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Discussion Starter #1
For those who've had their engine built, did you bother with changing the valvetrain components?

I've been look at various brands and specs but having searched on here I struggled to find people talking about their experience with brands or timing duration etc.


I'm thinking about shooting for 800-850 hp with good response but keeping the torque relatively low (to avoid a gearbox build for now). Figured the extra rpm at the top end that'd be available with bigger cams and stiffer springs would help with the peak power figure.

So far I've looked at:

HKS (comes with springs)
Tomei
Saw LM do cams with their builds now albeit with no specs listed
Linney tuning
 

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For 850hp you dont 'need' headwork or cams and the smaller turbos wont pull as hard up top as the bigger ones but with turbos like the G25 you can now have almost 1000hp (FWHP) and they do move air up top.

Stock valve springs float at around 7200/300 but the cams will still be pulling on my first build where car ran 9.9 we put springs and no cams and car pulled well to 8000 rpm, fitting cams with no springs is pure madness.

If you want over 1000whp then IMO cams are a must the little Tomei Pon cams did well and made 1101 whp easily on mine with GT32 on pump gas

Its not until way more than that you 'need' bigger valves etc.

Of course wanting and needing are 2 different things.
 

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Discussion Starter #3
For 850hp you dont 'need' headwork or cams and the smaller turbos wont pull as hard up top as the bigger ones but with turbos like the G25 you can now have almost 1000hp (FWHP) and they do move air up top.

Stock valve springs float at around 7200/300 but the cams will still be pulling on my first build where car ran 9.9 we put springs and no cams and car pulled well to 8000 rpm, fitting cams with no springs is pure madness.

If you want over 1000whp then IMO cams are a must the little Tomei Pon cams did well and made 1101 whp easily on mine with GT32 on pump gas

Its not until way more than that you 'need' bigger valves etc.

Of course wanting and needing are 2 different things.
Thanks John. (y)

Well this is it really- want is probably a better term to use.
I figure if i'm going to build it (and it won't be a wild expensive build compared to some) I might as well do a few extras whilst i'm at it cus I only plan to do it once.

So a vote here for the 256 IN 264 EX Poncams from Tomei here?
They're actually some of the best priced cams. Their springs and retainers are reasonable too.


Also, do you have a link to the G25 turbo you mentioned? Are they on par with BorgWarner 6758 in terms of response?
 

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I've got flowed heads, uprated valves and seats and also cams. It's the Litchfield cams so not sure on the spec tbh but seems to idle fine and work well at lower revs. However also revs lovely, right upto 8500rpm.

As said, not seemingly needed for lower power. About to add a bit more in so should come in
 

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The Jun 264 will be fine on std valve train, running high boost may cause valve float.
A good ported cylinder head should give you plenty of benefits but only use a well regarded person to do so. Tim Radley is the man to speak to, he’s done plenty of Gtr work and builds for other tuners.
 

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High revs can also cause float, ramp of the camshaft lift needs to be matched to the springs As well as full lift.

Theres no point in running a double spring kit or a very strong single spring if not required as it takes more energy to open them robbing you of power.
 

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Discussion Starter #8
The Jun 264 will be fine on std valve train, running high boost may cause valve float.
A good ported cylinder head should give you plenty of benefits but only use a well regarded person to do so. Tim Radley is the man to speak to, he’s done plenty of Gtr work and builds for other tuners.
I'll take a look at the Jun kit too, thanks man. Have you got experience of the Jun cams?
I think for the cost of the springs and the small trade off of their stiffer characteristics i'll go for them regardless as I want it to rev and I guess i'll be running more than factoryish boost (~1.35bar at the minute).

I spoke to Tim at Racing Developments before and he's a top guy but the problem is that he doesn't do a drive in/out service. I'd have to drop the engine out and post it to him on a pallet. It's not a difficult job to take the lump out but the lack of space to do so puts me off a bit so was thinking ACS or LM for the build for the convenience if nothing else.
 

