Broken 4.1 NA Block

[ek02]

I broke the bearing webs on #2 and 3 mains. This is a NA 4.1 with a steel stroker crank and ARP studs, GN1 heads, Comp roller, etc. Maybe 325 HP without the nos. It had a 175 shot of nitrous on the last run. I usually run a 125 shot. It also shows a lot of cap walk on the block and caps. The pistons look perfect and the plugs were clean. There were no signs of detonation. The timing retards with a MSD Digital 6 ignition when the nitrous hits and there is a fuel pressure safety switch to turn off the nitrous if the fuel pressure drops on the dedicated fuel system. The only reason I can figure it broke and has cap walk is that the Buick 4.1 block is not strong enough to take the sudden hit of power from the nitrous. I have another block ready and a RJC girdle on the way. I'm hoping the girdle will solve the problem, but I will probably go back to the 125 shot. Any experience with NA's on nitrous on this site? I know there are a lot of boosted 4.1's out there that live with just a set of billet caps and studs.

 

[bison]

I've seen them take a few hits over 800hp with a turbocharger so I'd suspect a lot of detonation here

 

[ek02]

I suspected it too because of the metal transfer on the registers and caps, but the polish on the JE piston heads looks new. I guess you can have enough detonation to rattle the mains severly and not get the pistons hot enough to throw off any specs of metal. I run it rich and take out 6 degrees of 32 degrees timing when the nos hits, ands I run 105 octane race gas and very cold race plugs. My fuel pressure to the fuel solenoid could be dropping, but the pressure switch should shut down the nos system if it goes below 5 psi. I'm counting on the girdle to give me some more strength and not let the crank try to push out the bottom. The bearings looked ok, but were blue at the bearing parting lines, like the caps went egg shaped. At least I can reuse my crank and rods. The crank looks like new, as well as the rod bearings, which will be replaced anyway. My new block has to be bored .030, so it's new special order pistons and rings time.

 

[fuzzyGN]

What made you dig into the engine? Was it making noise? What compression is the engine? What times does it run in the 1/4 mile? I have a similar build but mine is not yet complete. It would be cool to compare notes. Not too many building N/A stock block stuff.

 

[ek02]

The engine developed a deep knock and was vibrating at 2000 rpm. The last time I ran it in the 1/8th mile, I had it jetted for a 175 shot. I ran 7.83 @ 95 mph on a 125 shot on MT street radials. The 60 ft was 2 seconds, so I have work to getting some traction. It didn't run any faster with the 175, but it may have been detonating on those runs. I had 9.75-1 compression on the old engine. I just ordered a set of .030 over JE's with 10-1 compression for the new block. You can probably go 10.5-1 with aluminum heads on pump gas. I have this V6 in a Toyota pickup with a Turbo 350, JW 3400 converter, Gear Vendors overdrive and a Ford 8" rear with 3.80 gears, a Detroit locker, and Curry axles. I have my spare 3.8 with big intake valve ported iron heads, T&D rockers, and a flat tappet cam in it now, and it does not have anywhere close to the power the 4.1 with the stroker has. I run a 600CFM Edelbrock carb on a ported Kenne Bell intake, and 3 into 1 headers that I built to match the old Kenne Bell headers dimensions. I have a Comp roller in the 4.1 with 108 degree lobe seperation and 228 int 232 exhaust @.050. The 3.8 has the same timing specs, but does not idle as well as the 4.1 due to less displacement. I see you have a Vega wagon. I put a Olds 215 aluminum V8 in one for a customer back in the 70's. It was like a V6 with 2 more cylinders. I helped on a V8 swap also. Those cars are light. It should be a nice running combination.

 

[fuzzyGN]

Mine is a notch up from yours and thus probabaly not very streetable. The car right now is only about 2340 pounds with an iron head V6. I am going to remove some weight but also add in a cage so I am not exactly sure where it will end up weight wise. Mine is a stock stroke (kicking myself for that), internally balanced, 4" bore, 13 to 1, aluminum heads, big solid roller 250 and 260 @ .050, 5200 stall in a TH-350, and currently 4.30 gears. I think it may have too much gear but it is still the 7.5 Vega rear. I am pretty sure I will need to do axle retainers so unsure of what to put into the car. I still run the torque arm so the choices are a little limited. I have speced out a 750 Holley HP but have yet to get it. I added a 4 into 1 blended spacer with a built in spray bar. Very cool piece. I plan on a 150 shot max. Since just the nitrous is about the same HP as the engine in the car now, I have stuck the new engine in the corner and turned to making the car safer. Full aluminum seats, cage, etc. Not sure what to expect but I think it will run pretty good. Besides the stroker crank I don't think I left much on the table for a stock block. The current stock stroke, 8.5 to 1, iron headed, $600 engine has run a best of 14.6 in the quarter. That was at 4500 foot elevation. I guess the HP of that one at about 175. Fun to kill Moosewangs with a V6 that cost less than their insurance for a few months.

