C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

The 421 is finally home.

Old 05-26-2009, 11:37 AM
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The only thing I would add to this discussion is to stock up on some Dana 44 parts... looks like you'll need em
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Old 05-26-2009, 11:46 AM
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Originally Posted by RacerX70CC View Post
The only thing I would add to this discussion is to stock up on some Dana 44 parts... looks like you'll need em

...and tires!!!
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Old 05-26-2009, 02:32 PM
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Going to be interesting on your trap speeds, I think you'll be in that mid 120 area too, but summer is upon us, it'll be a little harder seeing the real potential of your motor until fall arrives.... I think in good air 125-128 can be achieved, but as Neat said, its up to you and your skills to achieve.

On another note, for any new racers looking to have an engine built, I highly recommend Jim (TPI 421 vette)..... I've purchased some speed parts from him and everything went smoothly, but most importantly, he understands the C4 considering he is an owner and racer of one...... extremely important and very rare I might add.

good luck Rick !
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Old 05-26-2009, 04:34 PM
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Originally Posted by lltrevino View Post
Any power being left under the table?
I expected that from a "jsup" fan.
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Old 05-26-2009, 05:39 PM
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Originally Posted by corvette_bob View Post
It's been along time coming Rick, I'm happy for you. Now get that thing into the car and let's see some results......
Thanks Bob. You and I have talked about many different combo's for our cars over the years. I finally decided on one, and found an honest guy to build it.
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Old 05-26-2009, 05:45 PM
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Originally Posted by neat View Post
I don't remember saying that it wouldn't go 125, but I bust your dumbass so often than it's not inconceivable that I forgot about that particular comment.

In all honesty, I think it will go 125. Regardless of what I may have said in the past, jokes aside, it should go that fast. Assuming you can half *** drive it, assuming that it doesn't **** out the 4+3 the first time you go WOT, and assuming you find a decent track; there's no reason 125 isn't attainable.

Damn, that's a lot of assuming. Maybe that is why I said it wouldn't go 125?

I am no "Ranger", but I do ok. I don't know many that have got a manual tranny L-98 with the only mods being exhaust to a [email protected] mph (240rwhp/330rwtq).

We can "assume" that I couldn't care less about getting a 60 foot under 1.80. I am after mph then anything because eventually I would like to do some road racing with this car. We all know mph is the best way to vouch just how much power your car is making.

I will be weighing the car also. I would love to get the weight in the 3450 lbs with me in the car (200 lbs). I can't see it weighing much less then that with the slightly heavier bowtie block.
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Old 05-26-2009, 08:07 PM
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Does a 3.875" crank require a small base cam or just the 4" stroke? I am thinking of doing the same to my 400 if it doesnt require a cam change.
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Old 05-26-2009, 08:55 PM
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RICKY!!!!!! Its been a while bro. I hear BG was a scream. Glad to see a motor in house. All this to spank my Z06? Seriously buddy, I am really happy that you are this much closer to the final product. It has been a long undertaking and some ups and downs but you made it and I can hardly wait to hear this motor sing. Break her in and call me and I'll meet ya at Cayuga for a few passes. Hope the family is well.
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Old 05-27-2009, 05:58 AM
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Congrats man!
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Old 02-07-2019, 03:29 PM
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Originally Posted by ddahlgren View Post
I will be the idiot .. how did you get to 421 inches? What length rods can you get in there as well?
An "economy" 420SB is quite easy to build. I've built 3, using GM cast SB400 blocks. So far, ZERO issues.
MANY years ago, HOTROD magazine had an article on building a 420 from a 400 block. I tried their procedures on the first 420 I built-------------------------it's still in my jet boat drilling holes in the lake.

Here is the method for building a 420SB that I've done..
First, I used the bone stock Chevy cast 400 crank. The rod journals were OFFSET ground down to small journal 327 specs (giving a 3.85in stroke).
Block was bored .040 over.
The rods were bone stock 66-67 style 327 small journal rods with new ARP Wavlock rod bolts and the rod beams were very slightly smoothed (below), blasted and re-sized.

The rod bolt heads --------------- FACING THE CAM ------------- were slightly clearanced with a die grinder and sanding disc at about a 45deg angle (below). I did the rod beam smoothing, blasting and clearancing of the bolt heads at home on the workbench before having them resized by my machinist.

Hypereutectic, flat top pistons, for a SB400 with 5.7in rods, with valve notches were used. With the added stroke, and this piston combination, the pistons stuck up several thousandths above the cylinder deck. I had my machinist mill the piston tops a few thousandths to zero deck height.

I forget the cam specs (I've slept a few times since then), but it was a flat tapped hyd with about a .510 lift and duration about 235 @ .050 lift.
The heads are bone stock 400 heads (76cc chambers) which were slightly massaged and opened for stainless 2.02/1.6 valves. Screw-in studs and valve guides and roller tip rockers were installed.

I have always believed that a 4bolt main block was the ideal choice. But after many years of building engines, all the knowledgeable, experienced machinists/builders claim that FOR A SB 400 ONLY, the 2bolt block is the better choice. The reason is because main cap bolt spacing on a 400 block is wider than it is on a 350 block. Thus, the outer bolt holes in the 400 main webs causes a potentially weakened area of the webbing. So, supposedly, it's better to use a 2bolt block and use studs instead of bolts. I also always install a windage tray in all my engines.

Now, with all this said, you CAN spend a WHOLE LOT MORE MONEY going with an aftermarket block, heads, roller cam, rods, forged pistons, etc, etc, etc. BUUUUUUUUUUUUT, suddenly, before you know it, you're now well into the $$$$$$$$$$$$$ of a BB!!!
A 420, built like this, and kept below 6000rpm, will make a real killer SB-----------------------on a very reasonable budget----------------------------and the best part is, it is a pure drop in, bolt in where a 265-283-327-350 once resided. GREAT engine swap for your 57 Chevy.

One final note that I'd like to add.
I mentioned that I used 5.7in rods. Longer 6in rods are readily available for this kind of a build. But, for an all around street/performance/driver build, I just DO NOT like the 6in rods. Because with a 6in rod, the wrist pin is into the oil ring groove-------------------I DO NOT LIKE this feature! Also, the piston to be used with a 6in rod is REAL short. In my opinion, this becomes a greater potential for piston rocking occurring in the cylinder--------------increased wear. Thus, my reasoning for going with the 5.7 rods.
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Old 02-07-2019, 06:51 PM
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..... ZOMBIE ALERT ! … 10 year old thread resurrected …..
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Old 02-08-2019, 10:45 PM
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Originally Posted by C409 View Post
..... ZOMBIE ALERT ! 10 year old thread resurrected ..

Why would someone bump a ten year old thread????
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Old 02-08-2019, 11:20 PM
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Great looking engine and Jim will always go the extra mile to get it done right.
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Old 02-09-2019, 09:54 AM
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Maybe an old thread but very useful information if your building a 400 block. Since I have three 2 bolt 400 blocks I like it.
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Old 02-09-2019, 03:35 PM
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Yep, old but good. DZs suggestion on doing one on the cheap is invaluable. Not everyone has 10-15k to go fast.

Lingenfelter and Joe Sherman used to do the same thing, "Lots with little"
Precision machining and assy would make basic stuff live.

Last edited by cuisinartvette; 02-09-2019 at 03:36 PM.
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