Rockers and Compression Questions

[slepr1]

I pulled my 440 and 727 out of the big Doba. The 727 was sent in for a rebuild. I'm getting the engine freshened up with new 5090 edelbrock 75cc estreet heads, a new cam & lifters and some new roller rockers.

I called Hughes up for a cam suggestion based on my build and needs. They said I need more compression with those heads (I'll be at 9.5:1) and suggested I go up to 10.5:1. (I do use 100 shot of nitrous too). They also said their 1.6 ratio rockers will work. I call up edelbrock tech and they suggested I stay with 1.5 ratio rockers because that's what the heads where tested with. Edelbrock also said 9.5:1 compression is fine with those heads as they have a few crate performance engines that have 9.5:1.

Hughes suggests their cam SEH3642BL-8...
BB HYD FLAT TAPPET CAM 236/242 -108ºLSA
LOBE LIFT .364"/.375"

Lifters:
5003 HIGH PERFORMANCE HYD. LIFTER (QUIETER)
ASSEMBLED W/ HEAVY DUTY RETAINER & QUICKER, EVEN BLEED DOWN RATES

What do you think... Rocker 1.5 or 1.6?
Add compression or stay at 9.5?
Hughes cam or Engel?

 

[moper]

If you're spraying it I would stay conservative on the static compression. No reason to buy into the "aluminum needs another point or you'll be disappointed" BS. Same on the rockers. I like 1.5s and the right camshaft, rather than more rocker on a smaller cam. Especially if it's a street-predominantly package. Plus it's a good chance the 1.6s will need a little correction to get the right sweap because the heads were designed with 1.5s in mind. Just thinking out loud but that's where I'm heading.

 

[Challenger340]

Given the Nitrous shot, 9.5 would be my vote as well.
"Best" performance curves running strictly N/A would like slightly higher than 9.5:1 depending upon elevation, etc.

Forged Pistons right ?
If not, conservative tune is a good idea.

1.5's are fine.

 

[slepr1]

[QUOTE="Forged Pistons right ?[/QUOTE]

Yes. TRW 30 over

 

[rumblefish360]

Your build is conservative so I would stay with the 1.5 rocker and a 9.5-1 ratio. You’ll be fine.

 

[BSB67]

I pulled my 440 and 727 out of the big Doba. The 727 was sent in for a rebuild. I'm getting the engine freshened up with new 5090 edelbrock 75cc estreet heads, a new cam & lifters and some new roller rockers.

I called Hughes up for a cam suggestion based on my build and needs. They said I need more compression with those heads (I'll be at 9.5:1) and suggested I go up to 10.5:1. (I do use 100 shot of nitrous too). They also said their 1.6 ratio rockers will work. I call up edelbrock tech and they suggested I stay with 1.5 ratio rockers because that's what the heads where tested with. Edelbrock also said 9.5:1 compression is fine with those heads as they have a few crate performance engines that have 9.5:1.

Hughes suggests their cam SEH3642BL-8...
BB HYD FLAT TAPPET CAM 236/242 -108ºLSA
LOBE LIFT .364"/.375"

Lifters:
5003 HIGH PERFORMANCE HYD. LIFTER (QUIETER)
ASSEMBLED W/ HEAVY DUTY RETAINER & QUICKER, EVEN BLEED DOWN RATES

What do you think... Rocker 1.5 or 1.6?
Add compression or stay at 9.5?
Hughes cam or Engel?

Sometimes it is a relative question and answer. Are you having new pistons installed as part of the freshening? How did Hughes suggest you get to 10.5:1 CR? I would prefer 10.5:1 if I was already planning to put new pistons in. But if not, that will add a lot of $ to your build, and 9.5 is not that bad.

What was your compression ratio before? If it was 8:1 with a factory head, you're already be taking a big step in the right direction.

 

[slepr1]

Are you having new pistons installed as part of the freshening? How did Hughes suggest you get to 10.5:1 CR?
What was your compression ratio before? If it was 8:1 with a factory head, you're already be taking a big step in the right direction.

I'm reusing my pistons if they are ok (at the engine rebuilders now). The engine has less than 10K miles on it but was previously rebuilt in the mid 80's. I'm calling Hughes today. Tech guy Dave wasn't there on Friday to answer that question.
I can't remember what the compression ratio was. It had stock forged pistons (69 block) with factory 452 heads.

 

[BSB67]

I'm reusing my pistons if they are ok (at the engine rebuilders now). The engine has less than 10K miles on it but was previously rebuilt in the mid 80's. I'm calling Hughes today. Tech guy Dave wasn't there on Friday to answer that question.
I can't remember what the compression ratio was. It had stock forged pistons (69 block) with factory 452 heads.

Dave Hughes is the owner, unless there is another Dave there. In general, there were 4 different "stock" compression height pistons back then, not including domed high compression pistions. They could range from 7.8:1 to nearly 10:1. So until you get the part number off the top of the piston, its a guessing game.

