[Deadsquiggles]

I have a 451 Mopar stroker motor that's 10:1 and runs fine on regular pump gas. It has Edelbrock heads and .040 quench. From my understanding anything more than .040 is not effective quench.

See, from what I’ve been reading, it seems less than .060” is okay, and I’m right under that at .058” if I use a .040” gasket.

 

[Mark O'Neal]

I've rum .030...I've run .200......

 

[Deadsquiggles]

I've rum .030...I've run .200......

In your engine building experience, how big of a role does quench play in preventing detonation?

Also, I went ahead and submitted my order to FTI for a custom cam and sent off the Camtech form so I'm excited and hopeful Ed gets me squared away.

 

[Mark O'Neal]

It makes very little difference if any. For example, do true Hemis have a detonation issue with no quench? No, no they do not. As Jack Price used to say....."People eat with their eyes."

Ed will fix you up, it's what he does.

 

[408foureye]

It makes very little difference if any. For example, do true Hemis have a detonation issue with no quench? No, no they do not. As Jack Price used to say....."People eat with their eyes."

Ed will fix you up, it's what he does.

Mark, I think your a smart guy but I have to respectfully disagree. Significant lack of quench makes an engine prone to detonation, especially with a fair amount of ignition timing aggravating it. The best proof of this I can present is how horrible all of those mid 70s big block mopars and 460 Fords ran. I worked on a few of those older motor homes and trucks with those engines - they all rattled like marbles when you ran any worthwhile amount of timing, even with premium fuel. Some people tried water injection which didn't help all that much and the only way to stop the rattle was backing off timing to the point the thing fell on its face and ran hot.

After a proper rebuild on both 440 mopar or 460 Ford running the same heads, induction and ignition timing but different pistons (less quench and more compression), they had zero detonation issues, even pushing the total advance into the mid to high 30s. The 440s were by far the most transformed just with different pistons and the resulting quench reduction.

 

[CDW6212R]

Mark, I think your a smart guy but I have to respectfully disagree. Significant lack of quench makes an engine prone to detonation, especially with a fair amount of ignition timing aggravating it. The best proof of this I can present is how horrible all of those mid 70s big block mopars and 460 Fords ran. I worked on a few of those older motor homes and trucks with those engines - they all rattled like marbles when you ran any worthwhile amount of timing, even with premium fuel. Some people tried water injection which didn't help all that much and the only way to stop the rattle was backing off timing to the point the thing fell on its face and ran hot.

After a proper rebuild on both 440 mopar or 460 Ford running the same heads, induction and ignition timing but different pistons (less quench and more compression), they had zero detonation issues, even pushing the total advance into the mid to high 30s. The 440s were by far the most transformed just with different pistons and the resulting quench reduction.

Have you ever dealt with a Cleveland? Those for most had large open chambers, and 9:1 or near that. I have no need to build another, but I have both open and closed chamber heads. If I built one, I would prefer to do a stroker, and the piston would likely need the open chamber to bring the compression down some. Closed chambers had 63cc or near that, and the open chambers were near 75cc IIRC. It looks like doing a 408 Windsor short block with Cleveland heads might be more feasible, for better piston to cylinder surface area, and using an intake using a spacer for a Cleveland intake. I plan this stuff, but don't have a need for it.

 

[408foureye]

Have you ever dealt with a Cleveland? Those for most had large open chambers, and 9:1 or near that. I have no need to build another, but I have both open and closed chamber heads. If I built one, I would prefer to do a stroker, and the piston would likely need the open chamber to bring the compression down some. Closed chambers had 63cc or near that, and the open chambers were near 75cc IIRC. It looks like doing a 408 Windsor short block with Cleveland heads might be more feasible, for better piston to cylinder surface area, and using an intake using a spacer for a Cleveland intake. I plan this stuff, but don't have a need for it.

It's been such a long time since I built anything Cleveland. I do have a soft spot for them but they are kind of passe these days with their weird oiling system, plus its hard to get decent rebuildable blocks since the castings were so thin in stock bore size. I wouldn't bother trying to go 30 over on a Cleveland without sonic checking it everywhere. Even then I would be cautious running it at higher power levels.

