Modified K code stroker and should I fit Tri-y headers

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Modified K code stroker and should I fit Tri-y headers

Postby silverfox » Sun Mar 18, 2012 1:57 pm

OK here’s the dilemma……

I am about to take delivery of ’65 fastback K code that has its original engine, however its been modified and what do I do about the exhaust headers ?……some purists I know will put their hands up in horror at this point, but too late to go back now……………

The Kar is stock apart from the engine mods – Stroked to a 347, stock heads with larger valves and ported exhaust.

To all intents and purposes my intention has been to keep the Kar “looking stock”, save for Cobra intake, Cobra rockers covers and disc brake upgrade.

On a recent dyno, engine showed its really great in the 3000-4000 rev range from torque perspective (333-404 lb/ft) i.e. ideal for street use. Power output 379hp at 5700 revs and 407 ft. lbs of torque.

My dilemma is that its been recommended that I go t tri-y headers as the Kar ones will restrict the output………

I’m not sure what to do as
• this is new to me i.e. my knowledge is limited
• the Kar will come over to England and ability to change it after is somewhat restricted
• I’ve always tried to keep the Kar looking stock on the outside - however I’ve been told that Try-y’s were an option on the Shelby’s.

(Please note that I’ve had a new arvinode system made up by Waldron’s exhaust, so system at manifold connection will have to be modified……).

Can anyone help out on this as I’m in quandary as to what I should do -power output is not the most important factor – reliability and “normal” street use are my goals.

All suggestions/comments/ help would be really appreciated.
Regards
Chris
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Re: Modified K code stroker and should I fit Tri-y headers

Postby zray » Sun Mar 18, 2012 3:08 pm

tri-y's not an option on the '65 -'67 Shelby GT-350's. they were standard equipment & ALL street GT-350's of those years came with them. I doubt if you will lose much if any HP using them. Going to a full length header will give you more higher rpm power at the cost of low to mid-range loss of torque.

A perfect reproduction of tri-y headers are now available from Jim Cowles at Shelby Parts & Restoration in Green Bay, WI. They cost about $995.00

Other repros are available and vary in quality.

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Re: Modified K code stroker and should I fit Tri-y headers

Postby cobraboy » Sun Mar 18, 2012 5:28 pm

Welcome aboard Chris, glad you made it over here.
I am thinking of asking Waldrons to make me some centre mufflers. But I think I may wait until I have heard yours.
I will now let you carry on being eaten alive for modding a K code :D
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Re: Modified K code stroker and should I fit Tri-y headers

Postby Mad4HiPos » Sun Mar 18, 2012 6:00 pm

silverfox wrote:OK here’s the dilemma……
On a recent dyno, engine showed its really great in the 3000-4000 rev range from torque perspective (333-404 lb/ft) i.e. ideal for street use. Power output 379hp at 5700 revs and 407 ft. lbs of torque.

My dilemma is that its been recommended that I go t tri-y headers as the Kar ones will restrict the output………
Chris


Chris,

What was on the engine when it was dynoed?

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Re: Modified K code stroker and should I fit Tri-y headers

Postby GregS » Sun Mar 18, 2012 6:10 pm

It sure could be worse. In 1970 I seriously considered replacing the HiPo with an LT1 Chevy engine out of the Z28. The 360hp Chevy 350 sounded pretty good. Fortunately, common sense got the better of me! :)
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Re: Modified K code stroker and should I fit Tri-y headers

Postby silverfox » Tue Mar 20, 2012 2:56 pm

Mad4HiPos wrote:
silverfox wrote:OK here’s the dilemma……
On a recent dyno, engine showed its really great in the 3000-4000 rev range from torque perspective (333-404 lb/ft) i.e. ideal for street use. Power output 379hp at 5700 revs and 407 ft. lbs of torque.

My dilemma is that its been recommended that I go t tri-y headers as the Kar ones will restrict the output………
Chris


Chris,

What was on the engine when it was dynoed?

Dave



Mark,
Might be some time before I get it out this year to any shows, so if you're any where near Staffordshire on your travels, you're more than welcome to pop up when ...... thanks for the pre-warning on mods !

Dave,
Stock dizzy but with petronix retrofit, AED carb and Cobra hi-rise intake manifold anything else you need to know ??
I'm expecting to receive the dyno sheet via PDF shortly, so will let you all see the stats'
Chris
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Re: Modified K code stroker and should I fit Tri-y headers

Postby Mad4HiPos » Tue Mar 20, 2012 8:05 pm

silverfox wrote:Dave,
Stock dizzy but with petronix retrofit, AED carb and Cobra hi-rise intake manifold anything else you need to know ??
I'm expecting to receive the dyno sheet via PDF shortly, so will let you all see the stats'
Chris


Sorry Chris, should have been more specific. I was wondering what exhaust was used for the dyno test? Those dyno specs are nearly identical to the 347 I'm running...