 

[ek02]

Your combo sounds good for the strip. I street drive my truck or I would raise the compression, cam lift, and duration. My lift at the valve is only .526" I actually towed a flats boat for a couple of years with the stroker motor before I put on the NOS and started racing it. It had 12,000 miles on it then. The only problem I had was a broken Champion rocker stud. I replaced them with identical ARP screw in Chevy studs and have had no problems since. I have 2 fuel tanks and can switch from 93 octane in one tank to race gas in the other. The tank with race gas has a seperate fuel pump and system for the NOS fuel solenoid. Your roller cam and aluminum heads will make a big difference, I think. The bigger valves are closer to the center of the cylinder and flow a bunch better than irons. Your only giving up 20 or so cubic inches without the stroker crank. It should run strong. I am nervous about my 8" rear. That's why I don't have slicks. If I ever get around to putting a 9" rear in it, I think slicks would drop my 60 ft way down. You may want to think about a progressive controller for the nitrous system if you end up going up in smoke off the line. Also, a lower stall speed usually works better with nitrous due to the torque it makes if activated right off the line. At least that is what I am told. I had a 2800 converter in it when I ran the 7.83. I was not able to try the JW 3400 with nitrous before the knock started. I got the RJC girdle today, just waiting on JE to finish the pistons, then it's off to get the girdle fit and the block bored. Now if only Stage 2 blocks were not so high priced these days.

 

[fuzzyGN]

The converter is quite a suprise for sure. I contacted Dusty and that is what he recommended so I went with it. I can always have it restalled if necessary. Right now with the slightly built Vega 7.5 rear, I run cheater slicks and it holds up fine. I have upgraded 28 spline axles, locker, and a girdle. Of course with only about 175 HP so what. The big draback is the Vega pinion diameter is smaller than all other housings. To make gears fit, I had to turn down the pinion. I have run a best of 2.05 60 when it had the 4speed. I would dump it at about 4200 per the 2 step in the Digital 6. What does your truck weigh? I would think the 8" would be a bit good stronger than a 7.5. In fact, it may be a good upgrade choice for me. Since I don't have many cubes, I need to keep the weight down wherever possible so a 9" is just silly. With the weight and HP of the car a 9" is way overkill. I don't plan on tubbing the car so traction could be an issue. I currently have a 26 9 14 tire which is not very big. The larger sidewall of the 14 does help though. I could fit a slightly wider tire but would then have to step up to a 15 inch wheel. A nitrous controller may be in my future. For now though, I probably won't even run the nitrous. Should still run good without it. Since the engine sits so low in the car I didn't have room for a girdle. I am stock caps and ARP studs. Hopefully it will stay together. For what I have into this little project I could have had a slightly built LS engine. Not near as cool though.

 

[charlief1]

Well you could always find a 9 bolt out of an F body and shorten it up Erik. That would give you a stronger rear and still keep the arm, but it would be on the other side.

 

[ek02]

My truck weighed 2900 lbs on a set of portable DOT scales with 2 full tanks of fuel. It seemed a bit heavy, but I later found out one of the scales was reading a little high. My MT Street radials are 275/50-15's on 10" rims. An 8" rear will probably live for a while with an automatic trans. I like the Ford rears because I used to build them all the time when I worked for a dealer. I later went to work at a hi performance shop and I used to build the 9" rears for the bosses Top Alcohol funny car and T/A dragster. Also for one of his friends funny cars who's son later became a well known Top Fuel driver. They were Lenco housings and Sheiffer pinion housings and gears. The ring gear bolts used to come out s shaped after a good number of runs. Nowadays, they would not live behind a pro stocker. You will be fine with studs on stock caps, especially if you have a steel crank. Mine was fine until I kept uping the nitrous. I'm still trying to figure out what in the setup may have caused the detonation. The caps were banging up and down hard to transfer metal like that. I wish I had room for an LS in my truck, but I've had it for 38 years and don't want to cut the firewall. The Buick is such a nice fit, and I've had 4 of them in there over the years.

 

[Dusty Bradford]

I would run no more than 25 degrees of timing with a 175 shot and 9.5-1 compression.

Rich isn't actually safe, especially on a nitrous car. Rich is what burns pistons, lifts ringlands, etc when fuel puddles up. People think lean conditions do this but in reality many times it's too much fuel causing the issue.

 

[bison]

I would run no more than 25 degrees of timing with a 175 shot and 9.5-1 compression.

Rich isn't actually safe, especially on a nitrous car. Rich is what burns pistons, lifts ringlands, etc when fuel puddles up. People think lean conditions do this but in reality many times it's too much fuel causing the issue.