 

[slepr1]

I just came back from the engine builder. The cylinders will need to be bored out to 40 over. They were previously done 30 over. Looks like they weren't done properly. Anyway, problem solved...new higher compression pistons.

 

[wyrmrider]

measure your piston top to deck at tdc if at all possible and the TRW number
I say ixnay on 10.5 with stock open chamber heads and even the best street gas
(you would have to use a really big not really streetable cam)
Hughes does not give seat timing so no way to figure dynamic compression ratio
you have to guess at the "intensity" from the .050 numbers and I do not see the timing numbers -BOO-HISS-BOO
so
Engle .904 series (not the ones in the catalog) (Engle and MP measure at .008)
Howard with a (15) footnote in their online catalog (but they have others)
Lunati Voodoo,
Bullet (not Ultradine) .904 series (list online)
These and comp measure at .006 including comp XExxxHL series which are their only real MOPAR choices
but BVVC the cam tecs push what they know which are the .841 universal (cheaper to grind -even MP cams are better)
Crane special order .904 lobes crane measures at .004 (as do ELGIN, Summit etc)
So BVVC comparing these three classes of camgrinders
Jim at Racer Brown
Mike Jones if solid or Roller
if spraying check your ring gaps

if getting new pistons are you thinking custom say YES and get a quench dome design that goes above deck into the open chamber away from the spark plug
see examples on KB website
much less chance of detonation
less picky as to fuel and timing
the only other choice is closed chamber heads with mataching pistons
buying down thehole pistons or even 6 pack pistons and 0 deck
- well you can't rally get where you want to go with those heads
(unless this is a race only deal with low gears and race gas)

 

[BSB67]

measure your piston top to deck at tdc if at all possible and the TRW number
I say ixnay on 10.5 with stock open chamber heads and even the best street gas
(you would have to use a really big not really streetable cam)
Hughes does not give seat timing so no way to figure dynamic compression ratio
you have to guess at the "intensity" from the .050 numbers and I do not see the timing numbers -BOO-HISS-BOO
so
Engle .904 series (not the ones in the catalog) (Engle and MP measure at .008)
Howard with a (15) footnote in their online catalog (but they have others)
Lunati Voodoo,
Bullet (not Ultradine) .904 series (list online)
These and comp measure at .006 including comp XExxxHL series which are their only real MOPAR choices
but BVVC the cam tecs push what they know which are the .841 universal (cheaper to grind -even MP cams are better)
Crane special order .904 lobes crane measures at .004 (as do ELGIN, Summit etc)
So BVVC comparing these three classes of camgrinders
Jim at Racer Brown
Mike Jones if solid or Roller
if spraying check your ring gaps

if getting new pistons are you thinking custom say YES and get a quench dome design that goes above deck into the open chamber away from the spark plug
see examples on KB website
much less chance of detonation
less picky as to fuel and timing
the only other choice is closed chamber heads with mataching pistons
buying down thehole pistons or even 6 pack pistons and 0 deck
- well you can't rally get where you want to go with those heads
(unless this is a race only deal with low gears and race gas)

He already said he is using eddy 75 cc heads. Zero deck piston with a dish will probably be needed. From memory, probably 12 cc will put you in the low 10s on CR.

 

[rumblefish360]

He already said he is using eddy 75 cc heads. Zero deck piston with a dish will probably be needed. From memory, probably 12 cc will put you in the low 10s on CR.

Wyrm, a good guy with a wealth of information that means well is stuck on a single minded track.

Wrym, love ya man. But I have a question for you. The Ultradyn cams, do you know where they are measured at? I have a NF series solid flat tappet. Split duration, the two smallest on the list.

 

[wyrmrider]

Are those Eddy heads the open chamber ones- and do you own them already
If so I'd sell and get the closed chamber heads and matching pistons with more dish
keep the combustion chamber near the plug- hard to make the the open chamber no quench deal work unless race gas and race rpm
rumble- thanks buddy Ultradyne did not have .904 hyd cams but did have solids- Harold Berkshire designs so state of the art back in the day when many grinders were copycats (and still are)
get a hold of Bullet- they are usually easy to work with old timers
I would guess .020 but they could be tight lash or almost anything as Harold was up to speed- I would not think 30-30 ramps
the lash and the advertised may be different which makes comparing a lot of fun
what does it measure at .050- most everyone can agree on that

 

[rumblefish360]

I’m having a hard time getting intouch with them so much, so I gave up. I don’t give a **** about it anymore.

 

[Bicylindrico]

FWIW. I am running old L2295 TRW pistons which are .030" over with a 12cc dome. My calculations on a supposed untouched deck height block came in at 10.44:1 static compression and 8.58:1 dynamic compression with my chosen camshaft running 80cc chambered CNC'd Promaxx heads.

I had contacted Crower with these engine specs and they recommended .604"/.600" valve lift and 242/247 @ .050" duration camshaft with my 1.5 rockers. Needless to say, I don't really feel I need any nitrous with this build but I keep her on the street