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Re: Modified K code stroker and should I fit Tri-y headers

Postby silverfox » Wed Mar 21, 2012 4:08 pm

Mad4HiPos wrote:
silverfox wrote:Dave,
Stock dizzy but with petronix retrofit, AED carb and Cobra hi-rise intake manifold anything else you need to know ??
I'm expecting to receive the dyno sheet via PDF shortly, so will let you all see the stats'
Chris


Sorry Chris, should have been more specific. I was wondering what exhaust was used for the dyno test? Those dyno specs are nearly identical to the 347 I'm running...

Dave

Dave,
Having looked at the dyno video, looks like a custom shop manifold set up - looks like 4-2-1 on each side, no system attached beyond manifold as on dyno machine.
Chris
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Re: Modified K code stroker and should I fit Tri-y headers

Postby silverfox » Wed Mar 21, 2012 4:12 pm

silverfox wrote:
Mad4HiPos wrote:
silverfox wrote:Dave,
Stock dizzy but with petronix retrofit, AED carb and Cobra hi-rise intake manifold anything else you need to know ??
I'm expecting to receive the dyno sheet via PDF shortly, so will let you all see the stats'
Chris


Sorry Chris, should have been more specific. I was wondering what exhaust was used for the dyno test? Those dyno specs are nearly identical to the 347 I'm running...

Dave

Dave,
Having looked at the dyno video, looks like a custom shop manifold set up - looks like 4-2-1 on each side, no system attached beyond manifold as on dyno machine.
Chris


Dave,
meant to ask what are your engine specs ?
Chris
1965 Fastback 289 K Code - Hi-Po - Caspian Blue

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Re: Modified K code stroker and should I fit Tri-y headers

Postby Mad4HiPos » Wed Mar 21, 2012 8:36 pm

silverfox wrote:Dave,
Having looked at the dyno video, looks like a custom shop manifold set up - looks like 4-2-1 on each side, no system attached beyond manifold as on dyno machine.
Chris


Chris,

That sounds typical, unless you specify something different the builder will use whatever they normally have laying around for the dyno session, usually some kind of header. My experience anyway. That should still give you some idea about what to use in your car depending on how you want to drive it. The HiPo manifolds will be more restrictive than Tri-Y's which will be more restrictive than full tube headers. My engine specs look to be very similar to yours...very stock looking 66 GT350 engine with original Cobra intake, original HiPo dual point, original HiPo heads ported with larger valves, fairly aggressive Lunati solid cam, slightly modified 715 3259 carb, stock Tri-Y's.

I guess it all depends on what you are after. In my experience with this 347 engine it wants to breath! Full length headers would be a great benefit, the stock type Tri-Y's are choking off some IMO. I don't think HiPo manifolds would choke it too much more than Tri-Y's but I've never tested this so don't know for sure. Even with the HiPo manifold's I'm guessing you will still have ~270-290 RWHP.

My recommendation would be go with HiPo manifolds since it seems you are not after max HP but a more stock look.

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Re: Modified K code stroker and should I fit Tri-y headers

Postby silverfox » Thu Mar 22, 2012 4:21 pm

Mad4HiPos wrote:
silverfox wrote:Dave,
Having looked at the dyno video, looks like a custom shop manifold set up - looks like 4-2-1 on each side, no system attached beyond manifold as on dyno machine.
Chris


Chris,

That sounds typical, unless you specify something different the builder will use whatever they normally have laying around for the dyno session, usually some kind of header. My experience anyway. That should still give you some idea about what to use in your car depending on how you want to drive it. The HiPo manifolds will be more restrictive than Tri-Y's which will be more restrictive than full tube headers. My engine specs look to be very similar to yours...very stock looking 66 GT350 engine with original Cobra intake, original HiPo dual point, original HiPo heads ported with larger valves, fairly aggressive Lunati solid cam, slightly modified 715 3259 carb, stock Tri-Y's.

I guess it all depends on what you are after. In my experience with this 347 engine it wants to breath! Full length headers would be a great benefit, the stock type Tri-Y's are choking off some IMO. I don't think HiPo manifolds would choke it too much more than Tri-Y's but I've never tested this so don't know for sure. Even with the HiPo manifold's I'm guessing you will still have ~270-290 RWHP.

My recommendation would be go with HiPo manifolds since it seems you are not after max HP but a more stock look.

Dave


Dave,

Yours sounds pretty special as well.
Thanks for the advice on the headers, I think I will leave as original.
Chris
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