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Topic Review (Newest First)
02-18-2013 03:51 PM
janus may i push this ttt?
02-12-2013 04:52 AM
janus
Quote:
Originally Posted by F-BIRD'88 View Post
Just rebuild it 30 over with -5cc flat tops. get the block decked so you end up with a net
.040" quench clearance. EG: .028" gasket .012" deck. The heads are fine as is.
The cr will be 10:1 The GM LT4 Hot cam will work well.
There are many ways to juggle that and many gaskets to choose.
Hi F-BIRD,
First about the background of my idea.. Concerning this engine's bottom end I'm kinda on a budget because I'm back in college now and I'd really like to finish this before summer. Doing machine work for a SBC here (in Europe) can be kinda troublesome. For balancing, I'd have to send the whole cranktrain out to UK, for instance. So that's how I got the idea to use a good used stock LT1 rotating assy. The -5cc flat tops you mentioned would prolly be in the same range as the LT1 (imho they are 6 or 7 cc). Do you have a pointer as to why I should make overboring an item on my To-Do list?

As for the deck, I'd likely have the machine shop work on it since it can be done local, I'm probably gonna have it decked a little to make it sharp straight or IOW a 'true plane'. So I'm not sure how much deck I will end up with. I was gonna make a heads milling/HG decision after putting the bottom end together.

Imho it all adds up.. New pistons and while I'm at it I could also get some other rods or otherwise I'd prolly need some ARP rod bolts. Add in the machine work and shipping.. An LT1 rotating assembly would be almost in the same range for strength and weight but is cheaper, and if I can find one local I could also save some on shipping, plus it doesn't need balancing. Good idea!?

Quote:
Originally Posted by F-BIRD'88 View Post
Do not under gear it. slowing down a cammed motor does not work well.
Cammed motors need rpm.
the Mini Ram is not a low rpm induction system. It wants rpm.
The exhaust system will make or break it.
I'm gonna start with the 9bolt 3.27 I have in there now, but already have parts and plans for a 4.10 rear. Together with the later-LT1 T56 I have, that should give a decent but not too low geared drivetrain, the T56 being rather long in all gears. I was thinking that should be fine for something in the 3400 lbs range like a 3rdgen F-body?

I am aware that the MiniRam is, depending on displacement, more a mid- to high-rpm intake, but thanks all the same for reminding me

Exhaust system for now is a single 3" highflow Catco and mandrel-bent Hooker Aerochamber catback. Up front is a 'ported' 1 5/8" Hooker shorties system with a 3" Y-pipe.
Thanks a lot for your time and advice

P.S. I forgot to mention the cam I plan on using.. I already have a XR276HR, it's 276/281 (224/230 @.050") and .536/.544 w/ 1.6 RR, LSA 112 and IVC is 66. So a tad more than the LT4 HOT (218/228, .525/.525 @1.6RR).
02-11-2013 09:07 AM
F-BIRD'88 Just rebuild it 30 over with -5cc flat tops. get the block decked so you end up with a net
.040" quench clearance. EG: .028" gasket .012" deck. The heads are fine as is.
The cr will be 10:1 The GM LT4 Hot cam will work well.
There are many ways to juggle that and many gaskets to choose.

Do not under gear it. slowing down a cammed motor does not work well.
Cammed motors need rpm.
the Mini Ram is not a low rpm induction system. It wants rpm.
The exhaust system will make or break it.
02-11-2013 06:25 AM
janus well well... like so many times before ... life got in between ^^

so i'm still working out details for this build and i have hopes of completing it before summer starts

i recently came to the conclusion that by retaining the 12cc dished pistons (pre-90 L98 had these for the lower CR) I'd have a hard time setting up a decent CR and squish. so.. i got the idea of putting in a 94/95-up LT1 bottom end, since it's got flat top pistons and in general is lighter, stronger and said to be balanced a lot better than the L98/GenI bottom end i have.

