what are going to be my biggest obstacales? I plan on making my own EFI intake and run a FAST DFI, so I should only really have to worry about fitment right?

Randy

 

There's nothing too difficult about it, but whenever this comes up, I have to ask "why?". To me, it only makes sense if you are building a race car, and I don't think a 4th gen is a great platform for a race car. But it poses no real technical difficulty.

Rich krause

 

Rich,

there is that, but even your end is a little extreme for a LT1 based engine.

There is a point where, more boost, juice, power is just hard to come by and hold together in a LT based motor. The heads get to small, don't flow enough, block is week (compared to a Bowtie) etc..... It is a simple swap as far as the physical part, but it could also reward a a very high HP street car too. There is durabilty, better driveability, strength and more power to be gained from a SBC vs the LT motor. As you said it does make much more sense for a race car, and I would rather start with a 4 link rear or anything else over the F-body suspension for high end drag racing.

Bret

 

Bret: I think we are saying pretty much the same thing. If you want an extreme SBC powerplant, clearly a Bowtie or other aftermaket block is a better foundation than an LT1. But the LT1's practical limits are quite high, if you are talking about a street or street/strip car. While talking about "hp limits" is kind of misleading, it's worth pointing out that using LTx heads and the LT1 block, there are lot's of people making in excess of 600rwhp, and some approaching 900-1000rwhp.

A 4th gen chassis has major problems putting that kind of hp to the ground, and evey other driveline component also has to be upgraded to handle the hp without breaking. Going further than even the ~700rwhp range with a 4th gen. takes you out of the realm of a street car in terms of the compromises necessary to handle that much hp. It's not that the motor would make the car undriveable but that the transmission needed and the chassis setup required would cross the line from practicality to the point where it would be a chore to drive the car. Not to mention, who wants to deal with a full cage on the street.

So, what I am trying to say is that you can make more hp than you can comfortably live with on the street with the LT1 block. And if you don't care about the street, then you are building a race car. And a 4th gen doesn't make a good race car, so why bother?

Rich Krause

 

if we are talking 4 or 4.03" bore.... isnt the lt1 preferable because it is reversed cooled?

its a relatively strong iron block, uses mostly the same parts as sbc, but allows significantly higher compression


the only big things against it are just bore limitations and 23* head limitations right? which come into play when you want more displacement or extreme airflow

 

You make some good points. Just to add that larger stroke as well as larger bore is possible with a Bowtie or equivalent. Displacements in the ~450ci range are possible. The block is also just plain stronger - better materials, thicker deck, thicker crancase webs, etc.

But the bottom line is that you can make more power than you can "use" (in the sense I explained above) with an LT1 anyway, so I still say "why bother?"

Rich Krause

 

The swap is straight foward no real major hurdles.

As for the fourth gen not being a good race car chassis, lt1 motor being more than enough.... etc.. Why are you shooting for another 200hp out of your car Rich? Not flaming you in any way you just confuse the hell out of me. One statement you say xxx hp is more than enough and it is a bad chassis trying to sway someone away from doing the car when you are building something pretty wild yourself?

I say slap the aftermarket motor in and have some fun. Now I won't speak for anyone else but me personally I am enjoying the challenge of designing and building my own suspension for a T/A suspension. The four link/ladder bar thing is done to death already and if I wanted that I would go out and buy one of the 4000 rolling chassis forsale. It all comes down to will you make alot of money racing a T/A suspension.. No. Will you have fun getting it to go fast on something diff than the normal masses.. Yes

You can look at some of the serious stock suspension setups out there and some have gone crazy fast on a stock basically suspension... Look at neverlift, palonili (not sure on spelling) and such guys they have used and made the suspension work fantasticly. It is all in what you want.

Steven

 

Steven: mine's not a race car, it's a street car. It has (and will have) a street/sport type suspension. I think what I am doing is consistent with what I posted. The LT1 block is good for 900+rwhp, which is where mine will be next year. But the car will probably be the slowest 900rwhp car in the world due to the limitations mentioned and the weight. If someone wants to do a Bowtie, I say go for it! But that it just isn't real logical unless you want in excess of 1,000rwhp. If that's what you want, good!

