NA Stroker build
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Joined: Apr 2018
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From: Melbourne
NA Stroker build
Hi all,
I have an unusual (double) build coming up for two rally cars and would really love some feedback from people more knowledgable than myself.
I run Historic rally cars over here in Aus and have recently been allowed to use 63/4's as 'substitute' engines in my class, however, NO turbo's - must be NA!
I know, many of you will be groaning at the mere thought
Current thoughts are:
6 bolt 64 bottom end (have to use narrow pattern for the boxes we run) with 156mm rods and approx 10.5 high comp pistons (must run pump fuel - 98 Oct) with 1G (big port) head, 298 (or similar) cams, 1mm OS valves, beehives etc etc.
Being Historic, they MUST run carbs so twin 48's will be used. Torque is king on dirt so mega high rpm's, while fun, are not important.
Are we heading in the right direction? Would appreciate some constructive feedback.
Cheers, Steve
I have an unusual (double) build coming up for two rally cars and would really love some feedback from people more knowledgable than myself.
I run Historic rally cars over here in Aus and have recently been allowed to use 63/4's as 'substitute' engines in my class, however, NO turbo's - must be NA!
I know, many of you will be groaning at the mere thought
Current thoughts are:
6 bolt 64 bottom end (have to use narrow pattern for the boxes we run) with 156mm rods and approx 10.5 high comp pistons (must run pump fuel - 98 Oct) with 1G (big port) head, 298 (or similar) cams, 1mm OS valves, beehives etc etc.
Being Historic, they MUST run carbs so twin 48's will be used. Torque is king on dirt so mega high rpm's, while fun, are not important.
Are we heading in the right direction? Would appreciate some constructive feedback.
Cheers, Steve
Last edited by 2Sideways; Apr 9, 2018 at 07:47 PM.
That 98 octane fuel, is that RON or MON? If it's RON, you can prob run more like 11.5:1 compression. If it's MON, 10.5:1 will be good.
As for camshafts, you may want to get on the phone with Kelford, or GSC and see what they think about what cam to use for an NA build, and if one of them is willing to do a custom grind for you. NA cams will be quite a bit different from cams designed to run a turbo.
I would also talk with someone that knows what they're doing with cylinder heads. These heads barely need oversized valves in the 800whp range with a turbo. For an NA build, you may not realize any gains. Get Head Games Motorworks or 4Piston Racing on the phone and see if you can pick someone's brain.
Since you're running carb's, a custom intake manifold will already be addressed. But make sure you have a good header built to get the most out of your combo.
As for camshafts, you may want to get on the phone with Kelford, or GSC and see what they think about what cam to use for an NA build, and if one of them is willing to do a custom grind for you. NA cams will be quite a bit different from cams designed to run a turbo.
I would also talk with someone that knows what they're doing with cylinder heads. These heads barely need oversized valves in the 800whp range with a turbo. For an NA build, you may not realize any gains. Get Head Games Motorworks or 4Piston Racing on the phone and see if you can pick someone's brain.
Since you're running carb's, a custom intake manifold will already be addressed. But make sure you have a good header built to get the most out of your combo.
ER tried to make a High comp N/A motor like 8 years ago with spare parts they had. It was a complete turd. Not sure it cracked 150hp. I assume they played with cam timing but certainly not a custom cam.
Originally Posted by Dallas J
ER tried to make a High comp N/A motor like 8 years ago with spare parts they had. It was a complete turd. Not sure it cracked 150hp. I assume they played with cam timing but certainly not a custom cam.
Thread Starter
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Joined: Apr 2018
Posts: 4
Likes: 1
From: Melbourne
Thanks for the replies. Apologies for my own delayed reply, currently over in NZ with patchy phone service...
The inlet manifold is a fabricated item, made with as long runners as possible and still fit the sidedrafts in without hitting the strut towers.
It appears none of my 63 gear will be utilised now - currently looking for a 6 bolt 64 short motor and a decent gen2 head.
After reading through the replies (and more threads here) plus discussing with Evo engine builders here in Aus, we'll try and utilise a 94mm crank as well.
Still plenty to investigate but slowly piecing it together. Thanks for taking the time to reply.
s
The inlet manifold is a fabricated item, made with as long runners as possible and still fit the sidedrafts in without hitting the strut towers.
It appears none of my 63 gear will be utilised now - currently looking for a 6 bolt 64 short motor and a decent gen2 head.
After reading through the replies (and more threads here) plus discussing with Evo engine builders here in Aus, we'll try and utilise a 94mm crank as well.
Still plenty to investigate but slowly piecing it together. Thanks for taking the time to reply.
s
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N/A is not cheap power to make, they need fancy headwork and headers. With a 6-bolt head, I think this thing is gonna be a dog.
If it were my engine, I'd do this:
Evo 9 head on a 4G64 block, keep the 100mm crank. Have the carbs pointing towards the front of the car.
11.0-11.5:1 compression pistons. Swap out to a thicker HG if you've got pinging.