any input on this is welcome

another question i have is concerning milling the AFR heads i have.. the 67cc chambers are too big.
i'm considering getting the L98's block deck checked and straightened if needed, so whatever deck clearance i will end up with will dictate my need for HG and chamber size to reach the desired CR.
04-26-2011 04:42 AM
Bowtie man Yes if you are putting in ARP main studs. Be sure an at least line hone it to make sure it runs true. Good luck with your build an keep us posted.
04-25-2011 12:20 PM
janus Bowtie man, thanks for the input. Actually i will accept any good power below 6krpm i can get of course, the 350hp was just a minimum, anything higher that can be done on a rebuilt short block is fine with me i guess

I was assuming the same concerning the heads, thanks for clarification there. I'll go and measure the valve sizes next time i get to the garage. I did already CC one port / chamber and i got 67cc for the chamber, 197 for the intake and 66 for the exhaust runner, to make sure what i got.

From what i gathered, the stock L98 dish pistons are 12cc, so if piston to valve / head clearance is fine, the felpro 1094 should make a good squish clearance. I might have the block resurfaced slightly, but min. squish i'll get is somewhere between 0.35 and 0.40.

The arp rod bolts would be a nice insurance i guess. I would have that done by a machinist. What do you think about the mains? Do i need an align hone when getting better studs/bolts? Just trying to get a cheap bottom end build for now that will hold up for a few seasons (maybe 10-20kmls).

Any other input? Go ahead, i welcome it
Thanks again
Andi
04-23-2011 05:10 AM
Bowtie man We will start with the 195's. you do not need a lot of head to do what you want to do. I am sure the 195's have at least 2.02's. You could gasket match your heads an intake an that should be enough. Yes, they are on the big side. But porting them out will just make it worse. All you will be doing is handing them money.

The lower end is going to do ok with around 6000 rpm's. But, you need ARP bolts in the connecting rods. The lower end needs to be gone through an done right. Would be nice to balance the lower end.

All your parts need to work together or they will not compliment each other an will work against each other. That is why you need the right combination. I can not comment on anything else. Because you have not told us anything else about your engine.
04-23-2011 02:31 AM
janus ok some more specific question here:

i heard some of the early 1pc blocks are prone to cracking, anyone on this?

how is the L98 bottom end gonna hold up to 6krpm without balancing?

and do you think the AFR 195 are on the big side for this build?

thanks!
04-20-2011 07:51 AM
janus anyone else wants to chime in here please?
04-19-2011 08:03 AM
C.A.R.S.005 my brother has a 350 with 380hp with vortecs and they flow at less cfm but maybe the way they flow is different ? you my try contacting F-BIRD'88 he seems to know a'lot about sbc and how to get the hp out of them .
04-19-2011 01:56 AM
janus thanks all the same, but i'd rather have some input from people who have experience with at least one specific of my combo.
at any rate, i know for sure that the Gen I (SBC) & II (LTx) cams are the same, at least for the rollers and not considering the dowel pin. also, yes - i would venture to state the range for AFR 195 heads just starts at about 300-350hp
04-18-2011 05:39 PM
C.A.R.S.005 i looked up the specs and the heads you will work fine for 350hp and a lot more . i was not familiar with afr heads before. and like i said not sure on cam fit you could go with a compcams roller cam instead .
04-18-2011 05:20 PM
C.A.R.S.005 i was referring to corvette . what is the cfm flow rating on your heads ? and i'm not 100 % positive that the lt4 cam will fit any roller motor i think in only fits lt1/lt4 and the zz4 .
04-18-2011 11:42 AM
janus CARS, thanks for your reply. From what i recall the F-body 350 heads aren't that good of a head, maybe you were referring to the L98 Vette head, or maybe i'm just wrong =)
At any rate, as stated in first post i do have AFR 195 heads and a MiniRam intake kicking around, so i'd rather use these, than get the heads (i just got the shortblock, remember?) and spend time on them with porting.
What do you think?
04-18-2011 08:10 AM
C.A.R.S.005 and with the heads in my previous reply your compression ratio would be about 10:0:1 pump gas safe .
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