The early 351c 4bbl and most boss 302 heads had roughly 63-65 cc chambers IIRC but the massive runners needed filling with epoxy if you wanted any practical performance at realistic rpms. 73-74 4bbl heads had even larger chambers. 71 is the only year for the smallest open chamber 2bbl head. I would prefer the 2bbl aussie heads with the smaller closed chambers and smaller ports. I used to build 400Ms with the aussie 2bbl heads which ran really well. I dont know if anyone still imports or reproduces the aussie heads. I'm not completely sure of this but blue thunder at some point sold some 351c heads with smaller chambers. Also, pro comp had some small chamber 351c heads, but I'm skeptical of anything from them quality wise. Building a Clevor is tempting but it's more of a novelty these days because there are now so many better head choices that will blow away any of the old iron stuff, even with a bit of port work done to them. The only real benefit was the smaller main journals, but 351w stuff is pretty durable in comparison with a better oiling system that didn't need lifter bore bushings like the Clevelands did. I guess you could buy some Price motorsports intake spacers and run 2bbl closed chamber heads for some decent compression. You would have to drill the heads for coolant passages. I did this once and it wasn't really worth the hassle due to the better windsor head availability. They do look cool though.

 

[Cougar5.O]

I had a 2V 351C in a '71 Mustang. I would say I wish I had it today, but I bought it from some dumbass who forgot to put antifreeze in it and popped out a large triangle of water jacket (2" on a side ). Lucky my blacksmith turned mechanic grandfather knew how to do a nice shadetree repair drilling the end of the cracks, then just keep going and drill a batch of holes around the triangle, then get some brass and cork, and a lot of RTV and it was good as new. Almost. It wept a little - lol.

 

[408foureye]

71 was the last decent year for Cleveland heads. Upping the chamber size really killed them. My 71 Galaxie had a 400M with 71 2bbl heads with solid cam, single plane manifold and 800 cfm holley dp going through a C6 and 3.50 gears. It ran like a scalded rat and would rev past 6500 without valve float. I loved it because most people looked down on the 400M and thought it wasn't much to worry about. I was walking away from all sorts of big block powered stuff in that big heavy car.

 

[Cougar5.O]

That's pretty impressive for a motor that has a reputation as a dog. Then again, the 351W was considered a dog back then too. Before I did the repair to the water jacket, I bought what turned out to be a 400M from someone in my neighborhood. Talk about a motor that looks the same but has so many differences. Luckily it also had water in it and was rusted, so I returned it and got my money back. Eventually the Mustang was wrecked by some idiot who ran a stop sign. I got 10x what I paid for it in insurance, then sold it to a junkyard for what I paid for it ($150.) They called and asked about the engine having some sort of issue, I said "no idea what you're talking about". lol

 

[CDW6212R]

It's been such a long time since I built anything Cleveland. I do have a soft spot for them but they are kind of passe these days with their weird oiling system, plus its hard to get decent rebuildable blocks since the castings were so thin in stock bore size. I wouldn't bother trying to go 30 over on a Cleveland without sonic checking it everywhere. Even then I would be cautious running it at higher power levels.

The early 351c 4bbl and most boss 302 heads had roughly 63-65 cc chambers IIRC but the massive runners needed filling with epoxy if you wanted any practical performance at realistic rpms. 73-74 4bbl heads had even larger chambers. 71 is the only year for the smallest open chamber 2bbl head. I would prefer the 2bbl aussie heads with the smaller closed chambers and smaller ports. I used to build 400Ms with the aussie 2bbl heads which ran really well. I dont know if anyone still imports or reproduces the aussie heads. I'm not completely sure of this but blue thunder at some point sold some 351c heads with smaller chambers. Also, pro comp had some small chamber 351c heads, but I'm skeptical of anything from them quality wise. Building a Clevor is tempting but it's more of a novelty these days because there are now so many better head choices that will blow away any of the old iron stuff, even with a bit of port work done to them. The only real benefit was the smaller main journals, but 351w stuff is pretty durable in comparison with a better oiling system that didn't need lifter bore bushings like the Clevelands did. I guess you could buy some Price motorsports intake spacers and run 2bbl closed chamber heads for some decent compression. You would have to drill the heads for coolant passages. I did this once and it wasn't really worth the hassle due to the better windsor head availability. They do look cool though.

Thanks, yeah I've read all of that past 30 years history stuff, I built my two in the 1980 and 81 range. Back then everything was about stock parts, only intakes or headers were aftermarket available. Back then the only oil tricks were the restrictors, nobody had considered altering the lifter bores yet. If I built one again, it would be for a Ranchero I got for some parts, and then just to resell it. So building such an engine would be mostly for the fun of doing it, and slightly to sell. I have both of the 4V heads, a new Torker intake, the old TRW pistons that are too heavy, and my first car's block, I went .020 over with it to be conservative. The new Motorsports valve covers I got back then will go onto a 302(352) 3V engine for my other(keeper) truck. I love those flat VC's.

 

[Cougar5.O]

Just to get back on topic for a minute, I think we calculated DCR incorrectly.

