420 ci TBI motor

[doogie_h]

I have decided to do a 420 and have found a motor builder to build it who from his reputation is quite the man. He used to specialize in pro-stock motors and now does a little of everything, but mainly circle track stuff. The koolest thing I think is that he flows heads for a few nascar teams. A friend of mine had a motor by him and he said it looked like he butchered his heads because he cut so much away form the valve in the combustion chamber. My buddy complained and this guy said "Do you want flow? This guy used to work with Bill Grumpy Jenkins and still does stuff with him from time to time. We shall see. I hope to get a good deal.

I have a G25 GMC Conversion Van, the biggest one made. Not sure of the weight but it is the longest van they made. I will find out the GVW when I update later. I wanted to make a post of the build because I haven't seen anyone else with this combo in searching.

Combo -2 Bolt SBC stroked to 420
-AFR Aluminum Heads, not sure on the runner size (probably 210cc) or final compression ratio
-Hydraulic Roller cam- Not sure which cam yet
-1.6 ratio roller rockers
-Edlebrock #7525 Dual Carb intake manifold (Airgap)
-2 TBI to carb adapters (looking for 2 5.7 TBI's unported for cheap)I will hit craigslist!
-E.B.L.
-Summit/Mallory ignition kit with rev lmtr (box,dist,coil)
-Long Tube Headers in a 3 in Y to a singe 3.5 in pipe out to the back
-Fuel pump- tbi injectors use low pressure so I think I will use a supplemental pump to what I have in the tank.
I be posting pics as I get them. The motor is being built for me with the only stipulation being pump gas 93. I am considering 10.5/1 or better.

Tuning is going to be up to me. That I am not looking forward to. I am hoping for 550-600 hp/tq at 6000rpm. I am also upgrading the rear to a 3.90 and I have rebuilt my 700r4 with upgraded Sprague, Colene steels, corvette servo, "The Beast" drum upgrade, Shift-kit- need a new convertor but trying to pic cam first....

[BLOWN91350SS]

If you're building a 420 stroker, why not use a 4 bolt main block for a little extra insurance IMO. You got the right idea with the dual TBI's becuase that is the only way you will be able to supply enough fuel to feed the motor. I'm guessing your 420 should make over 400 HP when all is said and done.

Get a 255 LPH high volume fuel pump and you should be O.K with that. I think it supports something like 450 or 500 HP.

You're right though, tuning this thing is probably going to be a real biotch.

[b454rat]

2 bolt 400 blocks are stronger 4 bolts when they are splayed. If your gonna through all this, then it would be wise to splay the caps.

[GreaseDog]

would be even wiser to swap out your 700R4, unless of course it was built by a good local shop, with a VERY good warranty, full knowledge of what they were building for, and the willingness to stand behind it.

[Polecat]

yep. 700R4, only when built right will withstand logivity behind any decent power, not to mention a higher cost on converter.
2 bolt would be fine for 400HP, but agree, splaying the caps is best option if money allows.

[blown68ssrs]

What bore and stroke are you planning to make a 420?

[oldred95]

With aluminum heads you can realisticly run 10-11:1 pretty easy on pump gas. Heads and cam selection will make or break this build. Should make pretty nice torque though.

[doogie_h]

I plan of the splayed 4 bolt billet caps and girdle.

I am leaving the bore and stroke combo up to the engine builder. He is well aware of my goals and knows how to make horsepower. I did mention an article about longer rod length and a closer wrist pin in relation to the top of the piston. He is a very nice guy and listened but I could tell it was like a 16 year old telling me how to drive. So I said work your magic.

Oldred I have been reading alot of your posts and am in limbo with the whole maf/map issue. I know the E.B.L will not support a maf but will do alot of other wonderful things for me. Also they are about 5 minutes drive from here. I emailed ?Dave? is it. He said I could stop by and he had a few vehicles running the E.B.L. But I am seeing some pretty Tall cams used in various strokers. I am going to call comp/lunati and see what they recommend for a cam. But If I go MAF will that allow easier tuning? This is a big hurdle for me.

I hear what you guy's are saying about the 700r. The freind of mine who got me the engine builder hook-up, builds american Automatics for a living. Most of his work at this point is in drag cars. I rebuilt my trans in his shop with his instruction and we feel confident that 600-650 will be fine. I can go to a t400/4l80e but The drivetrain loss is far greater according to a few people that i have talked to. So more ponies to the ground and slightly better milage was the deciding factor in building a 700r4. The only weak spot left in my trans is the input shaft and thats easily fixed in about 5 hours should it break.

