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Discussion Starter #1
I've convinced myself that 256 cams are best for my application for 3 reasons:

1) Based on HKS data, the 256 produces the similar results as the 272 for both hp and tq: http://www.hksusa.com/images/?id=1440 http://www.hksusa.com/images/?id=1441

Now, whether or not this is *actually* true is another story. Anyone care to comment on the validity of the graphs?

2) According the article written by Lance Wolrab, additional valve lift doesn't produce that much benefit: http://www.to4r.com/techcylinderhead.html

3) I don't want an exotic valve train that is pricey and difficult to maintain due to exessive valve lift. Plus, regrinds for the NA could require lash caps in addition to aftermarket valve springs for cams with more duration
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I have an sp63 supplying the air and 75lb injectors delivering the fuel. Application is mainly for drag racing, and I don't plan to run much beyond redline.

Am I making reasonable choices here? I just want the head to breath better than it currently does.

Thanks,
-scott
 

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The problem is the situation changed depending on the complimenting mods done to the car. The biggest factors in my mind would be the turbo used and boost level.

Comparing these cams on a BPU car will be nice for a BPU car but may be absolutely no help for someone with a T72.

With that being said, I thin the 264/264 setup is great for cars up to the PTE67 where you could switch to 272's if you want more top end but after that, it seems an easiest decision to go with 272/272 at that point.

Power seems to fall off on the 264's for me at about the mid 7K RPM range and tapers off. If I were to go any bigger for my turbo I'd switch to the 272's. I'm basing this off of my experience with my T66 .70 and PTe67 GTQ with 264's.
 

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silvino said:
The problem is the situation changed depending on the complimenting mods done to the car. The biggest factors in my mind would be the turbo used and boost level.

Comparing these cams on a BPU car will be nice for a BPU car but may be absolutely no help for someone with a T72.

With that being said, I thin the 264/264 setup is great for cars up to the PTE67 where you could switch to 272's if you want more top end but after that, it seems an easiest decision to go with 272/272 at that point.

Power seems to fall off on the 264's for me at about the mid 7K RPM range and tapers off. If I were to go any bigger for my turbo I'd switch to the 272's. I'm basing this off of my experience with my T66 .70 and PTe67 GTQ with 264's.
What do you think would happen if you went with 272's using your 67 turbo? Any power gain...lag...torque gain/loss?
 

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I'm not saying I'm the authority on cams but my guess is that the lag gains would be small but the power would continue to rise on the top end making a bit more peak power and making shifting much later an acceptable option. That small lag increase is something I'm not willing to accept. This is also why I'm switching back to the smaller header.

On a street car, to me, a few hundred rpms lost isn't acceptable. In lower gears lag is accentuated it seems while in upper gears it doesn't feel as big of a deal.

TT_6SPD_95 said:
What do you think would happen if you went with 272's using your 67 turbo? Any power gain...lag...torque gain/loss?
 

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i run a 264 intake and a 272 exhaust, and my power continues to rise all the way through 7500+ rpm's

the staggered setup is getting more and more popular.
 

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Discussion Starter #7
mk4 & gte: Lance suggests the staggered duration in the to4r.com article referenced above. However, in my case, I must go with regrinds for the NA head, and I'm worried about valve lift causing coil bind. It seems that the consensus is anything > 9.25mm can cause coil bind:
http://www.supraforums.com/forum/showthread.php?s=&threadid=144155&highlight=coil+and+bind
http://www.supraforums.com/forum/showthread.php?s=&threadid=78928&highlight=coil+and+bind

Now, I'm sure a lot of guys run 272s on stock springs, but the aftermarket 264s/272s probably have a different overall profile than regrinds, anyway. In other words, I would think that the lobe profile on an HKS cam has a more subtle lobe center than a stock NA cam that has a stock lobe with a reduced diameter.

Again, I'm also basing my selection on the published HKS hp and tq graphs referenced above that show very little difference between the 256 and 272. However, I have a feeling those graphs are kinda bogus, anyway.

Thanks for the feedback.

-scott
 

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The graph could be accurate but if you're running on stock turbos then the chart won't mean much. We're obviously talking about an APU setup in this thread however. Jason S. from AEM saw solid gains on his BPU car with 264's alone. I wouldn't base your decision on that chart unless they claim it's an APU setup.

motorheaddown said:
mk4 & gte: Lance suggests the staggered duration in the to4r.com article referenced above. However, in my case, I must go with regrinds for the NA head, and I'm worried about valve lift causing coil bind. It seems that the consensus is anything > 9.25mm can cause coil bind:
http://www.supraforums.com/forum/showthread.php?s=&threadid=144155&highlight=coil+and+bind
http://www.supraforums.com/forum/showthread.php?s=&threadid=78928&highlight=coil+and+bind

Now, I'm sure a lot of guys run 272s on stock springs, but the aftermarket 264s/272s probably have a different overall profile than regrinds, anyway. In other words, I would think that the lobe profile on an HKS cam has a more subtle lobe center than a stock NA cam that has a stock lobe with a reduced diameter.

