opel

Do the 243 heads take the same size/length bolts as the 853 or 806?

If I understand this right the 2004 243's take different bolts than the 2001 to 2003 243's and the 853/806 is that right?

Rob 02

It's not the heads that used different bolts it's the block. Prior to '04 some bolts were longer (155mm) and some shorter (100mm). "04 and later were equal length (100mm).

Don't go by the model year of the car! Double check!

If you are not sure what block you have measure the depth of the holes. You cant reuse TTY bolts so you could just order what came out of the block.

Proir to '04.


'04 and later.

opel

Thanks, that clears it up.

The blocks from a 98 fbody I'm adding 243 heads It's going into a 99 FRC and I have new head bolt. Just wanted to make sure I got the right bolts.

Rob 02

I installed 799 heads which are the same casting as the 243's and glad I did.
Since the '02 already has the Z06 intake all I needed was a cam and springs.

The shop I took my head to took off .007" from the deck, triple ground the valves and did a little polishing. I decided to go with a thinner head gasket for better quench and slightly higher compression. With a CIA and a tune it is a beast compared to stock.

I see you have been a member here since 1999 so you probably seen it all.

JHrinsin

Same exact thing the PO did with the original LS1 engine in my '99 FRC. Milling the 243/799 heads 0.007" will remove 1cc from the chambers and using the 0.040" compressed MLS head gaskets will remove another 2.5cc compared to the 0.053" compressed GM head gasket that was stock. if the chambers were polished not sure how much material was removed. The net effect of the head swap with the milling and the gasket change means you have gone from 10.1:1 static to close to 11.1:1 static. That also really helps if you are planning a cam change as well.

Rob 02

The 241 heads on a stock LS1 had ~10.1:1 static ratio.
With the smaller combustion ratio of the 243/ 799 heads the stock ratio is higher on a LS1/ 6. More like 10.6 stock and with the above mentioned mods 11.3-ish. Detonation on premium fuel shouldn't be an issue since the thinner gasket reduced quench, especially if you have a 160 deg stat.

Any how, how is your engine running?

It seems like it should add about 20 ponies reliably with a possible increase in fuel economy. The torque should increase across the entire RPM range.
Combined with the benefit of the head upgrade, cam, CIA and tune there should be over a 100Hp gain over stock.

JHrinsin

It made +400 rwhp ran just fine until he suffered a ring land failure (stock LS1 short block) on #7 at a track event. The current engine has a forged short block along with the same cam, heads, intake, exhaust with higher flow rated injectors. The valve reliefs in the forged pistons dropped a few tenth of a point off the static compression ratio but it still makes +400 rwhp. Just make sure you watched the spark map to keep her out of denotation (and knock sensor induced timing retard) with that much static compression and premium pump gas, as well as duty cycle on the stock injectors.

Sorry for the hijack - now back to your normal programming.

BTW, you can't go wrong with ARP head bolts as long as you get the correct ones for your block as noted by Rob 02.

opel

This is the current specs on the engine I'm putting in.


TSP titanium retainers and .660 lift valve springs
TSP Magic Stick 4 camshaft 239/242@.050.649/.600 111.5 LSA
LS6 Intake manifold
ARP rod bolts
Made409whp@6400with a very mild tune. 12.4 AFR 26* of timing



And a vid of the engine in use.




I'm adding the 243 heads and swapping the cam, retainers and springs over to the 243's
Also doing all the normal stuff you do with a motor swap.

new front & rear seals and gaskets
new timing chain & gears
new oil pump
new balancer

Rob 02

Damn!

JHrinsin

Way cool in a 4-door E36 chassis!

My '99 FRC has a Comp 226/230 0.598"/0.610" lift 113 LSA camshaft with Comp 26926 dual springs (0.675") and trunion upgrade
stock 243 heads - GTO, not C5 Z06
LS6 intake, throttle body and de-screened MAF
LG long tube headers and C5 Z06 Ti cat back

Made 405rwhp @ 6200 RPM and 392 ft-lbs @ 4900 RPM with a conservative tune.

I need to add a thermostatically controlled oil cooler and 4-corner steam tube setup for track duty use to help protect the PO investment in the forged short block.

opel

[QUOTE=Rob 02;1596261429]Damn![/QUO

Yes he's dam fast at end of the straight I was hitting 110 he was at 124. I'm hopping the engine will help me close in on him a bit.