New pistons in an old bore

Posted By: Boise Chall

New pistons in an old bore - 05/10/11 03:26 PM

I posted a couple days ago about a 77 motorhome 440 I have with 8:1 compression 452 heads and cast crank. The motor only has 48,000 miles on it and the bores are clean with no ridge. If I get a piston rebuild kit to up the compression to 9.5 can I install them with the other original components without any problems ? what will it do to the balance ? I've never done a motor this way I've always gone all the way and got everything new, machined and balanced.

Posted By: RemCharger

Re: New pistons in an old bore - 05/10/11 03:37 PM

You know the answer....
I vote for just put it together. It will make 400+ hp if you tried not to.

How much more do you need for your streeter?

Posted By: JohnRR

Re: New pistons in an old bore - 05/10/11 03:43 PM

Quote:

You know the answer....
I vote for just put it together. It will make 400+ hp if you tried not to.
How much more do you need for your streeter?

I agree , maybe not the 400 HP part , just putthe 915's on it and run it as is , nice thing is it will run on 87 octane ...

Posted By: Challenger 1

Re: New pistons in an old bore - 05/10/11 03:47 PM

I have done it many times, hone the original bore and go with it. No it's not gonna be balanced and I have also ran them like that for many years. It'll work and be reliable.
I did the same thing a few years ago, took out the 8-1 pistons and stuck some 10.5-1 in there(440) and it really woke up and is still running today.

Posted By: court9155

Re: New pistons in an old bore - 05/10/11 03:59 PM

Id atleast get the rotating assembly balanced

Posted By: Boise Chall

Re: New pistons in an old bore - 05/10/11 04:30 PM

Yea I knew the answer but it was a question in my head so I had to ask. I need to get this thing off the stand and in the car before I think it to death. The bottom end will stay original I'll put a whiplash cam in it with an edelbroch torker 440 intake ( that i already have ) a Holley 800 dp carb ( that I already have ) MSD 6 AL ( that I already have ) 1-7/8 headers and swap the mechanical fan for a Taurus fan. I have a 2000 stall converter in a new trans and a 9-1/4 with 3:55 gears. Any thought on what HP the motor will make ?

Posted By: RemCharger

Re: New pistons in an old bore - 05/10/11 04:44 PM

425 (+/- 10). Sounds good, I'm a big fan of the800dp, but I would look for a 3000 stall if possible.
Last weekend I ran a 13.6 with my 383 Charger(street) with 3.23s and street tires at 4000 lbs. You should be able to top that.

Posted By: JohnRR

Re: New pistons in an old bore - 05/10/11 06:39 PM

Quote:

Yea I knew the answer but it was a question in my head so I had to ask. I need to get this thing off the stand and in the car before I think it to death. The bottom end will stay original I'll put a whiplash cam in it with an edelbroch torker 440 intake ( that i already have ) a Holley 800 dp carb ( that I already have ) MSD 6 AL ( that I already have ) 1-7/8 headers and swap the mechanical fan for a Taurus fan. I have a 2000 stall converter in a new trans and a 9-1/4 with 3:55 gears. Any thought on what HP the motor will make ?

What did Hughes have to say about your intake and header choice with their cam ?

Posted By: Boise Chall

Re: New pistons in an old bore - 05/10/11 07:30 PM

When I told Hughes about the set up I planned they said it should work great, Be quick from light to light and be able to do burnouts all day long. That may have been just their sales pitch but I think I'll be happy with it. I think it's worth a shot anyway if it runs like crap I'm not out much. I really only have to buy the cam, lifters and gaskets everything else is just parts I have laying around.

Posted By: JohnRR

Re: New pistons in an old bore - 05/10/11 08:13 PM

Quote:

When I told Hughes about the set up I planned they said it should work great, Be quick from light to light and be able to do burnouts all day long. That may have been just their sales pitch but I think I'll be happy with it. I think it's worth a shot anyway if it runs like crap I'm not out much. I really only have to buy the cam, lifters and gaskets everything else is just parts I have laying around.