Yup. Especially guys who usually tune boosted engines. Rich is like a grenade on N2O.

 

[ek02]

I never thought of a rich condition causing my problem. This is something I need to consider for sure. I had upgraded to a dedicated fuel system with more pressure, which would have made it run richer than before the upgrade. I also ran low on nitrous on the last run and it started missing badly because it was very rich at the end of the run. Thanks for that information.

 

[fuzzyGN]

Good info indeed. It does make sense when you think about it. I am just going to use one big pump but 2 regulators, one for the engine and one for the N2O. That way the tune can be refined for both on and off the bottle with little compromise.

Your weight does sound a little high but fuel is very heavy and you have twice as much. But really, anything under 3 grand is still pretty light. I looked and there doesn't appear to be too many aftermarket parts for the 8" Ford. TONS of stuff for the 9" obviously but there is just something about installing one I don't like. I feel like it is wimping out and not "engineering" a solution. Strong no doubt but I am pretty sure I don't need that kind of strength. Besides the cool factor for me has always been "be different." A Vega wagon isn't seen everyday. A Buick V6 instead of a V8, N/A instead of turbo, a 9"? Just doesn't seem to fit the formula. I think I can make the stock 7.5" rear live but for how much money? Once the axle retainers come into play we are pretty committed. Don't get me wrong, I think the 9" is a great way to go but just not for this car at this stage. I think you are correct about the crank. I believe it (stock flexy thing) is the root of many lower end issues. A steel crank and studs, at least at this power level, should be more than adequate. The LS route again gets away from the formula of "Why would you ..." or "What the heck is that?" I love hearing that at the track. That car gets more grudge challenges than any other car I have owned. To me that is what it is all about. For the Vega, a Buick is a bolt in. I think I am going to lower and move back the engine a little for better weight distribution though so the stock mounts are gone and custom stuff will be used.

Charlie, there is a guy building torque arms for the Vega which resides in the stock location. He builds them so they can be used on the stock rear or attached to a 9" with an additional bracket. Very cool piece. His website is Overkill racecars I think. His name is Justin Kill. Great H-body support.

 

[ek02]

I got the Detroit Locker from Summit, but it may be discontinued. Curry has axles, gears, an aluminum housing, and all the associated parts for the 8" Ford. I like the idea of one big pump for both systems. I already had one Edelbrock 7 psi pump for the engine, and had another on the shelf, so I used it for the NOS fuel system. It's surprising how many people know I have a Buick V6 at the strip because of the way it sounds with open headers, but they usually think it has a GN with a turbo. One night I was standing close to the truck with the hood open. A guy and girl walked up and looked at it, and the guy said " Someone had too much time on their hands". My wife thinks so too. At least she knows where I am.

 

[charlief1]

You would've enjoyed the looks of the guys on the street when I opened the hood of my Skyhawk. Car sounded like a V8 and the chasis even rocked back and forth at idle. You have no idea how many got suckered by that little car. Still wish she was in good enough shape to put back on the road but I'd have to kae it a tube chasis car to do it now since I tweeked the frame on the road courses.

 

[ek02]

If you had an odd fire in it, they sure did shake and sound like a V8. I had one I took out of a wrecked 3600 mile Skyhawk. I ran it for 265,000 miles and all I ever did to it was a roller chain and 2 valve jobs. I sold it to a guy that put it in a Jeep.

 

[charlief1]

If you had an odd fire in it, they sure did shake and sound like a V8. I had one I took out of a wrecked 3600 mile Skyhawk. I ran it for 265,000 miles and all I ever did to it was a roller chain and 2 valve jobs. I sold it to a guy that put it in a Jeep.

It started as an oddfire but when I spun the rod bearing I went evenfire and the high port heads. KB 1 & 5/8 tube headers and all the goodies I could afford at the time. Rhere and Morrison did the machine work on the block and that was a chunk back in the mid 80's.

 

[fuzzyGN]

Yep, I am V6 all the way. I sold off all of my Chevy V8 stuff years ago. I really like the weight advantage. My new engine with the aluminum heads, fully dressed with carb and N2O stuff will be way less than 300 pounds. Should be right near 275. That is 300 pounds lighter than an iron head SBC. If I go with the 8" I will have to look at Currie. I may end up with an 8.8 due to strength and it still has the bolt on rear cover. At least it doesn't look like I wimped out and went with a 9". Before I had a hood I would still hear people walk by and say "Oh, a V8 Vega." Really? Count the plug wires. It inspired my plate "V6 POWER" which says it all. Charlie, how about those headers ?

 

[charlief1]

Charlie, how about those headers ?

Gota finish up a truck today and I'll see about getting ou to the car and take them off Erik. Once I get them off I'll send you some pics.