Home | Register | Login | Contact Us

 
Auto Math
Classifieds
Forum
Gallery
Games
Garage
Tech Articles
Utilites
 
FAQFAQ    SearchSearch    RegisterRegister    Log inLog in    Log in to check your private messagesLog in to check your private messages    Forum Subscriptions1/4 Mile Table 

How to squeeze horsepower out of block prep?

 
Post new topic   Reply to topic    SMOKEmUP.com Forum Index -> Chevy - Small Block Gen 1
View previous topic :: View next topic  
Author Message
thesoundandthefury
Newbie


Joined: 04 Jun 2006
Posts: 16

794.06 points



PostPosted: Sun Jun 04, 2006 5:17 am    Post subject: How to squeeze horsepower out of block prep? Reply with quote

Hey all. I'm new here but I've read through alot of the posts in the search section and it looks like there's quite a bit of knowledge on this site so I thought I'd pick your brains. I've got a block that I've put a few hours of work into and I'm now at the stage where I'm gonna be dealing with the tolerance sensitive areas so I wanna be sure I've got the right info so I can plan a strategy and go from there. Namely what I'm after are secrets, tips, tricks, etc. that guys use when prepping their blocks to get more strength, longevity, and horsepower out of the engine.

Here are pics of what I've gotten done so far and some of the pics are areas that I've yet to address.

1969 Cast 400 Block



This is the area that's referred to as the "bulkhead" right? I've heard it helps to smooth these areas out. Yea or Nay?


What about up around these areas? Will smoothing the roof of the cam tunnel help with windage any?


Is there anything in this area that needs to be worked or improved upon?


I rounded off the ledges at the front return holes to make the oil's descent down the timing cove smoother.


Is there anything specific in the timing chain cove that should be addressed?


I've heard of three methods for controlling windage resulting from oil draining back through these holes: (1) plug them, (2) install oil restrictors, (3) install screw-in vent tubes that allow air to pass from the crankcase but no oil to flow back. For a street motor, which of these would be the best solution, if any?


I've heard that it's beneficial to enlarge these holes, but how much? Would quarter size be sufficient?


To the best of my knowledge, these are all the critical areas that I know to work on. If there are any other things that could be done that I failed to mention please clue me in. Just trying to make the most of what I've got. Thanks in advance for your feedback.
Back to top
View user's profile Send private message
Paul P
Member


Joined: 15 Aug 2002
Posts: 2403
Location: Townsend, Mass.
81574.74 points


1971 Chevrolet Chevelle

PostPosted: Sun Jun 04, 2006 8:33 am    Post subject: Reply with quote

thesoundandthefury,
Welcome to the site. I would assume you had the block sonic tested and crack checked before doing all this work to it. The 4-bolt 400 blocks are OK but if it was up to me I would go for a 2-bolt block and install splayed billet caps. The outer bolts on a 400 block don't have much meat to support them, it really depends on the appplication.

The photo of the rear main is one area I would smooth out. All that rough casting in that area as well as any others in the cam tunnel are prone to stress risers. Smoothing out all those areas would help keep things together.

The other area is the oil filter pressure relief valve. I would install a plug in it so all the oil gets filtered. This will ensure clean oil at all times just be sure to use a good quality filter and change it regularly. If you will be taking care of the motor as well as you have prepped the block I'm sure this would be a good mod to perform.

The oil return hole at the back of the block looks a little small in the picture with the pencil pointed at it. I know on most blocks it is opened up more than that half inch hole that you currently have there. You can see the outline of what it is normally opened up to in the casting. It is important that the oil gets back to the pan as soon as possible.

The block deck is another place to look as well. I think there was a post earlier on the subject of installing pipe plugs in the large holes in the deck to strenghten it. Smoke can probably point you to that one.

Looks nice for sure you have a lot of time invested in polishing there. Hope that is of some help to you good luck with it.
Back to top
View user's profile Send private message
96capriceMGR
Member


Joined: 23 Aug 2003
Posts: 814
Location: New London Wisconsin
20327.88 points


1996 Chevrolet Caprice

PostPosted: Sun Jun 04, 2006 8:42 am    Post subject: Reply with quote

Been awhile since I worked on a gen1 but on my LT1 the waterpump outlets were MUCH larger than the mating holes in the block, I opened them up to more closely match. I am running quite high compression for a street motor and kept a stock waterpump so I figured it was one of those can't hurt sort of things. I know the 400s have cooling issues so I would look and see if you can do any similar things. to just get the water to flow a little less restricted.
Back to top
View user's profile Send private message
Big Dave
Moderator


Joined: 04 Dec 2005
Posts: 2646
Location: Tampa Florida
119973.02 points



PostPosted: Sun Jun 04, 2006 11:49 am    Post subject: Powerful block Reply with quote

I noticed you polished the lifter gallery, even though few people will see it. I generally paint everything inside the block (after making clearance for my selected stroke) with GE Glyptol paint (about $78 a gallon). It allows for as fast an oil drain back as your polish job and holds any loose casting flash in place. Instead of polishing the crankcase are I would consider painting it. The bulkheads are the webbing's or parts of the block that support the main bearing caps. polishing them could relieve any potential for a stress riser to form, but a general casting flash remove is sufficient.

I agree on opening up the rear main oil return path. I plug the holes over the cam with pipe plugs and run screens front and rear to capture anything I forgot to check (routine maintenance includes inspection of valve train and springs). You can not block off the front and rear oil return holes as all the oil pumped up through the lifters returns through these holes.

