Flat pistons in 2.6 carby

[81pw]

Just wondering I have a stock 2.6 carby engine I want to put flat top pistons in ,how much can I shave off the head or not worry about shaving the head. will the car still run if it's to high compression for a carby set up. And will I have to retune the car for the flat tops. Cheers

[22dodge]

i race a 2.6 carby engine with flat top pistons. the MAX compression ratio I can achieve is 9:1. I've been struggling to get more for the past year. Not one tip I got on this board worked out to get me more compression.

[Billsy]

so you havent shaved the head/deck much and removed a link from the timing chain, and put on an adjustable cam gear?
there are guys here with race engines running over 11:1

a stock astron2 from a late magna has 9:1 from memory, you can shave plenty off the head before needing to modify the chain/gear

[Superscan811]

a stock astron2 from a late magna has 9:1 from memory

Close, it's 9.2:1

Not one tip I got on this board worked out to get me more compression.

Hmm
I remember informing you to use the Celica 22R pistons and chamfering the edges 3mm.
You wrote back saying that there was only 1mm of piston above the 1st ring landing if you remove the 3mm I specified.
EDIT: Sorry I re-read your post and you said 0.100" (2.54mm)








Unless the manufacturers in the U.S. are moving the rings much higher up on the cast pistons, for pollution, I can't see how that can be.
These are standard cast pistons for a 1994 TR Magna.





So even with our standard cast piston, there would be more than 4mm.

Cheers.

[cheaterparts]

i race a 2.6 carby engine with flat top pistons. the MAX compression ratio I can achieve is 9:1. I've been struggling to get more for the past year. Not one tip I got on this board worked out to get me more compression.

I still dont know why you cant get past 9:1 with flat tops - I ran 9.4:1 with dished pistons and an astron 2 head
and run 11.2:1 with flat tops again with an astron 2 head

you cant be removing enough from the head ( mine has 3.5 mm faced from the head 0.135" ) and zero decked pistons
and I still use a full lenth cam chain - no half links

[BIG26L]

I've got 10.25:1 with Series1 head, block and custom Coltspeed pistons.

Series1 head on Series2 should give you approx 12:1. I'm sure its been covered elsewhere here, for more info.

You have to be pretty careful with you ignition timing above 10.5:1, as they tend to spit out head gaskets, if you not.

[22dodge]

I spent over $400 on wiseco toyota pistons like was said to do on here, had them custom machined... only to find there isn't enough distance between the top of the piston and the top ring land. it didn't even make 3 runs on the dyno. but the first 2 runs netted over 250hp. compression ratio came up with nearly 15:1

I built another engine with a milled the head .120". I custom made my own cam sprocket and had to advance the cam 6°. no problem with chain length. however this package only made 180hp. I had to buy some custom made fly-cutters to put valve reliefs in the piston.

over the course of this year, I've spent nearly $10,000 (USD) trying to make a 2.6 perform at the level I can make a 2300 ford. My 2.3 ford engines crank out over 250hp and cost less that $2000 to build.

I've totally given up on the 2.6. I've pulled the engine and I'm installing a 2.2 chrysler engine which I should have done from the beginning.

[cheaterparts]

I spent over $400 on wiseco toyota pistons like was said to do on here, had them custom machined... only to find there isn't enough distance between the top of the piston and the top ring land. it didn't even make 3 runs on the dyno. but the first 2 runs netted over 250hp. compression ratio came up with nearly 15:1

so what failed did the ring land crush - making 250 hp on your first 2 runs would have me looking to see what else could be done on the 2.6 ( is there more hp to be made )
maybe a set of custom forged pistons would be the go

[astronturbo77]

why not use a magna series 2 m9 head with the kidney combustion chambers and do what my old man did (he is a machinist) use chev v8 pistons and over bore to make it 2.8????????????

