Author Topic: im sure everybody asks this..400 rebuild  (Read 836 times)

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Offline vikingstu

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im sure everybody asks this..400 rebuild
« on: April 30, 2016, 09:58:14 AM »
I just registered to be part of Hittman's family ....I'm needin to rebuild my 78 black n gold baby with a stock looking numbers matching 400 motor...the car is all original n good shape but is tinkin and tanking on startup...leakin out the rear main seal and catchin interstate 72 on fire due to a severe backfire that occurred i believe to a plugged up catylete converter issue...ive got a 79 brownie with a 403...and a blueie with the 4.9....none perfect but all are original gems...my needs are this...i want more horsepower..but want to keep the stock look for sure....dont want to take away its value but want it to be better than others...i have bout 5-6 grand to spend.....what should i do....i should say...what should i have the mechanic/engine builder do....thanks

Offline 72blackbird

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Re: im sure everybody asks this..400 rebuild
« Reply #1 on: May 01, 2016, 09:54:55 AM »
It all depends which 400 you have- if it's the L78 400 with a 500557 400 block and 6x-8 heads, you can forget about stroking it. This block is the notorious thinwall casting and can crack at the main cap dowels (yes- I've pulled apart more than one and seen it). You can roll the dice and use it, but IMO it's a waste of hard-earned money-stick a mild cam in it and be done, you can make up to 400 hp with it (and better heads), but it's inherently weak. Look for a 481988 400 block and use that instead.

The W72 OTOH can be stroked with the stock 6x-4 heads and make 450 hp/500 lb-ft even with stock heads- careful cam selection, carb and ignition tuning will make it a potent build that appears completely stock, but has double the factory output.

Geno

Offline tb

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Re: im sure everybody asks this..400 rebuild
« Reply #2 on: June 19, 2018, 10:46:35 PM »
I thought I would piggy back on this thread instead of starting a new one.......I'm in the process of rebuilding a 1977 w72 500557 block.  I have discussed outputs with him and will be in the range of 350hp and 400 ft lb of torque.  The builder has stated that he would like to use " Main Studs " to give it bottom end strength.   

My question is about the spring loaded slotted dowels that were only used on the w72 block. From what I read, these spring loaded slotted dowels helped induce less stress on the main web area during high RPM use.  Will this method of using Main Studs together with the slotted dowels further reduce stress on the the main web area or will this combination cause more stress. 

Thanks very much.