20 degrees is a lot. I didn’t think they bled off that much. Then again, I may have just forgotten!
Camshafts and Compression
- Thread starter Valman
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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That's pretty easy to solve, just retard the timing during cranking.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 26,133
- Reaction score
- 13,476
As to your Rhodes lifters. IIRC you can tune them with oil viscosity and/or oil-pump pressure/volume.
IMHO, I think if a guy worked with them, they could make an excellent street-strip combination; like a poor-man's VVT.
I shouldda tried them on my 292 cam but I wasn't smart enough back then. (1999)
IMHO, I think if a guy worked with them, they could make an excellent street-strip combination; like a poor-man's VVT.
I shouldda tried them on my 292 cam but I wasn't smart enough back then. (1999)
Yeah, I was thinking along those lines at the time - like a simpler VVT.
Possibly with a lower compression street engine (maybe 9.5:1 or so?) they would be more suitable.
I probably should have put a solid cam in this engine.
Newbomb Turk
Well-Known Member
IMO they are never suitable. If the cam is wrong you can't fix it with a squishy lifter. Like I said, yuou can run way more compression on pump gas than the smart people say. You just can't cut corners.
BSB67
Well-Known Member
Generally my choice. If you choose this path, because you are up against cylinder pressure, pay particular attention to actual valve events verses lobe events.
I always thought the point of them was to use the right cam for performance while having decent driveability, so don't have to compromise.
Newbomb Turk
Well-Known Member
Agreed. Actual timing events take precedence over lobe duration & lifts. I know more about this stuff now than I did 7-8 years ago.
Dumb or not it's probably the thing most are concerned with, with a street car. How many times the argument here where's the right line for X mod between performance and driveability for the OP's.
It is concept (streetability) I'm buying into less as a factor.
Yup. That's about the rate.
IMO, it depends. IF all I am doing is building a 100% street car just for cruising and having a good time with, while I do look at valve events, they are not my end all be all guide. No way. No how. It's real easy to get caught up in "paralysis by analysis" looking at too much. Now a race only or hot dual purpose car, I'll spend some time on. But something for the street? I make a decision and go have FUN!
Or even go bigger cam
Search some of IQ52's builds on here. Specifically what they did with a 7.35:1 440. Yeah, you read that right. He's proved time and again compression is not the end all be all. I try to preach it all the time, but get argued down so I just give up.
Eg. a 12's low cr vs 12's high cr car, both are still a 12's (or whatever) car the high cr probably feels stronger but you still can go fast with low cr.
Thanks RRR, I’ll check it out. We get talked into high compression by the ‘gurus’ sometimes I reckon. You don’t really need it.
I spoke with a few ppl when putting it together, in AUS & U.S. One a local Pro-Stock builder. The general consensus was you have 10.7:1, great quench, run it. In reality, it’s probably a bit high.
It's certainly true. The forum gurus and all the magazine articles have you believe your junk won't even fire off unless it's at least a flat 10:1 and it couldn't be further from the truth. The ONLY reason my slant 6 turned out with 10.6 is because the head fell off the broach on one end and I had to get that milled out on a Rottler. The chambers went from 59cc to 34cc. I had to utilize the head, because all the others I had needed seats and guides and that one did not and I couldn't afford that. So I chose a camshaft with a 71 degree IVCE. Now THEN I looked at the valve events, because I needed to in order to run on pump gas. Otherwise, I would have had the "obligatory" .100" milled off the head and been "around" 9:1. I think it ended up close to .180" milled off to get it back straight and clean. It was a lot.
Unless your use to running on the edge with CR it's probably better for most to give themselves a bit of a safety margin, especially since point of CR gives a fairly small reward hp wises, eg. around 3%.
BSB67
Well-Known Member
The point was you cannot directly compare SFT to HFT specs. He has a detonation issue with the 100% street car he already has. Should probably try to not make the same mistake twice.
Yeah I know that. The solid with the same duration "acts" about 10 degrees in duration smaller than a comparable hydraulic. I didn't seen anyone bring solids into the conversation. Maybe I missed it. Since he has a hydraulic, that's all I was discussing. I didn't see any need to muddy the waters.
Valman,
I am in Sydney. Your Rhoads lifters will make it easier, not harder, to crank the engine. I wouldn't be in a hurry to remove them just yet. I modify std lifters to work like Rhoads. While they crank up the low end, they also act as anti-pump up lifters on the top end. Not saying they stop pump up, but they will reduce it because of the bleed down feature.
