04-16-2015, 03:58 PM
(02-12-2015, 10:54 AM)rindel Wrote: hey guys,
i am planning on getting my 351w 4barrel rebuilt. It is #s matching stock but burning smoke. I mentioned this on another thread and after replacing valve seals and deep creep in combustion chamber, it still smokes. You can see black oil specs on rear of car.
My question is, the restoration place said they can bring the 351w to 400HP but they also quoted adding shift kit to my FMX trans. FMX trans is #s matching as well and in good shape. Do you think I need to do this?
Should I also add headers and replace original exchaust maniforld?
400 hp is easy to obtain with a 351W. Especially is you stay with the original compression ratio of 10.7:1 that was standard on the 4 barrel, M-code version.
The biggest drawback is the factory cylinder heads. The 69 casting 351W cylinder was the best small block Ford OEM cylinder head until the GT40. But they still have some drawbacks that need to be addressed to obtain 400 hp. In addition to standard cylinder head rebuilding the following areas need to be addressed.
1) The exhaust ports are very small and have a big casting bump in the roof of the port, thus they are very restrictive. Port work needs to be performed to improve the exhaust flow rates.
2) The rocker arms are not adjustable. So new rocker arms and studs (see item 3) will be needed. Likely roller rocker arms to get your 400 hp goal. Be careful of rocker arm selection if you want to install stock height valve covers. Most roller rocker arms require tall valve covers for clearance.
3) The press in rocker arm studs do not permit rocker arm adjustment and will pull out with the higher rate valve spring needed for a camshaft that will get you to 400 hp. The heads will need to be machined for screw in rocker arm studs and guide plates.
4) In addition to routine valve guide work, valve guide machining will likely be needed to fit the higher rate stronger valve springs.
5) Hardened exhaust seats will need to be installed for unleaded fuel. Machine work is required for that.
6) Larger intake and exhaust will likely be needed.
I spent a lot of time porting my cylinder heads with the guidance of the machine shop. Then had them machined for screw in rocker arm studs and guide plates, larger valves, and on and on... I reworked mine a lot. Most people buy aftermarket cylinder heads instead on all the work to the stock head.
Headers, yes. Short type like what JBA offers if you don't want to possibly fight fitment issues associated with long tube headers in these cars. Avoid inexpensive headers or you will constantly fight exhaust leaks. The stock manifolds on the 351W are too restrictive to get to 400 hp.
** 400 hp is not hard to obtain. But it is definitely more than a stock rebuild with a camshaft upgrade. I didn't mention, but an intake and carb upgrade would be in order as well.
As far as shift kits. In my opinion every stock automatic trans will benefit from one. It doesn't need to be aggressive. I have one in all my vehicles with an auto trans. Shift kits eliminate most of the clutch slippage that occurs during shifting. Thus, reducing wear and heat. The factory engineers soft imperceptible shifts (more on newer vehicles) into transmissions because most people don't want to feel the shift. Then they wonder why the transmission in their car is worn out at 100K miles. An auxiliary trans cooler is also beneficial. High temps are another life killer for automatic transmissions.
Best Regards,
Mike