Planning for an engine rebuild

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Which way should I proceed with my plan to rebuild?

  • build the 2 bolt main with the 4 bolt maincaps

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The plan for my car is to rebuild the short block in the near future, but not during prime driving seasons. When I bought the car three years ago, 2 cylinders were down on compression. When I did the top end and cam, the bores look good, but I suspect the rings may be bad. Since then while the engine runs very strong, I have wanted to build with forged flat top pistons to complement my Boss 351 style closed chamber heads and solid cam.

Here is my dilemma. The engine in the car is a 4 bolt main. Based on the ring ridge at the top of the cylinders I'll need to have it bored.

I have a nice 2 bolt main block with such a minor ring ridge that it may clean up with just a breaker and a hone.

So I have three basic choices

1) Build the 2 bolt main block and have a weekend of downtime with the car.

2) Pull the engine to build the 4 bolt main, have the car down for two months plus while machine work is done and and parts are gathered.

and finally the worst of both worlds

3) Use the two bolt main block, but the 4 bolt main caps and have the block drilled and tapped to be a 4 bolt main block. This gets me what I think will be the smaller overbore and the 4 bolt mains, but essentially all of the downtime.

Now as I understand it, 2 bolt mains are not really a liability until horsepower levels go pretty darn high. I like the idea of 4 bolt mains, and if the block is usable, I sure as hell am not going to get rid of it.

What say you genuises?

The plan includes a possible stroker crank if I can decide on a brand and the best displacement option-any advice welcome here.

 
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Born an I-6, spent the teenage, 20 and 30 years as a 302, but at 40 will reach full potential as a 351C.
1. I would dare any driver to drive a random, souped up 351C with power, and tell me whether it was a 4 bolt or 2 bolt main.

2. I am not a stroker fan. If I wanted a 429, I would be a 429. But that is because I am weak kneed at the proposition of building an engine without a complete set of operating specifications. I am a long term engine builder and want to get 250k miles out of my engines, and I doubt any stroker driven like I drive will have that type of endurance...with or without 4 bolt mains.

In conclusion, I would build the 2 bolt(you can always machine in the 4 bolt mains with the mains you have). If it isn't enough power, then you have the 4 in the bank.

 
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Hey Jeff -

How are you going to use that beast? Take her to the track on weekends, burnouts around town, daily driver, trailer queen? If it were me (and I can't believe I'm saying this after taking 1 1/2 years to rebuild mine) I would keep the 4-bolt block that in her and bore .030 over. Since you plan to replace the crank anyway, you won't have to worry about grinding the crank.

My 2 cents.

 
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Build the 2 bolt main block. There is no advantage to a 4 bolt main cleveland other than bragging rights.

You could probably sell the 4 bolt block and fund a good chunk of your rebuild costs.

 
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Thank you all.

I'm leaning towards actually pulling the engine and taking both blocks to the machinist to see which one is the better block in terms of cylinder wall thickness. Clevelands are such thin walled creatures that an overbore should be held to the minimum as dictated by the block, never just bore one 30 over cause that is the common overbore.

Tommy I think you are right, just can't bring myself to sell my 4 bolt main shortblock only to never find another one.

 
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Thank you all.

I'm leaning towards actually pulling the engine and taking both blocks to the machinist to see which one is the better block in terms of cylinder wall thickness. Clevelands are such thin walled creatures that an overbore should be held to the minimum as dictated by the block, never just bore one 30 over cause that is the common overbore.

Tommy I think you are right, just can't bring myself to sell my 4 bolt main shortblock only to never find another one.
That's probably your best bet. Unless you are going to run some high rev's the 2 bolt is just fine, if both are equally as good after inspection, sell the 4 bolt and use the money.

 
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Born an I-6, spent the teenage, 20 and 30 years as a 302, but at 40 will reach full potential as a 351C.
I am unaware of anyone who has bored a 351c up to .040 and had an issue. Don't know anyone who has done a .060, but sleeving is an option with the right mechanic.

My sample size would not be in the hundreds, but certainly 50 or so.

 
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Is the 4 bolt block the block that came with the car? If it is, build that one if you can. On stroker kits I've seen fewer dimensional problems with Scat than Eagle. The off brand stuff on ebay should be avoided like the plague. You can spend a lot more if you want to to but, the Scat stuff has worked well for me for hot street engines. If it is a street motor (6500 rpm) go for the cubic inches (408). If you want to race it (7200 + rpm) you'll spend a lot more and want to use a shorter stroke crank (3.85 or shorter) to yield a 393 or smaller displacement. Just my experience and opinion. Chuck

 
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You can easily get 500hp+ with no worries on a 2 bolt mains. As you stated get the thickness of the cyclinders checked and use the thickest. That is the weak link on these motors. Good luck!

 
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Oddly enough I was leaning towards a smaller stroker rather than the larger one. Then I learned that the 393 cranks were harder to balance than the 408's I definitely don't want the short compression height of some of these stroker combos, and I'd like the 6" rods. I was hoping to get the best grade crank possible internal balanced ie., Lunati or something equivalent but may use a stock crank offset ground to get a engine displacement of 377. Still thinking.

As to use, it will be a play car to be driven obnoxiously when the road is empty, driven mildly when the kids wanna ride, taken to the dragstrip with the intent of breaking into the high 12.s on street tires and at 3500-3600 pounds of car weight with a manual transmission and if I can find a legal top speed event I want to see a top speed of 160. I want to turn a true 7500 RPM. It can be done with these engines and fairly easily I believe, but I am still (and hopefully always) learning. I think that all this can be achieved at 351 CID, but I think it can be done with a bit less drama with some additional displacement.

