bainer1290

I'm looking for some advice on the engine build for my 72 Cutlass S. The engine and TH400 trans are out a 1971 donor car. Pistons are low comp so I will need to replace them and the heads are G with 2.00/1.625 valves.

My goal is to have good running, good sounding engine that I can drive on the streets with pump gas (premium is ok). I'm hoping to make close to 400hp and 500tq at the crank.

As of now the engine is almost fully tore down in my garage with plans to drop it off to the machine shop later this week.
The machine shop plan:
-clean an flux the block, heads and crank
-measure the bores and main/rod bearings
-remove/replace the cam bearings
-replace pistons with KB277's 10:1
-have the shop replace pistons on rods
-3 angle valve job, and I can clean up the ports at home

Questions:
-first off is my goal achievable?
-what kind of cam to go with, been looking at Comp 268H but not sure?
-I was looking at Flowtech Headers are they any good?

oldstata

Man Iam just about at the same point as you but know the machine work will go slow for me as funds allow.

any ways talk to cutlasefi about your cam needs I think the one your looking at is a bit small

Good luck looking toward to seeing your build

bainer1290

Yes I have seen lots of recommendations for cutlassefi on other threads, so I do plan to chat with him once I get the thumbs up from the machine shop on the block/heads.

The machine work is a big expense but thats how it goes...

68442CONVERTCO

Hi,


I think you'll be close to your goal, my build was similar except for large valve C heads.




Here's my build:

1968 455 block 40 over
Keith Black hyper. 277 pistons 10:1 CR
Comp Cams XE268H
Stock C heads
stamped roller rockers
guide plates
hardened push rods
Hooker 3902 headers
Carter AFB Competition 750 CFM
Edelbrock Performer intake
Ebay HEI

Dyno Results: 490 TQ 360 HP

Has a slight lope at idle 800 RPM.

bainer1290

How's those pistons turn out? I seem to be reading lots of good things on them.

Stock rods?

Did you have the rotating assembly balanced?

What rockers did you go with and are they adjustable?

68442CONVERTCO

My engine builder really likes the pistons even though the took a while to arrive.


Yes stock rods.


The balancing only cost $255. The engine builder kept apologizing for the cost of Oldsmobile engine parts, be prepared to spend about 25% more than Chevy parts.


Used the PRW stamped steel roller tipped rockers with guide plates. They are adjustable and fit under the stock valve covers.

bainer1290

Thanks for that info, still on the fence with rebuilding my heads vs trying to find a different set of used/rebuilt large valve ones or maybe a set of used aluminum ones...

GOSFAST

Just pulled from the dyno, 404 HP @ 5800 and 481# Torque @ 3800.

Comp ratio 9.7, Icon pistons, Comp hyd-roller cam, Eagle H-beam rods, H/Sharp rockers, all other OEM factory components (stock C.I. intake, Q-jet, stock exh manifolds). This is a 100% stock-appearing deal.

There was actually some area to get more power, but would have required some add'l head work. We did nothing here, basically a bolt-together build. I did have two issues, one was with the H-beams clearing the block, the other was the roller lifters clearing the valley-pan intake gasket. In the end it all worked out OK.

With an intake manifold change, maybe a different cam, and some head work I feel we could have gotten 475+!

Thanks, Gary in N.Y.

P.S. We tested with a 750 Holley also using a reverse adapter, made slight gain, 410 HP and 491# Torque!

RetroRanger

thats pretty awesome CI intake and manifolds !!!! thats exactly what i would like for my 455 well I have a performer but stock exhaust manifolds would be nice.

who was the builder ? where abouts in NY ?

Charly9g

Hi all. I'm in the middle of the same 455 build. 1971 low comp engine. Stock crank. Starting to take notes on all the info here. is it safe to take this block out to 60 over? And does KB make a 10:1 piston this size? (Block has to be bored anyway). And will the extra overbore (compared to 40 over) gain me anything if I don't get into stroking it, etc? I'm looking for a hi-torque cruiser, not a drag car. Thanks in advance. wfg4u@aol.com

Charly9g

Sorry, meant to add, I have an Edlebrock Performer Intake, Holley 750 CFM. No cam purchased yet. Plan on using either Edlebrock or Mondello Alum heads. Thanks.

bainer1290

From what I have seen I believe the KB277 comes in all the usual sizes from std all the way up to 60 over, it seems to be a good choice I think I am going to go with them.

bainer1290

Anyone have any recommendations for what to do with the stock heads?

Current valves are 2.00/1.625 curious if its worth the effort to go to a larger intake valve or just stick with what I have and save the cash for a aluminum set maybe down the road?

cutlassefi

Remember when you use any of the KB hypereutectic stuff you need to open up the top ring gap. Make sure your machine shop knows that when checking ring gap.

bainer1290

Yes that is a very critical point, KB specs here https://www.uempistons.com/installat...stallation.pdf

Do the pins get pressed into the stock rods on the KB pistons or are they just held in place with the retainer clips?

RetroRanger

Is that because they're hypereutectic or something else ?

bainer1290

Got the final pieces of the engine taken apart last night. Original pistons and bores look pretty good, might be just a hone if there is not excessive wear or taper.

