifting at 7 grand or anything

wph351

iTrader: (3)

Lots of options here. Would like to stay with these heads as I'm into them for pretty cheap. This is shaping up to be a midrange motor, so I wouldn't need anything capable of big revs. I'll check into the Howard's. I have 500 to work with on rockers. Are any of these compatible with stock valve covers?

Side note. Does anyone know if these heads take stock GM head bolts/head gaskets/valve seals?

bbond105

Texas Speed & Performance sell their own steel body roller tip rocker arms.

http://www.texas-speed.com/p-7364-te...oller-tip.aspx

wph351

iTrader: (3)

Those look decent. Anybody running these? We are considering the scorpions.

G Atsma

The jury is still out on whether aluminum roller rockers can live long on the street. To each their own. To play it safe, a nice roller-tip steel rocker like TSP's would work well and live long doing it. I know Comp sells steel roller rockers too, but have heard very little pro or con on them

wph351

iTrader: (3)

The chincy aluminum rockers have been my hang up on this. I don't trust them. I like the possibility of these tsp pieces. The pictures look they are modeled after stockers, but with a roller.

I would assume these would be suitable for heads with bronze guides?

G Atsma

I don't see why not.

Darth_V8r

iTrader: (4)

Nothing chintzy about yella terra. Mine been on two years at .650 lift