Klaptrap24
Hey guys, I would like to raise the compression of my motor (for more torques). What is the cheapest way to do this, without drastically shortening its operating life?
Motor is a '91 8v b230f with ~300k kms.
Turbo is out of the question, still on my p's.
nugget_940
531 head swap and get it shaved a little bit to bump up the compression
Klaptrap24
nugget_940;118914 wroteCould possibly get the head shaved
so i've heard, would anyone know how much would be reasonable to get shaven off?
Vee_Que
Basically with 300,000kms. You will kill the motor pretty quick, the only physical way to increase is machining the head. A 531 already has 0.3~ less compression than a 530 head. So it needs even more machining. To get a late b230f with 9.3~:1 c.r up to 10.5 takes possibly up to 0.8-1mm of machining. But then the 300,000km old rings and bearings will fail. Have had that happen to me before.
nickm
Change the Cam. Static vs dynamic compression
Klaptrap24
Vee_Que;118943 wroteBasically with 300,000kms. You will kill the motor pretty quick, the only physical way to increase is machining the head. A 531 already has 0.3~ less compression than a 530 head. So it needs even more machining. To get a late b230f with 9.3~:1 c.r up to 10.5 takes possibly up to 0.8-1mm of machining. But then the 300,000km old rings and bearings will fail. Have had that happen to me before.
Fantastic response, guess I'll keep the stock 530 for now then :)
Klaptrap24
nickm;118946 wroteChange the Cam. Static vs dynamic compression
could you please explain this?
Vee_Que
Any cam he goes for will have more lift and overlap. It will spend more time open in the combustion chamber. So you could get away with more compression, but once again, the sheer age of the motor with unknown history is against it.
Major Ledfoot
Get a cheap, spare engine and build it up as time and budget permits. Then swap it in when complete.
nickm
I will not comment on Engine condition.
A T cam would increase the dynamic compression ratio.
https://enginebasics.com/Advanced%20Engine%20Tuning/Static%20vs%20Dynamic.html
turbobricks.com/resources.php?content=camspec
Klaptrap24;118960 wrotenickm;118946 wroteChange the Cam. Static vs dynamic compression
could you please explain this?
Vee_Que
A T cam is not quite his goal. But yes. Anything decent will decrease it. It's why I have a fairly aggressive cam in my b20 with 10.75:1 c.r and it won't ping. Also tight squish.
jamesinc
I have a B230F lying around somewhere you can have for a couple cold ones if you want to go the spare motor route
nickm
A T cam will increase low end torque at the expense of high end power.
Other way would be to play with cam and/or ignition timing.
Vee_Que;118992 wroteA T cam is not quite his goal. But yes. Anything decent will decrease it. It's why I have a fairly aggressive cam in my b20 with 10.75:1 c.r and it won't ping. Also tight squish.
Klaptrap24
nickm;119000 wrote
A T cam will increase low end torque at the expense of high end power.
Other way would be to play with cam and/or ignition timing.
Vee_Que;118992 wroteA T cam is not quite his goal. But yes. Anything decent will decrease it. It's why I have a fairly aggressive cam in my b20 with 10.75:1 c.r and it won't ping. Also tight squish.
I was planning on running a K or H cam
Klaptrap24
Hey folks, thought Id ask for advice on this one,
I have a 531 head with big valves that I want to get shaved to bring the compression up to run a KG8 (13.4mm lift, 315 deg duration, 104 deg LSA)
If I dont get it shaved at all then static comp will be 9.5:1, which I think is way to low for the cam. I understand that with the large amount of overlap, compression will be bled off as the cam is turning. I also dont want to destroy my piston rings by running way too high comp. Would anyone have any idea on a good amount to get shaved off the 531?
Cheers
ramrod
Your rings won't destroy from higher compression ratio, more so caused by the thousands of pounds of combustion pressure on the power stroke and the extra stress on the pistons and rings due to the higher heat from the higher compression. The more you compress something the hotter it gets
Vee_Que
You aim for 10.5:1, so likely to be 46cc combustion chamber from previous research. But once again. The head shop can work the ccs out themselves.
ToomanyVolvos
Turbo out of the question? NSW dropped the Turbo ban on P platers long time ago. There are still some restrictions but a B230FT in a 240/740 is well inside the restrictions.
Klaptrap24
I'm fully licensed now, I want to build NA just because I like the sound and simplicity (drift car)
GingerNinja
Are you running carbs or aftermarket ecu? The KG8 is a big cam.