350 of a different color. 3.25" x 4.135"
 

Back in 1998 or so, Hot Rod Magazine ran an article on the "The Small Block Chevy Should Have Built". It detailed a 350 CI motor that had a 3.25" stroke and 6.20" rods in a 400 block bored to 4.145" or .030" over. Theoretically it would be a motor that made great power, got great gas mileage and would last forever. The rod/stroke ratio was the key as well as the complete compliment of parts that allowed for 11:1 compression ratio on 86 octane gas. They built this motor and the dyno numbers were pretty good. They made a shade over 400 hp and a stout 425 ft/lbs peak with the motor never seeing less than 390 ft/lbs (390 ft/lbs at 2300 rpm).
I am about to embark on the same journey. Many might say why would you waste a good 400 block on this! Well, to be honest, I wouldn't have if I hadn't stumbled on this 400 block that had lost it's low end with just 10,000 miles. Consequently, the rods took out about 1/2" of bore, just clean broke it off. Now the block would not work with a 3.75" stroke because the piston skirt would be unsupported at that stroke. I had the block Magged and it works perfectly for the motor described above....and it cleans up .010". The rods I'm using are 6.25" which allow me to use off-the-shelf 400 pistons designed for a 6" long rod. In other words, 1.125" compression height. I bought a complete set of .010" over CP pistons off of racersauction.com for $180. A rule change forced the seller to sell with the pistons only seeing dyno time. They checked out beautiful. I have aquired a large journal 327 crank and a set of Total Seal rings. All I need to do is get the machine work done and a set of AFR heads. I am using the same cam as Hot Rod did and that's the hydraulic roller Magnum 270 HR. Funds might force me into Vortecs but I will need to change the cam to a dual pattern. Overall cost might end up the same.
REACTIONS? OPINIONS? SIMILIAR EXPERIENCES?

Sounds neat but get a good 400 block. They aren't as rare as you seem to think, but 4 bolt blocks are expensive. Just find a good 2 bolt so you don't have to mess with the previous disaster.

The block I have is in perfect shape for what I am using it for. It is a two bolt with only 10,000 miles that will clean up .010" over. The damage done to the block when the rod/rods let go was limited to four small chunks taken out at the bottom of the bore near the main saddles. No damage to the water jackets or any cracks. The block has been clearanced and smoothed at the bottom of the bore, vatted and magged. In other words, the block is not a concern. You are right. I guess here in the west, 400's are not that hard to find. I have one in my Suburban, a bare four-bolt with a standard bore in the garage, one fresh .030" short block with an internally balanced SCAT crank, 6" Lunati rods and SRP Pistons. Finally I have this nice two bolt. There's a big swap meet in Albuq. the first week of May. Might be worth your while to make the trek from Colorado.

Just a little note here. Stock bore on a 400 is 4.125" so if the block is bored .030 your bore should be 4.155".

Auggie

he said he was gunna clean it up with a .010 bore.

Anyway, good luck with the engine!! Sounds like you got yourself a little project. Post results! good luck man

heh, keep the block you got man, if it ain't broke, don't fix it

good luck on this magical 350, let me know how the dyno numbers look in the real world and what kinda gas mileage the beast gets

The machine work will begin early next month. Typical performance stuff is planned: decked, squared, line honed, balanced, bored and honed with deck plates. I would really love to be able to convert this two bolt to four with a set of splayed caps but that might not be in the cards for this rebuild. The reciprocating mass is light enough to easily spin to 7000 rpm which is hell on the lower end but I'm sure the cam is going to peak at 6 grand. My first real numbers will be on a engine dyno but I don't expect the same numbers as Hot Rod because I am at 5000 feet above sea level. I used to follow the Super Chevy show around the western part of the US and cars at Bandamier Raceway in Denver lost in average about a 3/4 of a second as compared to Houston and Phoenix. I don't know the math but that's a lot of lost horsepower!!

I can fax this article from Hot Rod to anyone interested. Email me at sivaaib@flash.net with your fax number. Picture resolution will leave a lot to be desired but the story is what's important. Better yet, just did a search on altavista and here is one link with the article: http://www.purplesagetradingpost.com...r/techinfo/350 chevy engine.html
Don't forget the spaces between 350 and chevy and engine. Sometimes stating the obvious saves aggravation.