A cautionary note on plugging the bypass valve: be careful of early revs on cold oil as anything over 100 psi could rupture your oil filter (especially if it is a no name import).

As far as making horse power, about the only contribution the block makes, is having round holes perpendicular to the crank centerline, and having a square deck (flat and parallel to the crank centerline). The polishing and deburing won't hurt anything, but it doesn't contribute much either. A thorough cleaning is more important (rifle cleaning brushes run through all oil passages), and once clean keep it that way.

Big Dave
Back to top
View user's profile Send private message
af2
Member


Joined: 01 Sep 2003
Posts: 5558
Location: grassvalley, ca
71227.76 points


1933 Willys Coupe

PostPosted: Sun Jun 04, 2006 6:33 pm    Post subject: Reply with quote

You need to either sonic check that block or go ahead and bore and hone it to see if the deck will crack. I saw a motor that was plugged, decked bored and when the final torque plate hone was done the motor cracked to one of the center bolts. A total waste of time. That was a 4 bolt block and I don't know what the casting changes were but the 2 bolts have 2 less freeze plugs. That is the only 400 I will run Period. I am using a 2 bolt block now with a main girdle instead of splayed mains just to prove it works.
Back to top
View user's profile Send private message
SMOKEmUP
PostMaster


Joined: 30 May 2002
Posts: 3169

65097.54 points


1979 Chevrolet Camaro

PostPosted: Mon Jun 05, 2006 8:44 am    Post subject: Reply with quote

Nice job on the block, looks really nice.

Another thing to consider is having the lifter bores bushed to ensure correct geometry.

What's your target horsepower level?
Back to top
View user's profile Send private message Visit poster's website
clay
Moderator


Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Mon Jun 05, 2006 8:33 pm    Post subject: Reply with quote

Af2, I hope the girdle works out, and I can see where they do help to stabilize the caps somewhat, but I don't think they do as much to help the block. We had a 302 Ford block that failed with a girdle and it split starting in the middle of a main cap bolt hole, went up to the cam bore and right on up into the lifter valley. Every bulkhead was broken from top to bottom except the rear which I assume the transmission kept it from splitting. What was really amazing is that nothing else was hurt except the block. I have seen other pictures of failed 302 blocks and what we experienced seems to be very typical of how they fail. One good thing is that Chevy blocks in general seem to be much stronger that the light weight casting on the 302's. I'm not saying it won't work, just sharing experiences. Clay
Back to top
View user's profile Send private message
thesoundandthefury
Newbie


Joined: 04 Jun 2006
Posts: 16

794.06 points



PostPosted: Tue Jun 06, 2006 6:51 am    Post subject: Reply with quote

I appreciate all the input guys. I've surfed around and dug up a fair amount of threads on various boards looking for info in regards to "how much can it handle," and the general consensus on 400 4-bolt blocks seems to be that on average they tend to give out at around 600FWHP. From the get-go, I made a deal with myself that I would never expect anymore than 450FWHP out of this engine, so I think I'll be safe.

FWIW, when I bought this engine the previous owner had cammed it to about 360hp, (95% of everything else on the motor was bone stock and untouched), and it ran without any problems, but it was getting tired so I figured if I was going to go to the trouble of rebuilding it myself I may as well make the most of it. Due to the fact that nothing too extreme was ever done to it, including heads, I think it'll probably magnaflux okay. (Fingers crossed.) As far as bore: I'll never have a need to go past .030 over and plenty of stock blocks live at that spec so I think I'm good in that regard.

Once again thanks for everyone's feedback.
Back to top
View user's profile Send private message
af2
Member


Joined: 01 Sep 2003
Posts: 5558
Location: grassvalley, ca
71227.76 points


1933 Willys Coupe

PostPosted: Tue Jun 06, 2006 9:35 am    Post subject: Reply with quote

clay wrote:
Af2, I hope the girdle works out, and I can see where they do help to stabilize the caps somewhat, but I don't think they do as much to help the block. We had a 302 Ford block that failed with a girdle and it split starting in the middle of a main cap bolt hole, went up to the cam bore and right on up into the lifter valley. Every bulkhead was broken from top to bottom except the rear which I assume the transmission kept it from splitting. What was really amazing is that nothing else was hurt except the block. I have seen other pictures of failed 302 blocks and what we experienced seems to be very typical of how they fail. One good thing is that Chevy blocks in general seem to be much stronger that the light weight casting on the 302's. I'm not saying it won't work, just sharing experiences. Clay



Clay, Thanks for the info. The mains on the 400 are splayed towards the pan rails and not straight like the 350 and the Fords. For that reason is why I decided to use a girdle instead of going to 4 bolt and weakening the main web. If the block doesn't work out I will go to using the Mowtown or Bowtie block. Adam
Back to top
View user's profile Send private message
nwcc
Member


Joined: 11 Aug 2005
Posts: 453
Location: Pacific Northwest
158.80 points



PostPosted: Tue Jun 06, 2006 12:20 pm    Post subject: Reply with quote

If it was any other SBC I would say go with 1/2 fill of block filler. But, since its a 400 and I understand they have some cooling issues. Maybe a 1/4 fill of block filler wouldn't compromise cooling to much and could help stabilize the bottom end. This would help with reliability and power output
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    SMOKEmUP.com Forum Index -> Chevy - Small Block Gen 1 All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
Home | Contact Us | Automath | Cam Files | Dyno Search | Forum | Garage | Picture Gallery | Reaction Timer

Copyright 1997-2016 SMOKEmUP.com All rights reserved.
Advertising Info     Disclaimer     Privacy Policy