RB 512 freshen up

[doublekrossd]

Hey guys, looking for a little help on some things here. Back in 17 I had muscle motors of michigan build me a short block 512. I wanted it to run on pump gas, use my indy big EZ heads, and when they asked for a horsepower target I said let's go with 700. The horsepower number I understand can be fairly arbitrary but they asked and I picked one. It's in my 66 belvedere street car.
From day one the motor leaked oil like a screen door in a submarine. The motor makes great power and pulls like a freight train when it "feels right" but I feel like there should be a lot more to it. Compression is right around 10.5 to 11:1 so it's right on the brink of pump gas (from what I understand) I've got both 3.55 and 3.91 gear sets for it but only ran with 3.55 so far. I'll post a pic of the cam card below.
It's got a cope trans, with a muscle motors spec'd PTC converter. I think the converter is way too tight but they did tell me the motor was designed start making lots of torque fairly low. Either way, I can't hardly "get up" on the converter at all in a street light race scenario.
And after reading another thread on here about blow by, I think it's time to open it up for a little exploratory preventative surgery.
1) do we think it's cammed right?
2) will this combo hit my goal if 700+hp (I want low 10's once the suspension works right to smoke my neighbor's stupid z06 corvette)
3) should I opt for more compression and run better fuel or switch to methanol? We don't drive the car anywhere near as much as we thought we would so more power=more fun in less time right?
4) should I be able to rev, say maybe to 2500rpms or more, the engine before getting too much forward travel?? I've never driven a high stall converter and to be honest, not sure what to expect.

I'm sure I'll have more questions as this thread progresses, but this post seems long winded to begin with! Thanks in advance guys!

 

[Bluefish]

The lift is ok, your duration is real good, but the lobe separation is not good for your street combo. 112* tames it considerably. A 110* would be better and a 108* would really wake it up in the low to mid range power. 108* works good in heavy cars, it makes the engine come on sooner and harder making the car much more fun to drive. 108* may not be good with power brakes thou as you will have lower vacuum at idle in drive. I have a SFT 270/275@50 on a 110* with .650 lift and works real good in my 12.5:1 511. You would be much happier with a 110* lobe sep and the convertor may use a loosening to get some real good performance. My vert is a 8" 5500 stall and works really nice on the street, but i do some track time too. Good convertors don't have much noticable slip. I once had a sb408 with a cam on a 112* lobe sep and a 3500 stall. That combo was a pooch off the line, not a good combo for performance. Hope this helps.

 

[PRHeads]

Has it been down the track yet?

Have you done a flash stall test?

I’d be hesitant to make any changes until I quantified what I had.

To be getting 700hp(on a legit dyno) from that combo, the heads would have to be pretty good(ported), MW size, and using a big single plane intake...... along with 2” headers.

 

[doublekrossd]

The lift is ok, your duration is real good, but the lobe separation is not good for your street combo. 112* tames it considerably. A 110* would be better and a 108* would really wake it up in the low to mid range power. 108* works good in heavy cars, it makes the engine come on sooner and harder making the car much more fun to drive. 108* may not be good with power brakes thou as you will have lower vacuum at idle in drive. I have a SFT 270/275@50 on a 110* with .650 lift and works real good in my 12.5:1 511. You would be much happier with a 110* lobe sep and the convertor may use a loosening to get some real good performance. My vert is a 8" 5500 stall and works really nice on the street, but i do some track time too. Good convertors don't have much noticable slip. I once had a sb408 with a cam on a 112* lobe sep and a 3500 stall. That combo was a pooch off the line, not a good combo for performance. Hope this helps.

Ok, should I go up a little in lift since I would need a little help in the lobe sep. anyway? (1.5 harland rockers) Has a solid flat tappet cam, would a roller be better? When we put it together there was thought that aftermarket solid roller lifters don't last on the street. It has manual brakes so vacuum is not a worry. Is there a way to loosen the converter? Not sure if it's something that can be sent back and re-done or i just order a new one. Sorry for the elementary questions, just want to get it right this time as I'm a little pissy of the money that was spent at muscle motors for the product I got.

 

[doublekrossd]

Has it been down the track yet?

