Making a 350 out of a 327 (3892657)....

[Greg L.]

Re: Making a 350 out of a 327 (3892657)....

Thanks paul that was a good link on restamping, one of many but better than most.

I always get a kick out of when a question is asked and someone replies "check the archives" as though to say there is nothing new to be gained by asking the same question at a later date. That standard reply happens far more often on other sites than this one and I take it's because most people here are more willing to help than snap back with a comment.

I am quite aware of the debate of whether to restamp or not. With the GM of Canada docs that prove that this car is what it is I wouldn't think twice about having an actual 350 restamped anymore than restoring any other part of the car back to what it was or throwing a repop part on it. I however wasn't sure about stamping a 327 as a 350 because that may throw somebody for a loop down the road if they have to rebuild it....

I knew I'd get good answers here for the conversion and I thank those that helped with that but maybe I'll take the restamping part of my post over to a Camaro forum and see what they think.

As for "are you trying to start a fight?" What exactly do you mean by that Paul?

[Jim L.]

Re: Making a 350 out of a 327 (3892657)....

The block could be machined for a large journal crank. However, I'm not so sure this would be as easy a machining operation as it might seem, especially the rear main journal. Still, there are probably some shops with the capability and experience.

Are the main bearing cap bolt centers the same for small journal and large journal blocks? I would think that large journal blocks might space the bearing cap bolts slightly farther apart.

Jim

[Paul J.]

Re: Making a 350 out of a 327 (3892657)....

Thanks paul that was a good link on restamping, one of many but better than most.

I always get a kick out of when a question is asked and someone replies "check the archives" as though to say there is nothing new to be gained by asking the same question at a later date. That standard reply happens far more often on other sites than this one and I take it's because most people here are more willing to help than snap back with a comment.

I am quite aware of the debate of whether to restamp or not. With the GM of Canada docs that prove that this car is what it is I wouldn't think twice about having an actual 350 restamped anymore than restoring any other part of the car back to what it was or throwing a repop part on it. I however wasn't sure about stamping a 327 as a 350 because that may throw somebody for a loop down the road if they have to rebuild it....

I knew I'd get good answers here for the conversion and I thank those that helped with that but maybe I'll take the restamping part of my post over to a Camaro forum and see what they think.

As for "are you trying to start a fight?" What exactly do you mean by that Paul?

I should have used a smiley face. As you saw from the post I suggested, some people get "all riled up" when somebody talks about restamping. I personally believe that it won't make a bit of difference in 20 years because no one will be able to tell the difference between restamps and original stamps, and the market will reflect this. But that's just my opinion, I don't want to start the fight again.

In you're friend's case, I would'nt worry about throwing somebody a loop in the future as they would certainly investigate what they have, just as you have done.

As for the phrase "check the archives", I always appreciate the response from the sage members of this forum, and I know that they get tired of repeating the same information for each new member. That's why when someone asks a question that I remember from a past thread, I'll check the archives myself and always try to find the best thread and copy it to my answer. Although sometimes I'm also unsuccessful in finding the thread that I think will help.

Paul

[Clem Z.]

Re: Making a 350 out of a 327 (3892657)....

Are the main bearing cap bolt centers the same for small journal and large journal blocks? I would think that large journal blocks might space the bearing cap bolts slightly farther apart.

Jim

you are correct so that is why grinding the crank is a better idea unless you are going to use billet caps if you rebore the mains as you are thinning the original 327 cap with the over bore and they are not that strong to begin with. when we raced 327 we used "cap straps" and longer bolts

[Joe L.]

Re: Making a 350 out of a 327 (3892657)....

Are the main bearing cap bolt centers the same for small journal and large journal blocks? I would think that large journal blocks might space the bearing cap bolts slightly farther apart.

Jim

Jim-----


Yes, that is something one "loses" in the process of converting the block to larger main bearing size. However, if it were me, if I converted an engine this way I would definitely use aftermarket, billet steel main bearing caps with ARP bolts or studs.

[Tom P.]

Re: Making a 350 out of a 327 (3892657)....

Quote:
Originally Posted by Jim Lockwood (2750)
Are the main bearing cap bolt centers the same for small journal and large journal blocks? I would think that large journal blocks might space the bearing cap bolts slightly farther apart.

Jim

Jim-----

Yes, that is something one "loses" in the process of converting the block to larger main bearing size. However, if it were me, if I converted an engine this way I would definitely use aftermarket, billet steel main bearing caps with ARP bolts or studs.