Well if they said that then I guess you are good to go.

Posted By: superbyrd

Re: New pistons in an old bore - 05/10/11 10:59 PM

i was thinking not too fond of the intake/carb choice,but,you got the parts lying around,use 'em. it would be happier,and a broader power range with a 750 VS holley and a perfprmer RPM intake........

Posted By: JohnRR

Re: New pistons in an old bore - 05/10/11 11:57 PM

Quote:

i was thinking not too fond of the intake/carb choice,but,you got the parts lying around,use 'em. it would be happier,and a broader power range with a 750 VS holley and a perfprmer RPM intake........

you are preaching to the choir , that intake is a bad choice for that engine combo but he doesn't care , so run it .

Posted By: Boise Chall

Re: New pistons in an old bore - 05/11/11 01:53 AM

I understand that the intake and carb may not be perfect for this motor but I have the intake and the carb. It only takes an hour to change an intake and carb if I just can't live with them. If I just change them now I'm out $500 for a new carb and intake but if I try them and they work good enough for what I expect from the car I'm $500 ahead of the game. Your not making it easy for me to temporarily kick my habit of building twisted and wild cars. hahahhaha

Besides I'm not going to be drag racing it if I want to do some racing I'll go home and get my Challenger

Posted By: JohnRR

Re: New pistons in an old bore - 05/11/11 02:22 AM

Quote:

Besides I'm not going to be drag racing it

Which is why it's a poor intake choice, you can still use the carb , a dual plane would be better. If it were a street dominator then I would be all for trying it .

When you pose questions and ask for peoples opinions ... you are getting what you asked for ... if you were just looking for people to agree with what you are going to build, using what you have, then you should state that.

Posted By: gch

Re: New pistons in an old bore - 05/11/11 02:30 AM

Nothing wrong with the carb.It would like a dual plane a lot more though.Heck,even a used performer or CH4B would be fine for less coin than an rpm.
With the torker intake it would like a vacuum secondary carb best for your application IMO.It would'nt mind the low stall as much with the vacuum carb either.

But hey you have it so put it together,tune it,and get a baseline.Then see how much you can pickup by trying an intake or what ever else comes along.

I built my 496 with used/leftover parts except for the pistons and I chose the wrong ones for the compression I now want.It still runs pretty well.

Posted By: Rapid340

Re: New pistons in an old bore - 05/11/11 03:04 AM

Be careful putting new pistons in the original bore. The top ring will most likely travel higher than the old top ring and I doubt there is no ridge at all on an old cast ring motor like that.

Posted By: RapidRobert

Re: New pistons in an old bore - 05/11/11 04:31 AM

Quote:

Be careful putting new pistons in the original bore. The top ring will most likely travel higher than the old top ring and I doubt there is no ridge at all on an old cast ring motor like that.

My thoughts exactly. Need to take ALOT OF CARE w the ridge reamer & get it flush but not past flush all around the perimeter and pull the cutter toward you rather than pushing it around in a circle and changing positions often so you are pulling the cutter just right and I would dingleberryhone for the ring type you choose (single Moly) though I hear cast iron rings seal better if the out of round/taper is way out of spec but I'd prob still go w Moly

. Use what you have/get it running/tune/enjoy it then swap for better stuff later. Down time is

EDIT read the OP & on balancing I would get a $10 dollar Harbor Freight gram scale & weigh the new piston/pin/ring assy & compare that # to what you get weighing a decarboned piston/pin;/ring assy you remove. It's reciprocating weight which is cut in half in the bobweight formula so it's less critical but you'll have the facts in hand & can make an informed decision and if the new is heavier you can grind the "square" on the rod small end to even it back out as the rod small end is included in the recip weight part of the formula but you'll need to rig up a fixture to hold the rod C to C horizontle while weighing the small end on the ten dollar scale. Just something to consider depending on how far you want to get into it, so much for getting up & running ASAP!