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Just use a local half decent garage to drop the lump and take it up there, or just tell Andy to drop the lump and take heads straight off and send them to race developments.
I think rocky bhattel’s lump is tuned by Tim and it seems very quick and reliable and also when it was stripped for a refresh all was good.

good luck either way and keep us posted
 

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Rocky has an Rd built engine, just being finished. Will be for sale shortly. Sure AC, SRD or possibly even Litchfield would do the swap.

Contact g2guv on here is you're serious.
 

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High revs can also cause float, ramp of the camshaft lift needs to be matched to the springs As well as full lift.

Theres no point in running a double spring kit or a very strong single spring if not required as it takes more energy to open them robbing you of power.
I wanted to keep torque down on my build but still have the power so built a revvy engine. My heads and valve train are built to knock out 8500rpm without breaking a sweat. Weird revving off the clock. Love it.


How does boost cause valve float?
 

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High revs can also cause float, ramp of the camshaft lift needs to be matched to the springs As well as full lift.

Theres no point in running a double spring kit or a very strong single spring if not required as it takes more energy to open them robbing you of power.
Why would you fit a hi revving cam when the valves are known to float at 7200 rpm, a stock cam will pull way beyond that, boost does not cause valve float, if you fit a hi lift cam you need to fit the matching springs or you could get coil bind where the lift is so much the coils touch and become solid and you end up going to the bank to buy a new engine, my tomei springs would cope with 8500rpm but will not work with my new gsc billet cams.
 

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You have to pick your components so that they compliment one another.

Your initial question does not talk about the turbos you plan to use, but you need to consider the whole package since there may be no need for upgraded springs.

You can easily get over 1000 BHP with standard valve springs and pretty mild cams.
 

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Discussion Starter #14
You have to pick your components so that they compliment one another.

Your initial question does not talk about the turbos you plan to use, but you need to consider the whole package since there may be no need for upgraded springs.

You can easily get over 1000 BHP with standard valve springs and pretty mild cams.
Turbos is also what I'm mulling over.
Initially thought hybrid IHI but they might run out of puff above the stock rev limiter.
The 6758 get a great reputation but again, not sure if the extra rpm is a waste. But if they could have a nice flat torque curve to say 8000rpm, that'd be ace.

I see LM offer the G25-660 on their website for not much more than EFR money now but is probably too big for the power I'm shooting for I think?
 

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My engine is all standard just a refresh and rebuild with forged rods and uprated pistons, head and cams stock
Svm gtx30 turbos on stock manifolds
Monitored exhaust temps with a probe in each runner mapped very safe

Pump fuel v power 1.5 bar of boost at hubs
257908



E50 which is 50% v power, 50% ethanol, 1.8 bar of boost at hubs

257909


With 1000 hp maximum goal and wanted to utilise a standard gears in box I'd say head work and cams is a waste of money
 

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My engine is all standard just a refresh and rebuild with forged rods and uprated pistons, head and cams stock
Svm gtx30 turbos on stock manifolds
Monitored exhaust temps with a probe in each runner mapped very safe

Pump fuel v power 1.5 bar of boost at hubs
View attachment 257908


E50 which is 50% v power, 50% ethanol, 1.8 bar of boost at hubs

View attachment 257909

With 1000 hp maximum goal and wanted to utilise a standard gears in box I'd say head work and cams is a waste of money
You have a stock trans? What about clutch?
 

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You have a stock trans? What about clutch?
This is not in the hulk but my other gtr, svm cryo treated and superfinished standard gears,
Gtc 16 plate clutch,
Weldfix baskets,
Dodson circlips, drive locks and magnets.

Has been perfect so far with 928 hub hp max but I don't launch that car it's just a fast road car
 

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I ran 700lbs flat from just after 4k rpm to 8500rpm. I needed heads and cams to achieve a flat curve and higher trv band.

I'm not sure the smaller efrs would hold the torque at 8k rpm. I have the 7663
 
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