[doogie_h]

Now onto the question of horsepower. Am I missing some important part in my hp goals?

http://www.airflowresearch.com/chevy_dyno.php

A 383 (9.5 to 1 comp)with a similar setup minus the dual TBI's made over 500hp/tq. If I run 2 sets of BBC TBI injectors and have 1040 cfm of airflow, what is preventing me from at least attaining these numbers if not exceeding them?

http://airflowresearch.com/articles/article038/A-P1.htm

This 420ci sbc made over 535 with 195cc afr's and 11 to 1 comp on a mix of 93 and 100 octane. I think 10 to 10.5 to 1 is probably a better ballpark for me to ensure 93 octane, yes?

I am not asking to be a jack-ass, I want to be as realistic with my goals is all. And Tbi's are weird!

[GreaseDog]

i'd like to see actual chassis dyno numbers on a vehicle with identical drivetrains, except for a th350 in one, and a th400 in the other. the gain in parasitic loss of the TH400 is much less of an issue than the actual loss of drivetrain (tranny go bye bye!) that you're setting yourself up for. not only do 700R4s suck for durability, but the gear spacing is terrible if you're really building for a high performance application. look at the gear spacing between a TH350, a TH400, and a 700R4... its atrocious compared to the other two.

[doogie_h]

I must say i am far from an expert on transmissions. I was told that a 700r4 was basically a th350 with over drive. My buddy has a th400 in the shed with my name in it should i need it. But I put in 500 bucks worth of parts (Dealer Cost). And 8 or so hours in disassembly, parts cleaning, and reassembly. I talked to my buddy tonight and he said for where we are, might as well see what happens. He said that he's seen a 700r handle 800lb/ft for half a season. Who knows! If nothing else we can all see how long the 700r lives and maybe redefine it's capabilities. I have to get a motor that will lean on it first!

[bored&stroked]

The 700R4 WILL die, its only a matter of time. With the 600hp goal you'll need a healthy cam, that along with the aluminum heads will help support at least 10.5:1 on 93 octane. I would push closer to 11:1 myself. Run the eliminator heads and don't let the guy port em at all. You'll want a big convertor for that heavy van and lots of transmission coolers!

[mred]

tbi 420ci motor is senseless tbi.
you will only see 400 tops with that fuel system. you would need to upgrade to a fast system.
a tbi motor your just better off building a regular 350 with a small cam.
and the 400 small block i would go with the 2 bolt, my 406 was seeing 250 shot of No2 and it was well over 700hp with the n2o,it was carbed, and compression was at 14 so. the block is fine. the rod in #4 cyl is what gave up.
good luck with you choice
and a 700r4 thats real iffy.
you wont ever be really satisfied!
i know, i build transmission for a living.

[doogie_h]

tbi 420ci motor is senseless tbi.
you will only see 400 tops with that fuel system.

Why?

[Polecat]

find a TH350, it'll hold up to that, and weight alot less, and use less power...

[XLR8N]

well you have done your research for this build. nice pic with the AFR heads. i do not like lunati myself but thats my opinion. like everyone else has said. 2 bolt with splayed caps. (2 bolts have thicker walls) and a nice size TC. i have never ran a 700r myself but all i have heard can relate to the guys in this thread lol. gonna be a sweet van! lol.

[Old88]

What bore and stroke are you planning to make a 420?

I'm using a 3.875" stroke
4.155" bore
22cc reverse dome
for a pump gas motor

[Zero260]

The 700R4 WILL die, its only a matter of time. With the 600hp goal you'll need a healthy cam, that along with the aluminum heads will help support at least 10.5:1 on 93 octane. I would push closer to 11:1 myself. Run the eliminator heads and don't let the guy port em at all. You'll want a big convertor for that heavy van and lots of transmission coolers!

Die? Its going in orbit! No way a 700R can handle 600 ft/lbs of torque. A built 400 is the only way to go, if you are going to stay auto.

What you have, on paper, is definately orginial. But, IMO, it is far from feasible. Seriously man, what you have planned isn't a very streetable engine. And what you are putting it in isn't a very strip worthy ride.

Lets look at your power goal. The driveline and suspension for 600 ft/lbs is going to take a lot of buildup to get it to the ground. Why not go BB? ...lower stall speed, taller gears, a more mild cam, easier to tune, lower cost in machine work, lower compression ratio...etc

IMO, peak power numbers are a sales gimmick used to sell new cars and trucks. Its all in the power curve man.

[dave89iroc]

2 bolt 400 blocks are stronger 4 bolts when they are splayed. If your gonna through all this, then it would be wise to splay the caps.

agreed


and for 600 torque, I would go with a TH400 or a 4L80E

[Busted Knuckles]

Why do you want to build what looks like a high $$$ engine to lug around a land barge? It's not like you're going to be able to run any 12 second quarters and mileage will be crappy. Build a budget 383 and save your hotrod cash for a lighter and more fun ride.
Just my .02, though.