1973 ls4 454
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Instructor
Joined: Mar 2015
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From: Burleson Texas
1973 ls4 454
As a start for a 450 to 500 HP build how good is the bottom end of a 1973 LS4 454? Is it a 4 bolt main, steel or cast crankshaft, will the connecting rods hold up?
Thanks for any input.
Jim
Thanks for any input.
Jim
Race Director
Joined: Mar 2016
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From: Napa Valley California
I just purchased my '73 454 LS4 a few months ago. What I have found is the crank is cast, the block is a 2 bolt main, and the rods are a standard GM connecting rod. Should all work ok for 450-500 Hp unless you plan on driving it hard. I plan to build mine up to 450 - 500 Hp as well so I'll convert my, numbers matching, 2 bolt main block to a 4 bolt main block, put in a forged crank and high quality rods, pistons, etc. While I'm at it I'm researching tossing in a stroker kit unless it runs into machining nightmares. I don't plan to race it or punish it, but I want it to last a long time without worries.
Thread Starter
Instructor
Joined: Mar 2015
Posts: 151
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From: Burleson Texas
Can a machine shop drill and tap the block for new 4 bolt main caps?
I think 2 and 4 bolt blocks are the same just 2 more holes per main in the 4 bolt blocks.
Then just buy 4 bolt main caps and have the machine shop line bore to make sure everything is straight
Has anyone done this. What are the pros and cons?
Thanks
Jim
I think 2 and 4 bolt blocks are the same just 2 more holes per main in the 4 bolt blocks.
Then just buy 4 bolt main caps and have the machine shop line bore to make sure everything is straight
Has anyone done this. What are the pros and cons?
Thanks
Jim
Burning Brakes
Joined: Feb 2005
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For the HP numbers you're speaking you don't need the 4 bolt main caps, unnecessary!
We do these 100% stock-appearing builds all the time, I would recommend going the 4.250" stroke however! With all the right pieces you'll hit 500 HP, or be very close. These are all based on a 9.5:1 C.R. and yield 14"+ vacuum at idle.
Thanks, Gary in N.Y.
P.S. Having said all that above I would definitely go hyd-roller. BB's are easy, use a MkVI (stepped-nose) cam and a thrust plate platform, no more cam buttons or setting cam end-play. The roller yields an add'l 30+ HP just by design. It's already factored in to get the 500 HP number above!
We do these 100% stock-appearing builds all the time, I would recommend going the 4.250" stroke however! With all the right pieces you'll hit 500 HP, or be very close. These are all based on a 9.5:1 C.R. and yield 14"+ vacuum at idle.
Thanks, Gary in N.Y.
P.S. Having said all that above I would definitely go hyd-roller. BB's are easy, use a MkVI (stepped-nose) cam and a thrust plate platform, no more cam buttons or setting cam end-play. The roller yields an add'l 30+ HP just by design. It's already factored in to get the 500 HP number above!
Thread Starter
Instructor
Joined: Mar 2015
Posts: 151
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From: Burleson Texas
I'm not sure what is inside the engine. The guy I bought it from said he rebuilt it some year ago and put a solid lifter L88 435 HP cam in it. Wasn't the L88 rated at 430 HP and the 435 was a L71. Could either of those engines breath with the smog heads. So it sounds like a bench racing rebuild to me. I'll know for sure when I start taking it apart this winter.
Jim
Jim
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From: Napa Valley California
I'm the third owner of my '73. I was told that the original owner had replaced the crank and installed a high lift cam. When I crawled under to inspect the undercarriage I found that it didn't appear the pan had ever been off and the inspection in the engine bay revealed that the timing cover did not appear to had ever been removed. The engine idles nice and smooth so who knows what is inside. There are several performance parts manufactures who produce 4 bolt main caps and most performance machine shops can drill and tap the block for the 4 bolt caps. Yes I agree that the torque and horsepower range I'm looking to achieve can work well with 2 bolt main caps, but since I'm going through the entire car, why not?
Le Mans Master
Joined: Apr 2001
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From: Sarver Pa
2021 C1 of the Year Finalist - Modified
500 hp w/ 2 bolt caps and studs=no problem. This is my 2 bolt truck block that is going in my race car , I'm shooting for 600+ hp so I put 4 bolt billet caps on myself in a Bridgeport mill then sent it for line bore.
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Burning Brakes
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There's another option that many aren't aware of, modify the existing 2 bolt caps and sleep better at night!! The add'l (smaller) outer holes are installed where the OEM 4 bolt fasteners would normally be, allowing for 4 bolt caps to still be added at a later time if necessary/desired.
We've done a high number of this mod over the years where the customer was "wavering" on the subject!
Adding the ARP main studs and modifying the caps will take up to 650 HP without any issues!
Thanks, Gary in N.Y.
P.S. Absolutely no align boring/honing needed. Modify the caps, assemble the unit! We've done dozens up till now!
