396 engine rebuild questions

[Bill W.]

I have two original 396 engines that need rebuilt , one built about 6 days before my car and the other about 12 days before .. Engine one is complete but one cylinder was allowed to freeze & crack ,it would need at least one sleeve and it has a small crack about an inch long that goes down into the webbing below the cylinder . It also has lots of pitting in the other cylinders and could need multiple sleeves .
Engine two was an old drag racing engine I was told it was a blower motor . It has been bored to 427 and then some and has one cracked cylinder and would need all the cylinders sleeved . It has had one sleeve replaced in the past . It also has heli coils in most of the head bolt holes on the right side some of them are loose . What is the best repair for the head bolt holes ? New heli coils or thread inserts ? Both engines have very nice original stamp pads and I am told the work can be done without damage to the pads . I have been looking for my original block (17346) sense the early 80s these are the best I could find without stamping .which block would be the best to rebuild ?

[Donald O.]

Re: 396 engine rebuild questions

Bill,
I would recommend engine #1, the one that wasn't used as a blower race engine.
Don

[Michael H.]

Re: 396 engine rebuild questions

I agree with Don, except I would sleeve all of the cylinders to STD bore. That way you'll have more metal in the block to help dissipate heat.


Mike

[Patrick B.]

Re: 396 engine rebuild questions

A 65 only 396 has the same water jacket core as a 427 and can be treated as a 427 bore wise. I would run either engine as a 427 +.030 or +.060 before considering sleeving all 8 cylinders. An overbore of .060, .080 or 0.100 on the 396 bore would be a piece of cake.

[Joe L.]

Re: 396 engine rebuild questions

I have two original 396 engines that need rebuilt , one built about 6 days before my car and the other about 12 days before .. Engine one is complete but one cylinder was allowed to freeze & crack ,it would need at least one sleeve and it has a small crack about an inch long that goes down into the webbing below the cylinder . It also has lots of pitting in the other cylinders and could need multiple sleeves .
Engine two was an old drag racing engine I was told it was a blower motor . It has been bored to 427 and then some and has one cracked cylinder and would need all the cylinders sleeved . It has had one sleeve replaced in the past . It also has heli coils in most of the head bolt holes on the right side some of them are loose . What is the best repair for the head bolt holes ? New heli coils or thread inserts ? Both engines have very nice original stamp pads and I am told the work can be done without damage to the pads . I have been looking for my original block (17346) sense the early 80s these are the best I could find without stamping .which block would be the best to rebuild ?

Bill-----

Personally, I wouldn't rebuild either of these blocks. The first block would be OK with 8 sleeves except for the crack that goes down into the lower webbing. I don't know of any effective way to repair that.

The second block is scrap metal.

[Bill W.]

Re: 396 engine rebuild questions

DSC_1907.jpgDSC_1906.jpgDSC_1904.jpgDSC_1902.jpgpictures of the crack below # 1 cylinder . can it be fixed in that area ? I read they can drill and plug the cracks , but can they do it in the lower cylinder area ?

[Donald O.]

Re: 396 engine rebuild questions

What does your machinist recommend for a bore on the non cracked cyl?

I would definitely have the cracked wall sleeved, and depending on how much the others needed boring, might sleeve those as well.

I would also ask your machinist for his opinion on the lower crack, but I would use the block. If I had enough gas torches and the supply of gasses, I would grind out the crack and then refill it with fresh cast iron fill. Its not a difficult job, but is very heat intensive for the repair welding as the whole area has to be cherry red during the heat up, the welding and the the long tapered cool back down.

Don

[Bill W.]

Re: 396 engine rebuild questions

Pat . I did a quick check of the race block it appears to be about 4.274 or just under .030 over 427 and would need one sleeve . what do you think about that . Do you know anything about the head bolt hole repairs . If i went 30 or 60 over 427 would there be a over heating problem ?

[Wayne L.]

Re: 396 engine rebuild questions

I am rebuilding an original 65 396 engine. The VIN derivative stamping is 91 cars away from the car it is going into (one day?). The block was standard bore with a sleeve in #4 cylinder. Block is now 0.030" overbore. The machinist I have been using for years checked everything over, especially the sleeve to make sure it was tight, etc. He does a lot of high performance engines, and felt that the block would be fine, considering that most NCRS Corvettes do not get very many hard miles.
Bill, I would go with the first one (6 days). There are a few welders out there that can do what Don is describing. The last piece of thin-wall cast iron I had welded up was a 609 water pump. He took a day to get the two pieces up to temp. Then another day and a half cool down.

[Patrick B.]

Re: 396 engine rebuild questions

Pat . I did a quick check of the race block it appears to be about 4.274 or just under .030 over 427 and would need one sleeve . what do you think about that . Do you know anything about the head bolt hole repairs . If i went 30 or 60 over 427 would there be a over heating problem ?

Your block will be fine with a 4.280 bore and one sleeve. It will have the same wall thickness as a 427 block .030 over, and they have no problems. If replacing the helicoils is unsuccessful, there are a number of thread inserts with a larger OD that could be used. Keensert is one brand name but your machine shop may have experience with its own favorite brand.

The crack in the other block is a more difficult situation than using a 427 bore in a 65 Corvette 396.

[Bill W.]

Re: 396 engine rebuild questions

Pat thanks for your help

[Philip A.]

Re: 396 engine rebuild questions

Please help to educate me. It appears sleeving either block is acceptable. The aversion to block #1 is the crack in the webbing which I understand. Is the aversion to block#2 the head bolt threads or the fact it was used as a blower motor? If the threads, I think heli-coil type repair with studs (rather than bolts under the valve covers) should be OK. At least my thought over a crack repair. Does the blower use effect the block and how?

[Bill W.]

Re: 396 engine rebuild questions

Phillip on number 1 I would worry about the crack although I am told it can be fixed . on #2 the head bolt holes can be fixed with thread inserts . It is now bored to 427 + about .030 and needs one sleeve if the bore is left as is ,or 8 to be std. As for as being a blower motor I think it just means it had a short but rough life .

[Joe L.]

Re: 396 engine rebuild questions

Phillip on number 1 I would worry about the crack although I am told it can be fixed . on #2 the head bolt holes can be fixed with thread inserts . It is now bored to 427 + about .030 and needs one sleeve if the bore is left as is ,or 8 to be std. As for as being a blower motor I think it just means it had a short but rough life .

Bill------


Has the previous blower motor block been magnafluxed? Do you know that it doesn't have cracks? Has this block been checked to ensure that it hasn't been "stabilized" by having the cooling passages partly or completely filled? Many drag racing engines receive this treatment.

[Bill W.]

Re: 396 engine rebuild questions

Joe there are no visible cracks on the race engine. The block will be checked by the machine shop before any work is done. The cylinders will be checked and the final decision made on sleeves .The water jackets have not been filled . I am going to remove all the drains and freeze plugs tomorrow for a final check. It goes to the machine shop in about two months .