Bigals87Z28, I was referring to the first paragraph of his post:)

Auggie

ahh ok.. gotcha

Yeah, 2 + 3, carry the one....damn new math! Actually, these are the risks for getting on line after bed time. Should've just counted sheep...but I probably would have screwed that up too.

please keep us informed on how this goes. I have thrown around the Idear of a 352 and another guy around here (B4CTOM or something of that nature) is going to do it too. I am really interested in how this goes please keep up informed : )

I certainly will keep you posted. This combination has intrigued me for a couple of years now. When my L98 went sour, I decided now was the time. Although I have been lucky purchasing parts well below retail, it is not a budget build by my book. I could have built the L98 for much cheaper but I felt it was time pull the theories out of the closet, dust them off and see if they work. The superior design of today's cylinder heads was a decisive factor also. I feel like this project could be a lesson in the reduction of friction,as much as anything else. The rod angle should substantially reduce friction, as will the 1/16" piston ring pack, blue print quality machine work, true roller timing set and synthetic lubrication. We'll see!

Re: 350 of a different color. 3.25" x 4.135"
 

I'm sure that has to be wrong. I don't see how changing around bore x rod x stroke ratios are gonna change gas laws. If someone can explain how, please do.

Tom

Ugh...Tom! I am not physics expert but I will do my best to explain this one. The physics going on have nothing to do with gas laws but with the motors sensitivity to those laws. First you must be able to visualize this fact. A long rod motor has less rod angle at any given point in the stroke except for TDC and BDC when both are straight up. As the crank comes around from TDC or BDC and it begins to move, the pitch or angle of the rod as it moves through the bore is more extreme for a short rod. This extreme rod angle causes more friction in comparison to a long rod motor. Friction causes the motor to work harder to overcome this friction. It is this "load" caused by the increased friction, that raises a motor's sensitivity to an octane level. It is similiar to towing with a truck. If you drive the truck unloaded, it may be able to run normally without high octane gas. Once you start pulling a "load", the need for higher octane occurs. Can we agree on that?

Ok, let's move on. Again, put on the vision goggles...here's a tough one. Because a long rod motor has a longer rod, it will dwell at the top of the stroke (and bottom) for a longer period of time. This can be proven with a degree wheel. Because the piston is dwelling at the top longer, theorically, you can extract more power because you can lengthen the compression period where the motor begins it's work, building more cylinder pressure.
If we can prove that the piston dwells longer at top, physically what must then happen? The piston must travel down the bore at a faster speed than a short rod motor. This piston speeding down the bore, theoritically, causes a much stronger draw on the incoming air/fuel charge....a mini-supercharger, if you will....which is able to pack more air and fuel in a given stroke. All this should allow you to extract more power from the same amount of displacement. Now all this must be optimized by the proper components or the theory no longer is valid. Your cam must be ground for high lift and comparatively less over lap to allow more air when the intake is open and both valves closed during most of the TDC compression (read that as "roller cam"). You must have newer generation heads with their superior air flow and combustion chambers to allow an optimum movement of flow and combustion which also lowers the motors sensivity to octane (this is not restricted to long rod motors...all motors can benefit from this). Proponents of the concept like Smokey Yunick and John Lenginfelter believe there is alot to this. Other famous builders like Joe Sherman think it's a crock. I needed a rebuild, so I thought I would test it out for myself.

Sounds cool, let us know how it works out.

block
 

This has been the slowest build I've ever done. With 3 active kids, the magic combination of free time and money has been hard to find. Anyway, 90% of the parts are purchased.

Here is the block before being sent to the machine shop. I did manage to grind and polish the lifter valley. Amazing how quickly raw cast iron rusts. Now for a shot of WD-40!

I need a lesson in picture installation. Brought the size down to the allowed but still can't post. Any ideas? I've got some good shots of the SRP Sportsman pistons, the 6.25" rods, Clevite bearings, the Topline 906 heads, Total Seal Rings and the Cat 1.6 ratio rockers.

The plans for the block are for boring, honing /deck plates, line boring and decking to 0 - .005". I will be using the Moroso block water restrictors opened up another .060" or so in the deck to stiffen it up. They will be added before decking so the milling process will help keep them in place. If I can ever figure out how to post pics, I'll show the installation.