[22dodge]

I did everything people on here said, cutting toyota pistons, cutting holden pistons, etc. problem is that the angle of the valves with the high lift cams I'm running gets into clearance problems on the pistons. when cutting down the top of a toyota piston (even stock 22re cast) by the time I get the piston crown to clear the head, there's only .100" between the top of the piston and ring land. the cast piston gave me 12:1 and only 200hp. then the piston face cracked to the ring. so I went with forged wiseco toyota piston, had it professionally machined to fit. 2nd dyno run 250hp looking promising, made changes to carb, advanced cam timing 2deg, started the engine and started pull... just past 255hp a horrid noise came out and shut down the motor. failed 2 of 4 pistons.

I have a list of ALL engine bore sizes and there isn't a single V-8 anything that would increase compression. With a flat top piston, I already have the top of the piston out of the hole .010" the ONLY way to make more compression is to use a dome piston, closed chamber head or mill the head. the milled head makes problems where I have to cut over .140" valve relief into the piston to make adequate valve clearance which made for weak spot in the piston.

I cannot find an M9 head anywhere, I've asked numerous times on here for help finding one. I sure would like to know how anyone is getting 12:1+ compression on these engines, racing them and being successful as is being claimed. I build US engines (ford 2300, Chrysler 2.2 and GM quad 4's) generating upwards of 340hp (all motor) and having no failures.

[cheaterparts]

why not use a magna series 2 m9 head with the kidney combustion chambers and do what my old man did (he is a machinist) use chev v8 pistons and over bore to make it 2.8????????????

keep in mind that 22dodge in in the USA and they didn't get M6/7 or M8/9 heads on any of there 2.6s
and has been trying to get one for sometime

I cannot find an M9 head anywhere, I've asked numerous times on here for help finding one. I sure would like to know how anyone is getting 12:1+ compression on these engines, racing them and being successful as is being claimed. I build US engines (ford 2300, Chrysler 2.2 and GM quad 4's)

11.2:1 is what I've been running its under the 12:1 but I've been using 98oct petrol and thats keeps it safe
even flat tops need a bit of inlet valve fly cutting with 3.5 mm removed

my next build will run over 12:1 ( changing fuel to E85) however with a M9 head I have only 1 sorry or I would have worked out how to get one to you

the other option that I would have done is to get some custom made pistons - again I dont know how you go stateside
finding these in 1 off sets
here in oz its fairly easy I think special piston services were about $1200 Aus per set
I know sounds a bit pricey but they are made to the spec you need as in dome - fly cuts and ring lands
with enough strenth built in

[stealth]

well i cant belive that no-one has considered or even done this trick ,i know i have
weld the comp chamber and you can get them down 50cc and less ,yes it afects flow slightly but you achieve good comp numbers and the right work and it will make more power because of comp!
and yes its really expensive to do as the hole head will need heat treating and a full machine job but cant argue with good numbers
cheers stealth

[22dodge]

the time and cost of welding combustion chambers is rediculous. not only would all the chambers need to be identical in volume but flow characteristics are crucial. then you have to worry about distortion, machining, etc. buy the time it's all done, the cost would easily exceed $6000 USD

[BIG26L]

Why is everyone using series 2 heads on NA motors........ They dont work!

We use the series 1 head (approx 55cc from memory) as using a series 2 head (approx72cc??) didn't give enough gas speed/velocity threw the chambers.

We've seen 310hp on the engine dyno many (read like 20) years ago with 10.25:1 comp and I will be interested to see if it still makes its usual 175-190rwhp when it goes in the new car shortly.

[cheaterparts]

Why is everyone using series 2 heads on NA motors........ They dont work!

We use the series 1 head (approx 55cc from memory) as using a series 2 head (approx72cc??) didn't give enough gas speed/velocity threw the chambers.

We've seen 310hp on the engine dyno many (read like 20) years ago with 10.25:1 comp and I will be interested to see if it still makes its usual 175-190rwhp when it goes in the new car shortly.

