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402 BBC cam help

General engine tech -- Drag Racing to Circle Track

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prairiehotrodder
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402 BBC cam help

Post by prairiehotrodder »

i pulled apart a 402 BBC a few days ago that is dated 1971 on the block. I think it is a truck engine and has a "290" casting number on the block. It looks to have been rebuilt at one time but its all stock. When i pulled the stock cam out it had the groove in the rear cam journal. Is that normal ? Do i need to always have a cam with that groove ?
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GuysMonteSS
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Re: 402 BBC cam help

Post by GuysMonteSS »

If you are thinking it might be a "big truck" tall deck engine,it probably isnt.
The only tall deck truck engines were the 366 and 427 models.
And,AFAIK,the grooved rear journal cams were for the early 396.
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Re: 402 BBC cam help

Post by ProPower engines »

prairiehotrodder wrote: Fri Jan 08, 2021 3:44 pm i pulled apart a 402 BBC a few days ago that is dated 1971 on the block. I think it is a truck engine and has a "290" casting number on the block. It looks to have been rebuilt at one time but its all stock. When i pulled the stock cam out it had the groove in the rear cam journal. Is that normal ? Do i need to always have a cam with that groove ?


It depends on the block.
Some early 396 blocks needed the groove because they used a different rear cam bearing.
If you pulled and tossed the rear cam bearing already then look to see if the annular groove is in the block and the lifter gallery oil fed holes are drilled in the groove. If they are then no need to groove the rear journal.
An other thing to check is some cams did not have the two bypass holes drilled through the rear journal.
The rear bearing will have three holes in it and the rear bearing bore will be smooth with no groove if it is a block that needs a grooved journal.
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Re: 402 BBC cam help

Post by BillK »

If it is a 71 block it should not need the grooved cam as long as it has the correct cam bearing in it for 71. Look on the pad at the front of the engine and see if there is an engine code stamped there https://nastyz28.com/spmenu.html That might help verify what you have. If you are going to replace the camshaft bearings once you get the old ones out you will know for sure what you have.
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Re: 402 BBC cam help

Post by ProPower engines »

Also if the cam is from a real old manufacture I remember they used to just ad the groove regardless so it would work
in the older blocks as well as current for the time blocks as in early 70's engines.
But as Bill mentioned if the bearings are being changed it will be really obvious :D
Or if in doubt knock out the rear cam plug and check the bearing in the block for 1 or 3 holes.
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Re: 402 BBC cam help

Post by prairiehotrodder »

the rear cam bearing has one hole. Does that mean i really don't need the grooved cam ?
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Re: 402 BBC cam help

Post by ProPower engines »

That is correct.
I would remove the rear bearing just to be sure the oil holes are in the correct location and the groove is centered in the housing bore for the rear bearing.

I seen a block that some one just took a die grinder burr and carved a groove between the holes to save grooving a cam they got for a build.
If you were using a hyd. lifter it would be a problem with not enough oil but in my case the customers block as a solid lifter set up and the screw up acted as an oil restrictor of sorts.

Again you just never know what some one has done before you get into an engine [-o<
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