427 Tall Deck

[Chris Guthro]

Hello Guys! As im taking the body all off my frame and redoing it, i dont want to just put the old 305 back in it..its an 1987, tbi..Its not running right now but I want to switch it over to a Big Block, just wondering how much work it is to put a tall deck big block into it...These motors are around my area pretty cheap, any ideas will be helpful! And how can You convert them to run an aftermarket bbc intake?

[swb85]

You really don't want to mess with a tall deck 427. They are very low rpm torque motors with heavy internals that don't like to spin much over 3000 rpm. There's a reason they're cheap. The block can be a good starting point for a bigger inch bbc build though.

[Chris Guthro]

Its a truck for going back and forth through town n school, ive got a 5 speed focus for a daily driver, im only 18 and looking for a cheap big block.Im not worried about the gas mileage. it would be mated with my granny geared 4 speed as well. Would it fit between my crossmembers and would I be able to use my stock mounts?

[olblue81]

You can use the block as a starting point for a performance motor but to take an existing working engine and try to make some power out of it by bolting parts on will be disappointing.

They have a bulletproof bottom end, but the pistons are heavy because of 1 extra ring at the top. The heads are "peanut port" and are very low flowing and the intakes are cast iron with dual thermostats-heavy and hot. You can swap out the heads to something better flowing and change the intake to a short deck unit by using adapter plates but the compression ratio will still be low due to the large piston to deck clearance. Because of the higher deck height you will need to use a tall deck distributor.

It's been 20 years since I rebuilt one, but if I remember correctly the factory compression ratio was in the low 7s or high 6s.

Do some math on it and price out the parts you need to put a decent top end on the motor keeping in mind that no matter what head you put on it you'll probably still have a low compression motor. If you can buy the complete motor cheap enough, then go for it. It's better than a 305, but unless you were going for a complete rebuild from the bottom up you can end up with more money tied up in it than a 454 and make less power.

[Chris Guthro]

I wasnt planning on completely rebuildin it, i was considering buying one with low miles. Then buy a new intake, carb, and a cam. The reason I was asking about these blocks is that I cant seem to find a bbc around here thats a standard deck. Ive been trying to research putting these in our trucks but cant find out any info if it goes in differently than any other regular bbc

[bigunde]

If i remember correctly the accessory brackets are a pain to find as well. If you get one complete, that might help.

[KQQL IT]

Originally Posted by Chris Guthro

I wasnt planning on completely rebuildin it, i was considering buying one with low miles. Then buy a new intake, carb, and a cam. The reason I was asking about these blocks is that I cant seem to find a bbc around here thats a standard deck. Ive been trying to research putting these in our trucks but cant find out any info if it goes in differently than any other regular bbc

It requires a different intake or spacers than a standard BBC. and a new distributor which is unique the tall deck.

[b454rat]

I hear this all the time that they won't spin high RPMs. In a way that is true, they weren't designed to spin high, but they will go to 5k or so.

A friend of mine has one at his work. Guess the carb was acting up, took it off for a Holley 750, and woke it right up. It will bark the tires when he shifts. They factory carb on the tall decks have a governor to keep from sky'n the RPMs.

These are torque monsters, pushing almost 500 lb/ft of torque. Can't wait to see what mine will do.

Oh and for accessories, all the regular big block stuff goes on, depending what you have. I took the accessory off my 89 that had a 454 and bolted it up to my TD427. Only thing that won't is the upper A/C bracket.

[Chris Guthro]

Well i wouldnt be using airconditioning anyway, so if I found one out of a Bus or Truck with all the accesories would i be able to almost bolt it in my 87 4x4 GMC 1500? and will my bull low tranny bolt up? i like the sounds of a tourque monster in a 4x4 for cheap money

[olblue81]

If you get all the brackets then you're set. The bellhousing mount is the same as any other Chevy.

The one I have is in a C65 medium duty truck. It has the governor disabled on it and it will rev to 4500 or so but honestly it doesn't have any more power at 4500 than it does at 3500. Only reason to wind it that high is so that the revs are at around 3000 after the shift.

I don't want to rain on your parade. Like I said in my first post, it's better than a 305!

Here's a link to a Car Craft article on a 400 hp peanut port 454. http://www.carcraft.com/techarticles...ild/index.html

[Chris Guthro]

Well, is it a better motor for a 4x4 than a 350? because the only big block i can get my hands on here is a tall deck.Id like to do this swap just because i need a running motor for it too and dont want to wait to rebuild one

[80SPORT]

We had a tall deck 427 in a 1 ton 4x4 with an auto trans;the truck had 4;10 gears and it was a great package for towing;we pulled it from a medium duty and it bolted right in;we had to modify the exhaust slightly for the hi deck;we kept the original intake, carb and distributor.
Those old 1 tons with lug tires never drove well faster than 60 mph so rpm was never an issue.