Wolverine is right. Strokers are what I will call a less known factor. Durability is less certain. I want to make good decisions in the planning stage and then execute properly. That is why I am thinking early on about my options. I have used the old shortblock as a testbed for the cam change, the head change, the ignition change, I will be changing carbs for a bigger one in the near future. I want to know all is right with my set up before I tear it down and rebuild the short block. If I should damage a known worn component in the process, it will not a big deal.

 

Tnfastbk

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Oddly enough I was leaning towards a smaller stroker rather than the larger one. Then I learned that the 393 cranks were harder to balance than the 408's I definitely don't want the short compression height of some of these stroker combos, and I'd like the 6" rods. I was hoping to get the best grade crank possible internal balanced ie., Lunati or something equivalent but may use a stock crank offset ground to get a engine displacement of 377. Still thinking.

As to use, it will be a play car to be driven obnoxiously when the road is empty, driven mildly when the kids wanna ride, taken to the dragstrip with the intent of breaking into the high 12.s on street tires and at 3500-3600 pounds of car weight with a manual transmission and if I can find a legal top speed event I want to see a top speed of 160. I want to turn a true 7500 RPM. It can be done with these engines and fairly easily I believe, but I am still (and hopefully always) learning. I think that all this can be achieved at 351 CID, but I think it can be done with a bit less drama with some additional displacement.

Wolverine is right. Strokers are what I will call a less known factor. Durability is less certain. I want to make good decisions in the planning stage and then execute properly. That is why I am thinking early on about my options. I have used the old shortblock as a testbed for the cam change, the head change, the ignition change, I will be changing carbs for a bigger one in the near future. I want to know all is right with my set up before I tear it down and rebuild the short block. If I should damage a known worn component in the process, it will not a big deal.
HMMMM if you are scared buy a dog, Stroke it to 408 and be happy or stay safe and always wonder what could have been. Hell Stroke the 2 bolt block and save the for bolt for future use if needed. But from what I have read the blocks are the same just some are drilled for the 4 bolt caps.

 

droptop73

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Nothing wrong with building a 2 bolt block. Under severe use the main caps are going to walk no matter whether you use the 2 or 4 bold mains.

I'm with Tommy use the 4 bolt block to finance the 2 bolt build.

 
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I will argu that 4 bolt mains are not just for bragging rights...Ford did not put them on just for fun..And if ford new they would be fine up too 500 or 600 hp..Why would they waste the time drilling blocks that where not going to get close to that high? I my self wouldnt mess with a block that didnt have 4 bolt main and pushing above 450hp.....Sure it mite handle it..But for how long? bottom ends like to move around..clevelands love to rev high....Is it worth 2 extra months ? all counts on how much you plan to do...and how much money you got....But if your planning to run 12's..and still go 160? Man you going to need 600 hp....I wouldnt depend on the 2 bolt if it was me...But its not. i believe in over building my self....Just remmeber all cars that come from most car compaines over 300 hp are 4 bolt mains for a reason....They would not over engineer if they didnt have too.

 

Don65Stang

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I also agree to build the block original to the car if one of those is it. I also agree to take both to the mechine shop and build the nicer of the two blocks.

 
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I will argu that 4 bolt mains are not just for bragging rights...Ford did not put them on just for fun..And if ford new they would be fine up too 500 or 600 hp..Why would they waste the time drilling blocks that where not going to get close to that high? I my self wouldnt mess with a block that didnt have 4 bolt main and pushing above 450hp.....Sure it mite handle it..But for how long? bottom ends like to move around..clevelands love to rev high....Is it worth 2 extra months ? all counts on how much you plan to do...and how much money you got....But if your planning to run 12's..and still go 160? Man you going to need 600 hp....I wouldnt depend on the 2 bolt if it was me...But its not. i believe in over building my self....Just remmeber all cars that come from most car compaines over 300 hp are 4 bolt mains for a reason....They would not over engineer if they didnt have too.
I think your horsepower estimate is pretty damn close. And there is apart of me that thinks the same way. If I could find another set of main caps I'd definitely upgrade the 2 bolt block. I may also look into a main cap girdle, though I don't know a whole lot about them.

and all of you wanting me to sell my 4 bolt main block to finance the build . . . will you be bidding :D (It won't be sold, I am hoping to build a Maverick 2 door somewhere down the road.)

 

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"In essence, we'll be building the equivalent of a 9.2-1 compression ratio Boss 351C with a power output of apprximately 400hp. Virtually any 351C block can be used, since there are no differences in materials or strength. In fact the 2 bolt main cap block (part#-D0AZ-6010-C) is just as good as the 4 bolt main block (part#D1ZZ-6010-D) Even the caps seem to be of equivalent strength. So unless you already have a 4 bolt block, dont spend the extra bucks for this feature". Jack Roush, Hot Rod Magazine,Profecting the 351C...for the street. 1976

 

Don65Stang

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"In essence, we'll be building the equivalent of a 9.2-1 compression ratio Boss 351C with a power output of apprximately 400hp. Virtually any 351C block can be used, since there are no differences in materials or strength. In fact the 2 bolt main cap block (part#-D0AZ-6010-C) is just as good as the 4 bolt main block (part#D1ZZ-6010-D) Even the caps seem to be of equivalent strength. So unless you already have a 4 bolt block, dont spend the extra bucks for this feature". Jack Roush, Hot Rod Magazine,Profecting the 351C...for the street. 1976
Very nice! I've heard parts of that quote but not all of it at once.

 
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