Have you done a flash stall test?

I’d be hesitant to make any changes until I quantified what I had.

To be getting 700hp(on a legit dyno) from that combo, the heads would have to be pretty good(ported), MW size, and using a big single plane intake...... along with 2” headers.

No track time as of yet, planned on going with some family but the guy that got me into it can't seem to stay sober long enough to drive to the track... long story...
Heads are cnc'd to max wedge ports, matched to the indy single plane intake.

Vert flashes to about 3200 if I remember right, been since last summer when I drove the car

 

[zyzzyx]

Seal up all the leaks and put in the 3:91.

 

[PRHeads]

3200 flash stall isn’t enough for the best ET’s with the cam you have.

A street/strip car is a giant juggling act of compromises.
What helps one, detracts from the other.

Low tens will take a fairly serious effort in a full weight small tire B body.

An outing to the track to establish the baseline performance is highly recommended........ before you start throwing parts at it.
Otherwise you don’t really know what’s worth what when the changes are made.

 

[68 HEMI GTS]

I also think the cam is a bit off. How much does the car weigh? I’d bump the compression if low tens is the goal. Your also gonna need a convertor that flashes well into the mid 4 range or better. If it’s a PTC 9 1/2 they should be able to accommodate that. Sounds like something is a miss with the combo. I wonder if the cam was in retarded. What’s the intake/carb? Low 10’s on a b body requires a stout combo.

 

[Bluefish]

Ok, should I go up a little in lift since I would need a little help in the lobe sep. anyway? (1.5 harland rockers) Has a solid flat tappet cam, would a roller be better? When we put it together there was thought that aftermarket solid roller lifters don't last on the street. It has manual brakes so vacuum is not a worry. Is there a way to loosen the converter? Not sure if it's something that can be sent back and re-done or i just order a new one. Sorry for the elementary questions, just want to get it right this time as I'm a little pissy of the money that was spent at muscle motors for the product I got.

PRHeads knows way more than i do about the cams, but i like flat tappet, you just need to use very good oil, EDM lifters(direct oil) and keep an eye on lash. Rollers are only a 10th quicker most claim and good bushed roller lifters are very expensive. PRH picked my cam for my combo. He can get you what you need. Yes, convertor would have to be sent in to recalibrate if thats what you want to do. Are you looking for street/strip deal or just street? I think the 3200 stall and your gear are holding you back a bit as well. I think the 3.73 is a good street performance gear.

 

[Bluefish]

Low 10's will take a bit more than you have. I run low 10's at 10.06@134 and i still don't think i have 700hp. Car weights 3400 with me. 12.5:1 511 with cam above, 727 with 5500 stall and 4.10 gear. I'm using a MW port head as well(victor) and the Indy 400-3 single with an 1100 Dominator. I now have an Indy tunnel ram. I think your heads are better thou. I really think your gonna want a cam on a 108 lobe sep and some vert work first off. That will make quite a difference alone IMO.

 

[68 HEMI GTS]

Low 10's will take a bit more than you have. I run low 10's at 10.06@134 and i still don't think i have 700hp. Car weights 3400 with me. 12.5:1 511 with cam above, 727 with 5500 stall and 4.10 gear. I'm using a MW port head as well(victor) and the Indy 400-3 single with an 1100 Dominator. I now have an Indy tunnel ram. I think your heads are better thou. I really think your gonna want a cam on a 108 lobe sep and some vert work first off. That will make quite a difference alone IMO.

yep, your combo runs good. Add b body weight and your back to mid 10’s. People don’t realize how hard it is to get a b body street car to run down that far. Takes a pretty serious combo in a stout car with a good tuner to do it. I don’t see it with a 10.5:1 pump gas N/A motor unless the car is on a serious diet and extremely sorted.

 

[PRHeads]

Assuming the car is 3800-ish race weight, and reasonably well sorted out(correct gear/converter/hook, no fuel or ignition concerns, fresh air), I’d be looking to see 725hp STP on the dyno to put you into the lower 10’s in reasonable air.

Assuming 10% loss from the dyno into the car and at the track..... that’s 650-ish as it sits on the starting line.