Rich Krause

 

Rich's car rocks The ultimate street car!

I have often (and have been thinking more seriously lately) thought of doing a non-LT1 SBC in my car. The LT1/4 is a great motor no doubt about it. IMO it is more than adequate for 99% of the owners that modify it. However, I think there are two reasons for going to a non-LT1 SBC. First, as Rich mentioned, an all out drag car. Basically the route George Baxter has taken. Secondly, more NA power. There is a limit to how much "streetable" power you can make with an LT1/4 engine. A non-LT1 SBC allows you to run 14, 15, 18 degree heads, 45x cubes (if you want), basically the steps needed for big NA power.

Just my thoughts.
Jason

 

another reason to run a SBC is the cylinder heads. you could always convert them to reverse cooling, but an 18degree head etc would rock.. even with boost. you could make a LOT more power on less boost(read: pump gas).

Another thing, at high power levels.. around 1000hp you get to the point that the block IS probably distorting more than you like udnerload, and a better block would make bearings and rings etc last longer. Also, for those of us that road race, I don't think my poor LT1 can take 1000hp for 20minutes at a time

 

Rich,

True the LTx block is strong. Even though you and some other guys put alot of power thru them that doesn't mean there are not some crazy things going on with them running that power. It's like the LS1 cranks, guys have but 700rwhp thru them! That doesn't comfort me at all!

For the Bow Tie Blocks the little things like priority main oiling, extra thick deck surfaces, thicker main bearing bulkheads, all the lifter bores, cylinder bores, cam and main bores are all in the exact right spots. Throw 8620 steel main bearing caps to the equation along with a much more rigid block and then you take all the little things and the block is not somthing you have to worry about then.

What Jordon said is right, I would bet that it's definately doing things that you don't want it to do under load.

For drag racing you can a LT1/4, I just worry about it to a point when 900+rwhp is run thru it. Remeber the things you should push the limits with are the things that make power not take power. That's my rule.

Jason, there is much more NA HP out there in a conventional small block. Hell a 18 deg head 427 would make some stupid power and still be a streetable engine. We should talk about that when you come down.

Bret

 

I have no disagreement with anything posted here by the "regulars". If I wanted an "ultimate" SBC it clearly wouldn't be based on a production casting. Just trying to point out that a production casting has fairly high limits, especially when you are talking a relatively low revving forced induction setup. For 99.99% of even high performance uses, a stock casting is adequate.

Now, when you talk about something like a super hi-po NA car that needs to remain streetable, clearly a tradition Gen I block is better due to the choice of heads. Even here, unless you are talking about sustained high rpm use, a good stock block is probably adequate, IMHO. It's only when you get to the professional level competition that a race type block is truly needed. It helps to keep in mind that the bottom end is not the place to look for major power gains. It's in the induction system, heads, and valve train.

I was all ready to build up a stouter shortblock for next year until we got mine apart yesterday. ~8,000 miles with lots of track time since the last rebuild using a blower and nitrous on a stock LT1 block. Iron 4-bolt caps (not fancy billet caps) and it's an undesirable 0.040" over. 7/8 cylinders with 4-5% leakdown and 1 with 8%. Bearings look good as well. I'm just gonna clean it up and put in new bearing and rings.

The original poster hasn't really said what he has in mind. But unless it's way on the fringe he might want to put the two grand into the rest of the motor.

Rich Krause

 

Maybe this is an undesireable question but, if you are moving to a sbc, bow tie or whatever isn't the Al bowtie a better way to go than the iron?

 

If you like your block to weigh in at only 90 lbs. Weight reduction is a good thing but an iron block is so much stronger. What does a really good aluminum small block go for nowadays, $3500?

 

GM PN 10185075 aluminum block is $4,192 at Pace Parts. The tall deck version is $4,911. A basic iron Bow Tie is $1,418.