The TQ. I posted some pics of TQ mods in the Fuel & Air section, Dec 14, 2023. These WORK. Recently did the mods on a 6394 for a bloke in WA. A friend of mine with a 455 Pontiac ran 119 mph at Eastern Creek with the TQ modified. 3900 lb without driver, 3.36 axle, T400, Victor int man, street radials, reverse patttern cam, street registered & driven, 850 rpm idle in gear. He had little drag racing experience, running low 11s. NO tuning was done at the track such as ign timing, air valve [ AV ] position etc.
Comments on your TQ. There is no 6164 TQ in my master catalog, probably you have the 6461. It comes 98/137 jets & #2005 rods. I have never had to go more than about 2 thou bigger on the pri jets. 105 seems excessive. The Ferd 9000 series TQs here were 800s & had large 101 pri jets, but they also had much bigger pri air bleeds, which leaned the mixture. Probably for emissions. They also had smaller sec hi speed bleeds, 0.029" v the 0.039" used on the 6000 series carbs. The small size probably accounts for the smaller sec jets.
Since you have removed the choke, I would remove the x/over shaft that runs across the AV. Braze a small piece of steel over the opening left in the AV.
I NEVER use 1 1/4 turns on the AV spring, too loose. I use 2 turns. I would also go bigger on the AV opening, not 0.500". The opening also controls distribution as well as total air flow.
The top of the AV is bent forward. The original comp series had that straight. I straighten them sometimes. It starts the sec airflow earlier.
I have NEVER had to use the inner holes on the acc pump lever, only use the outer hole. These have a big 30cc pump & of course a very efficient design that doesn't need a heap of fuel to cover a bad design.
If you have the PCV hooked up, make sure engine vacuum is high enough to pull in the pintle. If not, cut off a piece of 3/8" bolt & drill a 1/8" hole through it; shove this inside the PCV hose.
If you need bypass air, drill the sec blades, not the pri because you could get nozzle drip.
If the engine is making a lot of HP, you should use 0.110" n/seats. Had to do this recently on a 440 I built that was laying over in 2nd gear. I just drill the factory seats. Use this chart to reset the f/level.
I am in Sydney. Your Rhoads lifters will make it easier, not harder, to crank the engine. I wouldn't be in a hurry to remove them just yet. I modify std lifters to work like Rhoads. While they crank up the low end, they also act as anti-pump up lifters on the top end. Not saying they stop pump up, but they will reduce it because of the bleed down feature.
The TQ. I posted some pics of TQ mods in the Fuel & Air section, Dec 14, 2023. These WORK. Recently did the mods on a 6394 for a bloke in WA. A friend of mine with a 455 Pontiac ran 119 mph at Eastern Creek with the TQ modified. 3900 lb without driver, 3.36 axle, T400, Victor int man, street radials, reverse patttern cam, street registered & driven, 850 rpm idle in gear. He had little drag racing experience, running low 11s. NO tuning was done at the track such as ign timing, air valve [ AV ] position etc.
Comments on your TQ. There is no 6164 TQ in my master catalog, probably you have the 6461. It comes 98/137 jets & #2005 rods. I have never had to go more than about 2 thou bigger on the pri jets. 105 seems excessive. The Ferd 9000 series TQs here were 800s & had large 101 pri jets, but they also had much bigger pri air bleeds, which leaned the mixture. Probably for emissions. They also had smaller sec hi speed bleeds, 0.029" v the 0.039" used on the 6000 series carbs. The small size probably accounts for the smaller sec jets.
Since you have removed the choke, I would remove the x/over shaft that runs across the AV. Braze a small piece of steel over the opening left in the AV.
I NEVER use 1 1/4 turns on the AV spring, too loose. I use 2 turns. I would also go bigger on the AV opening, not 0.500". The opening also controls distribution as well as total air flow.
The top of the AV is bent forward. The original comp series had that straight. I straighten them sometimes. It starts the sec airflow earlier.
I have NEVER had to use the inner holes on the acc pump lever, only use the outer hole. These have a big 30cc pump & of course a very efficient design that doesn't need a heap of fuel to cover a bad design.
If you have the PCV hooked up, make sure engine vacuum is high enough to pull in the pintle. If not, cut off a piece of 3/8" bolt & drill a 1/8" hole through it; shove this inside the PCV hose.
If you need bypass air, drill the sec blades, not the pri because you could get nozzle drip.
If the engine is making a lot of HP, you should use 0.110" n/seats. Had to do this recently on a 440 I built that was laying over in 2nd gear. I just drill the factory seats. Use this chart to reset the f/level.
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