[Chris Guthro]

Yea, Im really considering this now, from what i read their monsters for low end tourque! and would a regular BBC cam work?

[b454rat]

Most BBC parts will interchange with these. The decks are .400" taller, so if you swap some 049s or 781 with an aluminum intake, you will need to run spacers and an adjustable distributor.

The cranks are forged, rods are forged with 7/16 bolts, blocks are 4 bolt, heads and heavy ass pistons are the downfall. Swap in a 1/2 stroker crank and bore .60" over, got a 496 torque monster.....

[olblue81]

Originally Posted by b454rat

Most BBC parts will interchange with these. The decks are .400" taller, so if you swap some 049s or 781 with an aluminum intake, you will need to run spacers and an adjustable distributor.

The cranks are forged, rods are forged with 7/16 bolts, blocks are 4 bolt, heads and heavy ass pistons are the downfall. Swap in a 1/2 stroker crank and bore .60" over, got a 496 torque monster.....

That's what I always planned to do with the 427 I have rusting away in the barn. Still hasn't got done...

[sierra4x4]

I put a 427 tall deck into my 74 Gmc 4x4 so if you have any question I will do my best to help you out. There are a couple of things that a lot of people don't know about tall deck BBC's like most don't use peanut port heads. The heads they use are basically a 781 or 049 but they use tiny 1.84 intake valves instead of the normal 2.06 valves. I know this for a fact because I have torn down a lot of tall deck's. If you use a stock TD intake then any sbc/bbc distributer will work fine but if you go with a after market intake then you will need to modify the distributor. I had a strong 350 in my truck before the swap and I will tell you that the 427 has a ton of low end torque and with a little more cam it will easily go to 5000rpm. When I did mine I used regular 454 water pump and power steering brackets and used the td 427 alt bracket and any sbc/bbc motor mount work. It was a easy swap and I got a very cheap big block. Here are a few pictures and as you can see it looks right at home in there.

[Lonnies Performance]

I have a TD427 in my pickup also. I still have the stock pistons/bottom end, but put on a set of early closed chamber 396 heads... raising the compression to 9:1. & letting it breathe. Headers fit with no problems. Used all regular BB waterpump & all brackets, even the AC. I only had to modify the aternator bracket to bolt to the intake. I originally ported the factory TD intake to match the heads, but later switched to a Weiand Team G intake & 750 Holley. Not the best intake for a heavy truck, but the only direct fit aftermarket tall deck intake for oval ports.

The bottoms ends are all steel crank, HD rods, 4 bolt main. I shift mine at 5800-6000.

Runs 13's on 35" BFG mud terrains... so I'm happy with the results.

[sierra4x4]

One more thing. I've seen a lot of 366 TD's using the oval port heads with a round port intake. I don't know what they were thinking at the factory. All the 427's that I've seen use the large oval port heads with a large oval port intake.

[Chris Guthro]

I want to thank you all for the info! its good to know that most bbc parts are interchangeable! is there rebuild kits for these TDs? How hard is it to use a set of aftermarket heads from say a 454?

[sierra4x4]

Any bbc heads from 65-90 will fit on a td. You need to be careful if you use gen 5 1991+ heads to make sure they will seal because the water jackets are slightly different. I have used Gen 5 91+ heads on older blocks with no problems but it is something to watch for. The only part that don't interchange with low deck bbc are the pistons, pushrods, intakes and of coarse the block has a .400 taller deck and the water pump is different it usually mounts the fan really high so it is centered in the big truck rad. Here are a couple pictures the first one is a 1991+ gen 5 head and the second is a 65-90 head.

[Chris Guthro]

Thanks! im not an expert on engines but what would you guys suggest for a mild but yet very budget freindly TD build? since you guys have done them before. Like if you had a 1000 bucks to put into a TD 427 what would you buy for a mild performance mods?

[b454rat]

Probly a set of longer rods, car 427 pistons, 049 or 781 heads, Xtreme Energy 268 cam, headers and an aluminum intake.

[BigBlocksRule]

The reasons they didn't like to rev was the 4-ring pistons, they're heavy as bricks, plus the valvetrain/cylinder heads are built for high velocity, not large amounts of airflow.
Sell the steel crank and get a Scat cast 4.25" stroke crankshaft, a set of Scat's rods and Speed Pro hyper pistons to fit and build a 489/496. Torque rules and cubes are the way to get it.

[b454rat]

I was gonna suggest a stroker too, but that will be more than a grand. I looked into at one point, could have gotten a rotating assembly for roughly a grand. It was a cast crank, as I don't need a steel one. Wasn't gonna drop the coin on a gas motor when I could have a Cummins and beat them all!!!!

[Chris Guthro]

B454rat, thanks..ive been lookin them parts up and they seem to be in my budget, what kind of power numbers would I expect to see with them mods? with headers and a set of true duals