TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - Horsepower limits of a Service Block?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

Horsepower limits of a Service Block?

 Post Reply Post Reply Page  <1234>
Author
Message
jpnjim View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Nov/25/2007
Location: New England
Status: Offline
Points: 1544
Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 3:42pm
Originally posted by shootist shootist wrote:

Well since the service block is ultimately a small bore 390/401 block (to my knowledge, correct me if that is wrong) I know 800-900 is easily doable in the stock setup without even going 4 bolt mains because I have done it and a few AMC friends of mine have done it. Now if you go 4-bolt then I would say 1,000 would be easily reachable without hurting the block. What I have seen on the otherhand in 401 bore blocks and I find to be the most likely weakness is the thin cylinder walls. Out of all the block damage to the heavy webbed blocks (for which I have seen) I find blown out cylinder walls the most common. I believe this has a lot do do with mold shift causing some thinner areas but that is just an educated guess. The other types of damage I have seen have been such a mangled mess it is hard to determine what exactly happened because cranks and rods flopping loose in the crankcase at high RPM tends to destroy stuff pretty well.

Anyway, I wouldn't be at all concerned with block failure at or under 1,000 HP with reasonable levels of prep which you mentioned doing. I am putting 14lbs of boost on my 401 now with a ProCharger and there are a few others out there doing the same.

great reply,
thanks!

Makes me wonder how many of the 401's with failed walls were bored +.045, +.060, or more (?).
I also wonder how much strength a std, or .010-.020 over 401 gives up compared to a Service block with 4.125 or less of a bore(?)

It's a shame that some of the others sawed themselves in half before they could tell what went wrong,
but if it was like a 302 Ford splitting in half,
or a Buick 455 spitting out the mains I think it would be obvious.

Thanks for the info,
The strength of running a Service Block seems to be worth the cubes given up, and the slightly less flow/more valve shrouding of the smaller bore.
71 Javelin AMX P-code Go pac 360/4spd/3.91's
was Green/green now T/A red w/blk leather

88,89&98 Jeeps
Back to Top
Lyle View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/17/2014
Location: None
Status: Offline
Points: 773
Post Options Post Options   Thanks (0) Thanks(0)   Quote Lyle Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 4:48pm
I believe I read Pentske sleeved some race engines right from the start.  
Back to Top
one bad rambler View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jan/09/2008
Location: On The Island
Status: Offline
Points: 1524
Post Options Post Options   Thanks (0) Thanks(0)   Quote one bad rambler Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 6:06pm
I find it hard to believe that 800HP is the limit...Harmonic`s can be an issue...i never realized how much a crank flexes untill it was showed to me on a dyno with a strobe light...Several years back we were sent 3 engines to be dyno`d ...At the customers request we were asked to push all 3 to failure (Through Boost) then they could be gone trough for future improvements ...This was done on a chassis dyno...his goal was a reliable 1,200hp to the wheels out of a 3.5l Mitsubishi V6...The money spent was mind blowing 
68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
Back to Top
Hurst390 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Apr/20/2008
Location: Decatur Ill
Status: Offline
Points: 3662
Post Options Post Options   Thanks (1) Thanks(1)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 6:41pm
Originally posted by shootist shootist wrote:

I know 800-900 is easily doable in the stock setup without even going 4 bolt mains because I have done it and a few AMC friends of mine have done it.

I don't agree with that. I would bet the farm your walking the cap with 2 bolt mains at 8-900 hp.
Pull it down and you will see how shiny the mating surface is on the caps and block.
SC/Hurst Rambler

11.62 120

100% Street Legal
Back to Top
Lyle View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/17/2014
Location: None
Status: Offline
Points: 773
Post Options Post Options   Thanks (0) Thanks(0)   Quote Lyle Quote  Post ReplyReply Direct Link To This Post Posted: Feb/09/2018 at 10:41pm
An article on crankshafts:
http://www.hotrod.com/articles/crankshafts-how-to/
Notice picture #3 in the article and the material of the "stronger" crankshaft that has been removed.
Big "IF" someone spent the money or could order a billet crankshaft with much less mass then the current crankshafts available then I believe 1000 + HP could reliably be made. All the other pieces are there - just the missing link, my opinion. 
Back to Top
jpnjim View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Nov/25/2007
Location: New England
Status: Offline
Points: 1544
Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 5:48am
Originally posted by Lyle Lyle wrote:

An article on crankshafts:
http://www.hotrod.com/articles/crankshafts-how-to/
Notice picture #3 in the article and the material of the "stronger" crankshaft that has been removed.
Big "IF" someone spent the money or could order a billet crankshaft with much less mass then the current crankshafts available then I believe 1000 + HP could reliably be made. All the other pieces are there - just the missing link, my opinion. 

thanks Lyle,
do you mean this picture?

71 Javelin AMX P-code Go pac 360/4spd/3.91's
was Green/green now T/A red w/blk leather

88,89&98 Jeeps
Back to Top
jpnjim View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Nov/25/2007
Location: New England
Status: Offline
Points: 1544
Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 5:49am
Originally posted by Hurst390 Hurst390 wrote:

Originally posted by shootist shootist wrote:

I know 800-900 is easily doable in the stock setup without even going 4 bolt mains because I have done it and a few AMC friends of mine have done it.

I don't agree with that. I would bet the farm your walking the cap with 2 bolt mains at 8-900 hp.
Pull it down and you will see how shiny the mating surface is on the caps and block.

Interesting,
did you go to 4 bolt caps at that point and did the caps stop walking?
71 Javelin AMX P-code Go pac 360/4spd/3.91's
was Green/green now T/A red w/blk leather

88,89&98 Jeeps
Back to Top
Hurst390 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Apr/20/2008
Location: Decatur Ill
Status: Offline
Points: 3662
Post Options Post Options   Thanks (1) Thanks(1)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 5:55am
If you want to be safe? I wouldn't recommend 2 bolt mains at anything over high 600's
SC/Hurst Rambler

11.62 120

100% Street Legal
Back to Top
Hurst390 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Apr/20/2008
Location: Decatur Ill
Status: Offline
Points: 3662
Post Options Post Options   Thanks (1) Thanks(1)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 6:17am
My experience has shown me that 2 bolt caps showed signs of cap walk @ 700hp..
That was an iron headed 420 that ran 145.11 mph 1/4 mile @ 2950#

My advice would be to make the investment in 4 bolt caps...

The guys running 900 hp 2 bolt mains..what do they run and how long have they been together?

SC/Hurst Rambler

11.62 120

100% Street Legal
Back to Top
purple72Gremlin View Drop Down
AMC Addicted
AMC Addicted
Avatar
Charter Member

Joined: Jul/01/2007
Location: Illinois
Status: Offline
Points: 14369
Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 7:14am
Originally posted by Hurst390 Hurst390 wrote:

My experience has shown me that 2 bolt caps showed signs of cap walk @ 700hp..
That was an iron headed 420 that ran 145.11 mph 1/4 mile @ 2950#

My advice would be to make the investment in 4 bolt caps...

The guys running 900 hp 2 bolt mains..what do they run and how long have they been together?

I would agree. I myself would be leery too
Back to Top
 Post Reply Post Reply Page  <1234>
  Share Topic   

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.063 seconds.
All content of this site Copyright © 2012 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or