HEAD jobs --(sparrow)

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

yeah...

looking to do a bit of work to my stock gem 1600 (out of '75 TX sedan). At the moment it hauls heaps good once the secondaries kick in, so i want to attempt a power increase. I'm only considering a bit of head work like port/polish intake and exhaust and then get larger valves. I'll also get the head surface machined while i'm there i guess. Don't really want to do anything to the motor that involves taking the slut out of the car...if i have to go to that effort...a better motor is going back in...

What other small mods. should be done if i'm looking at doing this work ??
Any ideas on how much ??

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Have a decent port job performed.
Smooth the bump above the sparkplug out.
Smooth all the ridges out of the combustion chamber particularly around the valves.
Polish the combustion chambers and exhaust ports.
Go for 44mm inlet valves.
Stiffer valve springs.
Swap the cam for something which operates at a somewhat higher RPM (30/70 is typical).
Match port your inlet manifold or better yet swap to twin webers, don't forget to match port your weber manifold too.
Match port your exhaust manifold or extractors.

As for prices... I had them somewhere for everything bar the porting, but... somewhere....

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

hehehehe HEAD JOBS

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

talking about 30/70 cam i got one 4 sale!!

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

gene, how much 4 the cam? what are the surfaces like?

krem

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

$90
good as

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

Start with a TC/TX/TD head if you can. Clean up the ports themsleves, remove the casting marks and try and smooth the inner radi of the bends, take 2,5mm off the head face. If you have a later model head, you will also have the smaller exhaust valves, get the head machined to fit the bigger earlier model ones, buy these new if you have to. Do not polish the intake ports, and clean up aound the valve seats in the combustion chamber. Get a mild crow cam, they have 5, I'd reccomend the 2nd one or else you will need to machine valve recesses in the pistons for a bigger cam. get a set of extractors, and a 2.25" exhaust with a straght through and a hot dog. A downdraught weber is a simple mod, and now your engine could really use one (assuming you dont have one already). Then "recurve" your dizzy, this is VERY simple to do yourself. It is hard to change when the timing actually starts to advance, as to alter this, you need to have a different set of springs, but you can increase your static advance for improved bottom end grunt. If you can advance your distributor at idle and your revs increase, then your engine can use more static advance. You should aim for about 16-18 degrees static advance and still keep the 36 degrees total advance. This is done by reducing the slot in the distributor. Pull it apart and you will see what I am talking about. If you make the slot smaller, you will get less total advance, but
if you increase your static advance, then you can achive the same overall total advanvce which is needed for full power. With all these mods, you will be looking at around 100 horsepower, for an outlay of a mere $1000. Just think if you spend a little more and install a 4ZD1, you will have more power from the engine (probably about 130 horesepower) and this will be in stock configuration, just go and put the extractors and carb on that beast and then you will be going fast.

old forum · hod rodder Joined: 04 Oct 2001 Posts: 15499

machine head ~ $70-80 for a big skim like 2-3mm.
new valves ~ $20 each
valve springs = $90
new cam ~ $160-180
port job ~ $150
extractors ~ $170
2.25" exhaust ~ $80
straight through muffler = $110
hotdog/resonator = $55
downdraught weber ~ $50-70
adaptor plate = $45
VRS gasket kit ~ $130
Total = about $1100 for around 100 horsepower. The G161 requires much more compression, especially with a bigger cam. This is why I recomend more compression (through head shave) and a milder sort of cam as too big a cam will need valve reliefs machined in the tops of the pistons, and if the head isn't machined for increased compression, the valve reliefs might not be needed (probably will) but the engine will not pull very hard through the mid-upper rev range. For $1100, I know what I would be doing, an engine swap. For more details, send me an email.