Whats the accepted reliable max RPM for a 3T-C bottom end?

**Turdinator** · 07-03-2008, 05:25 PM

The question is as per the title. The background is: I have just had the head on my 3/2tg hybrid reco'd and ported. It was skimmed in the process too. When i re-assembled i put in new chain guides where i could. I have found that the power band is kicking in 500 to 750rpm later than it used to. I intend to play with the cam timing to fix this but it got me thinking, could i get some larger chokes for my webers and rev the bugger higher?

I currently won't take the engine over 7000rpm. Could i safely and reliably rev it to 7500 or even 8000rpm on a std bottem end?

**w810sc** · 07-03-2008, 05:47 PM

I believe the jetting and the cam timing has something to do with it since you have had the head ported and skimmed.

Have you though about dialing in your cams with a dial indicator?

I think someone mentioned that the 3T-GT rods can handle up to 8krpm.

**w810sc** · 07-03-2008, 05:52 PM

found it:

Originally Posted by TheToyman75

I personally have swung the stock 2TG rods and stock 3T-GTE rods to 8500rpm on a very regular occasion.

in the "3T Versus 3T GTE conrods"

**Turdinator** · 07-03-2008, 07:34 PM

Originally Posted by w810sc

I believe the jetting and the cam timing has something to do with it since you have had the head ported and skimmed.

Have you though about dialing in your cams with a dial indicator?

I think someone mentioned that the 3T-GT rods can handle up to 8krpm.

Yes i plan to have a play with the cams tomorrow. It was more of a hypothetical question. I have on occasion missed a gear and over revved to 8000+ and not had any problems. But there is no power up there either and i believe in my case this is due to the chokes...

Anyone know about the std 3TC rods? I thought i had read its more the rod bolts that are the problem?

**MRMOPARMAN** · 07-03-2008, 09:06 PM

when your building a motor as highly stressed as yours

you shoulda replaced the rod bolts as a mattor of course anyways

**Rodger** · 09-03-2008, 03:13 PM

Turdinator,

OEM Toyota stuff was built to last and built to run hard, Nothing like those rattly yank V8 things with spagetti rods. Notice how all the performance places sell all sorts of brands of better rods for them.

My 2T 1740cc motor with stock rods (shot peened and stress relieved) with OEM bolts regularly ran to 8500, about 6000km worth of supersprints, hill climbs and motorkannas. The motor is back in my 3tgreen '22 and as I was preparing it I check and kept the bearings in it. It produced the 85 odd rwkW at the last ACT dyno day with a milder cam than what I ran.

What drove me to remove it from the race car was that in the last months of running I kept stuffing cam gear/dizzy gears. The first combination with TRD cam lasted most of the engines life then within a couple of hours got the gears so hot they melted, The second set lasted five laps at a drive day at Wakefield.
I now beleive it was my choice of oil as this is all I can put it down to. About the same time (early 90's apparently so I have read) oil companies canged their oil additives and reduced the amount of high pressure ressistive stuff making what was good for an old engine now not good.

Long story, but your motor should run to 8500 on stock rods. Just choose a good competition oil that is suited to the older engines and keep an eye on the dizzy drive gear.

If you are going to compete in any track work then good baffiling in the sump is also what is needed.

Regards

Rodger

**Turdinator** · 13-03-2008, 06:51 PM

Thanx Rodger. That was exactly the sort of answer i was looking for.

Interesting about the dizzy gear. I'd never heard or even thought of this happening. What oil were you using at the time?

**joey** · 13-03-2008, 08:03 PM

Would advancing or retarding the cam timing make the power kick in that little bit earlier? Reason i ask is that the cams i have in my 2tg dont kick in till about 5500 rpm and feels as if its about to peak at 7000... i havnt really had the balls to take it past there as im a tad worried about throwing a rod through the block or something similar, so if possible i'd like the try and make it kick in atleast 500rpm earlier.
Cheers, Joey

**Turdinator** · 14-03-2008, 09:16 AM

Originally Posted by joey

Would advancing or retarding the cam timing make the power kick in that little bit earlier? Reason i ask is that the cams i have in my 2tg dont kick in till about 5500 rpm and feels as if its about to peak at 7000... i havnt really had the balls to take it past there as im a tad worried about throwing a rod through the block or something similar, so if possible i'd like the try and make it kick in atleast 500rpm earlier.
Cheers, Joey

Yes. Basically by reducing the overlap between the cams you can lower your powerband. There have been a couple of threads on it. Search something like playing with cam timing. Sillycar chick started the thread i think.

And depending on the tune of your carbs you should be able to safely rev a standard 2t bottom end well over 7000rpm.

**Rodger** · 16-03-2008, 01:44 PM

Of course if you have only single OEM valve springs which start to rattle at 6000rpm.

I started using the latest version of GTX. The same oil brand I had used on and off before then. I also used Valvoline and Penrite, all were good, before.

I checked my dizzy after last Friday's track day at Wakefield Park and after running in high 30's air temp and engine temps above normal and reving to the 7000rpm power limit for the current cam, I saw no significant wear (certainly not what I saw when the whole saga happened before).

I was running Castrol Edge 25-W50 on Friday.

Regards

Rodger