Ummmmmmmmmmmmmmm, I'm 99.9999% positive that small journal SBs (265, 283, 327) and large journal SBs (262, 267, 305, 307, 350, etc, etc) have the same center-to-center main bolt dimensions. BUUUUUUUUUUUUUUUUT, absolutely for a fact, the SB400 blocks have a different main cap bolt center-to-center dimension.
I'll have to check to verify that tonight (providing I can easily access a 327 block). If I can access a 327 block easily enough, I'll pull off a cap and bolt it onto a 350 block and take a picture and post it (fish stories are ONLY credible if you take a picture of the fish).

[Clem Z.]

Re: Making a 350 out of a 327 (3892657)....

Quote:
Originally Posted by Jim Lockwood (2750)
Are the main bearing cap bolt centers the same for small journal and large journal blocks? I would think that large journal blocks might space the bearing cap bolts slightly farther apart.

Jim




Ummmmmmmmmmmmmmm, I'm 99.9999% positive that small journal SBs (265, 283, 327) and large journal SBs (262, 267, 305, 307, 350, etc, etc) have the same center-to-center main bolt dimensions. BUUUUUUUUUUUUUUUUT, absolutely for a fact, the SB400 blocks have a different main cap bolt center-to-center dimension.
I'll have to check to verify that tonight (providing I can easily access a 327 block). If I can access a 327 block easily enough, I'll pull off a cap and bolt it onto a 350 block and take a picture and post it (fish stories are ONLY credible if you take a picture of the fish).

you are correct i was thinking about the bolts for the windage tray are different. if you bore them the cap will get thinner on the bottom,the thrust side and you don't want that unless you plan on "strapping" them.

[Greg L.]

Re: Making a 350 out of a 327 (3892657)....

I should have used a smiley face. As you saw from the post I suggested, some people get "all riled up" when somebody talks about restamping. I personally believe that it won't make a bit of difference in 20 years because no one will be able to tell the difference between restamps and original stamps, and the market will reflect this. But that's just my opinion, I don't want to start the fight again.

In you're friend's case, I would'nt worry about throwing somebody a loop in the future as they would certainly investigate what they have, just as you have done.

As for the phrase "check the archives", I always appreciate the response from the sage members of this forum, and I know that they get tired of repeating the same information for each new member. That's why when someone asks a question that I remember from a past thread, I'll check the archives myself and always try to find the best thread and copy it to my answer. Although sometimes I'm also unsuccessful in finding the thread that I think will help.

Paul

Ya okay Paul I get it now. Sorry for snapping back.

[Tom P.]

Re: Making a 350 out of a 327 (3892657)....

OK, for those who are interested, here are the differences (main journal bores) between a small journal, large journal and SB400.
The first picture is a small journal (327) main bearing cap bolted on a large journal (350) block which shows that the bolt centers are the same.


The next 3 pictures are comparrisons of small journal (327) and large journal (350) main caps. As can be seen the overall height of both caps IS THE SAME! This means that the 350 caps are thinner at the bottom of the cap. Also, notice they share the SAME number on the caps---3951!






This picture is a comparrison of a 350 and SB400 cap. As can be seen, there is a noticeable difference in the bolt centers. I placed the bolt holes of one side of the caps even with each other so that the difference in bolt centers is quite obvious.


This picture is a comparrison of the small journal (327-lower), large journal (350-center) and SB400 caps.
Notice PARTICULARLY the difference in the location of the notch for the bearing caps as well as the notches in the block for the bearing tangs.


This last picture is the main bolts. The short bolt is for small journal blocks and has an 11/16in head. The long bolts are for BOTH large journal blocks and SB400 blocks and have 5/8in heads. Even though as shown above, the small and large journal caps are the same height, the difference is the placement of the threads in the blocks. Small journal blocks have the threads beginning at the edge of the cap register (that's the recessed area in the block where the cap fits). Large journal blocks have a pilot hole that is about 1/2in deep BEFORE the threads begin.

[Clem Z.]

Re: Making a 350 out of a 327 (3892657)....

your picture showing the bearing insert tang notches is one reason to turn the crank mains rather than bore the block as putting the notches back in the block and cap would be a problem for most shops. later 350 4 bolt caps were made from nodular iron instead of plain cast iron for extra strength. the counter bore was used to prevent the block crank bore from being distorted when torquing up the mains as there was less material between the block crank bore and the threads in the 350 due to the larger bore diameter

[Joe L.]

Re: Making a 350 out of a 327 (3892657)....

OK, for those who are interested, here are the differences (main journal bores) between a small journal, large journal and SB400.
The first picture is a small journal (327) main bearing cap bolted on a large journal (350) block which shows that the bolt centers are the same.


