chet300h

I have a chance to pick up a early 70's 400 SBC. I was thinking this may be an interesting swap for the l98 in my 87. Anybody try a swap like this? performance potential? Will the tuned port intake work?
Thanks.

Pete K

It (stock tpi) will be a restriction, but would stll make alot of torque, and be alot of fun to drive.

Mojave

It will bolt up like any SBC, but the TPI will be an even bigger restriction than on a 350. Don't expect to make any power above 4K.

rodj

But you will be able to run a 1:1 rear end

Mojave

I agree that it will make tons and tons of low end torque, but eventually you reach a point where some horse power would be nice.

87 is 1 piece RMS and any 400 is a 2 piece RMS. Also, there might be some difference in the dip stick location.

Quite frankly, the 400 offers nothing you can't do with a regular L98 or any other 350. I'd just get a 383 crank (can be had for cheap) and do a budget 383 build. Any increase in displacement will require some intake mods to really make it shine.

chet300h

Would the 2 piece rear main seal be an issue? I know the l98 is a one piece but that should not give any install issues? Or am I wrong? Also I will need a fuel pump plate. anything else needed?

Thanks

rodj

You need a flywheel /flexplate to suit the 400 which has early 2 pce seal.

A 168 tooth flywheel won't fit inside a 4+3 bellhousing

heck

Just did that swap in my 90 conv., 78 400 block from a truck, built it into a 406, used edelbrock rpm heads, tpis big mouth manifold with fully ported and matched slp runners / plenum/ 36 lb hr. injectors / twin 58 throttle body, works great, however will be upgrading to mini ram someday, and as far as flywheel I used a 153 tooth / just had to drill the block for the parallel bolt patern

heck

drilling was for the starter mount / sorry

TPiS

Correct-


The TPI style intake is pretty RPM restrictive on a large engine. The bigger the engine, the less RPM you can run. It reaches the harmonic efficiency limit sooner in the RPM range.

Also, its a good idea to run a little lower compression on the big engines with TPI because they fill the cylinder so well that you can get some cylinder pressuer spikes depending on what cam you're using etc....

Big inch TPI engines are alot of fun, but really suited for heavy cars or for pulling a trailer etc...


Jim

CFI-EFI

Please explain "harmonic efficiency limit"





The TPI will bolt to the 400 long block. You will need a flywheel or flex plate with a two piece rear main seal bolt pattern. Also, it will have to have the correct balance for the externally balanced 400. As stated a 400 flywheel (168 teeth) won't fit inside of a Corvette bell housing, but a 400 flex plate (168 teeth) will. If your car is an auto, you can ise a stock 400 flex plate.


[QUOTE=chet300h Would the 2 piece rear main seal be an issue? I know the l98 is a one piece but that should not give any install issues? Or am I wrong? Also I will need a fuel pump plate. anything else needed?

Thanks [/QUOTE]The one and two piece rear seal cranks have different flywheel bolt patterns. You can use the fuel pump block off from your L98.

RACE ON!!!

vader86

No way in hell would i put a TPI on a 400+ ci engine.

Think about breathing thru a straw below 100ft of water.

Caboboy

Nothing but 400+ cubic inches

There are a lot of us here that've done this swap, mostly with great success. If it were me, I'd jump that block if it fit the following criteria:

1. It doesn't have too much core shift;
2. It's a 2 bolt main;
3. It hasn't been previously bored more than 10 over.

All this assumes it's a sound piece. A factory 400 that meets the above tests can actually be a better choice than an aftermarket block for specific applications (smaller CID) in that it's already been heat cycled and is a hellofa lot less expensive. Aftermarket blocks are subject to quite a bit of core shift........quite often more readily than the factory blocks were. Even if you weren't sure about your final decision, I'd jump on it if it's a good one; they're getting harder and harder to find. You'd always be able to sell it if it didn't work for your final decision.

Beach Bum

For what its worth, in my opinion, you can actually take an L98 corvette with a bone stock tpi set-up from throttle body to manifold into the 11's with a 383 or 400.....

A few years back, for kicks I pulled the Superram off my 383 motor and put on a stock TPI and ran 12.0's @ 112 with deep 1.5x 60 fts.... would have easily gone into the 11's, but my transmission was set-up for 6000 rpm shifts that day and it would simply make a lot of noise at the top of each gear with no acceleration.... I estimated at the time a 11.8 @ 114 mph if I would have been set-up for 5000 rpm shifts. This was in roughly a 2500-3000 ft DA on a 900 ft track.

As a note, my 383 had an lpe 219 cam, AFR 190 cylinder heads, headers, 3000 rpm Vig converter, 3.45 gears...... and the weekend after had run 11.4's @ 118 mph with my Superram.

I obviously recommend an aftermarket intake with that set-up, but you can always do that later on quite easily..... and in the meantime, that little stock tpi just might surprise you and the set-up was truly a hoot to drive and the 3000 rpm converter was definitely not too much converter for that set-up, in fact, it was probably perfect for the stock TPI in both performance and driveability, whereas it was too tight for the Superram.

Good luck with whatever you decide !

cmcbunch

I had a 92 camaro with an aggressive 383 with dart 215cc heads, comp cams 238 int dur 6 deg advanced, 1.6 roller rockers and stock 1985 tpi converted to 90-92 speed density. And what these guys are saying is true. You are gonna wind up with an engine that has explosive torque/ throttle response and big *** brick wall at 3750-4000 rpm. This isnt a bad thing if you prefer torque to hp (as i do).
pros - good gas mileage, outstanding throttle response, smooth idle.
cons- lower peak hp, narrow powerband

This car ran 13.0 with 2.73 gears and a stock transmission with one wheel peel. It wasnt a dragster but it was potent at highway speeds.

TPiS

I probably won't explain it since there is a chance you might think it's BS.

LT4POWR

You looking to build a stump puller?

Mojave

While I agree you can get more cubes, with a stock TPI, you can't say he's gaining much with those 17 extra cubic inches. To avoid dealing with 2 pc RMS issues, flexplate/flywheel issues, and possible dipstick issues, I'd just get a 1 pc RMS 383 stroker crank and be done with it.

Caboboy

You're minimizing the potential difference...........this sounds like an AFR thread

A 421 is like a 383 on steroids.

chet300h

I have installed the "www.corvetteplenum.com" ported plenum with the ported SLP runners and big mouth intake. I don't think it will have a breathing restriction or will it? I'm going to have the 400 internally balanced so that it can use the standard balancer and flex plate. They actually sell a scat crank on ebay that is internally balanced. The only real thing I might have an issue with is the dipstick. I hope it is worth the effort?