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Discussion Starter · #1 ·
Hi I have just bought a 1967 Camaro that has been a drag car in the past. What I want to do is place it back on the road running pump gas. The motor is a 1970 402 BB that has been built and setting rapped up on a stand since 1980. Everything in the bottom of the block is from a 427. The pistons are T.R.W. L2239N .30 over also from a 427. The heads are number 3919840 rectangular port with 2.19 - 1.88 values. I think the heads have been shaved. I know I can not use the high rise intake and two holley 600 on the street so they will have to go. I do know the car ran 10.4 -10.8 in the quarter mile. I am waiting to buy a cam and intake until I see if you guys can help me get the compression down from 12-1 without to much work. Or should I sell the motor and start over with a create motor? Thanks for your help.
 

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Are you sure about those piston #'s ??? That would indicate that your 402 has been bored 0.156 oversize,which sounds kind of excessive.Maybe it is a 427 block,bored 30 over.Anyhow,those pistons & heads should have a cr of well over 12.00:1,more if the heads were shaved.There is no simple solution here,you will either need pistons with a smaller dome,or open chamber heads with a bigger combustion chamber in order to use pump gas..
Guy
 

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I would check the block casting noumbers. 70 402 motors were a lighter casting and most won't go .125" over.

The last customer came in with a 402 bored to .125" had to have three sleeves in it. I told him it was junk, a waste of money. But, the customer is always right..
 

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Discussion Starter · #4 ·
Checked the numbers

Hi Guys
I checked the numbers again on the block. The back reads, D -7-70 on one side and 3969854 on other. The side casting is HIPER - PASS K-2. Front Pad reads, CEOA3765-8 this must be a replacement block. The piston number is L2239N .30 I thought this was a 402 maybe I am wrong, it would not be the first time or the last.
 

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Discussion Starter · #6 ·
If that is the case what a waist of good parts. I have heard of the machine shop that did the motor and I really thought they would know better. I guess just like someone else wrote, The customer is always right. So they just did it knowing better. I am thinking of placing this one a side and buying a create motor. Thanks for your help. :(
 

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If it was a drag motor there is a chance that the block has been filled, this would have enabled the builder to go way overbore and there wouldn't appear to be a problem until you had a major failure.
 

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Discussion Starter · #8 ·
It is very tempting to just put it together and try it out but it is a cost thing. If I have to buy roller cam, rockers and intake with carb and it does not work I am out some bucks. I know they say if you can not afford the toys then do not play with them. That is not the case, I just do not want to throw money away. I can not run the intake because of the height out of the hood. In Pa. that is not legal. The carb numbers are, List-4224-s 0774. I am not done checking things out and building the way it is might still happen.
Ha Double_v, I am not sure what you mean by the block being filled. That is new to me. Would that mean just between the piston walls? I was able to measure from inside the water jackets in a couple of places and from the outside to inside the wall thickness is 1/4 inch + or -. Between the cylinders is 5/8 inch. I know this should be done in thousands but that is the best I can do with what I used. I am going to try to attach some pictures. Maybe there is something about this motor that you guys see that I may be missing. Thanks for the help. All is being very helpful.
 

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I used to use that same carb/intake setup back in the early seventies. Those 660 carbs are called center squirters. Always load up bad at low rpm. unless the idle circuits are restricted. Actually a terrible setup, when compared with whats available now. But, back in the day, thats what we had..

"Filled block" means the block is filled in the water jackets with waterproof grout (cement). About the only way you could expect the thin walls to last. Most "filled" blocks are race only. Tho I have used them on the street if filled only to the tops of the freeze plugs (short fill). You would need at least an inch of water space below the inner deck. For coolant circulation.

The problem with the thin walls is that they are not concentric. They are much thinner between the cylinders, low in the block, than they are on the thrust side upper cyl.
 

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Discussion Starter · #10 ·
Bobcrman you have been a lot of help and I have learned some things from you that I did not know. I think what I am going to do is what F-Bird-88 has suggested. Tell me what you think. Maybe change the pistons to something less radical. Then call crane cam or Comp cams and tell them what I have and see what they would use in it. The heads may be a problem but maybe if I use Milodon Copper Head Gaskets compressed thickness of .060 Might help some. The head gasket bore size I am thinking would be 4.530 does that sound right? Not sure about what intake and carb yet. I will check with Summit and see what they have. Vacuum should not be much of a problem for my brakes are not power and I am using a M-22 trans. Hopefully the motor will stay together and I will not be picking up pieces along the road. I guess most of the parts I have to buy can be used again on a new block. Any ideas on pistons? Thanks
 

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Inexpensive low compression pistons for 427's are hard to find. Even the stock cast ones are 10.25-1 compression. I would look for some 1973 and later open chamber small port heads. I do a lot of 781 and 049 heads. Both oval port but thats all you want for street use. These will get the compression down to pump gas. Sell the big port heads. They go for good moneys to the restorers. 4.503 gaskets will also help kill some compression.

For the street use a dual plane intake such as Performer with a 780 vac secondary can't be beat for reliability and performance.

Good luck calling Crane. The place was auctioned off last spring!!
 

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Discussion Starter · #12 ·
Bobcrman That sounds like a plan. Did you mean 4.503 gaskets or 4.530? The heads will be on the market tomorrow. I did not know that Crane sold out last week. I appreciate all the help from you and the rest that answered. I hope to have some pictures on in the coming weeks. I will keep you as a contact on my sight. Thanks Again
 

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Take a look at the underside of the pistons you have, if they are a solid dome they can be machined down to a flat top if desired. I wouldn't give up the big port heads, just grind and polish them to a semi-open chamber configuration. Only way I would consider oval port heads is if this engine wasn't going to see revs over 5500, at that point a 427 is just getting started, you need to rev it up 7000+ and you will have scary power.
 

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Discussion Starter · #14 ·
ericnova72
I looked at the pistons tonight and they look like solid dome. After reading your post I started thinking that that block almost has to be a 427 and not a 402. Sure enough I found the block casting number to be a 1969-72 402, but they used the same number on 1967-70 427. That would make sense why all the parts, heads, pistons .30 and crank are from a 427. So now I have to start all over with what to do. To get the compression down.
 

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Combine some machining of the dome with some chamber deshrouding work, since it works two-fold for you. It will lower the compression ratio, at the same time increasing air flow if done correctly. CC the chambers after the rework(30cc syringe and an old cd work) so that you can determine how much to take off the dome to hit your target compression. Don't forget to allow for your piston-to-deck clearance if the block isn't zero decked along with gasket volume in your calculations.
 

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Discussion Starter · #16 ·
What is chamber deshrouding work? I understand the cd but what about the syringe, can you explain please. The block is not zero decked so I will take that into account. I did some research on the block to find that it might be a 427 and not a 402. I checked the casting number again and it comes up to ways. a 1970 402 or a 1968 -1970 427. Do you know anyway to tell the deferents? I can not figure out the pad number, CEOA3765-8 CE is a replacement block but do you know what the rest of the number means? I really like your idea it sounds like it would really do the trick. Thanks
 
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