The crank does have a bit more wear, what do you think of it? Will it need to be polished and grinded?

bainer1290

The cylinders look pretty good, a few closeups of the ones with some coating not sure if it was due to the engine sitting for a while or ???

bainer1290

Talked tot he machine shop the other day, the block and crank were fluxed and came out good. The bores had some taper so going 30 over with KB pistons and the crank needs to be cleaned up so 10 under on the rod/main bearings. The shop is pretty backlogged so said it would be about a month for them to bore/grind the crank. Good thing its winter.

Whats everyone's thoughts on having the rotating assembly balanced, is it necessary? I talked to another shop and they said since the KB pistons will be lighter it would be unnecessary but not sure I understand that, something about being overbalanced?

oldstata

If your replacing pistons /rods or if the crank is not from that yes you need to balance

bainer1290

Crank is original, same with rods, just changing from stock low compression to KB277 pistons.

oldstata

I would balance it

bainer1290

Yeah I guess if I am going that far why not pay a little more to get it done too.

Any other opinions on balancing?

cutlassefi

Find another shop.
Overbalanced means that they would need to take weight out of the crank, not add it. But I'd bet it wasn't perfect from the factory, never seen one that was.
However I will say an overbalance is better than an underbalance, that can cause premature wrist pin/piston boss wear. An overbalance would typically shake a bit more at idle but smooth out as revs increase. BUT that all depends on how far out of balance it is to begin with. Have it balanced.

bainer1290

Thanks for the reply cutlassefi. Luckily the shop I have doing my work is not the one that gave me the advice about the overbalance... That was a different shop that I called before I decided where to go. Sounds like the balancing is the way to go so I will be getting it done.

I appreciate the input from both you and oldstata. I will still need a cam soon, just wanting to get the bottom of the engine started first

dc2x4drvr

Couple thoughts, line hone the mains and don't turn the crank until the bores are mic'd.
Have you researched clearances, they are critical for a long lasting short block.

bainer1290

You think line honing the mains is necessary for this build?

I was going to have the rods resized and have their side clearance checked, seen some articles on them being tight.


For piston clearences from KB (4.156 bore, 30 over std):
-Piston to Wall 0.0020-0.0025
-Top Ring Gap 0.027 (4.156x0.0065)
-Second Ring Gap 0.0166 (4.156x0.0040)

For bearings (10 under std):
-Rod Bearings 0.0025-0.0027
-Main Bearings 0.0031-0.0033
-Rod side clearance 0.015-0.020

What do you think of these clearances?

oldstata

I would line hone . Are you going with arp bolts ? If yes then a big yes to it .

bainer1290

I was going to change the rod bolts to ARP's but thought of re-using the same main bolts. I'm trying to stay within a budget but I also want to have a good dependable street engine that I can have some fun with. So what do you think about the main bolts?

bainer1290

Was just reading another article, said if I was to go with arp main studs then align hone is necessary but using arp main bolts does not sound necessary. I am not trying to cheap out just don't want to go overkill when I do not need to...

Thoughts?

dc2x4drvr

The lower end IMO is everything when building a strong short block, by line honing and then grinding the crank to achieve your clearances you'll end up with a better result, than taking whatever the bearings and crank give you. I like ARP studs on the mains, bolts for the rods. just my .02

bainer1290

I defenitely need to have the crank grinded 10 under and I will have the bearings to the machinist before that happens. What does a line hone job cost?

cutlassefi

You're going to have tell him what clearances you want. He has to align hone the block, then install the bearings to get a size. then grind the crank accordingly to achieve your goal. Most guys won't go thru that trouble so if you're paying for it make sure that's the way he does it.
Most align hone jobs run about $150.00.
New bolts or studs is a good way to go as well.

bainer1290

That makes sense to me, for some reason I though an align hone job was much more than that, for a couple hundred its worth it.

Also I will get new arp bolts for the mains, studs look like they would be overkill for my setup. The most I will ever do to this engine other than what is in this thread is maybe add aluminum heads one day no more than that.

What do you think?

bainer1290

And would they bore the cylinders before or after they align hone the crank?

What about decking the block?

dc2x4drvr

Thanks Mark, I believe the lower end is the key to a strong short block-line hone, check the bore size, install bearings, compute journal size..grind the crank to achieve clearances.

cutlassefi

In this order;
Align hone
Square deck
Bore (preferably with a BHJ Bor Tru but I doubt he has one)
Hone with torque plate

dc2x4drvr

Yup, x10, my build exactly..

bainer1290

Excellent thanks guys.

bainer1290

Question on heads, costs and recommendations.

I currently have a set of all stock G heads that I was going to have cleaned, fluxed and a basic 3 angle valve job done on. I was then thinking of maybe having them machined for 2.07 intake valves at the same time, they currently have the small 2.00 intake and 1.625 exhaust valves in them. I have now come across a set of all stock large valve C heads that I could pickup for a couple hundred bucks. I have read multiple times that all the heads flow nearly the same and have the same size chamber, the only major difference is on the ones that have the large valves.

So the question is should I buy the C heads or have 2.07's installed in my G heads? Factors to consider:
-I think the G heads have hardened exhaust seats which is better for today gas correct?
-Will 2.07 valve's even fit in the G heads, seems tight in there already?
-What's the cost to have the G heads machined to 2.07 intake valves?