ProTopline 906 Vortecs
 

These are at the head shop now getting full treatment on the exhaust side. These Toplines have better flow characteristics than the stock Vortecs which except for the exhaust flow would have worked fine for me. I will be using Manley Street flow valves. Long rod motors are sensitive to the exhaust side and really need something approaching 80% exhaust to intake flow to optimize this combination.

6.25" Rods from Dynoflow & Total Seal
 

These rods sold for $385 plus ship. They are 4340, light (610 grams) and supposedly good for 600 hp plus. Way more than I need but for $385......!!!

SRP Pistons & Clevite bearings
 

Next pictures posted will hopefully be of the assembled short block. Hopefully very soon.

Cool beans ;) DO you plan on dynoing it? And what kind of HP/torque do you expect?

Yes, I am. My goals may seem small to some but I'm looking for 300 rear wheel horsepower and 20 plus MPGs on 87 octane with a 4:10 rear and a T56 six speed. This link outlines the motor as Hot Rod built it. http://www.airflowresearch.com/artic...le03/A3-P1.htm

I couldn't find the AFR's they used. They are out of production and I got tired of waiting for a set to show up on Ebay, racersauction, etc. They were basically the 180cc's with smaller valves and smaller chambers. Hopefully these Topline 906's will give me similiar results but they definetly need help on the exhaust side which I am addressing.

I am using the exact same cam. It is very short on the duration to build cylinder pressure and it will have it's limitations as far as top end breathing. We'll see.

Oh, yeah. I am at 5000 ft. I will need at least 385 at the crank to reach my 300 rwhp. If you take their 412 HP peak and subtract 15% for this altitude and it's barely over 350. Doesn't look good. We'll have to see.

I remember that story. Didn't they use rods from a 300 ford 6 banger that were machined to fit the crank?
And wasn't the cubic inch like 345 or something close?

I was greatly impressed with the damn near flat torque curve. I wanted to check into building this engine. But time,$$$ and no block to work with stopped me before I got started. I'm curious how this is going to work out.
I definatly be watching this post!:D
Good luck!

Looks like a good start so far, I'm intrested in what it will dyno at when you get it finished... Good luck putting it together and keep us up to date.

Ahh, the magic engine combo...

My dads cousin built a similar engine. Well, similar in that it had almost the same cam, ported stock heads with 2.02/1.60 valves, and 350 cubes by the traditional method. 425hp on the dyno. I could ask the torque too, but I bet there would be no surprises.

Anyway, good luck with your build.

I have to agree with tom's statement about the bottom end having much effect on knock.

Just stating a static compression ratio and what gas you can run with it doesn't mean much.

Dynamic compression is a much better indicator for which type of fuel to use since it takes into account many other factors.

At your elevation you could probably run even more compression than the magazine and still get away with low octane fuel.

wes, how's the build up going? I remember that engine when they built it. They have done a 351W Ford should have built. It should be interesting to see that combo with a set of vortecs on it. What cam are you running? If you have already said it I missed it.

Jason

I have to agree that the theory tests conventional thinking. I'm not going to spin a bunch of facts because until I see dyno figures and get some seat time, I'm not sure the theory holds water either....but it is my duty as a newly appointed "Senior" member of this website to test it! ;)

What has always interested me is "free horsepower". Not free in the sense of what parts costs (as you can tell, this is no "budget" build) but more finding ways of making power that don't affect gas mileage and driveability adversely. This motor will play out that obsession. Every free horsepower trick I can afford, I will throw at this motor and we'll see....

That selection I did copy from the article. I'm using a Comp Cams 270HR10 retrofit roller. I will be using the recommended 1.6 ratio rockers. The specs are .500 lift with 215 degrees of duration at .050. These specs are with 1.5 ratio rockers.

I'm sure you'll make a bundle of power, probably a fair bitmore than a typical 350 would with the same parts.

I have the same motor sitting around ready for when my L98 pukes. 400 block, Forged 327 crank, 6.125" Eagle H-beams, SRP Pistons and Iron Eagle 215cc heads with 2.08s.