Posted By: Boise Chall

Re: New pistons in an old bore - 05/11/11 04:37 AM

JohnRR,
I think we got off on the wrong foot on this post. I value your opinion just as much as everybody on this forum. I'm not trying to discount your opinion in any way. Yes your probably right this may not be the perfect intake or carb for this motor it's probably not the perfect motor for this car and most likely won't stay in it for more than a couple years. Yes I should go spend $10K on a bad**s stroker motor but I'm not going to spend that kind of money on a car that might be worth $10K on a good day. If you look through the thread I never asked if it was the perfect intake for the motor. I asked if I could put new pistons in an old bore and if it would screw up the balance and How much horsepower the people on this board thought it would make.

Posted By: superbyrd

Re: New pistons in an old bore - 05/11/11 10:54 AM

okie dokie. after careful inspection,making sure there is absolutely no ridge of any kind at the top of the bores, new pistons/old bore should work fine.
as for running and how much HP, if your actual compression ratio comes in anywhere near 9.5 to 1, with all the parts you have stated,and sticking with only your original questions, 350 or so on a good day. should have decent torque down low,lumber/slobber it's way through the mid range,actually start moving up about 4000 rpm when it starts running out of steam,and absolutely eating gas,and spark plugs.
balance won't be affected,since it won't pull hard enough on either end to have to worry about it.
you asked.....................slap it together and enjoy

Posted By: Boise Chall

Re: New pistons in an old bore - 05/11/11 03:14 PM

wow !!!! I had no idea an intake could make that much difference. If I put this intake on this motor will it make my other cars run like crap too ????????? I better not use it because god knows that if I put it on the heads will absorb the intake and it will never be able to be taken off again !! Then I'll just have to have the car crushed or burned to destroy the EVIL intake so it could never destroy another car again. Jesus Christ guys it's an intake a couple bolts and it's off no harm no foul.. Just let it go before you end up in therapy.

The intake and carb setup ran just fine on the low compression 75 440 hp with 906 heads stock cam and 727 with factory stall that was ghetto rigged into a 73 satellite when I drove it just 3 weeks ago !!!!

Thank you to all that answered the original question without all of the drama... JohnRR and Superbyrd it's ok guys just let it go !!! hahhahaaha

Posted By: HotRodDave

Re: New pistons in an old bore - 05/11/11 06:08 PM

I have an M1 single plane on my low compression 360 with a comp XE 268 and low end Tq is no problem even with the 2.76 suregrip and stock 318 TQ converter. Throttle response is great. Bolt your intake on and don't worry about it, you have a lot more cubes than I do.

My only concern is the top of the bore being distorted, you will be getting a lot of blow by with out a fresh bore/hone. If you really want more compression and your bores are still good then just mill the deck of the block .060 or so and use a thin head gasket and keep the original pistons with ne rings.

Posted By: superbyrd

Re: New pistons in an old bore - 05/11/11 09:59 PM

let what go? i said slap it together and enjoy.
i was offering an opinion,just like you asked for.
from your description,and the parts you have,sounds like it will be a,...um,...real,..um,....decent running combo/motor/build,etc...

Posted By: RemCharger

Re: New pistons in an old bore - 05/12/11 04:03 PM

Quote:

Yea I knew the answer but it was a question in my head so I had to ask. I need to get this thing off the stand and in the car before I think it to death. The bottom end will stay original I'll put a whiplash cam in it with an edelbroch torker 440 intake ( that i already have ) a Holley 800 dp carb ( that I already have ) MSD 6 AL ( that I already have ) 1-7/8 headers and swap the mechanical fan for a Taurus fan. I have a 2000 stall converter in a new trans and a 9-1/4 with 3:55 gears. Any thought on what HP the motor will make ?

The only reason this combo would not be perfect is the diesel convertor. Gears kinda suck too. BUT,,, The torker is as good as the SD holley, and the 800 is about 6.3 times better than a 750 vs. Hard to say if you could put an rpm under the hood, which will slow you down anyway.

I have a torker I keep around to lend out , when a buddy needs one. Have to tell everyone to get their own, its not for sale..