Honestly, I think the current combo, as it is would struggle to dip into the 10’s.
But...... you have to start somewhere.

 

[biomedtechguy]

From day one the motor leaked oil like a screen door in a submarine.

Possibly a bad PCV valve and/or plumbing issue? Having either a PCV valve "system" with a breather or a vacuum pump can improve the performance or hurt it if not setup properly.

Compression is right around 10.5 to 11:1 so it's right on the brink of pump gas (from what I understand)

Keep it there, and do nothing that would raise it (like thinner head gaskets). I believe Jim Laroy would agree, raising CR when you are at 10.X:1 isn't the best place to find power, given the 8:1 beasts he's put together. My perspective is you risk engine damage and losing power if you raise the CR because of how you use the car and fuel availability. You may well wind up with piss poor timing or detonation and that will cost more power than a point or so of compression would add.

I've got both 3.55 and 3.91 gear sets for it but only ran with 3.55 so far.

3.55 depending on tire diameter should be a good compromise gear ratio. 3.91s will definitely kick you in the *** off the line if your tires can handle it, but highway driving is going to SUCK, and w/a 512 you shouldn't "need" more than a 3.55.

should I opt for more compression and run better fuel or switch to methanol?

See above "no". My concern about running methanol is washed down cylinder walls and contaminated oil.

should I be able to rev, say maybe to 2500rpms or more, the engine before getting too much forward travel??

YES! It seems like your torque converter is too tight!
I'd also say check all aspects of your ignition system, including the timing at idle and up through the RPM range. You may not have enough advance and/or it may be too lazy a curve.
ALL of the above is JMO and YRMV.

 

[68 HEMI GTS]

I love the Internet. I think I’ll find an HVAC forum and give advice on once I finish paying this guy to install my furnace...

 

[Bluefish]

Your car is heavy, so the 112*lsa, your 3.55 and tight convertor are all hurting you if you want to run low 10's. Their has to be some compromise here to get where you want to be.

 

[biomedtechguy]

I love the Internet. I think I’ll find an HVAC forum and give advice on once I finish paying this guy to install my furnace...

Right? That is what I was doing, but I have some ideas, and I just thought it's ok to share them, especially with "JMO/YRMV"
Since you and most people know more than I do, maybe you can point out where I'm obviously wrong? I'll edit or delete my post, because I don't want to mislead anyone.

 

[doublekrossd]

Possibly a bad PCV valve and/or plumbing issue? Having either a PCV valve "system" with a breather or a vacuum pump can improve the performance or hurt it if not setup properly.

3.55 depending on tire diameter should be a good compromise gear ratio. 3.91s will definitely kick you in the *** off the line if your tires can handle it, but highway driving is going to SUCK, and w/a 512 you shouldn't "need" more than a 3.55.


YES! It seems like your torque converter is too tight!

I'd also say check all aspects of your ignition system, including the timing at idle and up through the RPM range. You may not have enough advance and/or it may be too lazy a curve.
ALL of the above is JMO and YRMV.

I've got the correct adjustable pcv in it, as i was hoping to at least slow down some of the leaks, which it no longer blows the dipstick out at high rpms...

Still might try the 3.91, not much highway driving, maybe up north where it's 65 for 15 miles.

Ignition is good, it's all daytona systems. Distributor has been gone through, all in to 38* (maybe 36) by 2000 rpms.

 

[doublekrossd]

Your car is heavy, so the 112*lsa, your 3.55 and tight convertor are all hurting you if you want to run low 10's. Their has to be some compromise here to get where you want to be.

I'm gonna have to pull it down to look at things for oil leaks and inspection anyways, can't hurt to swap a cam. Maybe I'll switch the cam and rear gears (since I already own them) and see what it does. I'd like to swap out the old steering box for an update while i'm in there too but that's another topic.

 

[doublekrossd]

Oh, the carb is a 4150 pro systems. Iirc, flows right near 1000cfm. The higher it revs the better it runs and keeps pulling. I've had it over 6500 a few times and it's a hoot! Lol but I want more

 

[Bluefish]

Contact Dwayne(PRH) for a cam, he will get you what you need.