I use the later head as I've been able to get better power from it than I could with the astron 1 - so it works for me
by machining a lazy 3.5 mm of the series 2 head get get about the same chamber size
the later head can use quite a bit bigger valve than std as they are a bit small for the port I agree


as for 310 hp on an engine dyno to make 175-190 atw - you need to fix some of the losses in the gear box - thats a lot of loss
in the drive train ( or some rubbery figures )
I also watch with interest with you results

[LEE]

23 years ago when i was an eager 4th year apprentice at coltspeed , Ron owned an ex group C LB lancer (converted to sports sedan when Grp C died), we ran forged flat tops , series1 head with series 2 valves (aftermarket flat back stainless) ported head , custom big cam and adjustable deg wheel, no balance shafts, 50mm throttle bodies really a basic combo , and this motor beat porsche RSR, 13pp sport sedans , 6cyl sport sedans (full frame and glass panels, we ran full steel )and did a 24hr event at winton( actually about 12hrs out of a 4 car team) , even a dirt track event on full slicks , only beaten by MRT group G 2.2 turbo , midmount dato 1600 rally car, this motor was good for over 250hp atw, this motor saw 7500rpm constantly and did a whole season with 2 oil changes ( the original Castrol R ) and pump the tyres up , the thing was insanely reliable and basically was the test mule for his customers cars , if it didnt break in the lancer , damned if a customer could do it , Ron wasnt shy of keeping the boot buried , and originally it never ran a rev limiter , yes there was some 9 grand over revs aswell, testimony of the product and a decent engineer

[stealth]

the time and cost of welding combustion chambers is rediculous. not only would all the chambers need to be identical in volume but flow characteristics are crucial. then you have to worry about distortion, machining, etc. buy the time it's all done, the cost would easily exceed $6000 USD

$6000 are you serious wow !
i reckon about a third of that around $2000 tops !
cheers stealth

[cheaterparts]

the time and cost of welding combustion chambers is rediculous. not only would all the chambers need to be identical in volume but flow characteristics are crucial. then you have to worry about distortion, machining, etc. buy the time it's all done, the cost would easily exceed $6000 USD

$6000 are you serious wow !
i reckon about a third of that around $2000 tops !
cheers stealth

I was thinking to myself 6K sounded over the top before you posted
and the more I think about it if the head were clamped down onto a solid plate distortion
could be kept to a min - maybe a bit of straightning
machining would be fairly light
most of the work would be by hand with the die grinder and burett

[BIG26L]

23 years ago when i was an eager 4th year apprentice at coltspeed , Ron owned an ex group C LB lancer (converted to sports sedan when Grp C died), we ran forged flat tops , series1 head with series 2 valves (aftermarket flat back stainless) ported head , custom big cam and adjustable deg wheel, no balance shafts, 50mm throttle bodies really a basic combo , and this motor beat porsche RSR, 13pp sport sedans , 6cyl sport sedans (full frame and glass panels, we ran full steel )and did a 24hr event at winton( actually about 12hrs out of a 4 car team) , even a dirt track event on full slicks , only beaten by MRT group G 2.2 turbo , midmount dato 1600 rally car, this motor was good for over 250hp atw, this motor saw 7500rpm constantly and did a whole season with 2 oil changes ( the original Castrol R ) and pump the tyres up , the thing was insanely reliable and basically was the test mule for his customers cars , if it didnt break in the lancer , damned if a customer could do it , Ron wasnt shy of keeping the boot buried , and originally it never ran a rev limiter , yes there was some 9 grand over revs aswell, testimony of the product and a decent engineer

Lee, I own that exact Motor you are talking about! and have done since 1996. Ron freshened it up earlier this year, so she's ready fight another day for use in my new tarmac rally car thats being built atm!

One of Ron's customers bought the Ex-groupC lancerin 1991 and then transfered all the running gear into his road registered LA 2door in 1993 which I bought in 1996 and continued to use in ClubCar's (IPRA for you youngsters) till the end of 1999 when the car was sold as a roller. It then saw 3 years of road use in my brothers triton. After which it has been in storage till about a year ago, when I delivered to Ron for a freshen-up.