Light 156mm rods
Lighten the crank as much as possible (see: FFWD Butcher crank)
Light flywheel
BIG cams. Like, Kelford 280s? Whatever works with the MIVEC.
Head ported for your purposes.
Dual valve springs, titanium retainers, HLA, usual stuff.
K20 Race-style header. Same idea, in a configuration that works for your chassis.
Having big camshafts and MIVEC will give you the top end without sacrificing as much in the mid-range. Both of these things should allow you to run a higher static compression ratio, since the dynamic compression and cylinder pressure would be lower.
Properly built, I think this thing makes 225 WHP, possibly more, and it could rev out to 8,000. Carbs are a bit of a killer, though.
If it were my engine, I'd do this:
Evo 9 head on a 4G64 block, keep the 100mm crank. Have the carbs pointing towards the front of the car.
11.0-11.5:1 compression pistons. Swap out to a thicker HG if you've got pinging.
Light 156mm rods
Lighten the crank as much as possible (see: FFWD Butcher crank)
Light flywheel
BIG cams. Like, Kelford 280s? Whatever works with the MIVEC.
Head ported for your purposes.
Dual valve springs, titanium retainers, HLA, usual stuff.
K20 Race-style header. Same idea, in a configuration that works for your chassis.
Having big camshafts and MIVEC will give you the top end without sacrificing as much in the mid-range. Both of these things should allow you to run a higher static compression ratio, since the dynamic compression and cylinder pressure would be lower.
Properly built, I think this thing makes 225 WHP, possibly more, and it could rev out to 8,000. Carbs are a bit of a killer, though.
Last edited by RS200; Apr 14, 2018 at 04:09 PM.
Thread Starter
Newbie
Joined: Apr 2018
Posts: 4
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From: Melbourne
Cheers.
Yes, quite correct about the limitations of the carbs but I'm kinda stuck with them due to our class...
We've arrived at a similar engine combination ourselves but still considering the smaller crank for a higher rpm threshold. We're also trying to keep it on 98 (RON) for practicality - we occasionally do long distance events in remote areas (still access to pump fuel though) but running a higher comp ratio would mean having our service crew carry large quantities of race fuel, which isn't ideal.
The car's rear drive (and RHD) and we run a pedal box (no booster) so it won't matter which side carbs/exhaust run which frees things up a little.
Thanks again for everyone's input, things are coming together. I may put up a build thread for (the 3 ����) people interested in an NA build.
Cheers, S
Yes, quite correct about the limitations of the carbs but I'm kinda stuck with them due to our class...
We've arrived at a similar engine combination ourselves but still considering the smaller crank for a higher rpm threshold. We're also trying to keep it on 98 (RON) for practicality - we occasionally do long distance events in remote areas (still access to pump fuel though) but running a higher comp ratio would mean having our service crew carry large quantities of race fuel, which isn't ideal.
The car's rear drive (and RHD) and we run a pedal box (no booster) so it won't matter which side carbs/exhaust run which frees things up a little.
Thanks again for everyone's input, things are coming together. I may put up a build thread for (the 3 ����) people interested in an NA build.
Cheers, S
Thread Starter
Newbie
Joined: Apr 2018
Posts: 4
Likes: 1
From: Melbourne
Cheers.
Yes, quite correct about the limitations of the carbs but I'm kinda stuck with them due to our class...
We've arrived at a similar engine combination ourselves but still considering the smaller crank for a higher rpm threshold. We're also trying to keep it on 98 (RON) for practicality - we occasionally do long distance events in remote areas (still access to pump fuel though) but running a higher comp ratio would mean having our service crew carry large quantities of race fuel, which isn't ideal.
The car's rear drive (and RHD) and we run a pedal box (no booster) so it won't matter which side carbs/exhaust run which frees things up a little.
Thanks again for everyone's input, things are coming together. I may put up a build thread for (the 3) people interested in an NA build.
Cheers, S
Yes, quite correct about the limitations of the carbs but I'm kinda stuck with them due to our class...
We've arrived at a similar engine combination ourselves but still considering the smaller crank for a higher rpm threshold. We're also trying to keep it on 98 (RON) for practicality - we occasionally do long distance events in remote areas (still access to pump fuel though) but running a higher comp ratio would mean having our service crew carry large quantities of race fuel, which isn't ideal.
The car's rear drive (and RHD) and we run a pedal box (no booster) so it won't matter which side carbs/exhaust run which frees things up a little.
Thanks again for everyone's input, things are coming together. I may put up a build thread for (the 3
) people interested in an NA build.Cheers, S
Not really a contribution to this thread, but I'm going without boost because of no wastegate arm, so I'm basically NA right now. I've been surprised at how driveable it actually is. It's a 9.7 compression 2.4L with a MIVEC head on 272s. It's pretty funny how useable the power is like this, I'm guessing it's like 150hp? 2-4k RPM is all I've used it for, I don't know what happens up top like this.
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