We've done a high number of this mod over the years where the customer was "wavering" on the subject!
Adding the ARP main studs and modifying the caps will take up to 650 HP without any issues!
Thanks, Gary in N.Y.
P.S. Absolutely no align boring/honing needed. Modify the caps, assemble the unit! We've done dozens up till now!
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
There's another option that many aren't aware of, modify the existing 2 bolt caps and sleep better at night!! The add'l (smaller) outer holes are installed where the OEM 4 bolt fasteners would normally be, allowing for 4 bolt caps to still be added at a later time if necessary/desired.
We've done a high number of this mod over the years where the customer was "wavering" on the subject!
Adding the ARP main studs and modifying the caps will take up to 650 HP without any issues!
Thanks, Gary in N.Y.
P.S. Absolutely no align boring/honing needed. Modify the caps, assemble the unit! We've done dozens up till now!
We've done a high number of this mod over the years where the customer was "wavering" on the subject!
Adding the ARP main studs and modifying the caps will take up to 650 HP without any issues!
Thanks, Gary in N.Y.
P.S. Absolutely no align boring/honing needed. Modify the caps, assemble the unit! We've done dozens up till now!
Although Ligenfelter proved 30 years ago that 2 bolt mains and 3/8" rod bolts would hold 600 horsepower....aand ported Oval port heads would get you there.....
Jebby
Race Director
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From: Napa Valley California
I agree and understand the point you are making, 2 bolt mains will hold up under 500-600 hp. What is the harm in installing 4 bolt main bearing caps and building the extra strength into the bottom end? Whether it's truly needed or not.
Drifting
Joined: Aug 2004
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From: Lubbock TX
"What is the harm in installing 4 bolt main bearing caps and building the extra strength into the bottom end? Whether it's truly needed or not.?
Eats into the overall budget. That cash could be put toward something that would make an actual difference - like upgrading to a roller cam or bigger valves in the heads, etc.
I've seen tons of 2-bolt 454's at the 600+hp level with absolutely no issues. Thank goodness GM made the registers full-width on all big blocks, not at all like 2-bolt vs 4-bolt smallblocks. That single difference is what makes 2-bolt big blocks so much more capable of handling heavier rotating assemblies and higher revs.
Eats into the overall budget. That cash could be put toward something that would make an actual difference - like upgrading to a roller cam or bigger valves in the heads, etc.
I've seen tons of 2-bolt 454's at the 600+hp level with absolutely no issues. Thank goodness GM made the registers full-width on all big blocks, not at all like 2-bolt vs 4-bolt smallblocks. That single difference is what makes 2-bolt big blocks so much more capable of handling heavier rotating assemblies and higher revs.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
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From: New Braunfels Texas
Go full floating with a Wiseco or SRP piston....have the assembly balanced up....
Use a Speed Pro plasma moly ring pack (file fit). With some King bearings all measured out and a Fel Pro PTFE main seal....you have one nice meat and potatoes short block ready to take on what you can throw at it.....
Jebby
Last edited by Jebbysan; Oct 29, 2016 at 10:00 AM.
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
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Stock GM stuff is very strong. Had many near stock bottom end 2 bolt blocks do amazing things and live.
My old 427 (26 years old now) has original GM/TRW heavy forged pistons (11.0), 3/8" rods with new bolts, stock GM steel crank and 2 bolt mains with stock bolts. That thing has endured 7500 RPM shifts for years and for a long time ran 2 stages of N20. Ran high 9's #136+ MPH on the juice, low-mid 11's@118MPH with solid flat tappet cam and GM ovals, low 11's/high 10's@123 N/A with Merlin ovals and Comp street roller cam.
A nice 496 with some port work on your original heads and a hyd roller cam along with nice intake can easily be a 650 HP pump gas engine. Real mild version could make 575-600 easy.
JIM
My old 427 (26 years old now) has original GM/TRW heavy forged pistons (11.0), 3/8" rods with new bolts, stock GM steel crank and 2 bolt mains with stock bolts. That thing has endured 7500 RPM shifts for years and for a long time ran 2 stages of N20. Ran high 9's #136+ MPH on the juice, low-mid 11's@118MPH with solid flat tappet cam and GM ovals, low 11's/high 10's@123 N/A with Merlin ovals and Comp street roller cam.
A nice 496 with some port work on your original heads and a hyd roller cam along with nice intake can easily be a 650 HP pump gas engine. Real mild version could make 575-600 easy.
JIM
Team Owner
Joined: Jan 2006
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From: Crossville TN
To a question asked above:
The L-88 was rated at 430 HP; but that was to discourage folks from buying it. That rating was at a low rpm point, so actual HP at 6500 rpm was more like 560 HP. The L-88 was a very powerful engine at that time.
The L-88 was rated at 430 HP; but that was to discourage folks from buying it. That rating was at a low rpm point, so actual HP at 6500 rpm was more like 560 HP. The L-88 was a very powerful engine at that time.