4.03" bore
3.5" stroke
KB151 pistons - 1.774 CH, 6.5cc valve reliefs
5.955" rod
0.040" HG 4.100" bore
Your 0.018" deck height seems about correct
With a 60cc chamber, we get 10.27:1 CR

Using the cam you specified, 35-320-8, we have 60 deg ABDC intake close and this calculator says your DCR is 8.47:1

I screwed up on mine also, using the 0.050" IVC event versus seat, so mine is 7.54:1.

 

[408foureye]

DCR is kind of a grey area. You have to also consider overlap and look at cranking compression at specific rpms. Anything around mid 8:1s on pump gas is theoretically ok. It's also going to factor in things like vehicle weight, gearing, total ignition advance, cylinder filling, stroke etc.

My past experience tells me the less overlap the cam has, the more even cylinder pressure you build across the rpm range which makes things more predictable, but a tight LSA coupled with high DCR can be trouble if the cam is on the smaller side.

 

[Deadsquiggles]

Just to get back on topic for a minute, I think we calculated DCR incorrectly.

4.03" bore
3.5" stroke
KB151 pistons - 1.774 CH, 6.5cc valve reliefs
5.955" rod
0.040" HG 4.100" bore
Your 0.018" deck height seems about correct
With a 60cc chamber, we get 10.27:1 CR

Using the cam you specified, 35-320-8, we have 60 deg ABDC intake close and this calculator says your DCR is 8.47:1

I screwed up on mine also, using the 0.050" IVC event versus seat, so mine is 7.54:1.

I guess that shows the variability with the online calculators cause this one gives a DCR of 8.9:1 with the same SCR of 10.3:1. Who knows I guess. At this point, I’m just gonna out my trust in Ed to give a cam that was properly designed with all this in mind.

 

[Cougar5.O]

I guess that shows the variability with the online calculators cause this one gives a DCR of 8.9:1 with the same SCR of 10.3:1. Who knows I guess. At this point, I’m just gonna out my trust in Ed to give a cam that was properly designed with all this in mind.

Yeah, they use the 0.050" lift closing point, then end up in a place that's about halfway between what the Wallace racing site shows at 0.006" & 0.050" closing point. It may be a better way to calculate it, who knows, it's mostly meaningless. There's no magic to cam selection for detonation resistance once one knows whether you're using iron heads or modern design aluminum heads and some idea how good a VE your engine will achieve.

 

[Mark O'Neal]

I've seen an iron-headed 331 Cleveland run 7s, naturally aspirated, in NHRA in G Altered, as well as dominate ProStock.

A "dog".......hardly.

If it weren't for boost, most people today would have to stick to minivans.

 

[Mark O'Neal]

Mark, I think your a smart guy but I have to respectfully disagree. Significant lack of quench makes an engine prone to detonation, especially with a fair amount of ignition timing aggravating it. The best proof of this I can present is how horrible all of those mid 70s big block mopars and 460 Fords ran. I worked on a few of those older motor homes and trucks with those engines - they all rattled like marbles when you ran any worthwhile amount of timing, even with premium fuel. Some people tried water injection which didn't help all that much and the only way to stop the rattle was backing off timing to the point the thing fell on its face and ran hot.

After a proper rebuild on both 440 mopar or 460 Ford running the same heads, induction and ignition timing but different pistons (less quench and more compression), they had zero detonation issues, even pushing the total advance into the mid to high 30s. The 440s were by far the most transformed just with different pistons and the resulting quench reduction.

No....it doesn't. But a " fair amount of ignition timing aggravating it" certainly does.

My father had a Cabriolet with a 460 that rattled. I changed the cam, bumped the compression, ported the exhaust ports..and added a set of headers. Pulled Donner Summit in second under at the speed limit with a 36' Beaver fifth wheel behind it. Never rattled.

If you're trying to "fix" low cylinder pressure with timing, I guarantee you, it's going to detonate.

 

[408foureye]

No....it doesn't. But a " fair amount of ignition timing aggravating it" certainly does.

My father had a Cabriolet with a 460 that rattled. I changed the cam, bumped the compression, ported the exhaust ports..and added a set of headers. Pulled Donner Summit in second under at the speed limit with a 36' Beaver fifth wheel behind it. Never rattled.

If you're trying to "fix" low cylinder pressure with timing, I guarantee you, it's going to detonate.

There was nothing to really fix. Those smog motors used in heavy duty chassis were speced to run mid 20s total timing even though the same motor with same cam in a car or pickup ran mid 30s total timing. People would get tired replacing cracked exhaust manifolds and watching coolant temps creeping up trying to pull a hill, so the only long term solution was a rebuild with better pistons that didn't run .200"or more in the hole depending on the production year. EGR kept that issue somewhat under control, but it would carbon up so fast and still run like crap.

 

[Mark O'Neal]

Sigh.