The next 3 pictures are comparrisons of small journal (327) and large journal (350) main caps. As can be seen the overall height of both caps IS THE SAME! This means that the 350 caps are thinner at the bottom of the cap. Also, notice they share the SAME number on the caps---3951!






This picture is a comparrison of a 350 and SB400 cap. As can be seen, there is a noticeable difference in the bolt centers. I placed the bolt holes of one side of the caps even with each other so that the difference in bolt centers is quite obvious.


This picture is a comparrison of the small journal (327-lower), large journal (350-center) and SB400 caps.
Notice PARTICULARLY the difference in the location of the notch for the bearing caps as well as the notches in the block for the bearing tangs.


This last picture is the main bolts. The short bolt is for small journal blocks and has an 11/16in head. The long bolts are for BOTH large journal blocks and SB400 blocks and have 5/8in heads. Even though as shown above, the small and large journal caps are the same height, the difference is the placement of the threads in the blocks. Small journal blocks have the threads beginning at the edge of the cap register (that's the recessed area in the block where the cap fits). Large journal blocks have a pilot hole that is about 1/2in deep BEFORE the threads begin.

Tom------


Good information. As far as the main bolt spacing issue, I must have been confusing the 400 block with the 283/327/350. I knew that one was different but I thought it was between the 327 and the 350.

[Greg L.]

Re: Making a 350 out of a 327 (3892657)....

Ya thanks for the pics Tom!

[Thomas H.]

Re: Making a 350 out of a 327 (3892657)....

Tom,
Thanks for the pictures and excellent information. In the last picture of the three main bearing cap bolts, what is the length of the 327 and 350 bolts?I have CE block ( small journal 327 3959512 ) that I would like to stroke out to a 383.The main bearing cap bolts are 5/8 and the length is 3 5/16. Are they 350 bolts are 327 bolts?
Thanks again Tom

[Tom P.]

Re: Making a 350 out of a 327 (3892657)....

Tom,
Thanks for the pictures and excellent information. In the last picture of the three main bearing cap bolts, what is the length of the 327 and 350 bolts?I have CE block ( small journal 327 3959512 ) that I would like to stroke out to a 383.The main bearing cap bolts are 5/8 and the length is 3 5/16. Are they 350 bolts are 327 bolts?
Thanks again Tom

I'll check and let you know. BUT, since you say they have a 5/8 hex head, I'm 95% sure they're the longer bolts for large journal blocks. All the small journal blocks (as I remember) had bolts with the 11/16 hex head.

[Clem Z.]

Re: Making a 350 out of a 327 (3892657)....

Tom,
Thanks for the pictures and excellent information. In the last picture of the three main bearing cap bolts, what is the length of the 327 and 350 bolts?I have CE block ( small journal 327 3959512 ) that I would like to stroke out to a 383.The main bearing cap bolts are 5/8 and the length is 3 5/16. Are they 350 bolts are 327 bolts?
Thanks again Tom

read this before you start and i would install 4 bolt main caps. place you old bearings in the block an place the crank in those bearings after coating them with axle grease
slowly rotate the crank and grind a minimum of .060 clearance anywhere the counter weights might touch the block and try NOT to grind more than about .070 any place it touches the block (use a JUMBO size paper clip as a gauge if you don,t have feeler gauges)
next assemble two connecting rods and pistons, one connecting rod and piston for the left one connecting rod and piston for the right, use old bearings coated with axle grease and no rings on the pistons, assemble them to the crank and grind anyplace the rods touch the block, grind minimum of .060 clearance and try NOT to grind more than about .070 any place the rods touche the block (use a LARGE size paper clip as a gauge if you don,t have feeler gauges)move them to the next journal and repeat until all 4 journals and 8 connecting rods clear. now assemble all eight rods and pistons without rings and install them in their correct locations and recheck everything carefully.
next install the cam and index it correctly with the timing chain/gears, rotate the engine slowly and look for clearance issues, between the cam and rods/rod bolts ,you will need to use a small base cam if there are major clearance issues but in most cases if your cams lift and duration is under about 230 at .05 and .500 lift there should be minor if any clearance issues, usually the outside edge of a rod bolt head is the only area needing a touch up.

once everything clears, wash all the parts VERY CAREFULLY ,TWICE and re-oil then send out to be balanced now you might ask why do that! well, first you'll know its done correctly, and that a correctly built 383 will have a very significant hp and torque advantage over any similar 327 or 350</B> my advice unless you are a experienced engine builder i would buy a complete short block already built