Timing belt for 4agze

This is my first time replacing a timing belt on anything and I am trying to decide which belt to buy.

Engine is a 4agze running 14 psi from the supercharger. Rev limit is 8600rpm.

Would the oem belt be okay or should I spring for one of the "high-strength" belts?

The OEM belt is good, they're made by Gates from what I understand...and now Gates belts aren't even bright blue anymore so you don't get any engine bling from them

In reply to GameboyRMH:

Sweet. Its amazing how expensive the HKS/Toda belts are compared to OEM.

He HK$ belts are probably made by Gates.

In reply to Dr. Hess:

In reality this probably very true. The hks belts do look pretty though...

You can call up Gates tech support and ask them. Phone number is on their web site. They may have one of their super-duty belts available for it. They'll let you know. I wouldn't worry about it. A Gates standard belt will be fine and the motor is non-interference.

If the only mod has been more boost... no problem... BUT if you are running more valve spring, then you might want to use a shorter change interval... but for the most part OEM belt is tough to beat... many Atlantic engines run them (but they are serviced every 1000 miles or less)

As to the HKS, Toda and power enterprises belts... I know they are built differently, using Kevlar, and other superior materials....

I'd think cam lobe shape (valve acceleration mainly) would play as much or more of a role as valvespring strength.

Only mod is the high boost pulleys and a tune.

Fitzauto wrote: Only mod is the high boost pulleys and a tune.

Stock works fine.....

Knurled wrote: I'd think cam lobe shape (valve acceleration mainly) would play as much or more of a role as valvespring strength.

agree.... you can't get a much bigger cam in there without changing up the springs...

It is interesting that many Atlantic engines* do run a stock belt. * - Cams around 312 degrees, with lifts approaching 12mm seat pressures around 75#s (stock cams are 240 with 7.5mm lift, seat pressures around 35#s)

oldeskewltoy wrote: (stock cams are 240 with 7.5mm lift, seat pressures around 35#s)

35 pounds?

I see enough big block solid-roller stuff that my first instinct is that you forgot a naught. 1000lb over the nose and several hundred on the seat is the norm, there.

You do NOT want to float a roller lifter. That usually means the end of the world as far as the engine is concerned.

In reply to Knurled:

Minimum stock 4AGE valve seat pressure is 35 pounds. The valve train parts are TINY compared to a big block. No rockers, the cam sits right above the solid lifter which sits right on the tip of the valve stem. The valves are a just bigger than an inch in diameter, and the lift is only around 0.295" or so.

In reply to ae86andkp61:

Indeed... versus intake valves way over 50mm in diameter, long and thick stems (giggity) and lift numbers in the .650-.800" range.

With great airflow comes great valvetrain stress.

Oddly enough, it's more or less accepted that valve train weight "upstream" of the rocker is irrelevant. However, you do NOT want to float a roller lifter. That tends to knock the wheel off of the end, which causes all sorts of money to fall out of the engine.

Perversely, hydraulic rollers last longer than solid rollers because there is no lash in the system. Solid rollers skid and bounce a little when in the lash area, which is why they beat up the needle bearings and need replaced/rebuilt every 3000 miles or so, or whenever the lash starts opening up radically.

you'd be surprised what a 4AG head can flow.... (@ 28") I don't usually test beyond .354 (9mm) lift, but the intakes @ .354 I can get to flow around 210-215, stock is 175-180, and the exhaust I can manage about 150-155, while stock is about 118-120

Intake valves are 30.5mm (1.200), and the exhausts are 25.5mm (1.003")

I'm not surprised at all. The engine is very similar to one of the best 4 cylinder racing engines designed in the last fifty years. I still kick myself that I didn't buy that SR5 for $100 when I had the chance. Knowing now what I didn't know then, I'd have bought it and slapped a 4AG in it (or a "7AG") and had a ball. But this was Knurled pre-Mazda, I was a Subaru guy just coming out of Fords and I didn't think there'd be room for my 302 under the hood. Oh well.

It still pales to what a BBC can do, though, on a per-cylinder basis Yeah, displacement this, displacement that, but output in the 150-200hp/cylinder range at moderate RPM - with TWO valves/cylinder! - needs big heavy valves and cam lobes that look like Legos

This is exactly why my daily driver has 16 valves and a turbo. And my fun car has a rotary.

Well stock gates belt is on the way now. Excited