Cheater......... I know what i'm talking about, which is why I don't get involved with a lot of the rubbish and bullshit that get thrown around here!
I know there's a difference in the figures. Different exhausts, diff ratio's and tunes for different torque curves make for different power figures at the wheels!

Andrew

[cheaterparts]

Cheater......... I know what i'm talking about, which is why I don't get involved with a lot of the rubbish and bullshit that get thrown around here!
Andrew

No worrys - I'm still watching with interest

as I do with any modifide 2.6 as you Know I run one myself - hopefully again next season after a rebuild

[LEE]

Big26L is there a chance i know you then ??, that 2.6 was first built with cast pistons , that broke the ring lands , the second rebuild was done with forged with stock head and carbs, the third was injected and revised pistons with thicker crowns ,big port and valve head , that was the bulletproof motor , i can honestly say I had a hand in that build along with installation and hitting the start button for the first time on a saturday afternoon , he was a great mentor , Im glad there is still alot of coltspeed mitsu stuff still around, and I was glad i was there at the beginning of the 2.6 era, there nearly was a spaceframed scorpion going to be built , but he couldnt pass up the deal on the starions, the scorp would of been insane , but time consuming, the start of his grp A era was just as exciting.

[BIG26L]

LEE, More than likely we know each other.
I've got in its last spec, Sleeved block, the special teflon coated pistons,etc....... It still has the same throttle bodies and that ugly square tube fuel rail on it, to.
Ron still has the GroupA Starion. Although it hasn't turned a wheel in anger for a couple of season now.

[LEE]

name big26L ?? yeah i get regular updates on the old man , good friends with his son David.Actually should give the old boy a good kick in the nuts ( he knows why too!!! ha ha)

[22dodge]

no-one is still giving any answers that I can use. What is a series 1 head vs a series 2 head? how are you guys making 12:1? I've spent about $10,000 on these POS 2.6 engines over the year and I'm down 100hp over what I can build a 2300 ford. first problem with the crappy 2.6 was smoking rod bearings. I went through 5 bottom ends in 5 weeks. I solved that with going to a dry sump setup ($2500 for this system). the MOST compression available here is 9.2:1 compression ratio and that's a flat top piston. I had to relief the piston for valve clearance .060". I then had the head milled .120" which required me to cut over .140" valve relief. still not anywhere near the compression or power I need.

I can get nearly 300hp out of a 2300 ford for a total cost of $1500 USD. I built a 2.2 chrysler engine which makes 325hp. the 2.6 is just crap for making any power. so What do I need to do? if I can't get some power soon, I'm about ready to take my piles of 2.6 motors along with 6 custom made performance cams right to the crusher.

[Billsy]

Edit:
i think hes referring to astron2 vers, 1,2,3 heads
Astron 2
series 1 should be M1-5 (these have a sharp turn radius in the ports)
series 2 M6-8 (have improved port shaping)
series 3 M9 (and reportedly some M8 castings) and are the kidney shape chamber

Chamber volumes
astron1 around 54cc
astron2 series 1 and 2 around 70cc
but i couldnt find the M9 specs anywhere. but i know they are posted on the old site somewhere
http://www.sigma-galant.com/archive/mod ... file=index


what specs are the cams your using?

[cheaterparts]

the M9 head had 58 cc from memory - Id check it but a mate has my burett atm

[22dodge]

cam profile is .480" lift duratio 262@.50" lobe center of 108.

[stealth]

mate is .480 cam lobe lift or at the valve?
now saying that i will say this
if you want to run .520" at the cam it wont work in the standard set up no matter what there is no room for the top of the piston and vavle reliefs will leave it to thin
you have to raise the cam by and vavle train .110" and yes that means the ports need to move up as well !
but if it cost $6000 to get your comp cambers welded then this mod would be worth twice as much !
just use the chrysler 2.2 engine way cheaper bang for buck!
cheers stealth