My Formula 350 I just bought about 3 weeks ago is STONE stock, except for a set of SFCs and runs 14.25 with 147k on the clock. Maybe if I convert my old NOS Cheater setup for the TPI I can have a reason to add my 352ci sooner. I would love to have a stone stock L98 running mid 13s.. but check the HP differences in my L98 compared to the 352ci(carbed) waiting its turn. :hail: :hail: :hail:

Assuming desktop dyno is off I only added "HP manifolds" instead of "Small tube headers" just too keep the numbers more conservative/Real world.

The 352ci is on a home-made engine stand that allows me to run the motor!! I will have to get pics of that too...:D

You must be running a pretty healthy cam to get those numbers! Can you give details?

I'm jeolous of your engine stand. Mine is a '82 Suburban.:) It came with a big block originally, so it has the big cooling system and ultimately ends up being my "break-in" mule for all my motors.

The cam is a Mechanical Roller, 255dur @.050 .575 lift on a 110 LCA...currently looking for the stupid Digi-cam

Ok I got pics...

this time Ill post em...lol

Cool engine stand. It's nice to break in cams and tune up without the whole installation hassle. Just eliminates most of the gremlins, I'm sure. Check out this link if you haven't seen it already. Tom is a regular contributor who is building a similiar combo for big power numbers. http://www.outlawperformance.com/my1...arodragcar.htm

Yeah, that was the biggest surprise for me. Those torque numbers were the kind you see on good 3.48" and 3.75" strokes, not 3.25" !! That's when I knew I had to try one!

Assembled Protopline Vortec
 

Finally got the ProTopline Vortecs back from the porter. They are currently flowing at a respectable 78% Intake to Exhaust ratio. I complicated matters by insisting on some mild pocket work on the intake side. In stock form the Vortecs are in the 68% range, so doing more work to enhance flow on the intake would, as you would imagine, throw things even more out of wack. It took fairly extensive exhaust work to get them to the 78%. I wish I had taken photos prior to assembly to show the work. I won't post flow numbers because different flow benches flow different numbers even of the same make of manufacturer. In this case, we would have to compare heads on the exact same bench with the exact same set-up for the numbers to be valid for comparison. Besides, like the racers say, "You don't race flow benches". As you can see, steam holes were drilled. The heads were milled to a 62 cc chamber. The assembly was complete with Manley Street Flo valves with the turned down stems and Comp Cams Dual Springs that were called out for the cam I'm using.

The machine work is poking along on the block because of my indecision. At first I wanted a deck height of .005" to zero. My plan was to use the head gasket to create the necessary piston to head clearance, which in this case, would be .035" because I am using steel connecting rods. Now I read that this may not be the hot set-up because this gap between the head and the block created by the gasket should be minimized. Apparently this gap, if excessive, allows unburned gases to "hide" during the combustion process which will contribute to high hydrocarbon levels when the car is emissions checked. High hydrocarbon levels are already going to be a problem with my 10.5:1 compression ratio. I don't want to contribute to the problem and not pass. The only alternative I know of is set up my deck height in the .010"-"015" range and use a shim gasket but no one makes a shim gasket for the 400 block. I could modify a 4.140 copper gasket with steam holes. Anyone have ideas?

Re: 350 of a different color. 3.25" x 4.135"
 

I'm frustrated with people using HP numbers. All it is was calculation to show the equivalent work of steam engine verses horses. Torque is what moves your vehicle down the road. Consider the
​​​F1 v10 engines that ran 12,000 tpms. Their torque numbers were in the 200 foot-pound area and would not have been fun in a street vehicle in spite of the high hp numbers.

Re: 350 of a different color. 3.25" x 4.135"
 

Look at the date --- 2003 :doh: You're late by 2 decades.

Re: 350 of a different color. 3.25" x 4.135"
 

Torque and (horse)Power are inseparable, you look at both all the time whether you think so or not. Everybody can agree that increasing area under the torque curve makes a car faster. If you want to calculate area under the torque curve then you add up the area of a bunch of small rectangles of (Torque * RPM).

Hmmm..... (Torque * RPM).... that looks really familiar..... where have I seen that before? :)

Also, torque at tire is what moves the vehicle. And there is a transmission with multiple gear ratios between engine and tire. And every gear shift results in a massive change of torque at tire. If you plot Torque vs. MPH through the gears then you will see that Torque can be multiplied with gears but Horsepower cannot. Horsepower wins races. :nod: