Toymods Car Club Inc: Tech & Conversions => 3tg manifolds on 2tg head (which one flows better, attn rod)

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thetoyman75
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Re: 3tg manifolds on 2tg head (which one flows better, attn rod)	Thu, 16 January 2003 00:58

OK... Talk about a can of worms so I'll split it up a bit ! CAMS. Firstly 2TG and 3TG cams will interchange ! So any cam grind you can get for a 2TG will fit in a 3T-GTE. The reason there are more grinds for the 2TG is that not many people play with the cams in the 3T-GTE, Turbo performance is relativly new when compared to N/A performance ! Then you have to consider that in a N/A engine the cam does all the work as far as dictating how much air gets into the head. (Valve size and ports aside) With a Forced induction engine the Turbo jams it in there so the cams are generally paid alot less attention. A Turbo's cams also use a whole different set of rule as depending on your desired result Overlap is not such a good thing ! VALVES Ok excluding the 11111-88220 head the 2TG's and 3T-GTE's have the same size valves ! The first version of 2TG head (88220) has smaller valves on both the inlet and exhaust. 2TG Valve Size: Intake - 43mm (Up to April 1973) (88220 Head) - 44.5mm (April 1973 Onwards) Exhaust - 37mm (Up to April 1973) (88220 Head) - 38.5mm (April 1973 Onwards) HEAD FLOWS Ok Head flow is ONE of the more important characteristics of a head. But it isn't everything. You also need to consider the chamber design, Sqish area's, the actual flow direction and turbulence, the placement of the spark plug or plugs, Airspeed and probably a dozen other things I have no idea about. The second thing to remember is the cams will dictate just how much air gets in. Headflow figures are measured at certain lift points of the valve. If your cams only give you 300 tho lift then there is no point worrying about what happens inside the head when you have 400 tho Lift as the cams don't get there ! I for example had my head rebuilt to suit the engine I am building. It was flowed and the cams were made to accomadate the figures we acheived. In turn the intake manifold and Throttlebody needs to meet the same flow requirements or its all a waste of time. 2TG v's 3TGTE To be honest I can't answer which one is best ! There is still so much I haven't had the time or money to test ! The heads use a different port design and both work very well in there designed applications. In stock form the cams and intake manifolds limit the engine opperation long before the heads do. If you take the cams and manifold out of the equation then in stock form you can make a base line comparison. I used a 88261 EFI 2TG head (As per my engine build) And yes it does perform better than a 3T-GTE Head flow wise how much better varies at each lift point. As for chamber design and squish areas etc. The 3T-GTE head is apparently a better design. I am not really able to offer an opinion on that as it is too far out of my ability and learning. BUT Before you all go ditching your 3T-GTE heads bring it all back into context ! You only need the head to flow as well as your cams and intake manifold can support ! You also need to remember that an intake manifold can not only restict but increase the airflow thru a bare head. A well designed intake manifold will channel in more air than a bare head will flow alone (Even on a flow bench when the air is being channeled) Then there is the ancient mystical voodoo art of head porting ! I can only evaluate the performance of my Personal 2TG head. I am still trying to obtain a well ported 3T-GTE head for comparison. Given the 3T-GTE's better chamber design then it would be desireable for a ported 3T-GTE head to outflow a Ported 2TG head. I honestly have no idea if it will but I have never seen Toyota, TRD or TTE use a Turbo 2TG head ! Also a mild port job on a 3T-GTE will generally cost less than fitting a 2TG head. Classique 71, Mate Head flow figures should be treated like Dyno Figures in my opinion. They need to be from the same machine at the very least. Different places take varying levels of care in ensureing there machines are calibrated correctly. There is also quit a technique to getting it right. That being said I'd love to see your head flow figues when you get them. Can you find out if it is measured at 28 Inches of Mercury and of course the lift points for each value. Hope that helps ! [Updated on: Thu, 16 January 2003 01:01] [Report message to a moderator]

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