Again, I'm also basing my selection on the published HKS hp and tq graphs referenced above that show very little difference between the 256 and 272. However, I have a feeling those graphs are kinda bogus, anyway.

Thanks for the feedback.

-scott
 
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why do you have to settle for regrinds?

it looks like you will be fine with the 256/264 package? they do not put you into a susceptible range for coil bind?

lmk what you think

-gte




motorheaddown said:
mk4 & gte: Lance suggests the staggered duration in the to4r.com article referenced above. However, in my case, I must go with regrinds for the NA head, and I'm worried about valve lift causing coil bind. It seems that the consensus is anything > 9.25mm can cause coil bind:
http://www.supraforums.com/forum/showthread.php?s=&threadid=144155&highlight=coil+and+bind
http://www.supraforums.com/forum/showthread.php?s=&threadid=78928&highlight=coil+and+bind

Now, I'm sure a lot of guys run 272s on stock springs, but the aftermarket 264s/272s probably have a different overall profile than regrinds, anyway. In other words, I would think that the lobe profile on an HKS cam has a more subtle lobe center than a stock NA cam that has a stock lobe with a reduced diameter.

Again, I'm also basing my selection on the published HKS hp and tq graphs referenced above that show very little difference between the 256 and 272. However, I have a feeling those graphs are kinda bogus, anyway.

Thanks for the feedback.

-scott
 

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Discussion Starter #10
IS300GTE said:
why do you have to settle for regrinds?

it looks like you will be fine with the 256/264 package? they do not put you into a susceptible range for coil bind?

lmk what you think

-gte
Hmm... well, as far as I know, there isn't an aftermarket exhaust cam for the GE motor that has the distributor gear. I don't believe, for example, that the VVT-i motors have this problem. However, the NA non-VVT-i motors run a distributor-based ignition.

In my case, I use the distributor but for crank/cam position, only. I converted the ignition over to wasted-spark using the AEM.

-scott
 
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motorheaddown said:
I've convinced myself that 256 cams are best for my application for 3 reasons:
..
2) According the article written by Lance Wolrab, additional valve lift doesn't produce that much benefit: http://www.to4r.com/techcylinderhead.html
Scott,

From what I've read, the NA exh ports "should" flow more than the TT's. I have flow #'s from a stock NA (gianttomato's) head and a stock TT head somewhere, but haven't taken time to compare them.. Just pointing out that the differences between the GE and GTE heads may be another thing to consider when sizing the cams.

Mike
 

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Discussion Starter #12
Re: Re: 256 vs. 264 vs. 272 pros cons?

Slasher48 said:
Scott,

From what I've read, the NA exh ports "should" flow more than the TT's. I have flow #'s from a stock NA (gianttomato's) head and a stock TT head somewhere, but haven't taken time to compare them.. Just pointing out that the differences between the GE and GTE heads may be another thing to consider when sizing the cams.

Mike
Mike,

You're correct, however, the intake ports are another issue. According to Lance Wolrab (to4r.com), the intake ports on the NA are 4mm side-to-side and 2mm top-to-bottom smaller than the TT head. :( That's the major draw back to the NA head.

-scott
 
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Additionally, I was told by someone at Performance Factory that the NA intake ports only roughly equal the size of the stock TT's after max porting. :(

Mike
 
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Scott,

I see that you are in Dallas. If you are looking for a great machine shop, look to no other place than

Stoid Racing
10420 Plano Road #105
Dallas, TX 75238
(214)503-8044

I'm taking my NA head there to get worked and everything.

Ryan
 

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Discussion Starter #15
rwsupra.com said:
Scott,

I see that you are in Dallas. If you are looking for a great machine shop, look to no other place than

Stoid Racing
10420 Plano Road #105
Dallas, TX 75238
(214)503-8044

I'm taking my NA head there to get worked and everything.

Ryan
Ryan,

Thanks for the reference. Actually, I've already had a head worked on by Competition Machine. They come recommended by Jotech Motorsports. They did a good job (3-angle, new seals) on the head I'm running now. I'll talk to Stoid on my next motor project which is about to start.

-scott
 
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Whats the benefit of running 164/272? Good spool with good topend???

just curious as I am getting ready to do cams with my 71GTQ. What do you think Mike??
 

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I'm running the HKS 246 cam on the intake side of my NA head, but those lash caps that are needed for the regrinds make me nervous... so for now I'm still using the stock exhaust cam. :(

I think either the 256 or 264 would be a good choice for the SP63.
 
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